'87 350 TBI vapor lock problem

[Longbed]

Hi guys. New to the group and my truck is vapor locking. It's a 1987 3/4 ton with a 350 TBI. It only happens in hot weather or when I've been hauling a heavy load uphill and the engine bay gets hot. It just shuts off while driving- classic vapor lock. I can restart it but unless I stop and let it cool down it just gets worse until it won't even start.
Im thinking about re-routing and insulating the fuel lines. They run right down the back of the motor. Not a lot of room for air flow back there. And not really enough room to insulate them. Has anyone tried this? Are there other things I should be checking?
The truck has dual tanks but I only use the passenger side tank. The drivers side tank started leaking years ago (according to the previous owner) and has not been used in a long time. I replaced the tank and pump but it is still not working. But thats an issue for another time. I just want to solve this vapor lock issue first. Everything is bone stock, btw. Thanks for any advice you are able to give.

 

[87ChevyR10]

If the engine is getting hot enough to evap the fuel before it reaches the TBI, I'd be looking at a colder t-stat. My 1/2 ton has a 350 TBI and I have never had vapor lock. My fuel lines run in from behind the engine, too.

Another thought, what type of fan clutch are you using? It may not be functioning properly, thus not allowing enough air to circulate around the engine.

 

[bucket]

I doubt it's vapor lock on a FI truck. Weak fuel pump or failing ignition module is likely though.

 

[1987 GMC Jimmy]

I agree. You can borrow a fuel pressure tester from Autozone, and you can take your ignition control module to be tested while you're at it. Vapor lock is a more feasible problem with carbureted vehicles. In fact, the presence of the electric in-tank pump should rule that out for all intents and purposes. GM was having serious vapor lock problems with their P30 based motorhomes, and in 1984.5, I believe, they added a regulated electric in-tank fuel pump that cured the vapor locking with their carbureted 454's until 1989. Moral of the story is that TBI's should be naturally resistant to vapor locking by design.

 

[Longbed]

Thanks guys- this is good stuff. I have put in a colder thermostat and the fuel pump is fairly new (2 years but the truck is not a daily driver). The fan clutch is the original I think so I will look into that. Are there better aftermarket fans/fan clutches and is it worth investing in one? It gets very hot here in Colorado in the summer.
I will get the fuel pressure and ignition module tested as soon as I can and let you know the results. Do I just hook up the fuel pressure tester to the fuel line where is enters the throttle body?

 

[1987 GMC Jimmy]

You can get the Actron 01800001320 that threads in behind the TBI unit, which that's a fuel pressure adapter you can use to check fuel pressure whenever you want, or you can just tee it in where the fuel filter is along the frame rail. According to the reviews for the Actron piece, it seems that it needs an adapter fitting to work with pressure testers other than an Actron.