[xj] Fuel pump makes a surging sound, engine dies under load

XJ
1

I installed a Bosch 044 fuel pump about 6 months ago on my
Jaguar LS1 swap. The pump makes a surging sound at random
every second or two, almost like it’s getting a little gulp
of air or something. It’s done this since the day I
installed it. It does not matter whether the tanks are full
or empty, or if one tank or another is selected. Under heavy
throttle and/or high RPMs, the car will hesitate, almost
like it’s running out of fuel or the spark is being shut off
just for an instant. If you keep your for in it, the car
will jerk back and forth pretty violently. The problem got
worse on my way home today… worse than it’s ever been. It
actually stalled a couple times while cruising, but started
right back up.

Normal Bosch 044 on youTube sounds like this:
‘‘Rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
rrrrrrrrrrrrrrrrrrrrrrrrrr’’

My Bosch 044 sounds like this:
‘‘Rrrrrrrrrrbrbrrrrrrrrrrrrrrrrrrrrrrrbrrrrrrrrrrrr
rrbrrrbrrrrrrrrrrrrrbr’’

I tested the voltage at the pump, and it’s dead steady,
reading the same as at the battery posts.

Here’s a youTube video of my pump. It is not a constant
hum. You can hear the surging. Be aware that the Bosch 044
is a very noise pump.

The pump is installed inline where the old pump was. There
is plenty of fuel in the tanks. I have a 100 micron
stainless steel mesh cartridge Trick Flow fuel filter that I
installed on the inlet side of the pump. It’s all 1/2’’ fuel
hose from the tanks, through the fuel tank selector valve,
through the filter, and to the pump. There is also an LS1
Corvette filter/regulator in the engine bay. The tanks have
plenty of fuel. The pump and inline filter have about 700
miles on them.

Also noteworthy - the pump that came with the car got noisy
like this before I replaced it. The car also started cutting
out under load and high RPMs. The problem largely went away
when I installed the new pump, but not entirely.

What the heck is going on here? Any thoughts?

Thanks in advance, -Dave–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
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2

I installed a Bosch 044 fuel pump about 6 months ago on my
Jaguar LS1 swap. The pump makes a surging sound at random
every second or two, almost like it’s getting a little gulp
of air or something. It’s done this since the day I
installed it.

Since swapping the pumps did not help, Dave; you either have two dud pumps -
or, more likely, the fault is in-car…

…either the pump feed or the exit to the rail. As you have a non standard
set-up, things are a bit complicated - but no matter what; the pump should
be a constant hum, no ifs or buts…

*Invariably; open filler lids, run the pump - and verify that fuel is
returning, and to the selected tank only. This is to ensure that the fuel
return is not causing a bewildering problem…

**Clamp all three hoses at the changeover valve (to avoid fuel spill),
disconnect changeover-to-pump at the pump and connect a tank hose directly
to the pump - bypassing any inline filters installed. The inline filter may
be clogged, or too restrictive - run the the pump to see if there are any
changes. You can also test drive in this configuration…

Since you have the same symptoms on either tanks; it doesn’t matter which
tank you pick - but for correct return you must select the chosen tank at
the changeover switch. Theoretically; you may have clogged in-tank filters -
in which case the problem will persist during testing…

***Connect the pump output hose directly to main filter inlet - bypassing
the original hexagonal non-return valve - which may be blocked. Don’t know
the Corvette filter/regulator, or what it does, and how it is connected -
but I doubt if it is failsafe, so bypass it…

****Connect the rail hose directly to pump outlet; this will bypass the main
filter - and all but the in-tank filters…

Basically; running the pump only should clarify if any of these tests make a
difference. A steady pump ‘hum’, strong or soft - but constant it should
be…

It’s impossible to differentiate, by sound, between a pump fault, a feed or
delivery problem, or the pump sucking air through a bad connection/faulty
hose, or whatever. But unless the pump is defective - there is likely a
blockage, underfuelling the engine…

Frank
xj6 85 Sov Europe (UK/NZ)

It does not matter whether the tanks are full
or empty, or if one tank or another is selected. Under heavy
throttle and/or high RPMs, the car will hesitate, almost
like it’s running out of fuel or the spark is being shut off
just for an instant. If you keep your for in it, the car
will jerk back and forth pretty violently. The problem got
worse on my way home today… worse than it’s ever been. It
actually stalled a couple times while cruising, but started
right back up.

