[v12-engine] Fuel Pressure Regulators - Lucas


(Rob Roe) #1

Just discovered my 87 XJS has a 3.0 Bar fuel pressure regulator on
the inlet (right) side of the fuel rail and a 2.5 Bar fuel pressure
regulator on the outlet side (left) of the fuel rail. Could this
cause incorrect fuel pressure in the rail? Especially under heavy
acceleration? I tend to get unexplainable pinging under load and
rising engine temps. Have not yet checked the fuel pressure as I
don’t know the correct fittings to install a gauge.

Has anyone discovered a combination of fittings that allow for the
install of a fuel pressure gauge without having to cut the fuel
hoses?

Thanks in advance for your thoughts.–
87 XJ-S V12 Coupe
Bellevue/WA, United States
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(Billbo) #2

In reply to a message from Rob Roe sent Tue 7 Sep 2010:

I think you could make an inline tee fitting with 3
fittings. It would need to terminate to 1/4 NPT on the
branch side. It could be place between the rail and the
hose. The fuel rail threads are M14x1.5, so a swivel run
tee, and an adapter to get the branch to 1/4 NPT, then a
pipe coupling to give you a female NPT for your gauge of
choice. A local hydraulic hose shop could probably come up
with the fittings. Email me if you need some help describing
the arrangement.–
The original message included these comments:

Has anyone discovered a combination of fittings that allow for the
install of a fuel pressure gauge without having to cut the fuel


1990 XJ-S V12 5.3 Coupe, Marelli
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(Ed Sowell) #3

Rob,

Has anyone discovered a combination of fittings that allow for the
install of a fuel pressure gauge without having to cut the fuel
hoses?

Here’s something that will work. Go to an auto AC supply shop and buy a 1/4"
test port tee. It will have a Schrader valve with a core suitable for
refrigerant, so you might have to replace it with one rated for fuel if it
starts to dribble. Clamp two lengths of 5/16" fuel hose to it.
Unfortunately, the fittings that match the rail are hard to find but the
more easily found 1/4" BSPP fittings will do an a temporary basis; they are
a sloppy fit. You will need male & female. Should be able to get these at an
industrial hose & fittings supplier, or perhaps online.

Break open the connection to the right rail and insert between the rig.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us/ed/myJag.html

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(Bryan Burgess) #4

In reply to a message from Rob Roe sent Tue 7 Sep 2010:

As far as I understand it the inlet regulator is basically a
stop valve to hold pressure in the rail at switch off. I also believe in later vehicles they deleted this inlet regulator
possibly because the pump had a anti siphon valve.–
1985 XJS V12 HE TWR (Black Betty) - www.bryansplace.net
Gold Coast Qld, Australia
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(Ed Sowell) #5

As far as I understand it the inlet regulator is basically a stop valve
to hold pressure in the rail at switch off. I also believe in later
vehicles they deleted this inlet regulator possibly because the pump
had a anti siphon valve.

There are differing opinions on the purpose of the right regulator.
Personally, I think it is to do a first stage of regulation. If the first
one smoothes out pressure fluctuations and takes out some of the pressure
the second can do a better job of keeping rail pressure rock solid. That
said, many have removed the first regulator and the car runs.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

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(Rob Roe) #6

In reply to a message from Ed Sowell sent Sat 11 Sep 2010:

I suspect I installed the incorrect outlet FPR a few years ago.
The Bosch part number on the car is 0280160214 and is labeled at
2.5 bar. Correct Lucas part number according to my info is 73232.

From what I’ve been able to find so far on the web, the correct
Bosch part number is 0 280 160 293. I have a new 73232 on order
from Welsh. Boone says it’s new in the Bosch box. We’ll see what
Bosch number is stamped on the body.

Will also put together a fuel pressure testing set up soon. Thanks
for the advice on how to build one.–
87 XJ-S V12 Coupe
Bellevue/WA, United States
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(alex paterson) #7

In reply to a message from Bryan Burgess sent Sat 11 Sep 2010:

Jaguar used two fuel lines and regulators on early cars.
These lines are small in diameter and at the recommendation
of bosche a single line would not flow enough fuel.

