When the weather is hot and I have gotten the blazer at operating temps, I have a problem if I shut it off then after 3-4 minutes try to start it again. It catches for a second, then just cranks and cranks. If I wait another 10-15 minutes it startsnormally. It has been doing this for 3 months. ALWAYS starts after it has had a chance to cool down. I replaced the computer (had it flashed for my vin) and the engine temp sender by the thermostat. Ialso replaced the fuel pump relay in the glove box. It seems that the relay is getting constant voltage and works by using the ground as the switch (probably from the computer). Any ideas? Hot in Oklahoma!

 

short answer ICM get it tested.

 

had icm checked at local autozone and it passed. They did say that they might not be able to get it hot enough to fail. Any other ideas before I pay $71 on a guess?

 

How many cycles did they put it through? It usually takes ~10 to get it hot enough to cause failure (if it's going to).

 

Replaced the ICM and still does the same thing. Rechecked the fuel pump relay (new) and it does get power and can hear it latch. Wait the 10-15 min and click boom start.

 

To narrow things down you really need to check for spark and put a fuel pressure gage on it when you are having the problem.

 

It is getting spark - will run on ether when it happens. What am I looking for on the fuel pump pressure and how to tell the diff between a week pump and faulty regulator?

 

A faulty regulator will bleed off pressure after you turn the key off. A weak fuel pump won't bleed pressure when its off.