95 Lumina APV 3.1L - not starting - diagnosed my butt off

[richtazz]

What do the spark plugs look like? They may be fuel fouled from all the other issues. If they're black and sooty or wet, try cleaning and re-installing them and see what happens.

[Gill YM]

Cranking but not catching? Did I read it right??

fuel pressure too low.

[xphire]

Gill: Fuel pressure seems to be okay as it's spraying out a tremendous shower of fuel into the throttle body.

rich: Spark plugs are brand new, however they are black and wet just less than 1,000 miles later... and after a couple weeks of cranking to test if what I did worked. :P



In my last post, I stated that it was spraying a huge shower of fuel causing it to maintain a high rev and continue running for a while after the ignition was shut off. After someone came over to look at it, he told me to just let it run that way for a while, something I wasn't doing, and lo and behold after about a couple minutes it snapped back into normal operation within an instant. He said he thought it was because the computer was brand new and had to re-program itself. Sounds plausible enough. (one of the things I did while trying to get it to run was replace the computer and it hadn't ever been started during this whole process) I still don't know what -exactly- caused all of this, but it was one or more of the things I did/replaced. (see first post for list of things done)

Anyways, I really do appreciate all the replies, help and suggestions I received from all of you. You guys helped me get a few steps closer, sooner, to getting it finished... and now it's finished!


Well, almost... It runs and that's the main thing... runs great, actually. However, I'm once again getting the same 2 error codes from the computer as before... Vacuum/map sensor and coolant temp sensor. I have a Haynes manual that I bought but I can't seem to find anything about a vacuum sensor? I replaced the map once already as well as the coolant temp sensor and so it's probably an electrical problem.... wire probably grounding out somewhere.... A mechanic buddy suggested that it may be the EGR valve causing the map/vacuum sensor to trigger. any thoughts? oh, another reason he suggested the EGR as a candidate was because it still continues to run for a few seconds after the ignition is shut off, even now after it runs good.

[68haywagon]

The CTS is very important to the tbi engines. It tells the ecm what temperature the motor is at so it can regulate the correct amount of fuel. When the motor gets warm and the sensor is bad, you will get a very rich fuel mixture...to the point where it will not run. Replace that sensor it is only 6 to 8 bucks. I went through this already.

Mike

[xphire]

Originally Posted by 68haywagon

The CTS is very important to the tbi engines. It tells the ecm what temperature the motor is at so it can regulate the correct amount of fuel. When the motor gets warm and the sensor is bad, you will get a very rich fuel mixture...to the point where it will not run. Replace that sensor it is only 6 to 8 bucks. I went through this already.

Mike

You think the coolant temp sensor is causing it problems in the cold? I thought so too since like you said it regulates the fuel injection system and if it's dead or incorrect signals received, the ecm gives a constant value instead.... anyways, i've replaced it and found that it's a wiring issue because when i unplug the sensor, the gauge still acts like it's fully grounded... argh.

[richtazz]

There are two temp sensors on this vehicle. One is for the computer and is a two pin sensor located in the intake near the T-stat housing (AC-Delco part #213-928). The other is for the guage, and has 1 lead about 8" long (green wire) and is in the rear cylinder head toward the passenger side(AC-DEelco part #213-56). The guage being pegged has nothing to do with the excess fuel, as they use two different sensors.

[xphire]

Okay well I replaced the one that's on the manifold or nearby it in front... It's visible in plain sight... However, the computer (old and new) is still getting the CTS error and the gauge is still borked. Also though, the gauge works periodically and sometimes not. But anyway, I'll go and try to replace the other one located in the rear and see if that helps matters. thanks again

[jeffcoslacker]

Originally Posted by xphire

Alright, so the timing should be great now... However, I just noticed something really really weird... It's getting PLENTY of fuel but it's still not turning over... It is turning over SOMETIMES but not all of the time. When it's running, it looks like fuel is spraying way too much into the TB. It looks like a shower inside the barrel. This also causes it to diesel for a few seconds after the engine is turned off. So, I thought maybe it would be the fuel pump relay sending too much fuel, but it doesn't always start and it seems to always be getting plenty of fuel... I'm out of ideas...

That's exactly how my TBI Olds 5.0L Custom Cruiser acted when the Coolant Temp Sensor got damaged during an unrelated repair. The parts store gave me a sensor that fit the harness, but was wrong for the application. It was relaying erroneous info to the ECM, commanding full rich and making the injectors flow like you are desribing.

Until having someone crank the motor while I watched, and noticing that, I though for sure it was clocked 180 degrees out, as I'd had the distributor out for the other repair I was doing. It would crank and fire and kickback, cough, and diesel like it was outta time, and I about drove myself nuts static timing and trying one tooth this way and that way, and reversing it in the bore, checking firing order, etc.

Just thought I'd toss that out there in case it might have some relevance, somehow.

[jeffcoslacker]

Holy shit, I didn't even get this far down in the replies. I think the CTS is your answer, it sounds very much like my episode.