Normal Bosch 044 on youTube sounds like this:
‘‘Rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
rrrrrrrrrrrrrrrrrrrrrrrrrr’’

My Bosch 044 sounds like this:
‘‘Rrrrrrrrrrbrbrrrrrrrrrrrrrrrrrrrrrrrbrrrrrrrrrrrr
rrbrrrbrrrrrrrrrrrrrbr’’

I tested the voltage at the pump, and it’s dead steady,
reading the same as at the battery posts.

Here’s a youTube video of my pump. It is not a constant
hum. You can hear the surging. Be aware that the Bosch 044
is a very noise pump.

The pump is installed inline where the old pump was. There
is plenty of fuel in the tanks. I have a 100 micron
stainless steel mesh cartridge Trick Flow fuel filter that I
installed on the inlet side of the pump. It’s all 1/2’’ fuel
hose from the tanks, through the fuel tank selector valve,
through the filter, and to the pump. There is also an LS1
Corvette filter/regulator in the engine bay. The tanks have
plenty of fuel. The pump and inline filter have about 700
miles on them.

Also noteworthy - the pump that came with the car got noisy
like this before I replaced it. The car also started cutting
out under load and high RPMs. The problem largely went away
when I installed the new pump, but not entirely.

What the heck is going on here? Any thoughts?-----Original Message-----
From: Dave Y.
Sent: Friday, October 04, 2013 5:23 PM
To: xj@jag-lovers.org
Subject: [xj] Fuel pump makes a surging sound, engine dies under load

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3

In reply to a message from Frank Andersen sent Thu 3 Oct 2013:

Isolate and check. Great diagnoistic path.

One more idea: The pickups in the tanks are partially blocked.

One question: Why the Corvette filter regulator in the boot?

is there another regulator up front on the fuel rail?

So, perhaps the Corvette unit is at fault? either the regulating

part or the filter or both? Either might be a cause of fuel
starvation.

The irregular sound at the pump suggests fuel starvation before the
pump!!

Carl–
The original message included these comments:

Also noteworthy - the pump that came with the car got noisy
like this before I replaced it. The car also started cutting
out under load and high RPMs. The problem largely went away

–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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4

In reply to a message from Dave Y. sent Thu 3 Oct 2013:

Frank and Carl,

Thanks for posting! I guess I’ll start troubleshooting the
inlet side of the tank and go from there. At first I
thought it was the regulator ‘‘regulating’’ but as per your
comments it sounds more like a problem on the inlet side of
the system.

Also, the Corvette filter/regulator is a static regulator
used on the LS1 Corvettes. It supplies the required fuel
pressure to the LS1 fuel rails, and is also the system’s
fuel filter. I have since eliminated the Jag filter in the
spare tire well.

This car’s had a gremlin in it since I put it together.

From time to time I would experience engine hesitation,
mostly under heavy throttle. I hope this is what’s been
plaguing me all along!–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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5

In reply to a message from Dave Y. sent Fri 4 Oct 2013:

Trashy fuel tanks, never run right until they’re cleaned out
first… I just sealed yet another tank last week, bmw this
time. Runs like a BOH now!
Bill–
The original message included these comments:

This car’s had a gremlin in it since I put it together.

From time to time I would experience engine hesitation,
mostly under heavy throttle. I hope this is what’s been
plaguing me all along!

–
'75XJ6C about to be unlumped, '86 XJ6, '67 FHC, '75TR6
moultrie, ga, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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6

In reply to a message from Dave Y. sent Thu 3 Oct 2013:

Frank and Carl,

Thanks for posting! I guess I’ll start troubleshooting the
inlet side of the tank and go from there. At first I
thought it was the regulator ‘‘regulating’’ but as per your
comments it sounds more like a problem on the inlet side of
the system.

