Disco1 V8 Fuel Wiring / Wire identification help!

[RichardT]

Hi gang,
1997 Disco 1 V8, Gas.

I am having one of those weeks. My daily driver died in a McDonald's drive through last night. Got it towed home and testing showed no fuel pressure out of the fuel rail.

I have searched the RAVE high and low and cannot find any clear indication to the wiring setup of the fuel pump.

I want to simply be able to apply 12V to it in order to see if it is the pump or the electrics (one of a dozen solenoids or multi-solenoids).

Can someone please either tell me, or point me where I can get a clear wiring diagram for the fuel pump?

There are two connectors, I am assuming one is the sending/signal system and the other power to the pump. However I cannot get anything more than 5V (and 3V) across any of the leads ... so I am thinking maybe electrical. I don't want to start applying 12V randomly back there and fry something.

ANY advice or direction would be appreciated as I am at my wit's end!

Thanks!!

Richard

[red90]

The pump gets powered for a few seconds when the key is turned on. The signal comes from the EFI ECU to a relay. Check for power during those few seconds.

From the manual I have: The ECU and Pump relays are in the RH footwell behind a panel. The one with a blue base is the pump relay. The black base is the ECU relay.

[RichardT]

Thanks Red!
I am trying to figure out which wire is the 12V power wire ..
I THINK it is the larger C434 (square) connector, just cannot for the life of me figure which should be 12V ... and then which I can apply 12V power to in order to test the pump.
Getting a bit further down the rabbit hole!!

Richard.

[seatosky]

It's probably just a dead fuel pump. I had the same thing happen, and the relays were just fine. I was only getting 5 volts off the harness at the pump. My guess is that there is something in the pump which causes the 12v relay to click over to apply power to it, since it's a 4pin connector. If the pump isn't working, it won't ever apply 12v to the pump!

Only way to be sure is to have a new pump.... even if that ends up not being the problem, it will be the problem some day. My D1 with 200k on it is on its third pump...

[RichardT]

Thanks for the help everyone.
After going through the ENTIRE pump electrical system, I discovered it was a BAD PUMP :)

The sad part? My local parts shop wanted $1,600 (yes 1600) for the pump ... I found the DELCO pump motor for $150 and guess what - IT WORKS.

The only problem is that now I am loosing fuel pressure ... as I now know (suspect) the pump did not have a built-in check valve :(

So I need to buy an inline valve, remove the pump assembly and put it in there somewhere.

OH JOY!

Thanks for all the help folks, and will update with further details as they come along!

Richard

[Crs]

I had the fuel pump problem a few months back. One problem was the fuel pump wasn't putting out sufficient pressure. The mechanic couldn't identify the pump, but it wasn't from Land Rover. New pump and problem gone. They're pricey, but I don't think they're THAT pricy. Good luck.

[RichardT]

I had the fuel pump problem a few months back. One problem was the fuel pump wasn't putting out sufficient pressure. The mechanic couldn't identify the pump, but it wasn't from Land Rover. New pump and problem gone. They're pricey, but I don't think they're THAT pricy. Good luck.

I would agree that it may be due to a lack of pressure, but apparently this pump is adequate for the job.
Since I am loosing rail pressure as soon as I turn the vehicle off for any amount of time (or let the system idle and then hammer on the throttle from a traffic light) I am hoping that it would be a check valve.


Will keep you posted and include all the names/numbers etc when done in case someone else needs a similar solution.

Richard

[red90]

Have you first verified it is not the pressure regulator leaking? Losing pressure at idle does not suggest a check valve problem as the pump would still be running. The pressure is meant to drop as it follows the manifold vacuum pressure. That is why the regulator is connected to the manifold. You may also have a leaking injector, causing the pressure loss when off and flooding a cylinder when idling.

[RichardT]

Sadly I am not sure of any way to "check" the fuel regulator.

It could certainly be a problem with it, or a leaky fuel injector, but again, I am not seeing other signs as I am running perfectly fine at idle and only have the problem momentarily when I accelerate from a low RPM to a higher one (sudden increase in pressure).

I do not mind throwing $10 at a new part, but $200 at a new fuel regulator is a a lot if it isn't needed.

Richard

[red90]

....when I accelerate from a low RPM to a higher one (sudden increase in pressure).

Richard

That is what it is supposed to do and is normal. The fuel pressure regulator maintain a constant differential pressure across the injectors. When you press the accelerator, the manifold pressure rises and the fuel pressure follows the same pressure rise. Is there any other "problem" when accelerating?

A slow leak down when off is usually a leaking injector. You can check the regulator, by removing the return line to the tank. Put it into a bucket. Cycle the ignition to pulse the pump on. You should get a flow and it should stop as soon as the pump turns off. If it keeps leaking out, it has a problem.

[RichardT]

Cheer Landy! Will try that.

This morning, the beast was backfiring like crazy and running very rich ... now I am certainly leaning towards a faulty regulator.

Will rip the thing apart tomorrow and see ... there are times (like this) I wish I had a domesic instead - SO MUCH easier on the parts budget! :lol:

Will keep you posted.

Richard

[red90]

Cheer Landy! Will try that.

This morning, the beast was backfiring like crazy and running very rich ... now I am certainly leaning towards a faulty regulator.

That makes me think leaking injector, not faulty regulator. It could also be something else in the EFI system.

Do you have a manual? There are test procedures for everything.

[RichardT]

I do have the RAVE manual.

As the problem(s) only started when my fuel pump died, and subsequently replaced, I am thinking it is due to the increase in pressure from the new pump and the fuel filter (the old one was OLD, and after I poured he black ooze from it I could hardly blow through it). From what I have read, it could very well be leaking injectors (as you mentioned) or a faulty fuel regulator. both seems to have similar results.

As mentioned I'll be ripping it all apart tomorrow ... just frustrating having this type of problem!

Thanks again for the help!
Richard

[red90]

You have been measuring the fuel pressure, so you should already know if the regulator is faulty. You need to go to the section on checking fuel pressure in the manual and see if the pressure is correct.

A lot of things can lead to a rich mixture.