scottt80

I've got an '84 SR5 xtra cab 4x4 with about 150k on it. Nice clean, fairly original truck that had sat for a couple of years before I got it in a garage with stabil in the tank. It wouldn't crank when I bought it... carb was gummed up. I bought a replacement rebuilt stock Aisin carb and put on it and it fired right up.

I went and put fresh high octane gas in it and proceeded to drive it about 300 miles over the next week locally without issue.

Last Saturday I drove it an hour away on the interstate, did a few errands and headed home. About ten miles from home it starts losing power going uphill. I thought it may be out of gas... showed 3/8 of a tank but I had never had it that low before... all the gauges seem accurate otherwise. I put a little gas in it, it starts and I go to get back on the interstate... it dies going downhill on the on ramp... can't get it to start, call a buddy and we tow it home. Get home on level ground and it fires right up.

For good measure I replace the fuel filter... old one looked fine though. Did a few short runs and it behaves fine.

Today I take it about 15 miles, cut it off for 30 minutes, it starts fine... pull out in the road and it dies. Get it out of the road on level ground and mess with it a few hours later and it starts fine again. Fuel gauge again around 3/8. So I put about three gallons of gas in it. Does fine... but then dies in the driveway and won't restart.

So I'm a little stumped here... pouring gas in the carb it fires fine and will burn it right out. With a mechanical fuel pump I can't see that heat would stop it from working only when hot. I can't get the truck to idle out right so it does want to die at lights when you stop unless I run the idle up to 1500 rpm or so. I've hooked up all the vacuum lines. Aside from that it runs fine and normally starts right back up with just a pump of the gas. I bought a rebuild kit for the original carb but me and a buddy didn't have much luck rebuilding it... but do have it as a core or parts. From the way its acting it seems like a fuel delivery problem but that just doesn't make sense with the mechanical pump... the heat shouldn't bother it, right?

Any ideas? Thanks guys! I'm trying to come up with ideas before the weekend when I'll have some time to mess with it.

kawazx636

iTrader: (3)

I'd pull the fuel pickup tube from the tank (you should be able to get it out without actually removing the tank) and see if the fuel sock on the pickup is clogged up. Something similar happened to me before. My '83 would run perfectly fine for 15-20 miles and then start sputtering out. Turns out that I had a bunch of rust in my tank that would build up in the fuel filters and on the fuel sock in the tank essentially causing a blockage. If I let it sit for 5-10 minutes and let the rust debris settle, it would start up fine and drive for about another 10-15 miles until the debris built up again. It would happen more frequently as my tank became more empty because the concentration of debris would increase and the volume of fuel decreased. Also, another problem could be that your tank isn't vented properly and eventually the negative pressure will build up thus starving your fuel pump. The quick check for this is to simple leave the fuel cap off while you run it for a while.

kawazx636

iTrader: (3)

Oh, and make sure that you don't have two fuel filters. On my '83 there was one near the tank and one on the passenger side fender wall. If you have two and only replaced one then it could be the one that wasn't replaced causing you hell.

scottt80

Thanks... that makes sense on it picking up rust and stuff when its low on fuel. The fuel pump has been replaced at some point, it looks fairly new. The fuel filter I changed the other day was the one in the passenger side rear wheelwell. I'll try your tip about taking the gas cap off and see what happens. I may just need to start filling it up at half a tank till I can figure this out. It has to be something fairly simple.

kawazx636

iTrader: (3)

I'm not sure about the '84 models, but there is a fuel filter near the tank directly below the fuel filler door on the 79-83 models. Check to make sure you don't have one there also - that would be the one that would be causing you more problems if you do have it. Just follow the fuel lines coming off the tank and you should run into it.

scottt80

Thats about where this one I changed is... thus far thats the only fuel filter I've been able to find on the truck... and the old one looked fine when I changed it, it wasn't dark or rusty colored.

john22rebuilder

Anyway you could put an inline pressure guage and see what is happening during the stalling? Should be a pretty cheap permanent mod....

scottt80

Ok... I'm back to chasing this down. I've done a few short trips without issues... drove it today for about 15 minutes, cut it off for 15 minutes, restart it to leave and it dies totally. Full tank of gas in it.

It was about 90 degrees here today... I'm wondering if I'm having hot restart issues due to the ethanol content of the fuel? Vapor lock?

john22rebuilder

Circuit opening relay. (COR) try jump fp and b+ next time it takes a s.

scottt80

Where is this circuit opening relay that you're talking about? It has a mechanical fuel pump on it.

john22rebuilder

My bad. Didnt reread post. Efi has a cor.