Because the lines act as separate fuel rails coming from a
single source both require regulators to re combine to a
common return line. With a single regulator one line would
have to be dead ended and the only way to purge any air or
vaporized fuel is then through the injectors on that bank.

This means in the event of vapor or air lock the engine
would have to run on one bank in order to purge the line.

Very early cars had adjustable regulators, intermediate cars
had not and of course later cars had the single large
diameter square fuel rail that could manifold enough fuel
and only required a single regulator.

This change to the later single regulator is well worth
while installing on earlier cars.

Alex P–
alex paterson
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(Rob Roe) #8

In reply to a message from alex paterson sent Mon 13 Sep 2010:

Do you know the Bosch part number for the later single regulator?
My 87 is a Lucas car with the square fuel rail and two regulators.
I’m trying to make sure I have the correct Bosch regulators on my
car now. Seems there are several Bosch part numbers that would
bolt right in, but I’m not sure about which Bosch number is correct
for which car. I assume that the fuel pressure regulation would
vary from one Bosch number to another.

I suspect my car is running lean under heavy load and pinging
slightly causing it to heat up a little. It does fine under normal
driving.–
The original message included these comments:

Very early cars had adjustable regulators, intermediate cars
had not and of course later cars had the single large
diameter square fuel rail that could manifold enough fuel
and only required a single regulator.
This change to the later single regulator is well worth
while installing on earlier cars.


87 XJ-S V12 Coupe
Bellevue/WA, United States
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(Ed Sowell) #9

Do you know the Bosch part number for the later single regulator?

From what I’ve read, many people have simply kept the left regulator,
presumably the OE one for their car.

I assume that the fuel pressure regulation would vary from one Bosch
number to another.

Sometimes the different part number is due to different fittings and
mounting hardware rather than internals.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

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(Ed Sowell) #10

Alex,

I agree with most of what you say here but want to make a couple comments.
:

Because the lines act as separate fuel rails coming from a single
source both require regulators to re combine to a common return line.
With a single regulator one line would have to be dead ended and the
only way to purge any air or vaporized fuel is then through the
injectors on that bank.

I’m away from home so can’t go look at the OE preHE rails, now hanging on
the garage wall, but as I recall the two rails were connected by a crossover
so could, in principal, work with a single regulator on the left side.
However, that would make the right bank run at a little higher pressure due
to resistance of the crossover hose.

This means in the event of vapor or air lock the engine would have to
run on one bank in order to purge the line.

This is a bit of a simplification. I look at it this way:

The fuel has the opportunity flow in alternative directions at several
junctures. First, it can flow to one rail or the other. Then within each
rail it can flow forward or backward, since each rail looks like a
racetrack, i.e., forms a loop. Now, if a vapor pocket forms at some point
in one of the rails during post shutdown soak back the flow path that it is
in will offer more resistance to flow. Consequently, the fuel will
preferentially flow the other way, leaving the vapor containing path starved
of liquid fuel. Any injectors in that path will be spitting and sputtering
and nearby cylinders will be misfiring. That’s why there is often hard
starting and rough running with this setup when restarting after a brief
shutdown period. If the engine starts it will eventually clear because of
higher pressure and the cooling effect of fresh fuel coming to the rail.
Having leak free injectors, regulators, and non-return valve is very
important… keeps the rail pressure up thus reducing possibility of vapor
formation.

Very early cars had adjustable regulators,

Which had to be adjusted individually with flow to the other one pinched
off.

This change to the later single regulator is well worth while
installing on earlier cars.

Indeed, but the HE regulators can’t be used unless the entire HE EFI system
including the ECU is used. The reason is the HE regulators are
non-adjustable and have a higher set pressure than the preHE injectors need.
And you can’t solve the problem by using HR injectors too, because they flow
considerably less than the preHE ones.

I must give credit to Roger Bywater who advised me when I retrofitted an HE
rail to my preHE. This project is described in a write-up at my website. In
addition to greatly improving hot starts, it eliminates many clamped hose
joints thus reducing chances of fuel leakage and fire.

