EFI and Vapor Lock?

[JeepTruck]

Ok my brother has 87' Jeep comanche with 4.0 liter with 200.000 plus miles on it. In the winter time its starts ok but in the summer it will start when its cold but once it warms up you are stranded it will crank all day but it will not start. I thought fuel injection was supposed to due away with vapor lock so I don't think thats what it is. He says that adding wooden clothes pins on the fuel rail (multi port injection) seem to help the starting problem, but this was near the fall when the weather got cooler. I drove the truck allot this winter and never got stranded. It does seem to crank allot more to start then most fuel injected vehicles then I am use to, I don't know if this will help diagnose the problem.

He bought the truck a year ago in the winter so problem didn't show up till this past summer, and like I said no issues with it this winter.

 

Thanks in advance for everone's help

Dave

[BLHTAZ]

Welcome to the Club! :cheers:

 

I am REALLY curious as to why anyone would put clothes pins on the fuel rail :hmm:

 

When it does this, you need to check the basics and try to narrow it down. Check to see if there is spark and check the fuel pressure. I can only guess at it with such a broad list of possibilities, but I would think that it is likely a lack of fire, and probably going to be something to do with a heat soaked CPS or coil.

 

The Renix control system normally takes anyhwere from 2 - 4 seconds of turning over before it will start, so if you are within that range, there is no problem there.

[Eagle]

Vapor lock can occur only with the old, mechanical "puller" style fuel pumps mounted on the engine. If the fuel in the line vaporizes due to heat between the tank and the pump, the pump loses prime and can't pull fuel from the tank. This is not possible with the pump mounted in the tank -- the fuel is under positive pressure at all times.

 

Your bother's problem is something else.

[HOrnbrod]

There are a couple of TSBs floating around dealing with injector heat soak causing hard starting when hot. The "cure" is an intake manifold heat shield or a wrap around the affected injector, usually #3. AFAIK these TSBs were for the HO engines, but maybe there were some also for the Renix engines, no?

 

[Ed in North Ga.]

do a fuel pressure test- see what the hold pressure is- leak down test.

 

run the pressure up, let it sit, then test for pressure.

 

seems like the hotter it gets, the longer a renix takes to start- add a little bit of air into the mix, and it gets downright fun.

 

 

not.