94 Safari stalls at highway speeds

[RangerHall]

first post not but the last.
I recently bought a 94 GMC Safari van from a private seller. it has the vortec V6 4.3L in it and a automatic transmission.
My questions are and I have searched this site before for answers but I need someones opinion.
I live in Florida and right now its hot just like everywhere else.
I bought this van with 122,xxx miles on it. it had been sitting for about 2 years before I bought it with a bad transmission. I had a new tranny installed as well as an egr valve,airtex fuel pump and sending unit. I drove it for about 2 months and it started becomming hotter and hotter as the summer days went by. I can drive this van about 30 miles and not have any problem but if i drive for more than an hour it will start to hesitate and buck and then after a series of bucks it will stall out. now when I pull over I can slip it in neutral and (with the key on) try to recrank the engine. It will not start. however if i turn the key off and crank the engine it will fire right up like nothing is wrong with it. it has always cranked and started on the first turn of the key. tthen I can drive for 3-5 minutes and it will buck and hesitate agian and stall out with the same results as i mentioned.
I have checked for spark,it has good crisp blue spark
has a new fuel pump in it although it is not a delphi or ac delco pump.
it has all the ovious things replaced, spark plugs,wires,cap,button,fuel filter,and ignition module
distributer gear is good

I have not replaced the coil,since I though if it was bad it would do it all the time.
I have not checked fuel pressures since I dont have a gauge, but Im working on that.

the plug at the fuel pump and the fuel pump ground at the frame look good.

Im at witts end here, im on a very limited budget, 2 kids and work public service for the state of florida.
I cant troubleshoot by changing parts. I am mechanically inclined so if you tell me somthing dont think i wont understand it. any info on what else to look at would greatly help. I have read that these vans are fuel pump brand bias'ed should i start checking fuel pressures or should I start checking the coil?
thanks, Ranger

[chevymaher]

No actually a coil will work well cold and stop working when it is hot. I would check it when it is messing up. ICM in the distributor is also a place to look for heat related issues.

[RangerHall]

I failed to mention earlier I had it running like crap one day and had the doghouse cover off, when I got it to stall on its own, I checked the spark by removing the center spark plug wire on the distributed cap and bridging it with a screwdriver and placing it close back to the center point on the cap when I tried to crank it from the run position, I noticed a constant spark but it wasent blue and it would not crank and run. I then cycled the key, and it fired up with no problems. Watching the arc it was then blue. Thinking the engine running normally it would produce a more powerfully spark then if it was just cranking using only the battery I started thinking, ok its got spark it has to be a fuel related problem. If a coil gets hot enough to intermittently work wouldn't it take time to cool back off before operating agian? Cycling the key from run to off and back to crank and run is enough to get it started. I replaced the fuel pump relay also thinking it would be a quick fix. But it does the same thing. I drove it to work today and home and had no issues yet agian, it was in the low 80's and was kinda nice out for a change. No issues and I had the gas low enough the needle was in the red.
I swear this thing is cursed

[RangerHall]

Also it has a new icm in it the old one when I removed it had the grease dried up, I replaced it with a new one with a glob of dielectric grease on it. Should I look into testing the coil or start looking for a cheap ac delco fuel pump. Should have a FP tester comming to me this friday so I can check the pressures.

[chevymaher]

Friend of mines had consistent orange spark. Would not start. Same ordeal ran in the morning untill you turned it off. Would not start hot. One day it wouldn't start cold either. Had bright orange spark. Would jump a quarter inch gap testing.
I swapped in a extra coil I had laying around. Blue spark. Started and ran every since.
He kept saying it wasn't the coil for 2 days. Had fuel pressure. Finally I said let me plug the silly thing in and see. Can't hurt. Fired right up.

[deleteitall]

Also it has a new icm in it the old one when I removed it had the grease dried up, I replaced it with a new one with a glob of dielectric grease on it. Should I look into testing the coil or start looking for a cheap ac delco fuel pump. Should have a FP tester comming to me this friday so I can check the pressures.

What grease did you use? The ICM needs heat conducting grease/compound. Dielectric grease (as in spark plug grease) is heat insulating. Or was it a white grease packet that came with the ICM?

[RangerHall]

Yeah that's what I ment to say was the grease that came with the ICM. Not DE grease