I also have an '88 F250 beater that my mechanic had at his shop now over a year and still can't debunk. It has a 302 auto 4x4 It will run until climbing up hills then shuts off. If you let it sit 45 minutes, it fires back up and drive it away. Here's what was changed so far: coil, plugs, distributor module, inline fuel pump, plug wires, computer, eec/fuel pump relays & connectors. Tried to hot wire from battery straight to coil, died. Ran fuel line into gas can in cab, died. No codes to be found. Besides for pushing it off a cliff, any suggestions???

 

How steep a hill we talking here?

Run fuel line into gas can in cab? this truck have a carb?

When it won't start does it have spark? checked at the plugs? if so good steady spark? or just very weak intermittent spark?

Does it have fuel pressure? exactly how much does it have?

 

check all your ground wires.

 

Hill: small grades. No mountain or anything like that. Seems like when more pressure is put on the motor. It can even be caused if on the flats and hard on the gas pedal.

Fuel line: Fuel injected 302 Not sure how he bypassed everything and ran it out of a gas can but...

Spark is good

Fuel pressure: normal at if I remember correctly 30psi on his guage


What seems to happen is when it quits, power is cut to the eec & fuel pump relays till the truck sits for about 45 minutes. Then it'll fire back up...

 

Well, have you checked the exhaust system for restrictions, in CATS, or muffler? I do see you said it looses power. As said a loose ground, any way to bypass the inertia switch for the fuel pump? Not sure if your model had one.. If your losing power it sounds like a ground or overheating issue of some component. This is one if we can solve to keep adding info.

 

Spark is good

Fuel pressure: normal at if I remember correctly 30psi on his guage

Is that as tested when it will not start?

If it has good spark and the fuel pressure is up to spec but still fails to start, fill a squeeze bottle with some gas (clean empty squeeze type mustard or ketchup bottle for example) while someone turns it over, squeeze a moderate stream of fuel into the throttle body (remove air cleaner hoses), will it run while doing so? You can use starting fluid but use sparingly, doesn't take much. Either way just enough to verify it will fire or not.

 

Muffler/tailpipe new, not sure if cats were checked. Even if cats heat up and block, would that trip the power to the eec & fuel pump relays??? Also, wouldn't the cat be cherry red if it blocked??? Inertia switch - I would guess that running fuel out of a gas can into the motor (not sure how it was setup) would bypass that switch wouldn't it???

Fuel pressure: Held the same pressure even when the motor shut off & trying to re-fire... Sqeeze bottle, he did mention something about trying something like that but I don't remember if he did or not. I'll have to ask. By any chance, could it be possible that the injectors are overheating and kicking off???

 

Personally I've never heard of an injector that heats up and shuts off. If the cat is clogged there may be no visual signs, you would have to take it off and check it.

If your truck is getting good fuel, good spark, and is obviously in time it seems nearly impossible that it wont start. Go with your mechanic this time and watch him while he tests your fuel and spark. Honestly for a mechanic to have your truck for a year and still not be fixed is ridiculous. Honestly he could have replaced the entire fuel and electrical systems by this point.

 

I'll have the cat checked. I have been going to the same mechanic about 7 years now and he has done minor repairs all the way up to changing the gear set in my '94 F150 which was completed in 2 days. He is a very good mechanic and engine builder. The whole mention of the truck being at his shop for a year I should have explained more. It wasn't worked on a year straight, but when he had some free time to sink some hours into debugging it. I would have to guess that he had 20+ hours a month into it as time permitted. I told him from the start it was a no rush project but figure out the problem. Many hours of phone tag kicking around possible solutions along with internet searching.