Also, the Corvette filter/regulator is a static regulator
used on the LS1 Corvettes. It supplies the required fuel
pressure to the LS1 fuel rails,

As described, ‘static’ is dead wrong for the xk EFI fuelling system, Dave…

…the regulator varies the ‘raw’ fuel pressure from the pump according to
manifold vacuum. ‘Raw’ pump pressure is nominally 100+ psi, but will work OK
down to some 70 psi for a worn pump. This is partially a volume issue - a
low output pressure from the pump implies that it’s capacity is also
depleted…

Nominally, the pressure regulator ‘bleeds off’ fuel back to the tanks to
maintain desired rail pressure at all times - spec pressure is some 36 psi,
give or take, with no manifold vacuum. Manifold vacuum will drop this
further to basically maintain a constant pressure differential between the
rail and the manifold.

While I don’t fully understand your set-up, a likely scenario is that the
installed filter/regulator delivers a constant pressure to the rail. At high
loads, high fuel consumption, your set-up strangles supply to the rail,
leading to underfuelling - or alternatively, without the original regulator,
overfuels the engine. In both cases leading to engine misbehaviour…

Also; your Corvette filter/regulator may just block pump flow to regulate
pressure. This will cause the pump to labour against a back pressure, making
it noisy. The original set-up allows the pump to deliver its full flow at
all times, unimpeded; the pressure regulator just bleeds off excess volume.

An essential question is if you have the original pressure regulator
connected ‘as was’ - in which case you can, as a test, connect the rail hose
directly to the pump output, bypassing the Corvette system.

But for sure; reverting to the original system (why on earth did you change
it?) will in all likely hood eliminate your problems…

Frank
xj6 85 Sov Europe (UK/NZ)

and is also the system’s
fuel filter. I have since eliminated the Jag filter in the
spare tire well.

This car’s had a gremlin in it since I put it together.

From time to time I would experience engine hesitation,
mostly under heavy throttle. I hope this is what’s been
plaguing me all along!-----Original Message-----
From: Dave Y.
Sent: Saturday, October 05, 2013 4:43 AM
To: xj@jag-lovers.org
Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load

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7

In reply to a message from Frank Andersen sent Fri 4 Oct 2013:

I probably didn’t do a great job of describing my fuel
system, but it’s really simple: The fuel pump draws fuel
through all of the Jaguar parts plus a ‘‘pre-filter’’ with a
stainless steel element. It then pushes fuel up to the
engine compartment where the Corvette fuel pressure
regulator unit supplies a single and consistent fuel
pressure to the LS1 fuel rail (it is static in that it does
not variate with manifold pressure) and then the regulator
unit diverts the unused fuel back through the original
Jaguar return system.

My car has a GM LS1 V8, so if I were to use all parts of the
original Jaguar fuel system, the car simply wouldn’t run!

I am going to test the inlet side of the fuel system next
week. I suspect that my pump is starving for fuel. I don’t
know why yet… maybe insufficient flow through the fuel
tank selector valve, or perhaps a collapsed hose.–
The original message included these comments:

While I don’t fully understand your set-up, a likely scenario is that the
installed filter/regulator delivers a constant pressure to the rail. At high
loads, high fuel consumption, your set-up strangles supply to the rail,
leading to underfuelling - or alternatively, without the original regulator,
overfuels the engine. In both cases leading to engine misbehaviour…
Also; your Corvette filter/regulator may just block pump flow to regulate
pressure. This will cause the pump to labour against a back pressure, making
it noisy. The original set-up allows the pump to deliver its full flow at
all times, unimpeded; the pressure regulator just bleeds off excess volume.
An essential question is if you have the original pressure regulator
connected ‘as was’ - in which case you can, as a test, connect the rail hose

–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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8

In reply to a message from Frank Andersen sent Fri 4 Oct 2013:

I probably didn’t do a great job of describing my fuel
system, but it’s really simple: The fuel pump draws fuel
through all of the Jaguar parts plus a ‘‘pre-filter’’ with a
stainless steel element. It then pushes fuel up to the
engine compartment where the Corvette fuel pressure
regulator unit supplies a single and consistent fuel
pressure to the LS1 fuel rail (it is static in that it does
not variate with manifold pressure) and then the regulator
unit diverts the unused fuel back through the original
Jaguar return system.

