Just from what you've said, I would suspect the coolant temp sensor. If it reads hot all the time, you won't get any cold enrichment when starting. When the engine is actually hot, you don't need it. It would be super easy to check it with a scanner, though.

 

Why take a smooth road, when the potholes are so much fun!

 

I do. I believe that the MAF is used for the injector pulse width calculation if it is working and has values that have not gone out of bounds, when in open loop including starting. That said, if the MAF is hosed and is producing bad enough numbers it can prevent starting due to fuel delivery. If the MAF dies or gets unplugged the PCM goes to a speed density calculation without the MAF using other sensors. Once you get to closed loop then the O2 sensors determine injector pulse width and the MAF is used as the baseline for fuel trim calculations. That said, I don't know that this is the issue here.

George

 

George,

Yes, you’re right on the basic functionalities of the MAF; however, the OP stated that the PCM had already thrown a code for the MAF. This indicates that the PCM is already operating off the VE and MAP, ruling out the possibility of the MAF causing his ongoing no start condition.

Edit: I forgot to add, that unfortunately it looks like the OP bought a vehicle that was poorly maintained by the previous owner. Knowing that, if it were me, I’d have quite a large list of PM things I’d be removing and replacing.

 

Good point on the code. In this case the MAF may not be used. I don’t know if the PCM locks the sensor out until the code is reset or checks it at each start cycle. Either way, unplugging it before starting the process would confirm if that’s the sole offender. I suspect that this is not the issue but I was waiting on the answer to my question about warming up to see if going into closed loop fixes it or any restart even if cold fixes it.

George

 

Hey everyone, thanks for your insight in this thread.

First, I should have mentioned that I bought this car for $400 knowing that it didn't start. I'm planning on using this for the Gambler 500 series of off-road races where you purchase a car for around $500 and take it 500 miles offroad in an endurance race where the finish line is a junkyard. So I was well aware that the car had issues and planned on putting in some wrench time to get it running as a hobby project.

Secondly, as the previous owners appear to have neglected a lot of maintenance, I do plan on flushing all fluids and systems, changing all filters, the usual stuff. I live in Florida and the Gambler races I attend take place in both Michigan and Florida, so I want to make sure it is safe to drive on the highway.

With that out of the way, here's the results from this weekend's work:

1) We pulled all the spark plugs and tested compression on all 6 cylinders. Basically if the engine was bad I was going to scrap the whole project and recoup my $450. Luckily each cylinder was between 170 and 190, so the rest of the project is a go. All 6 sparkplugs were fairly new Bosch units and looked good and clean. Gap was within spec and there was no burning or buildup on the electrodes. Wires were also new and not cracked.

On a side note, disconnecting the steering column to get the middle driver's side plug was a real pain. At first we couldn't get it to retract towards the firewall, and then at the end it didn't want to pull back down over the splines. Also the steering wheel is about 10 degrees off and that was before we messed with the steering. I put it back on exactly how it came off, I figure I can always re-mount the wheel inside the cab to straighten it. The rag joint did feel pretty loose but I'm not really sure what is normal for them. I may revisit this once she's running to try and tighten up the steering, right now it likes to wander all over the road and steering is more of a suggestion than definitive, possibly a safety issue.

2) We replaced the Coolant Temperature Sensor with a new Delphi unit. The original sensor was installed but the little retaining notch on the top had sheared off letting the connector slide right off and throw the CTS code.
Lost a lot of coolant in the process and the stuff that came out looked pretty opaque and rust-colored so I plan on doing a comprehensive coolant flush and replacing the Dex-Cool with G05.

3) We did the Fuel Pressure test at both the service port and the fuel filter. Here are the results:
At the service port: Pressure reached 48PSI and dropped to 40 within 10 minutes. Subsequent test reached 50 PSI and also dropped to about 40 within 10 minutes.
At the hard line before the fuel filter: only reached 45 PSI but did not drop within 10 minutes. Tested again and only reached 30 PSI, did not drop. Tested a 3rd time and only reached 8 PSI.

Pretty sure the fuel pump is now toast because the car will no longer run after a spray of starter fluid. It will fire (and backfire) from the ether and then immediately die due to lack of fuel most likely.

With this in mind I will definitely be replacing the fuel pump as it's now putting out basically zero pressure. I don't think there is an issue with the fuel pressure regulator as the max output and regulated output were essentially the same. I also don't think there is a plenum leak because the pressure held very steady when connected straight to the fuel line.

So with those results, I think the hard starts were coming from a dying fuel pump that could not supply enough pressure to start but had enough to keep it running.
I do still want to take the intake off to visually inspect the spider injectors for leaks just in case.

4) The car is now only throwing the P0102 (MAF), P0449 (EVAP), P0452 (EVAP Pressure) codes.
P0118, 0155, and 0341 have all cleared after replacing the ECT sensor.

I'm just happy I got a solid 4.3 Vortec and 4l60e for $450. The body of the truck is also in excellent shape, no rust or major dents to speak of. If I throw another $600 in for tires, fuel pump, and any other assorted odds and ends I'll still be in around $1000 for a fun off-road and camping rig to take to the Gambler 500.

 

Be sure to use only a Delphi or AC Delco fuel pump. Confirm proper voltage at the pump and confirm pressure and leak down at the schrader when done.

George

 

Well I know it's been a while but I just wanted to report back in.

I purchased a new AC Delco fuel pump and dropped the tank yesterday. The old pump was an cheap Airtex as soon as I got the AC Delco in there it fires right up on the first crank.
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I plan on changing the fluids next, and I'm still getting the Evap leak codes, so I'll check those out next. Also I'm not getting anything from the blower motor when I turn the HVAC ***** so I plan on looking over the fuses.