efi vapor locking?

[schmooter]

installed mustang 5.0 and it runs good going down the road. my problem is when its hot and humid outside it dies. let it set for an hour or so and it starts right up like nothing happened. i have the bc tank w/ pump inside and am venting through the gas cap. is this my problem or is it my pump? whenever it dies i can pull off the fuel line and there is alot of air in it. i redone my vent the other day to vent better but it hasnt been hot enuf to die yet. dont know if this solved it or not. gonna see what yall thought?? thanks

 

[broncnaz]

Sounds like it may have been the vent in the cap over time they either get plugged up or just stop working.

 

[DirtDonk]

What condition are your fuel lines in and how tight are your connections? With air in the system, I would think it either a leak in a line, or a pump getting tired. Even a tired pump though should pump nothing but gas if it's submerged like that.
A leak that's tiny enough to let air in, but not leak fuel out, can be very hard to find sometimes. Look for a tiny amount of fuel on a line somewhere, or any kinks or loose fittings.

Good luck.

Paul

 

[canrel]

If your vent is plugged or very restricted, enough to cause the entire fuel system to be in vacuum, Removing the cap the cap would relieve it. you should hear it sucking in air if you remove the cap. then it should start.

If it is a fuel problem, you should be able to start it by giving it a little spray of carb cleaner down the throte. If it still will not fire then it is probably a fuel problem.

I have had a few coils and moduels, the ones on the side of the dizzy, do exactly as you discribe. Check for spark if it doesn't start with the carb cleaner.

Paul, I can see the "air leak" on a carbed engine with the pump pulling fuel from the rear, but how would air get into the line if it is pressured from the tank to the fuel rail?

 

[schmooter]

efi vapor lock

all connections are good and tight. went and drove it yesterday for a cple hours and it ran fine. but i was goin 50 mph the whole time. hopefully with the tank vented good now all my problems will quit. i doubt it though. i just think its something besides the vent line.

 

[Steve83]

The nature of "vapor lock" prevents you from ever finding bubbles in the line. And it can only happen at a heat source (like a metal fuel line running by the exhaust); not in a tank. If you have air in the line, then you have a leak. Does this EVER happen when the tank is full? I suspect the pickup tube in the tank is cracked or rusty.

 

[av bronco]

Try to pull codes, this will tell you if you have a pip signal problem or other sensor but most likeley it's loosing signal, common problem for tfi ignition.

 

[DirtDonk]

Paul, I can see the "air leak" on a carbed engine with the pump pulling fuel from the rear, but how would air get into the line if it is pressured from the tank to the fuel rail?

Push-schmush. Don't confuse me with logic. Hah! Yeah, good point. Didn't even think about that aspect.
Then again, this is a Bronco, and they can, and will, do anything they please sometimes. Logic and scientific fact be damned!
It's probably just practicing the "Bronco-Venturi effect" and the passing gas is pulling air in.
Then passing gas again on it's way out.

Thanks. Now I have to go back to the drawing board, as we used to say, and re-think the whole passing gas theory.

Paul

 

[trailpsycho]

I was also going to suggest the TFI module. They are notorious for going out in this series of electronics. I had to replace mine 3Xs last year--and yes, I was very careful and clean during the swaps...finally swapped the whole dizzy and its been fine since.

When they start to go out, you may notice a slight hesitation, change in RPM/idle quality then it will die, sometimes slowly (10-30 secs), sometimes almost no hesitation (<5 secs). Once cooled, it will run again. As they deteriorate further and further, the duration of running time it takes for the part to fail shortens...less than 15 minutes.

The way to know for sure is next time it dies, go to the dizzy---on the wiring coming off the dizzy there is a short section of wire with a plastic SPOUT connector--you remove this to set timing. You can pull the spout connector and it should fire right up....dont wait for it to cool down--you got places to go. You will be running on open loop (tables only) and the dizzy will not advance off the 10 degrees base-timing-- or whatever it was originally set at...but it will run well enough to get you home and back. Dont lose your SPOUT connector. You will need to put it back in once you get the new TFI in.

Hopefully, in your case, the vacuum in the tank was the culprit, but if it does it again. Pull the spout connector, I bet it will start right back up. Then you can go to a parts store and swap out the TFI or possibly just go ahead and get the dizzy TFI combo....or swap out another dizzy from another running vehicle.