Ok its a mail truck that sits on a S-10 frame and shuts down when it gets hot (usually after 15-20 miles of stop & go in +100* heat). We've had it at the dealer several times and all they...and our maint facilility are doing is throwing parts at it. So far they've replaced distributor, EGR valve and fuel pump (I think). I'm leaning towards the coil or even hot fuel ruining the pump...but I'm definately not a mechanic but think I have a better idea than the ones claiming to be. Any ideas?

*the reason we take it to the dealer is the maint facility is 75miles away and its cheaper (normally) to use local services*

 

I'd say its vapor locking itself. Just a guess though?

 

What year. In the old days (early electronics) bad ecm could be diagnosed by putting something cold on them. Boards would crack and work cold, but hot the cracks separate and stop working. I saw alot of Fords do this. A 10 pound bag of ice on the ecm would get you about two hours down the road

 

Most of ours are either 88-91. Grumman actually makes the conversion so its hard to know the exact year without digging deep.

 

You need to know if it is TBI or carbed, most are TBI.

Next time it does it, before it cools down and starts, take the air cleaner off and spray a flammable substance, such as carb cleaner ( check it first, some doesn't burn now ) while trying to start it. If she fires, you know it is fuel related, if not, Ignition.

Not sure what year they went distributorless on the 2.5, I know they were done by 92.

 

take the gas cap off and drill the plastic pressure plug and spring out of it that way it will vent that will also stop the vapor lock if that is what is causing your trouble might also check the computer to see if the board has a crack in it. I had an 88 blazer that was doing the same thing and after the dealer thru hundreds of dollars at it they finally changed the computer and it ran like a top.