[E-Type] V12 Carb -> EFI conversion: Fuel pump arrangements?

I’ld like to hear from those who has already done this conversion
as to how they went about with the EFI fuel pump.

Specifically, I’ld like to hear what arrangements they made to
ensure that the fuel pump will:

  1. not cavitate
  2. remain supplied with fuel at all times so as to not lose pressure
  3. be able to source the volume of fuel it needs.

One option I’m toying with is to mount an EFI fuel pump IN the tank
as on modern cars but mounting it in line with existing fuel lines
seems so much less work.

Mounting the pump in series with the existing fuel pump is easier
but I’m concerned that the existing fuel pump may actually act as a
restriction given that the EFI pump may require more volume than
what the existing pump can supply.

Mounting the EFI pump in the place of the current pump may result
in pressure loss during cornering and serious braking if the pickup
point does not have a suitable catchment area?

TIA
Philip–
'73 E-type V12 OTS '87 DD6 '80XJS:http://tinyurl.com/cqyeec
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In reply to a message from jagwit sent Thu 14 May 2009:

The etype s3 tank is internally baffled and the pickup point is
right in the lowest part of the sump, quite literally in the brass
tube/drain attachment coming out of the bottom of the tank.

I plan to fit an xjs fuel pump in the same place as the s3 fuel
pump. The xjs Bosch pump takes up slightly less space than the twin
SU pump.–
dogdog
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Philip,
Since the original pump was able to supply adequate fuel under the
worst circumstances why how could it be a restriction? And actually
the V12s have a return line so the pump was designed to move more fuel
than the engine needed.
pauls 67ots

I’ld like to hear from those who has already done this conversion
as to how they went about with the EFI fuel pump…

…One option I’m toying with is to mount an EFI fuel pump IN the tank
as on modern cars but mounting it in line with existing fuel lines
seems so much less work.

Mounting the pump in series with the existing fuel pump is easier
but I’m concerned that the existing fuel pump may actually act as a
restriction given that the EFI pump may require more volume than
what the existing pump can supply.
<<<<<<<<<<<<<From: “jagwit” philip@gpltel.com
Subject: [E-Type] V12 Carb -> EFI conversion: Fuel pump arrangements?


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In reply to a message from jagwit sent Thu 14 May 2009:

EFI fuel pumps operate at about 45 psi discharge, whereas fuel
pumps supplying carburetors operate below 3 psi. The XJ40s, which
I’m familiar with, have a recirculation line back to the fuel tank
to handle a substantial excess flow. The pump is rated at 220
liters per hour, and its a positive displacement gear-type pump, so
the recirc line is essential.
I believe the V-12s actually use two fuel pumps, as a rule.
Rather than mount an EFI pump in series with the old carb fuel
pump, simply replace it. The old pump will certainly restrict the
suction.–
The original message included these comments:

I’ld like to hear from those who has already done this conversion
as to how they went about with the EFI fuel pump.
Specifically, I’ld like to hear what arrangements they made to
ensure that the fuel pump will:

  1. not cavitate
  2. remain supplied with fuel at all times so as to not lose pressure
  3. be able to source the volume of fuel it needs.
    Mounting the pump in series with the existing fuel pump is easier
    but I’m concerned that the existing fuel pump may actually act as a
    restriction given that the EFI pump may require more volume than
    what the existing pump can supply.


Pete Peterson 70E(193K) 88 XJ40(250K) 88 XJ40(239K) 94 XJ40
Severna Park, Maryland, United States
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In reply to a message from Jaguarpete sent Fri 15 May 2009:

Phillip,

Swap out the standard SIII fuel pump with the XJS fuel pump.

I have had no issues with my FI fuel pickup in any normal
driving circumstances.

As others have mentioned, the SIII has fuel tank baffles,
and the fuel pickup is at the front low point of the tank. I
refuel before I get to less than 1/4 tank, but I do that
with all my cars anyway.

If you are going to do slalom runs or similar, and want to
be extra cautious, keep your fuel tank 1/2 full or more.

I would be very surprised if public road (legal) hard
cornering or braking would cause an issue, especially if you
stick by the minimum 1/4 tank refuel discipline. In any
case, in hard braking the fuel is going to be pushed to the
front of the tank, and that’s where the fuel pickup is located.

Terry–
The original message included these comments:

I’ld like to hear from those who has already done this conversion
as to how they went about with the EFI fuel pump.


73jagman
San Francisco, United States
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In reply to a message from 73jagman sent Fri 15 May 2009:

Thanks Terry

Sounds like thats the way to go.

I’ve had an experience where I fitted Megasquirt to a friend’s Land
Rover Defender where I fitted the EFI pump inline. The noise this
pump (brand new) made was horrible until I eventually found that
the pump was cavitating due to the fuel line from the tank to the
pump being too small.

This is why I was a bit reluctant to go the same route on the E.
Its easy enough though so I’ll try it!

Thanks a lot!
Philip–
'73 E-type V12 OTS '87 DD6 '80XJS:http://tinyurl.com/cqyeec
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Philip,

I will be trying an EFI conversion along AJ6 Engineering instructions. I already rebuilt all the XJS parts I need, including the fuel pump. What did you go for in the end what would you recommend based on your experience?

Many thanks

Rui

E-type OTS S3 1973

Rui, in the end, I mounted a submerged EFI pump in the main tank. That was not a good solution either because when the tank gets to about ¼, and I go around a corner, the fuel would move to the one side leaving the pump dry and that would have the same effect as switching off the ignition.

