Flooding with EFI?

[robertwb70]

I have a problem and I can't afford trial and error to solve it so I figured I'd come ask the experts first.

Car: 1992 nissan 240sx 5sp 240K miles entirely stock

problem: Car won't re-start more than once every 3-4 hours, doesn't seem to be heat related because you can start it and shut it off 2 seconds later and it won't re-start. When it does this I pull the plugs and they are gas soaked so the next time it wouldn't start I unplugged all the injectors, held the throttle open and it started for about 1 second, then I reconnected the injectors and it started. So it seems to be a fuel problem, I swapped the FPR with another I had and it made no difference so I'm thinking MAF meter or maybe O2 sensor or maybe even a coolant temp sensor but like I said I can't afford trial and error and I'm not 100% sure how to test these parts. The car runs OK when it does start, a little rich but it runs OK, and 2-3 weeks ago I tracked gas mileage and it was getting its usual 28 MPG so it's not a major wear issue I don't think.

Also I should mention that my GF recently put power steering fluid in the crankcase by accident which is when this problem became worse, it did it before that happened also though and it was progressively getting worse. I have drained and flushed the engine oil so that has been taken care of.

[nichols1992]

Getting it to start holding the throttle open could have been a coincidence. I would check and make sure your getting spark when it won't start. If you not getting spark and all your getting is fuel then your plugs will get soaked with gas.

[robertwb70]

I've done it enough times to rule out coincidence I think, and it's running so rich when it first starts you can not mistake it for anything else. I have also checked for spark about 6 different times when it failed to start and each time it was working (lack of ignition was my first idea).

I'd think it was injectors but what's the chance of all 4 going bad at the same time, not very likely, so it must be something that's controlling the injectors-just have to figure out what.

Any more ideas?

[nichols1992]

Check the fuel pressure. It's possible the fuel pressure regulator has failed. If it fails to regulate the pressure, it could get extremly high, so when the injectors open up they release more fuel than is required. One sign to look for is gas at the vacuum port. If it's leaking you know it needs replaced, but if it's dry it still could be bad. I had one go bad on a vehicle last week and it was dry. The fuel pressure was 120 psi. Needless to say it would bearly run. It didn't do it all the time, but it did it most of the time.

[carmo]

I'm pretty sure on that car, wide open throttle during start up equals fuel cut. That maybe why the car starts then. Try using a noid light. I found a set for $20 at the local advanced auto parts. See if maybe the light just stays on after you shut the car off. The coolant temp. sensor you can check by ohming out with a DVOM. good luck.

[robertwb70]

I did swap out the FPR but I don't know that the one I put on was good for sure and there is no Schrader valve to easily check pressure, I guess I'll have to insert a Y in the line to check it. What should the pressure be? I'm guessing 50-60 psi?

Also a good idea about the noid lights, that would eliminate quite a bit of the mystery about fuel delivery on port FI cars...sometimes I really miss carburetors. Could I make a really cheap DIY version with an old LED (I have a few around) or do these things have more electronics involved than that?

I've driven the car about 200 miles since the oil change and it does seem to be getting better gradually, at least it hasn't left me anywhere lately...

[carmo]

Fuel pressure should be about 10 psi less or so. And I'm not sure about the led noid light. I know "they" say not to use a test light because you'll fry the control unit. However, from the looks of it, that's all that are in my noid lights. I don't know if there is a set amount of resistance that needs to be there. Good luck. I got and 89 240sx control unit I can sell you if you do fry that one. It's the single cam engine

[robertwb70]

I forgot to mention that it is not indicating "check engine" so I'm thinking that means the computer has no idea anything is wrong...but then I hear nissans OBD isn't very good for a lot of things.

Hopefully I'll get some time to do more trouble shooting this weekend.

[robertwb70]

Well I think I finally got the starting problem fixed. I believe a new oxygen sensor did the trick, bit I also swapped out injectors so they could have been part of the problem. The old injectors were original 240K+ miles, the newer ones came from a junkyard motor of unknown mileage.

Fuel pressure was 33 psi, which is what chiltons specifies.

I found that if I pulled the fuel pump fuse the car would start fine and run for about 10 seconds, then sputter and die. It would re-start immediately though (no cycling the key) and run 10 more secs. Seemed like it would do this indefinitely. Put the fuse back in and it starts the first time, shut it off and try to start again and it would be flooded. Pull the fuse back out and it starts again.

Also want to mention that I checked to make sure the cat wasn't clogged and it was fine.

Maybe the vacuum in the cylinder was pulling gas through the injectors even with no fuel pressure? (pressure was verified) or is there something in the ecu that could bypass the fuel pump fuse somehow?

[carmo]

Vacuum pulling fuel through the injectors sounds unlikely but I've seen some very unlikely things happen before. Can you hear the fuel pump run after you shut the car off? It sounds like excessive fuel pressure to me but with your readings that can't be right. You could try putting the hose that goes from the regulator to the tank in a bottle and see if it actually is bleeding the excess fuel back but if it wasn't you would have excessive fuel pressure. I am perplexed and have been drinking soooo tomorrow will afford me fresh eyes and sober brain cells

[navysnail]

use a noid light, gm one will work with nissan injectors. check to make sure it doesnt just stay on all the time and that it does blink.

[robertwb70]

I pulled the whole rail out of the intake and cranked it some both with and without the fuel pump fuse out and I didn't see anything unusual. I'll see if I can get a noid light anyway and see what's happening when the engine is actually running.

[robertwb70]

Well I still haven't got a noid light and the cars been sitting, but I had to start driving it yesterday while I work on my other car.

Whatever the problem is it appears to be getting worse. Things I've checked since last time I posted-Catalytic converter, it's OKFuel pressure (again) 33psi at idle, increases with throttle application

maybe the new O2 sensor is bad already?

I tell you if there was an easy way to put a damn carburetor on one of these things...

[fixer]

sounds like injectors may be leaking, see if you can scan for dtc and ck data monitor on alpha. alpha readings should be around 95-110%, if alpha is always low its running on the rich side. you can ck injectors for leak by taking them out and leave connected to the fuel rail. cycle the key a few times and wait to see if any fuel leaks out when key is off. dont crank eng with injectors out unless you disable ign first

[robertwb70]

I took the injectors out and cycled the key before, didn't notice any leaking. I also cranked it for a brief test with the ignition enabled and it started to run. I'll pull the whole mess again and rig something up where I can test it better. And I might mention this is the second set of injectors it has the same problem with which would lead me to think it's NOT injectors.

Don't know what alpha/DTC/CK data is.

The routine now if I have to shut the car off and restart is to hold the throttle wide open and hope it starts, if not then I pop the hood and pull the fuel pump fuse THEN hold the throttle wide open and it starts without too much trouble, then I casually walk back to the front of the car and put the fuse back in, while it's still running...

[robertwb70]

Finally figured the problem out, it was the coolant temp. sensor.

Amazing that no one else has ever experienced this problem but at least it's fixed now.