My car has a GM LS1 V8, so if I were to use all parts of the
original Jaguar fuel system, the car simply wouldn’t run!

It sure explains the nee for a different set-up, Dave - I sure have been
flogging a wrong horse…:slight_smile:

Any engine would of course react the same to a blockage, pump ‘in’ or ‘out’,
so the problem can be dealt with the same way, but with different components
The xk EFI differs only in a variably fuel pressure, which is ECU related
operating the injectors - while I would have thought your ‘Corvette’ set-up
used the GM throttle body injection…?

However, the simplest way of eliminating a pump feed problem due to tank
filter, changeover or fuel line blockages would be to feed the pump directly
from a can. Confirming or eliminating the need for work in this area - and
since the symptoms are the same on both tanks; the common changeover valve
is definitely a suspect…

Since you are using the original fuel return; I would certainly check fuel
return - to ensure the return system is not causing problems. The pump is
designed, with either set-up, to deliver enough fuel to return excess fuel -
no return would imply lack of pump capacity…or a return problem, which may
interfere with fuelling…

You don’t mention having checked fuel pressures - to ensure that the
regulator is indeed delivering to spec…?

I quite agree that the ‘unsteady’ buzz of the pump sounds more like a feed
problem - it’s difficult to see anything that intermittently block the
outflow. On the original set-up both a blocked main filter, a failed
regulator or a failed return would interfere with pump operation, but the
fault would be constant - and the engine would then likely refuse to run
properly at any time…

Frank
xj6 85 Sov Europe (UK/NZ)

I am going to test the inlet side of the fuel system next
week. I suspect that my pump is starving for fuel. I don’t
know why yet… maybe insufficient flow through the fuel
tank selector valve, or perhaps a collapsed hose.-----Original Message-----
From: Dave Y.
Sent: Sunday, October 06, 2013 4:42 PM
To: xj@jag-lovers.org
Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load

–
The original message included these comments:

While I don’t fully understand your set-up, a likely scenario is that the
installed filter/regulator delivers a constant pressure to the rail. At
high
loads, high fuel consumption, your set-up strangles supply to the rail,
leading to underfuelling - or alternatively, without the original
regulator,
overfuels the engine. In both cases leading to engine misbehaviour…
Also; your Corvette filter/regulator may just block pump flow to regulate
pressure. This will cause the pump to labour against a back pressure,
making
it noisy. The original set-up allows the pump to deliver its full flow at
all times, unimpeded; the pressure regulator just bleeds off excess
volume.
An essential question is if you have the original pressure regulator
connected ‘as was’ - in which case you can, as a test, connect the rail
hose

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9

In reply to a message from Frank Andersen sent Sun 6 Oct 2013:

Dave;

I got it as well. Somewhat similar to the fueling system in my car.
I kept the Jaguar Bosch filter. But, the GM regulstor is on the
fuel rail of my LT1. Works just fine.

After my engine failure, I drained both tanks via the large nut on
the vottom of each. Oh well, but the fuel was a bit old, but clean.
No junk came out.

In your car, I join Frank in the belief that it is a prepump feed
issue.

The Jaguar system is complex, but will work if the components are
in order. Dirty tanks in any sytem will cause issues. Been there,
oh so many times in various critters.

