Okay, my car stranded me at work again today and this is getting annoying. ('89 IROC, L98)

Here's the problem: most of the time it starts like a champ with a second or less of cranking... but every so often, I'll crank it, it'll act like it wants to run, and then cuts out. After it cuts out, I can crank the hell out of it for as long or as many times as I want, but it doesn't even *try* to start. The best I can do is to leave it sitting for 10 minutes or more, at which point when I try to start it, it will run for a second and cut out like it did the first time. Full tank of gas. And I know it sounds like classic MAF sensor problems (trust me, I know those blues well), but the computer isn't throwing code 34 (or any others for that matter).

The odd trend that I notice is this: I've never had this problem in the morning. But it's not as easy as saying "oh, it's just a problem when it's hot then" because I've never been stranded when I turn it off to get gas either (at which point it's at operating temp). Today, for example, the car was sitting for 7+ hours while I was at work and still stranded me when I tried to leave--even with ample time to cool. Another trend I notice is that I always get stranded in the hottest part of the day (mid/late afternoon)--like today, for example (and we were in the 100s). I had my dad pick me up and take me home, and we just came back to my work to try to start it (remember, it's dark and much cooler at this point). While it didn't fire up immediately, it did at least try to start while I cranked it... gave it a little gas a few times, and finally it turned on and ran like a champ.

I know there are other threads out there with guys having the exact same problem, but I didn't want to hijack their threads so here this post is. I'll put up links to those shortly.

In the mean time, anyone have any pointers for me?

 

When was the last time you changed your fuel filter and have you thought about the fuel pump relay or the fuel pump being on its last leg? Also have you checked your fuel tank vent near the left rear tire and the fuel pressure relief valve in the engine bay?

 

I changed the fuel filter when I changed the fuel pump, which seems like it was nearly 2 years ago. I have thought about the relay, but not tested it explicitly yet. However, I have put a fuel pressure tester on it and I do get nearly 40 PSI at the rails. The pressure does bleed off completely in under 2 minutes, but it's safe to say that that's because of the original Multitec injectors still being on there (I know I need to change them). I don't expect that would affect starting, however.

As for the fuel tank vent... I know what you're talking about (I remember seeing that thing for the first time when I changed the fuel pump). I don't really know what to check for, nor do I know what it does (though I can roughly infer from the name). I do know that I had to get the filler pipe on the tank re-welded to the tank (it was leaking), and ever since that happened, I get a large rush of air either into or out of the tank whenver I remove the gas cap. That have anything to do with the tank vent?

 

When the car does this hook a fuel pressure gauge up to the fuel rail ,and crank the motor a few times.See if your fuel pressure goes down while cranking.My car started off doing the same thing as yours,and like 6 months later it wouldn't start at all.My fuel pump relay was bad

 

Anyone happen to have the pic that shows which relay is which?

 

I don't have a picture here ,but go on www.advanceautoparts.com and they do have a picture of it.
it's in the drivers side rear corner of the car,by the master cylinder mounted on the fire wall.It is the square relay with a straight across push in connector.Or at least on my 89 thats how it is.

 

Alright, I finally got it to not start at *home* for once (which means I actually was where there was some diagnostic tools). I put the fuel pressure gague on the rail and it is getting fuel... I tried cranking it over, and the system maintained fuel pressure. So whether or not the relay is going to go bad, it was at least working when it wasn't starting tonight.

So next guess... spark? Only thing I can think of to fail under such circumstances on that end is the ignition module. Off to buy one now....