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well i finally got this thing running. i went through 3 pump realays but thats not my problem (i think). it will start right up and can keep it running by foot, but when left to idle it dies after a few seconds. when i try to catch it, it sounds like its running out of gas. its not, i have a clear fuel filter on it and can see gas. i don't know, do you? i just thought, maybe the filter stopped up????? any help or ideas????
thanks

Could be crud in the carb. Spray a bunch of carb cleaner into the overflow tubes (they stick out over the barrels) and let it sit over night. You could even pull the relay and start it to run the carb out of gas before filling the bowl with carb cleaner through the tubes. It would start hard that way though, needs some gas in there. After it has soaked in run it for a while, trying to let it idle as much as it can so the cleaner runs the the idle circuit of the carb. It might be something solid tho that won't dissolve out of the way.

Someone on here once described a power cleaning process. Basically you get it running, rev it up a bit, then cover the top of the carb with a rag and your hand. The rag prevents the motor from giving you a hickee. It should die, but while it dies it will be sucking gas through every crevice in the carb and hopefully some of the crud with it. Might work even better combined with a carb bowl of gas with some cleaner mixed in.

What kind of carb is on it? Stock?

have you tried adjusting the carb, maybe someone has the fuel turned down...

Good point, the idle mixture could be cranked down or clogged at the needle valve at the adjuster screw.

all i did was take this motor out of one truck and put it in another. it started and ran fine in the other. i will try some of those suggestions though. thanks yes it is a stock carb.

If it ran in the other, it would seem the culprit is the present truck. A bad vacuum leak? Crud in the fuel system?

Anything you didn't swap along with it from the other truck might be involved. It sounds to me like a fuel problem, could have been some crud in the fuel lines that has made its way into the carb. Unbolt the fuel inlet at the carb, there is a screen in there that could have gotten plugged by whatever was sitting in the line. Look where the fuel line and return go into the carb and where they both come together there is a bolt that goes into that part. Unscrew that bolt and you should be able to get at the screen.

I could be wrong on the fuel thing, its just my feeling based on what you describe. You might also look at swapping the coil from the other truck, and I would go back over the vac ports on the manifold/carb and make sure they are plugged or hooked to something. You could also plug them all to make sure its not a leak elsewhere, even the distributor.

800xl, i've had all that apart and everything looked good. i did shoot quite a bit of carb cleaner through it and seemed to help some. actually got it running good enough for a short trip down the road. but with all the rain we've had it'siting behind the house in the mud. big dummy! i got a little excited.

and about that fuel pump relay... should it have power as long as the switch is in run position? by using a test light, mine only has power when switch is in start pos. when it starts and release the key it cuts power to the pump. i can keep it running with the pedal but does'nt idle long (a fwe secs.) thought that might be my prob. but i ran a hot straight from the batt. starts, runs, idles, dies the same way.

Let an old timer ask a maybe dumb Question. Has the float chamber a glass sight gauge on the side? And if so, can you see gas about midway up the glass after it dies?

The pump relay should be on when the key is turned to start, and after the motor starts. The reason it isn't on just when the key is on is so that it will stop if you get in an accident instead of feeding a fire under the hood.

Now that I think about it, that sounds sort of like water in the gas. That would explain a lot and why it is getting better. Try some gas line dryer additive in the tank, or some 99% (or high % as you can get) rubbing alcohol since it is the same stuff anyway.

yes, when motor starts and key is released,test light in line between fuel pump and power supply goes out? if this is correct, how does the pump supply fuel in run condition? does carb just work as a siphon(sp)? i have tried 3 relays and didn't think they were all bad. not doughting just asking, how could the coil be suspected also? it will probably be a while be fore i can tackle this thing again, since i start my every other 12 hour shifts untill Christmas. thanks for all the help.

There has to be a hold in circuit across the points of pump relay that keeps the relay energized by supplying power to it. This circuit would be initiated by the start relay.

The relay hold circuit is part of the alternator regulator. If alternator stops charging the fuel pump will stop. Make sure the alternator is charging.
That's how it was in my 79 and 80 models.

Thanx, Egg. I was too lazy to go run down my manual and then find a magnifying glass so I could decipher those minature wiring diagrams.

well that makes it a little more clear. my gen light does shine bright. i will check alt. as soon as i can. thanks egg. i could still have a little bad gas in the tank. i did pump out what it would pick up and only added about 2.5 gals of fresh gas.

i think a carb overhaul might work. if not try checking your choke

Dude... 6 month post gap here... cmon...

Hahaha

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