Fuel Pump - Intermittent Defect?

[Viich]

Hi, I've got an 02, and have a couple times had a no-start that cured itself. I replaced the fuel pump last fall after no start, tested, zero fuel pressure, power to the pump, seemed simple. Today, no start, and I got the same symptoms - no pressure at the rail, lots of power, checked fuse, etc.

This was on the way home after a weekend trip, ended up getting a ride back for wife and son, was going back to work, intending to get tools, parts, and come back the next night. Stopped at the car to pick up a couple things on my way past, and the car started. Ran all the way home, no issues. (~160km)

Any ideas? I'm stuck at fuel contamination and/or I made some bizarre mistake while replacing the pump. I plan on pulling the pump again to ensure there isn't a weak connection, maybe using some dielectric grease around the connections, and replacing the fuel filter. Other than that, the only thing I can think of is actually sucking the fuel out of the tank, but I'm not sure I want to get into that.

I also just read another bit about the transmissions, and I get occasional - maybe once or twice a week - hesitation on low speed shifting. I get the impression that I should change the fluid as the first step, then look at replace/rebuild of the valve body. I already think I'd probably put an engine and transmission into the car as long as the total price was < 10 000 as the body is in incredible shape for age and location. Is the 02 transmission a lost cause if I've already driven it through the winter with the occasional hesitation - ie. should I just wait for it to fail and replace it?

[sikbrik]

I'm no expert but which pump have you replaced? I had identical intermittent symptoms with the lift pump or feed pump or whatever it's called...not the main pressure pump. If there was enough fuel to fill both halves of the tank, usually okay. Let it sit a while if it was lower, sometimes worked, sometimes didn't. New feed pump, never happened again. Just throwing it out there. Good luck!

[Viich]

I replaced the right side pump. The sending unit on the left side has not been replaced, I'll take a look and see if anything is there. May just replace it, they're only $75.

[PierreC]

Had similar intermittent "fuel pump" problems many years ago and it turned out to be the fuel pump relay - apparently a dry solder joint causing the intermittent nature of the problem.

[cattlecar]

If you are certain you had power to the pump when it would not pump then it can be a bad pump and do exactly what you had happen. There has been some fuel pump problems on many makes where the ethanol dosed fuel has some contaminant in it that binds up the pump. The usual scenario is the the car is turned off and fuel added when this occurs. The belief is the "stuff" on the pump motor shaft gets bound when the pump body is cooled by fuel added but the armature and pump shaft stay warm and the whitish residue lets the contracted pump bushings lock the pump. When pump is cooled evenly or warmed evenly it is no problem. If this sounds like what happened then it may never happen again or you can replace the pump. I would try fuel additives to possibly clean the residue out of pump.

By certain about power to the pump, I mean connector to pump was probed and verified when it did it. Otherwise the relay suggestion is what you should test for.
Bad relays almost always show an excessive voltage drop even when car is running so they can be tested and you can have some peace of mind that throwing one in the car has some chance of being what is really wrong.

[Viich]

If you are certain you had power to the pump when it would not pump then it can be a bad pump and do exactly what you had happen. There has been some fuel pump problems on many makes where the ethanol dosed fuel has some contaminant in it that binds up the pump. The usual scenario is the the car is turned off and fuel added when this occurs. The belief is the "stuff" on the pump motor shaft gets bound when the pump body is cooled by fuel added but the armature and pump shaft stay warm and the whitish residue lets the contracted pump bushings lock the pump. When pump is cooled evenly or warmed evenly it is no problem. If this sounds like what happened then it may never happen again or you can replace the pump. I would try fuel additives to possibly clean the residue out of pump.

By certain about power to the pump, I mean connector to pump was probed and verified when it did it. Otherwise the relay suggestion is what you should test for.
Bad relays almost always show an excessive voltage drop even when car is running so they can be tested and you can have some peace of mind that throwing one in the car has some chance of being what is really wrong.

I didn't have a multi-meter when it happened this time, and it's never happened on fueling, any relation to fuel seems to be when the level is low, making the sending unit plausible. I'll grab my meter and check the voltage drop at the pump tomorrow night.

PS - just thinking, is there an easy way to test the relay at the relay rather than digging down to the pump? Just thinking about sticking a wire in there, but that might create some drop on its own with the jerry-rigged connection

[Viich]

Figured I might as well wrap this one up.

So, after the intermittent defect became semi-permanent and I had to tow it I had to look at it in extreme detail. There was voltage at the connector at the sending unit, the last place to check without pulling the pump and letting it dry. I had done a bunch of other testing as well, but moot really as there was voltage there and the pump wasn't on.

Everything pointed to a bad pump, but I didn't think it should be as I've already replaced it once.

After pulling the pump and sending unit, there was some burning at 12V line on the sending unit assembly where it goes through the plastic and the connection for the electrical comes through. Tested the resistance, and the connection was obviously bad - Kohm range. 0.6 ohm on the ground. Tested the pump outside the car, pumped strong, so we dremeled out the burned wire and got enough space to solder to the pin, did so and filled the hole with JB weld.

May or may not work as a permanent fix, but should at least last me until I can get a sending unit assembly.

[Viich]

The temp fix worked fine on a 13 hour drive - had the part and tools to install, so wasn't as nervous about it as I would have been, and we had time to install the new sending unit before the return trip.

[Allen]

Nice work.