ok i posted about a starting prob i have on my 99' blazer. It seems thatnow the temps are 39 and below it starts up no matter how long of a time period it sits, but if temps are45 and up it happens if it sits more than 20 mins. could this be a bad coil possibly? I would think a bad FPR would act up anytime no matter the temp. The MAF sensor is fine and so is the fuel pump. I seafoamed it and it idles like brand new. I have narrowed it down to this problem happening on a half to full tank of fuel and temps above 39. im really stuck. Last resort is the new MFI unit.

 

I'm wondering if this isn't ignition related. Have you had your coil and ICM tested? Autozone or Advanced Auto should be able to test these components, but you will have to remove them from the truck for them to be tested.

To eliminate a fuel system problem, you really need to do a pressure test as well as see if the pressure steadily drops after the key is turned off. It is normal to drop a few psi at the instant the pump turns off, but if it continues to drop, there is a leak somewhere.

 

Thanks man, I had the front susp. rebuilt on it last week and while it was in the shop i had the techs monitor the fuel pressure for 3 hours and they said it did not have a delayed start or pressure drop. next week i will take the ICM and coil to have it tested and i am going to purchase a fuel pressure gauge so i can check it myself. my one concern is what does coldtemp and fuel tank level have to do with itif its not an ignition problem.

 

I guess I missed the 1/2 to full tank criteria for this problem. So you are saying that if you stay below 1/2 tank, the problem does not exist? When you remove the gas cap, do you hear a hiss? If you do, does this allow the truck to start better? Does it do it consistently above 39*F and 1/2+ tank of fuel?

 

yes especially on full to half. basically the truck starts its best on the last qaurter and i dont liek running under that anyway. i will try the gas cap trick in hopes that it will hiss. i wondered that last summer it would only do this in the if i filled up when it was 90+ degrees. if i filled up in the late evening or night when it cooled down it was fine.

 

If the ICM is going out? It wont work when hot, once cold it works. Temps below 39 might be the magic number, for now. This might not be related to fuel at all. Like Swart suggested, get the ICM tested. Have them test it like 6 times in a row to make sure it works when hot.

 

Ok im basically convinced that it is the ICM i will remove it and have it checked tomorrow. it is now dipping down to the high 30's and the blazer jsut fired up fine after sitting alittle over an hour.

 

Hanr3, i did not have a chance to get my ICM checked today, had alot running around to do, but i accidentally rested my foot on the throttle and it started right up.I did this 5 times and the fuel pump relay kicks right on loud and she fired. I dont see what that is about because as you know the throttle is basically an "Air Pedal". You think it could have something to do with the Idle Air Control?

 

That is a definite possibility. I would remove the throttle body and give it a good thorough cleaning. Remove the IAC valve and clean the pintle and it's bore. The IAC valve can get gummed up and not operate properly.

 

yea, what he said. ^^^^^

Pull that EGR out too.