99 Yukon - fuel delivery issue?

[letsbangout]

I'm trying to track down an issue with my Yukon SLT. This is like the third time I've had trouble starting it with the engine cold (but still warm outside), and it's gotten progressively worse each time. The first, I had to turn it over 4 or 5 times. The second, I turned it over countless times, to the point where I thought it'd be flooded, so I went and had lunch and came back 45 minutes later, it started up just fine. This time, I'm not so lucky.

After instance #1 and #2, I had codes illuminating the Check Engine light. I've had persistent problems with the O2 sensors (which I'll have to replace eventually), but I now had a new code both times - the MAP sensor. I replaced the MAP sensor yesterday with a Delco replacement part and I still couldn't get it started. So I disconnected the battery, waited 30 minutes, connected it back up and it started the first time. I ran it like a champ for probably half an hour, took it to the gas station and dumped like 9 gallons of fresh 93 octane on top of the 3 or so gallons it had before.

This morning, I went to start it and the same thing - it turns over and fires up, but will not run for more than a second. I bought a code scanner which reports no codes. I also had someone turn on the ignition and I can hear the fuel pump in the tank running for 2 to 3 seconds initially. But I'm still suspect of the fuel pump and the oil pressure cutoff switch. That I can troubleshoot, I just can't get to it because the distributor is in the way, so I can't see it either. The only way I'd know where it is, is because a friend sent me an engineering diagram showing it on the driver's side behind the distributor. I thought of pulling off the connector and jumpering across it to enable the fuel pump full-time, but I'm still not sure it's the right connector I'm pulling off, as the colors don't correspond to the colors in the wiring diagram, so that's out (unless someone has a wiring diagram showing colors other than my Haines book, tan/orange/grey - still the prospects are slim because I can hardly get to that particular cable because it's so short).

So I'm looking for some troubleshooting guidance. I suppose I can buy a fuel pressure gauge, but I'm also very limited in what I can do in a public parking lot, which is where it sits now. I feel like any more money/time into trying to fix it myself under these circumstances would be futile. However, any advice is much appreciated. Thanks!

 

[SunlitComet]

Oil pressure switch is no longer involved in fuel pump control on the '99. Do you have a factory security system installed?

 

[letsbangout]

Oil pressure switch is no longer involved in fuel pump control on the '99. Do you have a factory security system installed?

Interesting! That gives me hope.

My truck has a keyless entry remote, but I've got to assume there is no security system. The unlock button of the remote itself stopped working a couple months after I bought the truck, so I use the key to enter and it's never set off an alarm. I also don't recall seeing it on the dealer's window sign for this truck, which I have. Nor do I have an insurance discount listed for an alarm on my declaration page. But I'll take one more look at the dealer sticker and update this thread if I find that it does.

 

[992dr]

Do you notice any lites flashing on you console? The security lite inparticular.

This is what I went through. To put it bluntly, it sucked.
http://www.gmfullsize.com/forum/showthread.php?t=199600

 

[letsbangout]

Do you notice any lites flashing on you console? The security lite inparticular.

This is what I went through. To put it bluntly, it sucked.
http://www.gmfullsize.com/forum/showthread.php?t=199600

I thought the lights were mostly normal - ABS, Seatbelt, Airbag, etc. I know I've seen the solid orange "security" light a few times while starting it. I'll give it a jump and try it again, taking particular note of the lights this time.

But I'm a little stumped about the nature of the thread you posted (I read the whole thing). The thread starter mentioned something about a "passlock" system causing his car not to start. But that applies to cars that use a key with an embedded resistor, i.e. the ones that have the little black bumps on the surface of the key itself, right? So if I'm understanding that correctly, I'm not sure how a new ignition was solvent in fixing his problem, or why he had to do a "relearn" procedure if the key and the keyless entry are both passive devices.

But one other thing I should note, the windshield wipers work very intermittently in my truck (but it seems like once they start working, they work for as long as I need them). I believe they're tied into the ignition, so I guess it's possible the ignition could be the root cause of the failure to stay running and the intermittent wipers as well.. but one would think if the ignition were to blame, there wouldn't be any fire at all, which isn't the case. I'm still trying to figure out how an ignition would solve the guy's problem in that thread, and we don't know that it did either, because he never posted again after the one involving the "relearn" procedure.

 

[SunlitComet]

To make more confusing for you. There was a recall for the wiper system because of cold solder joints.

 

[letsbangout]

To make more confusing for you. There was a recall for the wiper system because of cold solder joints.

No, actually that, and your other post, greatly simplify things for me... Thanks for the insight! Now I have no evidence, anecdotal or otherwise, that an ignition problem is in play.