Carl–
The original message included these comments:

Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load
In reply to a message from Frank Andersen sent Fri 4 Oct 2013:
I probably didn’t do a great job of describing my fuel
system, but it’s really simple: The fuel pump draws fuel
through all of the Jaguar parts plus a ‘‘pre-filter’’ with a
stainless steel element. It then pushes fuel up to the
engine compartment where the Corvette fuel pressure
regulator unit supplies a single and consistent fuel
pressure to the LS1 fuel rail (it is static in that it does
not variate with manifold pressure) and then the regulator
unit diverts the unused fuel back through the original

–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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10

In reply to a message from cadjag sent Mon 7 Oct 2013:

So…

I drained both tanks and took apart the inlet side of the
fuel system. The fuel pre-filter was caked with brown stuff,
probably rust. Fuel would not pass through. The fuel tank
selector valve, which has 1/2’’ fittings, was restricted down
to about 3/16’’ inside the valve at both inlets. I cleaned
the filter element and installed a free-flowing 1/2’’ brass
tee, and the pump REALLY quieted down. The car ran great!

At the end of my 15 minute ride home, the pump got noisy
again. I went and started the car an hour later, and the
pump was quiet again. Hm. Did it cake up again?

I also had an issue on the return side. The fuel pressure
was at about 67 psi at the rail. On the LS1 system, it’s
supposed to be 58.5 psi. I suspect that with the pump now
flowing properly again, it was over flowing the return
system. (The pump I installed flows A LOT of fuel.) I
replaced one of the return valves, which was also very
restrictive, with a piece of straight 3/8’’ tube, and the
fuel pressure came down to 61.5 psi. I did not have time to
do the other side. There is a chance that I filled up one
tank, and the pump sucked some air from the other side.
Maybe that’s where the noise came from. I really don’t know.

Hm!–
The original message included these comments:

I got it as well. Somewhat similar to the fueling system in my car.
I kept the Jaguar Bosch filter. But, the GM regulstor is on the
fuel rail of my LT1. Works just fine.
After my engine failure, I drained both tanks via the large nut on
the vottom of each. Oh well, but the fuel was a bit old, but clean.
No junk came out.
In your car, I join Frank in the belief that it is a prepump feed
issue.
The Jaguar system is complex, but will work if the components are
in order. Dirty tanks in any sytem will cause issues. Been there,
oh so many times in various critters.

–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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11

In reply to a message from cadjag sent Mon 7 Oct 2013:

So…

I drained both tanks and took apart the inlet side of the
fuel system. The fuel pre-filter was caked with brown stuff,
probably rust. Fuel would not pass through. The fuel tank
selector valve, which has 1/2’’ fittings, was restricted down
to about 3/16’’ inside the valve at both inlets. I cleaned
the filter element and installed a free-flowing 1/2’’ brass
tee, and the pump REALLY quieted down. The car ran great!

At the end of my 15 minute ride home, the pump got noisy
again. I went and started the car an hour later, and the
pump was quiet again. Hm. Did it cake up again?

I also had an issue on the return side. The fuel pressure
was at about 67 psi at the rail. On the LS1 system, it’s
supposed to be 58.5 psi. I suspect that with the pump now
flowing properly again, it was over flowing the return
system. (The pump I installed flows A LOT of fuel.) I
replaced one of the return valves, which was also very
restrictive, with a piece of straight 3/8’’ tube, and the
fuel pressure came down to 61.5 psi. I did not have time to
do the other side. There is a chance that I filled up one
tank, and the pump sucked some air from the other side.
Maybe that’s where the noise came from. I really don’t know.

Hm!

Since you did several operations simultaneously, Dave, it’s touch and go
whether your noise problem stemmed from the clogged filter, the changeover
valve, clogged returns - or excessive pump capacity…:slight_smile:

The pump noise could be related to either, as would excessive fuel pressure.
One may muse on engine behaviour at full throttle; while it may indicate
starvation - it may also relate to the fuelling system fitted. Ie, fuelling
being controlled by throttle position, among other things, excessive
pressure may cause fuelling anomalies - with odd engine behaviour. Don’t
know the capacities of the Bosch 044 pump and its suitability for you
‘Corvette’ set-up…;0

You have of course ‘bastardized’ the fuel delivery and return system, Dave -
but it is in itself of no engine running consequences…

