Need some advice. Have a 4.3 in a 97 blazer, relatively new (less than 30,000 on it) that cranks amazingly from a cold start, but if driven more than 5 minutes gets harder to start the longer it's been driven, but never completely fails to start. Engine is not overheating. Thought maybe the starter solenoid was getting hot so I replaced that and no change. Newish spider and regulator (but same motor and spider did not have cranking issue in the last vehicle it was in), checked all fuses and vacuum lines, any ideas? Also worth noting that it has new plugs, wires, cap, and rotor, already all double checked and tested, not the cause of my problem.

 

If starter won't turn over engine when engine is warmed up usually starter is heat sinked, via bad bushings, brushes ect. pull starter and have it checked out, most parts stores can do it, but sometimes load tests don't show bushing and brush trouble, sometimes they need tore down and a visual check done

 

Interesting problem! Will be following for updates.

 

I'm with odat. It's very common for a warn starter to act up only when hot, and then progressively get worse.

 

Replaced starter 4 days ago, still the same problem. Someone said possible ignition coil getting too hot, going to try swapping out the one off the old motor later today and see where I'm at.

 

Ok lets start over, is it a no crank situation or a no start situation - in your first post you stated that the starter solenoid was replaced, if that was all that was replaced have the starter checked out. The coil shouldn't have anything to do with a no crank situation - no start yes

 

It always eventually starts, but really rough and sometimes 4-5 attempts before success when hot. It always tries to start. Entire starter, not just solenoid, was replaced. Sorry if I'm wording things in a confusing way, I am far from a mechanic, just had this truck long enough to know how to tinker on it.

 

Ok its a no start situation, If you haven't already do the fuel pressure checks. there is a sticky on this sight that gives you the steps and how too's. A failing fuel pump can work well cool but the longer it runs it heats up and doesn't supply the needed fuel pressure for a quick restart. Remember Murfeys laws good parts fail and do at the worst times. And check for codes even if the check engine light isn't on, if you don't have axcess to a scanner most parts stores do and will read them for you

 

Fuel pressure is good when cold (haven't checked hot yet) and I tend to lean towards it not being the fuel pump because the old "turn the key on and let it sit for a second before cranking" trick to give the pump time to pressurize the lines doesn't work. Have also cleaned the throttle body and run a fuel system cleaner through along with a GM top engine clean treatment just to make sure crud wasn't my issue. I have replaced so much dumb stuff trying to fix this lol. If it costs less than 20 bucks and there is a remote possibility that it's the cause, I've replaced it already. Sorry for long time for updates for the curious, hubby pulled a dummy and crushed his arm/hand in an ATV accident so mechanic stuff has been on my back burner.

 

Hard to start 4.3L when the engine is hot is a classic symptom of failing ignition control module (ICM). Have it bench tested about 10-12 cycles.