Hi all,

I just replaced my fuel pump. It was making groaning noises, and I believe that's what was causing other problems. It does run better now, but the main problems still persist. The car will randomly stall out sometimes, usually doesn't want to start back up. I don't hear the fuel pump prime when this happens. Also, while I'm driving the RPMs will suddenly drop to almost nothing and then catch and go back up to normal levels. When the car won't start, I've noticed that the CEL doesn't come on when ignition is ON.

Other than the stalling it runs perfect. There's no warning sign that it's even going to stall, almost like the engine is just getting cut off.


Things that have been replaced:
Fuel pump - today
Fuel Injectors - February 2010
Spark Plugs - June 2010, about 12K miles ago, NGK standard plugs
Ignition wires - June 2008, 40K miles ago, Nissan OEM
Fuel Filter - December 2010, 4K miles ago


Anyone have any ideas on this?

 

Maybe a bad fuel pump relay? $10-$20 item and its easy to swap out to check. On my 91 SE it was in the trunk behind the panel about a foot left of the latch.

 

Ecu codes?

 

T-piece plumbed into the fuel line after the filter with a pressure meter ................. what's the pressure doing when the car stalls?

 

Replaced the relay a few hours ago. Waiting a bit to see if it acts up. The problem seems very random, so I'm trying to avoid any stop lights so I don't get stuck in the middle of the highway.

What else could cause the engine to cut out while throttle is open, and also to stall at idle and not start back up for a few minutes?

 

No ECU codes. Going to try reseating the ECU harness, maybe it's a loose connection. It doesn't happen often enough to really test with a pressure gauge. I did test it after installing a new pump.

Idle pressure: ~34PSI
Pressure with vacuum to pressure regulator unhooked was around 50PSI.

 

Fuel, spark, & air!!!!!!!!!!! Sounds like a possibly bad fuel pressure regulator.....also....

 

So you cannot leave the gage connected or what?

 

The gauge has a very long hose on it, wouldn't even know where to mount it, and the fact that it has a bleeder valve makes me paranoid. :P

Anyway, out of curiosity I took the trim cover to the ECU off, started the car, and wiggled the harness. Car stalled immediately. Repeated a few times, did the same thing. Took the harness off, put it back on and re-tightened, wiggled the cabling, no more stalling.


Still have a few questions.
1) Could this bad connection somehow cause the transmission to kick out of overdrive into 3rd while cruising?

2) I connected the fuel pressure gauge T-adapter between the fuel injector rail and fuel filter, started the car up, pressure was around 34PSI, but after turning the car off, the pressure dropped to 10PSI within roughly 30 minutes, is this supposed to happen?

 

In cases like this I dont even mount the gage properly - I thread the hose through the door seal and let the meter sit on a suitable box etc on the passenger floor for the few times one need to confirm either correct or incorrect operation of the fuel pressure. If all the seals/bearings/hoses/joints are brand new one should in theory not lose any pressure on the fuel system once the engine is switched off .................. in practice your experience is fine IMO with a 18 year old piece of worn mechanicals - my FP holds slightly longer - can probably do around 2 hours before pressure is down to 15 PSI or so.................... implication is that after a long sit, you may have to wait a second or so for the rails to get pressurized before the start process is immediate as one tends to expect from this setup

As for the wiggling thing:

Remember Wiking? ..................... he has an excellent legacy and writeup on exactly this phenomena and how to go about cleaning/sorting the contacts issue on these vehicles - enjoy yourself here for a few hours

Your box is most likely responding to the loss of reliable TPS signal via that ECU connector hence its funky behavior