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As stated in my earlier posts, the 1985 XJS was purchased with a frozen engine and the electrical components stripped of the car.
I have replaced the engine with a GM 350 and I am in the process of wiring up the fuel pump. In the trunk area, I have located the fuel pump relay and I have no power going to the fuel pump harness. I have power from the main relay to the fuel pump relay.
At the fuel pump relay,
I have constant 12v at the brown wire.
I have switched power on the Pink/Black wire.
If I send the orange wire to ground, the relay clicks and sends power to the Brown/Slate wire.
The orange wire switches on fuel pump relay
the ground via the ECM, but I have no ECM.
How can I wire up the relay to get it to turn on the fuel pump when I turn the ignition on.
I believe I have to use a relay for the fuel pump.
If I go from the Pink/black wire directly to the fuel pump it works, but I am afraid to power the pump directly from the Pink/Black wire which is switched Ignition power.
All the other circuits work.
Is there a way to create a switched ground for the orange wire?
If not, how do I wire up the fuel pump relay to get it to work when I turn the ignition on
the fuel pump supply comes through the master really which is located next to the fuel pump relay , so if the master relay is bad in any way , the fuel pump system wont get power
I have no power going to the fuel pump harness. I have power from the main relay to the fuel pump relay.
At the fuel pump relay,
I have constant 12v at the brown wire.
I have switched power on the Pink/Black wire.
If I send the orange wire to ground, the relay clicks and sends power to the Brown/Slate wire.
That's as good as it gets. The brown/slate powers the fuel pump so, if the pump isn't getting 12v, you have an open circuit on the brown/slate.
The orange wire switches on
fuel pump relay
the ground via the ECM, but I have no ECM.
How can I wire up the relay to get it to turn on the fuel pump when I turn the ignition on.
Permanently ground the orange wire. Not a very safe arrangement, but the pump will run whenever the key is 'on'.
I believe I have to use a relay for the fuel pump.
If I go from the Pink/black wire directly to the fuel pump it works, but I am afraid to power the pump directly from the Pink/Black wire which is switched Ignition power.
All the other circuits work.
Is there a way to create a switched ground for the orange wire?
If not, how do I wire up the fuel pump relay to get it to work when I turn the ignition on
Trace the open circuit on the brown/slate and you should be good to go. Is there a brown/slate wire at the fuel pump? There should be.
Yes. There is a Brown/Slate wire at the pump. I checked as far back as I could go to check continuity on the Brown/Slate wire and there is not an open in the circuit.
When I ground the Orange wire from the FP relay, the pump turns on. The main relay is working as it sends power to the FP relay.
Lack of a ground signal from the Orange wire seems to be the problem. This Orange wire gets the ground signal from the ECM, but I have no ECM in the car as stated above.
One other query:
My fuel pump experiment:
What is the nominal fuel pressure at the outlet of the fuel pump? Some say 80-100 psi. Is that correct?
I require a pump that can flow approximately 67 GPH at 43 psi.
If the Jaguar fuel pump is not up to the task, I will have no choice but to purchase a different fuel pump to meet the needed PSI required.
My plan is to use the Jaguar XJ6 fuel pump and an adjustable FPR to get the required 43 psi I need to run the aftermarket EFI system I am using.
In my 85 XJ6, I am using a Jaguar fuel pump and running a TBI system for the last 2 years with no problems whatsoever.
However the GM TBI system works with a lower fuel pressure and the internal FPR controls the fuel pressure.
Yes. There is a Brown/Slate wire at the pump. I checked as far back as I could go to check continuity on the Brown/Slate wire and there is not an open in the circuit.
OK, good!
When I ground the Orange wire from the FP relay, the pump turns on. The main relay is working as it sends power to the FP relay.
Right and right ! So, obviously, you DO have power to the pump
Lack of a ground signal from the Orange wire seems to be the problem. This Orange wire gets the ground signal from the ECM, but I have no ECM in the car as stated above.
So the ground the orange wire permanently if you simply want the pump to run with the key 'on'.
Or divine a switching system. One old school idea is using an oil pressure switch to ground the orange wire. No oil pressure, no fuel pump. The second step of this plan would be a bypass that allows the pump to run with the key in the 'start' position. You could easily do this with an extra relay, triggered by the starter circuit, that grounds the orange wire when cranking. When the key is released the pump circuit then relies on the oil pressure switch to ground the orange wire. This will work fine unless your engine is slow to develop oil pressure.
Excellent idea Doug. I think I will find a way to use the oil pressure switch to ground the orange wire.
I traced the orange wire back to the ECU plug which was still in the trunk. I may have to run a wire from the trunk to the engine bay to use the oil pressure switch.
Any word on the fuel pump pressure??
Thanks guys. I will setup the Jaguar fuel pump I have to see how it works with my setup. You never know until you try. EFI system I am using another view of EFI
The 67 GPH rating as mentioned is the requirement for engines developing 500-600 HP under race conditions.
The engine I am using was built to make a tad over 400 HP and is not going to be used for racing so the GPH rating could be a lot less.
Hopefully. I will be able to post the results of my experiment over the weekend with some pics.
No power to fuel pump