Replacing the changeover valve with a ‘T’ is not uncommon, and the fuel pump
will now feed from both tanks at all times - and cannot, arguably, really
suck air from an empty tank. The return system is entirely independent on
the feed, the only thing required is that it is a return - to ensure proper
working of the pressure regulator…

Nominally, the ‘T’ will continuously equalize the level of the two tanks by
gravity, even while driving. However, pumped volume is a factor here; as
long as the pump is running it will run at max capacity - and the return
flow will take the path of least resistance. With you ‘straight through’
modification of one of the return valves; if you select the opposite tank
the ‘unmodified’ return valve will now be closed - and all fuel will now go
through the ‘modified’ valve. Which may then fill up faster than the gravity
transfer trying to equalize tank levels…

So, if you have modified one return valve; you should also modify the
other - or always select the ‘unmodified’ tank…:slight_smile:

It’s perfectly possible to fit a pump with a capacity that overwhelms the
return system - it’s silly, of course, but possible. The remedial action is
to fit pump with the proper capacity, but that said; return malfunctions
are not uncommon - either by valve failure or indeed valve clogging, and may
indeed cause problems as you describe - excessive fuel pressure an pump
noise…

If you modify both return valves, and together with the feed ‘T’, the
problem with excessive pump capacity may persist and the pump should be
changed…

Frank

The original message included these comments:-----Original Message-----
From: Dave Y.
Sent: Wednesday, October 09, 2013 1:42 PM
To: xj@jag-lovers.org
Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load

I got it as well. Somewhat similar to the fueling system in my car.
I kept the Jaguar Bosch filter. But, the GM regulstor is on the
fuel rail of my LT1. Works just fine.
After my engine failure, I drained both tanks via the large nut on
the vottom of each. Oh well, but the fuel was a bit old, but clean.
No junk came out.
In your car, I join Frank in the belief that it is a prepump feed
issue.
The Jaguar system is complex, but will work if the components are
in order. Dirty tanks in any sytem will cause issues. Been there,
oh so many times in various critters.

===================================================
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12

In reply to a message from Frank Andersen sent Tue 8 Oct 2013:

I cleaned the filter and then replaced the fuel selector
valve with the tee, so I’ll never know with 100% certainty
if the fuel selector valve caused enough restriction to make
the pump cavitate. However, given what I saw and heard, I
bet that it was part of the problem. The return valves
addressed an entirely new problem - too much volume!

The Bosch 044 pump is pretty impressive. It will supply 280
LPH of fuel at 4 bar (about 58 psi) which is more than some
electric fuel pumps free-flow at 0 psi. I used it because
my supercharger will need a lot of fuel at a very high
pressure (up to 5 bar) to produce over 600 flywheel hp.
Knowing what I know now, I would have picked a pump that
flowed slightly less fuel, and used a voltage booster to
squeeze more out of the pump under heavy throttle, but oh
well…

The tanks take a long time to settle. After my 15 minute
drive home, my left tank was reading 3/8 and my right tank
was reading empty. It took about 2 hours for them to level
out. While driving, the left tank fills up very quickly,
even with the right return valve open. I hope they fill
more evenly when I replace the right return valve with a
piece of 3/8’’ tube.–
The original message included these comments:

Since you did several operations simultaneously, Dave, it’s touch and go
whether your noise problem stemmed from the clogged filter, the changeover
valve, clogged returns - or excessive pump capacity…:slight_smile:
Nominally, the ‘T’ will continuously equalize the level of the two tanks by
gravity, even while driving. However, pumped volume is a factor here; as
long as the pump is running it will run at max capacity - and the return
flow will take the path of least resistance. With you ‘straight through’
modification of one of the return valves; if you select the opposite tank
the ‘unmodified’ return valve will now be closed - and all fuel will now go
through the ‘modified’ valve. Which may then fill up faster than the gravity
transfer trying to equalize tank levels…

–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

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13

In reply to a message from Frank Andersen sent Tue 8 Oct 2013:

I cleaned the filter and then replaced the fuel selector
valve with the tee, so I’ll never know with 100% certainty
if the fuel selector valve caused enough restriction to make
the pump cavitate. However, given what I saw and heard, I
bet that it was part of the problem. The return valves
addressed an entirely new problem - too much volume!