So, you either have to fit a surge tank inside the fuel tank (some cars have a surge tank / fuel pump / fuel level sender integrated as one unit) or you have to fit a surge tank somewhere in the car and then pump the fuel to the surge tank using a low pressure pump and then pump fuel from the surge tank to the engine using an EFI pump. Best option is to have the EFI pump submerged inside the surge tank (swirl pot). Having learnt my lesson with my OTS, this is exactly what I did with my Jensen Interceptor.

I used a surge tank from an XJS but you get ones from the likes of Summit. They seem pricey though.

I’ve done this two different ways.

My car is dual fuel, running both lpg and petrol.

My original setup was to use the etype twin SU pump to fill a swirl pot situated in the top right hand rear corner of the car. This gravity fed a standard XJS Bosch pump and the excess fuel returning to the back of the car from the engine bay was fed into the the swirl pot. The swirl pot had a return to the tank as its topmost of the three hoses.

This system will work fine for non dual fuel users and was running happily until I fitted lpg…

I changed it to an inline high pressure pump from a land rover and this system also works fine. The return goes back to the main tank.

The reason I switched was that after fitting lpg, I run almost exclusively on lpg and rarely use petrol, as lpg is half the price of petrol and is a higher octane fuel. This meant the circulation of fuel between the swirl pot and the front of the car continued ad nauseum, with little net flow between the tank and the swirl pot. The fuel thus heated up every time it looped into and out of the engine bay, rather than being mixed or replenished with the larger reservoir of cool fuel in the main tank. This eventually kills the Bosch style pumps, as the only thing keeping them cool is the continuous supply of cold/cooler fuel from the tank, as opposed to a limited recirculating supply of slowly warming fuel.

I have the original swirl pot if someone wants to buy it.

There is a picture of the new in-tank pump in one of my old photo albums if you click on “old site”.

kind regards
Marek

This is what I did. Works really well. Sends all the hot fuel back to the tank, submerged fuel pump.



69E’s setup is exactly what I had and this is what causes fuel starvation going around corners when the tank gets to about ¼ or less.

I learnt that it is imperative to have a surge tank to ensure that fuel pressure is maintained at all times.

Like Marek, I also learnt that fuel returned from the engine MUST go back to the main tank otherwise the fuel in the surge tank gets too hot.

I haven’t had the 1/4 or less issue, you must be on 2 wheels :grinning:

As for the surge tank, again I’m having no fuel pressure issues regulator and gauge works perfect.

Pictures appended

Swirl pot showing fuel pump bracket and all four inlets It is housed into the right rear fender behind the radio aerial|666x500 !


My SU electronic upgrade points saver pcb


Note fuel pickup from the original screen which is in the sump - no slosh problems here!


Modified top plate

kind regards
Marek

Thank you all, extremely useful!

Roger AJ6 Engineering also speaks about the swirl pot to avoid cavitation. I have one from the donor XJS that i could use.

But I plan a reversible conversion and would like minimum visible modifications.

Philip, I was thinking about your approach but having the swirl pot there would mean getting rid of the standard spare wheel.

Just seeing Marek’s last post, very ingenious custom made swirl pot for minimum impact, i was considering putting the XJS pot there but won’t fit so its a possible way ahead if i go for the swirl pot. Which pump are you using, it looks very small, can it be controlled by the standard Lucas 16 CU ECU ? I recall reading that Phillip and Marek use Megasquirt .

69E, neat simple solution, could it be that S3 has a baffled tank , also the pump has 3 wires - how do they interface with ECU, is it on/off and + and Ground?

For all the immersed pumps, any danger of a spark in a connector provoking a catastrophic fire ?

Thank you again. I will possibly open other threads on specific conversion issues it would be great to hear your experiences, namely :

  • Location of the ECU (16 CU, quite big)
  • Heater connection to left water rail near to the AirValve
  • and more

By the way, what is the mpg savings on a normal mixed tour ?

Best regards,

Rui

As I said, it’s a normal Land Rover pump from any fuel injected Land Rover.

The Lucas 16cu simply grounds a relay winding to control the pump.

I don’t use the Jaguar AAV, I use two Bosch electronic ones from a SAAB.

There is no danger from sparks, unless you are in a James Bond or Steven Segal movie, in which case your car will blow up promptly on queue if you are the baddie.

kind regards
Marek

My ECU is from Emerald UK, I was fortunate that it came with a wiring harness loomed for the fuel pump.

The original kit from emerald came with a swirl tank and exterior HP pump. I ran it for a year then didn’t like all the high pressure stuff under the bonnet, kind of made me nervous and the gas was getting very hot. So scraped it and went with my current system which runs great.

Hi Rui
I fit the ecu on right side of the bulkhead close from the passanger firewall panel.
another place could be just behind the glovebox. I thing there is enough place for. you just have to build a bracket.
Here is where I ve placed the 16CU.

Michel,

Nice and perfect for the wiring , thank you for the photos. What did you do with the fan, I have the fan in that place, my car has AC. Other possibility I am considering is to put the ECU about the same place but vertical against the firewall, in the end the S3 has plenty of leg space and 7-8cm wouldn’t make a big difference with the passenger seat further back.

If you happen to have other photos of the conversion you mind sharing, here or pm , it would help me to see how did you solve other issues such as connection of the heater box, wire routing in engine bay, etc.

Best regards

Rui

Dear Marek,

Many thanks for this additional useful information, i saw your posting only now, waiting for some components before i resume works - I may leave it for the winter to enjoy some summer driving. Now rebuilding the bonnet.

Kind regards
Rui