Vapor Lock???

[Rick Norwood]

I have a rather peculiar problem with My 1994 Dodge Grand Caravan 3.3L. This has happened multiple times spread out over the last 10 years. Every couple of years after a rather long drive, then a stop, it spits, sputters, has very little to no power, and will ultimately die. It will usually start right back up, idle fine, but when you shift into gear, it acts up as described. If you let it set for about 15-20 minutes, it will usually start up and run fine without the syptoms as described.

The First time it happened I was lucky enough to be within a mile of the dealer, who diagnosed a bad fuel pump before it was ever on the lift. He showed me what he said was the culprit, which was a fuel filter that was full of black particles and soot. He replaced both the pump and filter and it ran fine for a couple of years and it started doing the same thing. Another new fuel pump and filter and we're running again (all under warranty). About three years ago it did it again and this time we went to a different dealer and since we were no longer under warranty, we wanted to know what was actually going wrong before just throwing $500 at the problem. Nothing was ever found, no codes, pressure was good, everything looked fine. No problems until today when it started again, no dash or check engine lights, it just wouldn't run. We let it sit for 20-30 minutes and started it right up and drove it home without incident.

My question is, are these vehicles known for vapor locking? It sure acts like that is what it was doing. We live outside of Phoenix and the temp today was 110° F although in previous times, the temp wasn't that hot and was ruled out as a factor.

Any one had the same problem? I am planning to put a new fuel filter in it tomorrow, but any other advice would help.

[RickMN]

You usually don't get vapor lock on a fuel injected engine. The fuel pump keeps the pressure pretty high in the fuel rail and that's what eliminates vapor lock. This actually sounds more like either a clogged fuel injector or an injector with an intermittant short. A clogged injector would leak gas into the cylinder after a shutdown or leak too much at idle, causing rough running. Try dumping a bottle of Chevron Techron fuel injector cleaning fluid into your tanks. It's the best add-in cleaner on the market. The problem could also be a bad fuel pressure regulator--which also might explain the frequent fuel pump failures. If the Techron doesn't solve the problem, it's time to find a good technican and have them run a fuel injector resistance and current draw test on each injector. Also run a scope pattern on the fuel pump and a pressure check on the regulator.

[Rick Norwood]

Originally Posted by RickMN

You usually don't get vapor lock on a fuel injected engine. The fuel pump keeps the pressure pretty high in the fuel rail and that's what eliminates vapor lock. This actually sounds more like either a clogged fuel injector or an injector with an intermittant short. A clogged injector would leak gas into the cylinder after a shutdown or leak too much at idle, causing rough running. Try dumping a bottle of Chevron Techron fuel injector cleaning fluid into your tanks. It's the best add-in cleaner on the market. The problem could also be a bad fuel pressure regulator--which also might explain the frequent fuel pump failures. If the Techron doesn't solve the problem, it's time to find a good technican and have them run a fuel injector resistance and current draw test on each injector. Also run a scope pattern on the fuel pump and a pressure check on the regulator.

Thanks for the reply Rick. I installed a new Fuel Filter this morning. The old one did not really seem plugged. I'll try the Techron. But just where is the Fuel Pressure Regulator?

The baffling part is the imtermitent problem. I really don't think it is any one injector, as the engine will barley run when in this mode even with the accelerator floored, it sputters. A fuel pressure regulator sounds more like it because it would affect all of the injectors. I have had this vehicle looked at by Three different Dodge Dealerships and nothing could ever be found.

The only other thing I noticed is that there is a high pitched whine or whistle that you can hear toward the rear of the van while it is running. I was told this may be the sign of a bad Fuel Pump, But I am not sure if this is a normal sound for a fuel pump in these vans or not.

[ericktj]

Even when vapor lock is hard to happen in fuel injected vehicles..it will happen if conditions for temperature-pressure are meet... and are more related to ethanol content on gasoline, You actually get ethanol vaporized and creating the vapor lock, this could happend on any vehicle, I'd seeing this on my buick lesabre, my mercury villager and my brother grand caravan, just happend when weather is VERY hot, over 100's... I solved this problem releasing the vapor from fuel line and preventing more vapor lock by putting additional gas on gas tank to cool gas a litlle bit.

Regards

Erick