BTW, I initially used 2 preHE regulators in parallel so as to allow each to
operate at the design nominal opening. Later, one failed and rather than
buying a new one I re-plumbed it with the remaining good one. It runs fine,
even though it obviously has to be open further since it’s handling the
entire return flow.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

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(konrads) #11

In reply to a message from Ed Sowell sent Mon 13 Sep 2010:

The late style fuel rail with one reg also has o ring seals for the
top of the inj so you need the injectors also the rail bolts to the
manifolds so you will probably need those as well but that
eliminates all the fuel hoses and is a much better set up.

press remains constant throughout a closed system only flow can be
effected by a restriction.
Nick–
The original message included these comments:

However, that would make the right bank run at a little higher pressure due
to resistance of the crossover hose.


Nick Morland 86XJ-S 88XJ-S6.0L5spdAJ6 TqPlus88VP 73XJ6 97XK8
Scotts Valley Ca, United States
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(SD Faircloth) #12

In reply to a message from Rob Roe sent Sun 12 Sep 2010:

Rob,

For your specific vehicle…'87 XJS V12 HE

The A Bank regulator is Bosch # 0280160234 3.0 Bar
B Bank regulator is Bosch # 0280160293 2.5 Bar

The A bank regulator acts as a damper for fuel pressure
fluctuations between the fuel pump and the rail.

Obviously, the B bank regulator controls rail pressure, of more
precicely…the pressure differential of the injector tip and the
intake vacuum.

If (for whatever reason) you remove the A bank regulator, the B
bank regulator would still need to be the same Bosch part number.

SD Faircloth
www.jaguarfuelinjectorservice.com–
The original message included these comments:

I suspect I installed the incorrect outlet FPR a few years ago.
The Bosch part number on the car is 0280160214 and is labeled at
2.5 bar. Correct Lucas part number according to my info is 73232.

From what I’ve been able to find so far on the web, the correct
Bosch part number is 0 280 160 293. I have a new 73232 on order


www.jaguarfuelinjectorservice.com
Jacksonville, Florida, United States
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(Ed Sowell) #13

Nick,

The late style fuel rail with one reg also has o ring seals for the top
of the inj so you need the injectors also the rail bolts to the
manifolds so you will probably need those as well but that eliminates
all the fuel hoses and is a much better set up.

True. I would have preferred that rail in my retrofit but changing the
entire EFI system was over the top for me.

press remains constant throughout a closed system only flow can be
effected by a restriction.

Not true when there is flow. Friction results in pressure loss.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

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(Rob Roe) #14

In reply to a message from SD Faircloth sent Tue 14 Sep 2010:

Thanks SD - the outlet fuel pressure regulator on the car right now
is a Bosch 0280160214 (obviously the wrong one). It looks
identical to the other part numbers, but I suspect the internal
pressure setting in that FPR is lower than the 0280160293 causing a
lean condition under heavy load. At least I hope that has been the
case, so a new correct FPR will solve the lean running condition
under heavy acceleration. I’m also cleaning the sump and sump
screen to ensure there is not debris that gets sucked into the
screen when the pump is running at maximum and then settles back to
the bottom of the sump when there is less suction. I want to
change the hoses in the boot anyway to ensure I have fresh R9
rubber in the high pressure side of the pump. I’ll probably
replace the fittings and hoses on the high pressure side under the
car as well. And, of course intall a pressure test port on the
fuel rail. I get the new FPR, fuel pump and sump screen today, so
I should have feedback for the forum in a few days.–
The original message included these comments:

The A Bank regulator is Bosch # 0280160234 3.0 Bar
B Bank regulator is Bosch # 0280160293 2.5 Bar


87 XJ-S V12 Coupe
Bellevue/WA, United States
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(SD Faircloth) #15

In reply to a message from Rob Roe sent Tue 14 Sep 2010:

Rob,

Every FPR that I have seen, is stamped on the regulator, with the
Bar pressure, and the mfg part number.

Don’t have any info on your Bosch 0280160214. May or may not be
2.5 Bar regulator, but apparently the fittings fit.

