3Fe starting issues

[mp_cude]

I posted this on the main forum, but local advice is always good.

The past couple days I have been having starting issues. 91 fj80, currently 92k miles. I only have the problem when I have been driving for a while in the hot desert. At first it would be brief, now it takes ten minutes or so to restart. The only other odd thing about the truck (and not sure if they're related) is the fuel tank builds a ton of pressure, the fumes pouring out will moisten your hand, and nearly blow your hair back. Fill up, 30 second later re open the cap, and the fuel tank will lurch. A Buddie of mine mentioned vapor lock, but I have never dealt with that, so I don't know. Thanks.

 

[mountain cruiser]

Most likely your charcoal canister is junk, my 62 had the same problem and the tank wasn't venting properly. Tossed my canister and the problem went away. Just disconnect yours and see if it helps the problem.

 

[Tools R Us]

I posted this on the main forum, but local advice is always good.

The past couple days I have been having starting issues. 91 fj80, currently 92k miles. I only have the problem when I have been driving for a while in the hot desert. At first it would be brief, now it takes ten minutes or so to restart.

IIRC the 3FE rigs had a problem with the fuel pump relay and wiring, causing this type of problem? Search on the '80 forum, there is an old thread on the problem/test/fix.

The only other odd thing about the truck (and not sure if they're related) is the fuel tank builds a ton of pressure, the fumes pouring out will moisten your hand, and nearly blow your hair back. Fill up, 30 second later re open the cap, and the fuel tank will lurch. A Buddie of mine mentioned vapor lock, but I have never dealt with that, so I don't know. Thanks.

This sounds normal. Today's gas isn't anything like your dad's gas, the formulation has significantly changed. One of the issues is the vapor pressure (boiling point), the fuel must be volatile, evaporate when injected into the motor, but needs to stay liquid as much as possible in the tank.

In the old days I removed charcoal canister/purge systems, wouldn't do it today. One of the functions is to hold pressure, the is helps greatly with the boiling problem. Another is to purge the vapor and burn it in the motor, so at least you get some fuel value out of it.

Unfortunately the earlier systems aren't as good as the newer ones, when stressed (high heat, altitude change, etc) can be overloaded and vent pretty good, but they are better than nothing. If removed, atmospheric vented, you will lose more fuel to evaporation, it will boil off anytime it's hot and with altitude change. The first components that evaporate are the most volatile, so you will lose more fuel and the remaining fuel will have less performance.

Tank vapor has nothing to do with vapor lock. Fuel injection systems run under high enough pressure that they rarely, if ever, have vapor lock problems. As long as the system holds pressure when the motor is off, the fuel can't vaporize. Even if there were a system leak, the vapor would be quickly pushed into the tank when the pump started and the start delay would be brief.

 

[mp_cude]

IIRC the 3FE rigs had a problem with the fuel pump relay and wiring, causing this type of problem? Search on the '80 forum, there is an old thread on the problem/test/fix.

I did narrow it down to the EFI relay. I replaced it, and that solved the issue. Would I need to rewire the box? I'll also look up that thread, and read it.

 

[Michael Hanson]

Yes upgrade under the box to 12 gauge or this will not work for long,I have a 1991. MIke