The Bosch 044 pump is pretty impressive. It will supply 280
LPH of fuel at 4 bar (about 58 psi) which is more than some
electric fuel pumps free-flow at 0 psi.

Something here doesn’t quite gel, Dave…

…the spec pressure you mention of LS1 is 58,5 psi - and I assume that this
is then the spec pressure of the filter/regulator. What is the ‘raw’ output
pressure of the pump…?

In perspective; a V12 on full song uses about 50 - 60 litres of petrol per
hour, and even given your supercharger your engine will hardly use more than
twice that at maximum throttle. When cruising you likely use some 10 -15
litres per hour - the rest, 250+ litres, is continuously pumped back into
the tanks. And the original system was unlikely to cope very well with
that - neither supply nor return…

The point is that the fuel pump must deliver enough fuel to maintain the
spec injection pressure at all times - there is no need to exceed that by
more than a small margin. As Paul very rightly points out; modifying the
Jaguar fuel system is usually unnecessary - and I ‘think’ that it would have
bee able to cope in original configuration, including the original pump,
with the higher demand put on your set-up. 600 hp requires just 3 times the
amount of fuel compared to 200 hp.

In other words; your modifications are arguably forced on you by the pump,
rather than the actual needs of your engine…:slight_smile:

The long time take for the tanks to equalize is a separate issue, but rather
odd. One step here is to see if the tanks equalize more quickly if to open
the tank lids - lack of proper tank venting will interfere with the
crossfeed…and carries considerable risk of tank implosion. Also; inspect
the fuel lines from the tank to the ‘T’, the crossfeed goes from tank to
tank via the ‘T’ - so any filter clogged between the tanks and the ‘T’ will
cause transfer delays…

Modifying the other return valve will ensure that equal amounts of fuel goes
to each tank - the ‘right’ return may have failed, preventing flow through
that tank…

But I still think you should consider your choice of pump…

Frank
xj6 85 Sov Europe (UK/NZ)

I used it because
my supercharger will need a lot of fuel at a very high
pressure (up to 5 bar) to produce over 600 flywheel hp.
Knowing what I know now, I would have picked a pump that
flowed slightly less fuel, and used a voltage booster to
squeeze more out of the pump under heavy throttle, but oh
well…

The tanks take a long time to settle. After my 15 minute
drive home, my left tank was reading 3/8 and my right tank
was reading empty. It took about 2 hours for them to level
out. While driving, the left tank fills up very quickly,
even with the right return valve open. I hope they fill
more evenly when I replace the right return valve with a
piece of 3/8’’ tube.

The original message included these comments:-----Original Message-----
From: Dave Y.
Sent: Wednesday, October 09, 2013 3:35 PM
To: xj@jag-lovers.org
Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load

Since you did several operations simultaneously, Dave, it’s touch and go
whether your noise problem stemmed from the clogged filter, the changeover
valve, clogged returns - or excessive pump capacity…:slight_smile:
Nominally, the ‘T’ will continuously equalize the level of the two tanks
by
gravity, even while driving. However, pumped volume is a factor here; as
long as the pump is running it will run at max capacity - and the return
flow will take the path of least resistance. With you ‘straight through’
modification of one of the return valves; if you select the opposite tank
the ‘unmodified’ return valve will now be closed - and all fuel will now
go
through the ‘modified’ valve. Which may then fill up faster than the
gravity
transfer trying to equalize tank levels…

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

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14

In reply to a message from Frank Andersen sent Tue 8 Oct 2013:

Yea, the fuel pump is definitely creating some problems for
me, but it also highlights the fact that this system was not
designed to support a 600hp supercharged engine. The fuel
selector valve is the one that’s really got me scratching my
head - it is VERY restrictive.