SD Faircloth
www.jaguarfuelinjectorservice.com–
The original message included these comments:

Thanks SD - the outlet fuel pressure regulator on the car right now
is a Bosch 0280160214 (obviously the wrong one). It looks
identical to the other part numbers, but I suspect the internal


www.jaguarfuelinjectorservice.com
Jacksonville, Florida, United States
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(Rob Roe) #16

In reply to a message from SD Faircloth sent Tue 14 Sep 2010:

SD,
It is stamped with 2.5 bar and the inlet is stamped with 3 bar. Is
the bar setting the same as fuel pressue psi? Guess I don’t
understand the relationship between bar and psi. The Bosch
0280160214 bolts right up and the car runs. I’m just hoping it’s
internals are somehow different allowing lowing psi at load and
therefore causing a lean condition. We’ll see when I get the new
and measure the fuel pressure.–
The original message included these comments:

Every FPR that I have seen, is stamped on the regulator, with the
Bar pressure, and the mfg part number.
Don’t have any info on your Bosch 0280160214. May or may not be
2.5 Bar regulator, but apparently the fittings fit.


87 XJ-S V12 Coupe
Bellevue/WA, United States
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(alex paterson) #17

In reply to a message from Rob Roe sent Tue 14 Sep 2010:

Early cars had adjustable regulators set to 30psi on both.
The later cars should have 2.5bar or 36psi on both. These
later regulators are linked to the vacuum on the manifold.

Under heavy acceleration when manifold depression is close
to atmosphere the pressure on these regulators will increase
to 3 bar or about 44 psi.

1 bar = 14.5 psi.

T in a pressure gauge and at idle you should see about 35
psi. When you stab open the throttle the gauge reading
should rise.

You cannot use a second higher regulator to limit surge
because the lower one will blow off first. The pump provides
a continuous stream of fuel.

The only way to check it is to get a gauge and put it in
line and look at it when you are driving.

Alex P–
alex paterson
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(Rob Roe) #18

In reply to a message from alex paterson sent Tue 14 Sep 2010:

Another twist. The sump had quite a bit of debris and the sump
strainer/filter was quite dirty. This was odd as I’d done a
complete clean up about 4 years ago when replacing the fuel tank.
Anyway, replaced all the hoses, fittings, fuel pump and filter
while I was in there. Made sure I used R9 fuel injection hose.
Also replaced the outlet side fuel pressure regulator with a Bosch
part number 0 280 160 293 which is sold as EAC4864 from one supplier
(old part number was 0280160214 sold under Jag part number 73232 by
another supplier). I don’t know the difference between the two
part numbers, but several posts had luck with the Bosch 0 280 160
293 so that’s what I installed. I’ll install a fuel pressure gauge
next week and report on pressure findings. I suspect the reason my
car was running slightly hot under heavy load and also slight
pinging was the result of running lean due to fuel starvation
because the sump strainer/filter was blocked.

The lesson is…to check that darned sump strainer/filter more
often!–
The original message included these comments:

The later cars should have 2.5bar or 36psi on both. These
later regulators are linked to the vacuum on the manifold.
Under heavy acceleration when manifold depression is close
to atmosphere the pressure on these regulators will increase
to 3 bar or about 44 psi.
The only way to check it is to get a gauge and put it in
line and look at it when you are driving.


87 XJ-S V12 Coupe
Bellevue/WA, United States
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(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #19

Rob Roe wrote:

The lesson is…to check that darned sump strainer/filter more
often!

The lesson is to do away with the thing and install a replaceable
inline filter instead.

– Kirbet

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(Rob Roe) #20

In reply to a message from Kirbert sent Thu 16 Sep 2010:

Kirbert,
Any recommendations on which in-line filter would work? I
think the molded hose between the sump and the fuel pump inlet
is 1/2’’ ID. The length of that hose that could accommodate an
in-line filter is very short, around 2.5’’. I’d appreciate any
type or even part numbers you’d recommend.–
The original message included these comments:

The lesson is to do away with the thing and install a replaceable
inline filter instead.


87 XJ-S V12 Coupe
Bellevue/WA, United States
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