The only other thing that comes to mind is the crankshaft sensor. When I first got the truck, most of the time I started it, the engine would turn over slowly right before it came alive. Knowing how many revolutions the starter has to make to start the engine, I ruled out the possibility of a "bad spot" in the starter motor. I had the battery checked and it's within 20 CCA of its 550 rating, a non-issue in warm sunny Florida. Cables are good and tight, etc. Finally I read a TSB that says if the crankshaft sensor is working intermittently, it can advance the spark timing as much as 50 degrees in the computer, causing difficulty in turning over and perhaps even cracking the starter mount. That particular problem has subsided over the 11 months of ownership, but I'm still suspect. Though I have a hard time believing that sensor wouldn't throw a code that I could see with my consumer-grade code scanner.

 

[SunlitComet]

It does throw a related P0338 code as for as the tsb goes but it has 1 or 2 others as well.

---------- Post added at 06:27 PM ---------- Previous post was at 06:26 PM ----------

while you are looking around ensure the integrity of grounds on your thermostat housing.

 

[gpracer1]

I thought the lights were mostly normal - ABS, Seatbelt, Airbag, etc. I know I've seen the solid orange "security" light a few times while starting it. I'll give it a jump and try it again, taking particular note of the lights this time.

But I'm a little stumped about the nature of the thread you posted (I read the whole thing). The thread starter mentioned something about a "passlock" system causing his car not to start. But that applies to cars that use a key with an embedded resistor, i.e. the ones that have the little black bumps on the surface of the key itself, right? So if I'm understanding that correctly, I'm not sure how a new ignition was solvent in fixing his problem, or why he had to do a "relearn" procedure if the key and the keyless entry are both passive devices.

But one other thing I should note, the windshield wipers work very intermittently in my truck (but it seems like once they start working, they work for as long as I need them). I believe they're tied into the ignition, so I guess it's possible the ignition could be the root cause of the failure to stay running and the intermittent wipers as well.. but one would think if the ignition were to blame, there wouldn't be any fire at all, which isn't the case. I'm still trying to figure out how an ignition would solve the guy's problem in that thread, and we don't know that it did either, because he never posted again after the one involving the "relearn" procedure.

There is no resister in the key, like my vette has. The resister is in the steering column where the key goes in. When you turn the whole ignition, it sees the resister turn. If it does not and you start it, it will run for about 2 seconds then die. It disables the fuel pump relay, but will still get the fuel pump prime every time you try, which is why it will start then die. The security light will flash or be solid and it will be in tamper mode for 10 minutes. If you wait 10 min, then it will start if you try after that.
If it happens and you are desperate, you can jump the proper slots where the fp relay are and drive (not recommended).

I have a Viper HF550 and it has remote start. To fool the passlock, there is a bypass module they install and they match the resistor setting on the bypass to the value of your truck. After time, this value can change since we are talking only a few ohms per different "code". I actually had Directed Electronics (Viper) send me the instructions on how to set up.
In my case I just disabled the entire fu@#ing system in the PCM.

 

[letsbangout]

There is no resister in the key, like my vette has. The resister is in the steering column where the key goes in. When you turn the whole ignition, it sees the resister turn. If it does not and you start it, it will run for about 2 seconds then die. It disables the fuel pump relay, but will still get the fuel pump prime every time you try, which is why it will start then die. The security light will flash or be solid and it will be in tamper mode for 10 minutes. If you wait 10 min, then it will start if you try after that.
If it happens and you are desperate, you can jump the proper slots where the fp relay are and drive (not recommended).

I have a Viper HF550 and it has remote start. To fool the passlock, there is a bypass module they install and they match the resistor setting on the bypass to the value of your truck. After time, this value can change since we are talking only a few ohms per different "code". I actually had Directed Electronics (Viper) send me the instructions on how to set up.
In my case I just disabled the entire fu@#ing system in the PCM.

Wowowow.. I never would've thought about something like that, but it makes perfect sense. The symptoms of my problem completely resemble the passlock issue you've described with the ignition switch. I've also thought about doing what you said, bypassing the VCM control of the fuel pump relay and just keying it off of the ignition (though I'd lose the "no oil pressure cutoff" protections). Of course I'm not far enough along in my troubleshooting to know for sure, but I will be shortly.

For absolute clarity, and because the guy in the other thread never wrote back to confirm complete solvency of his problem, can anyone describe what's necessary to get the computer to recognize the new ignition switch's resistance value? Is this something you can do i.e. 1) without a code scanner, 2) with standard OBD-II, 3) with a snap-on style advanced code scanner, 4) only at a dealership, etc?

Also, so that I completely understand how this problem comes into play - what are the indications of it? From looking at the other thread, I guess the orange SECURITY light would be solid, or?

Thanks a bunch for all of the responses!!!