Do you have a flow map (pressure vs. volume) chart for that
stock Bosch pump? I can almost guarantee that it is
incapable of supplying 200+ LPH of fuel (roughly what I am
going to need) at 5 bar. My current pump is moving about
280 LPH at 4 bar, and will supply about 265 LPH at 5 bar
under boost.

Using the Jaguar engine horsepower & flow might not be the
best way to estimate the amount of fuel I’ll need. There
are a lot of factors to consider, including the huge
parasitic loss of driving a supercharger.–
The original message included these comments:

The point is that the fuel pump must deliver enough fuel to maintain the
spec injection pressure at all times - there is no need to exceed that by
more than a small margin. As Paul very rightly points out; modifying the
Jaguar fuel system is usually unnecessary - and I ‘think’ that it would have
bee able to cope in original configuration, including the original pump,
with the higher demand put on your set-up. 600 hp requires just 3 times the
amount of fuel compared to 200 hp.
In other words; your modifications are arguably forced on you by the pump,
rather than the actual needs of your engine…:slight_smile:
But I still think you should consider your choice of pump…

–
1985 XJ6 LS1 - For pictures go to www.buyrcars.com
Pittsburgh, PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

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15

In reply to a message from Frank Andersen sent Tue 8 Oct 2013:

Yea, the fuel pump is definitely creating some problems for
me, but it also highlights the fact that this system was not
designed to support a 600hp supercharged engine. The fuel
selector valve is the one that’s really got me scratching my
head - it is VERY restrictive.

It certainly is not meant to support the indicated capacity of the pump you
fitted, Dave…

My line is really to find what sort of capacity is required to feed your
engine set-up, and indeed if the system would then be adequate to supply
that amount - even if a slightly large pump would be required. There is of
course no engine problem having a higher than required pump capacity - it
will only take as much fuel as is required…

Do you have a flow map (pressure vs. volume) chart for that
stock Bosch pump? I can almost guarantee that it is
incapable of supplying 200+ LPH of fuel (roughly what I am
going to need) at 5 bar. My current pump is moving about
280 LPH at 4 bar, and will supply about 265 LPH at 5 bar
under boost.

I don’t have the flow chart handy - only that it adequately supplies 5,3
litres of V12 up to 250+ hp. My line would then have been to use the pump
specified used for the engine fitted - then considered the boost pressure of
the turbo fitted to compute roughly how much extra fuel would be required.
All that said; I seriously doubt if the Jaguar chassis and drive train could
handle 600 hp…:slight_smile:

Using the Jaguar engine horsepower & flow might not be the
best way to estimate the amount of fuel I’ll need. There
are a lot of factors to consider, including the huge
parasitic loss of driving a supercharger.

Basically fuel consumption is a matter of air volume moving through the
engine - the proportion of air to fuel is a constant. The fuel consumption
is independent of fuel pressure - the fuel control uses fuel pressure as a
parameter for correct mixture. The supercharger simply adds air to the
engine, proportional to the boost pressure - and of course; engines vary in
how efficiently they use fuel…

As an aside - how does the LS1 control fuelling in relation to supercharger
boost. Ie, is the engine stalling out under high loads due to it not knowing
that the supercharger is adding air - leaning out the mixture…?

Frank
xj6 85 Sov Europe (UK/NZ)

The original message included these comments:-----Original Message-----
From: Dave Y.
Sent: Thursday, October 10, 2013 10:37 AM
To: xj@jag-lovers.org
Subject: Re: [xj] Fuel pump makes a surging sound, engine dies under load

The point is that the fuel pump must deliver enough fuel to maintain the
spec injection pressure at all times - there is no need to exceed that by
more than a small margin. As Paul very rightly points out; modifying the
Jaguar fuel system is usually unnecessary - and I ‘think’ that it would
have
bee able to cope in original configuration, including the original pump,
with the higher demand put on your set-up. 600 hp requires just 3 times
the
amount of fuel compared to 200 hp.
In other words; your modifications are arguably forced on you by the pump,
rather than the actual needs of your engine…:slight_smile:
But I still think you should consider your choice of pump…

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

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