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My truck eats fuel pumps


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Calling all you EFI experts (not Mega anything)

I have a 1992 RRC 3.9 efi auto and it is currently eating in-tank EFI pumps at the rate of one every 3 weeks!!!

The symptoms are that it starts hesitating when applying throttle, and it progresses to the state where if you apply the accelerator it just dies.

It will restart some times after switching the ignition on/off several times but not always.

When it is running it pulls well and will accelerate very well at the traffic light grand prix.

If I fit a new pump it works fine for a while but then it just starts again. I have been fitting Delco EP240 units at £25 rather than the complete gauge/pump housing at £110.

Where should I start looking?

How about a box of matches and an insurance claim??????????????????? :(:angry:

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Hmmmmm

Tad off.

The fuel pumps on 3.9s are run via the ECU and a big bosch relay

When you turn on the ignition the fuel pump should run then trip out at pressure with a Zzzzzzzzzzzzzzz Click type noise.

Check earth on furl pump, clean / check / replace relay, and check fuel pressure in the rail in case the PRV is on its way and the fuel pump working too hard

Other than that no idea !

Nige

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Hmmmmm

Tad off.

The fuel pumps on 3.9s are run via the ECU and a big bosch relay

When you turn on the ignition the fuel pump should run then trip out at pressure with a Zzzzzzzzzzzzzzz Click type noise.

Check earth on furl pump, clean / check / replace relay, and check fuel pressure in the rail in case the PRV is on its way and the fuel pump working too hard

Other than that no idea !

Nige

well the bl?'**dy thing has stopped yet again the pump is running for the prescribed 3 seconds and then cuts out but it still won't start. I cant find any place to attach a pressure gauge unless I cut into the fuel rail and solder a fitting. Any more suggestions would be welcome.

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Are you sure it is the fuel pump?

Mine had simlar symptoms where it would run perfectly for a while then start missing and then stop - just like fuel shortage.

Bought a new coil and temp sensor. While fitting the coil I found one connector was very loose.

I would check your wiring, especially earth connections.

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Hullo Roger, trouble with the rangie???

You need a bit of shopping;

Rail Street for a pressure gauge reading up to about 60-100 psi, air fitting that screws in the gauge, length of rubber hose and a schrader valve connexion bit(like a tyre gauge).

Then Al Hai'ir, look for a late Disco 1 fuel rail, they have a schrader fitting in them for reading fuel pressure.

If no fuel rail then you need to cobble the gauge above or if you are stingy an oil pressure gauge into the fuel system. Don't try any fitting permanently into the fuel rail unless its silver soldered or better.

When you have access to fuel pressure level the you should see 36 psi with engine dead, start the motor and pressure should drop to 32-33 psi, rev it to reduce manifold vacuum and pressure should rise back to 36.

Tolerances on pressure are about 4 psi, any more and your ECU mapping would be somewhat out.

Probabilities are that the fuel pipe, fuel filter, fuel pressure regulator or return pipe are restricted. Either with gunge or bin caught by a rock. The fuel pump shifts a lot of fuel and the return pipe is busy, so any restriction makes the pump work hard for its living. A new pump off the shelf works good and then deteriorates quickly.

You will probably have passed a lot of current through the fuel pump relay just lately so it would be worth fitting a new one in your environment.

Good to hear you're still about,

Regards,

jw

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Hi JW

This seems to be a hot problem as if i leave the motor to cool down (yeah that happens really quick here!) it will restart no problem. i.e. when i went back to last night at 11.30 it started on the 2nd turn of the key, and this morning it started immediately. When i checked last night the stepper motor was only finger tight and after i tightened it it started ok. I cant get to Al Hair at least until this weekend, but i have a pressure regulator arriving tomorrow.

When you coming back to the ME??

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Roger, temperature may well have an effect on your problem, however, I think that it is essential to follow the main symptoms. The combination of hesitance while accelerating (probable weak mixture) and the eventual demise of several pumps suggests a problem in the fuel supply area.

The availability of a schrader fuel pressure check point (via the Disco 1 fuel rail) and a suitable pressure gauge kept under the drivers seat means that the fuel part of diagnosis is a simple plugin check. (Don't ask how I know this)

The Disco 1 suffered from poor connections on the fuel pump power feed, I don’t think yours does since a new pump cures the problem straight away and remains good for a period before failure. Bad connections fail and keep on failing under load.

Do your new pumps come from the GM dealer or one of the many other outlets? Just wondering about a supply of “copies” from a dubious source, IIRC JP used the same pumps successfully, heard from him lately?

Returning to the ME? Not going anywhere at the mo. Managed to stop something heavy moving by using my foot so I am shuffling round the house in a wheelchair. Hope to be walking by Xmas. Should have been in UAE this week for the Desert Challenge and hoped to do a bit of job-hunting as well but that’s on hold at the moment.

Be interesting to see what your fuel pressure is like,

Regards,

jw

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My RR had a poor connection in the EFi loom for the fuel pump, it would run but not with enough power, replacing the wire (bypassing the harness connector) cured it.

Fault was found (after MUCH faffing around) by sticking a spare 12v battery in the boot and running the pump on that :blink: you could hear it run faster.

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