Chevrolet Repair: 1997 Blazer engine shuts off while cruising, engine oil pressure, definite direction

Question
1997 Blazer fuel pump was going, fuel system crud which caused occasional stalling on downhill.  Put in gum out.  Then car began to get very hard starting.  Took to dealer had fuel system cleaned out and fuel pump replaced.  Now 50% of the trips when engine is warm engine just shuts off as you are cruising along. Like I have taken it to work 6 times and 3 days it has shut off on me. Pull over, stop car, restarts just fine.  But yesterday wouldn't start at all when warm.  Waited for tow truck 45 min.  He clicked door locks on/off, car started.  He towed it to dealer and it did it again. Don't know if these are related. Dealer says he can't find anything wrong but every other day the engine cuts off!  Thanks for ANY insight! Deborah
PS The engine "cut off due to crud" about four times over 3 months before we had the fuel system serviced so you can see it has gotten much worse since service!

Answer
Hello Deborah,
That "crud" bothers me a little. Wonder if it's all gone.

For some insight....I personally would connect a fuel pressure tester to it, and I have a tester with a hose long enough that I can have the gauge inside the cab while driving. When it decides to die...look immediately at the tester, and see if the pressure is still where it is when the engine is running, or if the pressure drops BEFORE the engine dies.
This will give you a definite direction.
The fuel pressure should actually stay up till after the engine dies...actually till after the engine oil pressure drops.

Then, once you are sure the fuel pressure isn't the problem, you will need to check for spark. That will be very hard the times that it just starts right back up. But the times when it won't start....that's a great time to check the spark.

Electronic devices can have thermally triggered intermittent opens, or shorts, and since you said " when engine is warm ", it would seem like you never have it die when the engine is cold??

A little point of interest...the ecm doesn't use sensor readings and control the engine until it reaches operating temperature. If all of your problems are at operating temperature, that might be something to keep in mind...but in no way do I mean to just replace the ECM...it could also be a sensor problem.

The progressively getting worse could be just coincidence, and could be totally unrelated to crud.

And that tow truck driver thing about the locks....it is remotely possible that a loose wire connection could have been jiggled or somehow effected during that, and re-established good contact, albeit temporarily. Same for the restarting after dying.

Van