Need an opinion - 2nd fuel pump in 8 months

[OnTheRoadAgain]

My 91 Q45 went in (towed) when wouldn't start. 1st diagnosis was fuel pump, (8 months old) under warranty still, but for parts only.

After repacing the pump, they said it ran, but didn't run right, cut off etc. The fuel pump control module was bad in ADDITION to the pump.

NOW, they are saying the WARRANTEED fuel pump wasn't bad at all, it is the Control Module ONLY.

Here is what happened:About an hour before the car broke down, as I was about to shut off the motor, I heard the pump was humming loudly. This is what it sounded like 8 months earlier which led to the 1st pump failure. I drove home, stopped for a newspaper, when restarted is idled a little low and rough. It was noticeable but I was hoping just some vapor lock or something. Come to think ot it now, this "vapor lock" feeling happened a lot prior to the 1st pump replacement.

At the traffic light, when I stepped on the pedal, it stalled. Felt like no fuel on trying to restart. Towed to shop. Several mechanics came out, tried tapping the tank area with a wrench / hammer while starting. There was no sound coming from the pump when key was turned on.

Sounded like a bad pump to me: 1. no fuel like symptom2. no sound from pump w/ key on3. loud humming earlier that night.

QUESTION:1. they originally said the new pump DID get the car running, though poorly.

2. Did the warranteed pump do damage to the Control module?3. does it even sound possible that the "warranteed" pump is now ok?4. are they responsible for the latent damage to the control module?

This is a large regional auto repair center, and to say I'm unhappy with having to pay labor $275 to replace THEIR bad pump in only 8 months is an understatement. NOW, they are telling me the control module is $575, and their pump is ok? Seems to me that THEIR pump took out MY control module?

1. DOES THE CONTROL MODULE GO BAD WITHOUT THE PUMP GOING BAD?2. DOES IT SOUND LIKE THE PUMP WENT BAD? (humming, no sound when key on, and the fact that it started AFTER it was replaced?)

Thanks for any help, I've read everything I could about the pumps and modules, but need some qualified opinions.

Modified by OnTheRoadAgain at 7:09 AM 9/29/2007
Modified by OnTheRoadAgain at 8:30 AM 9/29/2007

[elwesso]

Its sort of an exponetial decay sort of thing. As the pump wears, it puts more strain on the control module, which causes the pump to wear out more, which then causes more wear on the control module...

Generally, if your fuel pump FAILS its the best idea to get a new pump AND control unit. you can most times get used control units (because you can get them for $50-100 each, buy 3-4 of them and youre still under the cost of new) and theyll be fine.

My guess is the control unit is bad. Pick one up off a member here on NICO for a decent price, swap it out and see if it makes it better.

[Q45tech]

An educated electronic technican/engineer [not usually found at dealer or shops] would look at the pump current waveform [amperes] and measure the pump revolutions [rpm]. Evaluate the system.

Ethanol in gasoline can corrode, tarnish, wear a fuel pump fast if water or acids are not cleared from the ethanol manufacturing process.

How does the interior of tank and the filter sock on pump inlet look?

Dealers know that frequently the new pump takes out the old worn FPCU so they insist on changing both at same time. Covering both bases ensures that short of fuel problems they don't get themselves in your situation.

Careful there are aftermarket look a like Chinese copies of Nissan fuel pumps at major chain stores............they usually work ok on non turbo 300zx but fail fast on turbo and Q45 applications due to extra demands in fuel flow.

[maxnix]

Several mechanics came out, tried tapping the tank area with a wrench / hammer while starting. There was no sound coming from the pump when key was turned on.

This is a large regional auto repair center, and to say I'm unhappy with having to pay labor $275 to replace THEIR bad pump

These guys had no idea what they were doing.

If it wasn't an OEM pump (least expensive from Joe), then all bets are off.

Yes, your FPCU could have been damaged initially, or even by the new pump if it was non-OEM. As Q45tech says, only way to guess on the latter is to look at the wave form and current draw while operating at various RPM.

[OnTheRoadAgain]

thanks for the quick replies. Sounds like I could be in a viscious circle here... pump then control unit over and over if these are aftermarket pumps. I have no idea where these pumps are made.

I don't think the tank should be dirty, it was drained 8 months ago, filters changed...

[texasoil]

$275 to R&R a fuel pump? I am a 'fatfitoldfart' and even I can do it in under an hour.

FPCU failures are almost always overheating of the ground connection on the circuit board. For some weird reason, they chose to connect this high current lead to a very thin section of the circuit board foil--when there is a nice wide section 1/2" away. I have installed a wire 'jumper' from the OEM terminat over to the wide foil area and even connected the adjacent terminal blade (not used in OEM connector) and made a double pin ground connector to reduce possibility of overheating that frail connector.

[Q45tech]

To my knowledge fuel tanks are almost never removed for draining and cleaned inside. Few are even examined for rust or corrosion where the fuel pump sock sits against the bottom.

[maxnix]

I don't think the tank should be dirty, it was drained 8 months ago, filters changed...

Removed and steam cleaned is something more than a drain.

Look inside and if you see any film at all, remove and steam clean.

[OnTheRoadAgain]

maybe I'm mistaken, but I thought they (said they?) pulled the tank, hence the 3 hrs labor. What is the labor time for in the car replacement?

is there a drain from beneath the car? or is the tank completely enclosed in the trunk?

[DrewQ45]

I have two control units and a fuel pump if you need it.

zerothread/245407

If you're handy, you can do the work yourself by the way. There are some pretty clear instructions somewhere on this site.