Carb questions (1 Viewer)

[Southbound]

So while I'm troubleshooting my electrical system today I have a buddy that will be trying to figure out what's going on with the carb. Neither of us know much about how carbs work.

Here's the background. A couple of days ago my truck stalled and though it would start back up fine it would stall whenever I gave it gas. It had been running like a champ before. We met a local mechanic who proceeded to take off the two jet bolts and then cleared the inside of them with a thin steel shaft. That didn't seem to have much effect so he then took off what looked lke the main gas inlet to the carb on the top left and cleared what looked like pretty obvious sludge from the entrance with carb cleaner. The truck then proceeded to run but badly. It would shudder a lot and backfire.

I was just happy to have the truck running and was trying to get to my next destination in Guatemala. Unfortunately on the highway a couple hours later the same thing happened, stalling when I pushed on the gas pedal. Having seen what the mechanic did I tried the same thing. When I took off the main gas inlet I didn't see any dirt but I did see what looked like a valve that was closed. I moved it open with a thin piece of steel and fiddled a bit with the jets and the next thing I new the truck was running strong, ridiculously strong. The problem now is that I smell tons of gas when I'm driving and it seems I'm down to an even more ridiculously low mpg than normal. The truck is idling roughly at about 500 rpm vs. a smooth 900 rpm idle before any of this. And I get some backfiring when decelerating.

So I'm trying to figure out how to get the carb back to efficiency. I don't understand why it would have been so out of whack after the mechanic first cleaned it and I also don't understand what stupid things I might have done by messing with the valve and jets. My friend is going to spend some time today reading posts of carbs but any other advice you guys could give specific to this situation would be very helpful.


Thanks so much!!!

Mark

 

[60wag]

There is supposed to be a small sceen where the fuel line enters the carb. I think you might need to unscrew the compression fitting from the carb to get to it. Its a last level of protection for crud that makes it past the main fuel filter. Is the screen in there? It sounds to me like some crud has made it into the carb and thats the real source of the problem. Definitely replace the fuel filter if you haven't already. As for clearing the blockage.... Back flushing it with compressed air might help. Rinsing out the fuel bowl might help. Both would be easier with the carb off the truck. Another trick that might help is the "rev it up and cover the air inlet to produce a massive vacuum in the carb". That can clear blocked passages. When shoving a wire through the main jets, be careful. They are aluminum and it doesn't take much to damage or enlarge the hole. As for the fuel smell, I'll bet the connection at the carb is leaking since it has been apart several times already. Another option would be to remove the top half of the carb to be able to clean or inspect it. Be very careful doing this as there are several tiny balls, springs and rubber seal that are likely to pop out. If you've never had a carb apart before, I'd try to find a shop to work on it. Good luck.

 

[Southbound]

Thanks, it could very well be just a dirty carb.
I just took off the air filter and tried a Jim C. test - I sprayed carb cleaner into the barrel and looked to see whether the engine choked or revved. Apparently if it chokes that is a sign of a rich mixture and if it revs that means the mixture is lean. Anyway, the engine stalled immediately so I'm assuming the mixture is very rich. Maybe the crud had been clogging for carb for so long someone had compensated by tuning it extremely rich and now that the crud is gone I need to retune the carb? I don't know, I might tinker a bit with it but I know so little it would probably be smarter to take it to a mechanic.

 

[60wag]

Is the fuel level visible on the window? Maybe the float valve is stuck open, overfilling the bowl and flooding out the carb?

 

[John McVicker]

Find out anything yet? I am sure you checked but any chance it is a dirty fuel filter? Easy to check. Stalling when you give it gas sounds like fuel starvation BUT you said a heavy gas smell which doesn't sound like starvation. What do the plugs look like. Reading those may help figure the root problem. What electrial problems were you having? Often electrial problems can mimick fuel problems.

 

[RAWHEAD REX]

Where were you driving? to Guatamala? I've been south before and bought some bad fuel and my truck did the same thing.Things got better after I got some good fuel in it.I must have driven for 2 hours trying to get to the border.My fuel filter was all clogged also.It never did that again.I never bought gas down there again.Sometimes you can't help it.

 

[Southbound]

Could have been dirty fuel. I've already had to change my fuel filter three times in four months driving down to here Guatemala.

I had major electrical problems when my second battery system imploded. Thought I fixed it but now they're back. Extremely depressing. I'm going to give it one more shot and if that doesn't work I'll see if I can find a Toyota dealership down here. You think electrical problems could mimic fuel problems even in an fj60 with a mechnical fuel pump and a carb? The only electrical part of the fuel system I know about is the fuel cut off solenoid which I tested and seems to be working fine. How else do you think fuel flow could be affected?

I might skip the carb problems entirely and go diesel. I'm headed to Guatemala City tomorrow with my Spanish teacher/translator to go engine shopping. As near as I can tell conversions are very common here and very cheap...I'll let everyone know how it goes.

 

[cbmontgo]

Check your 4 vacuum ports at the right base of the carb. Those little guys have given me similar trouble when they get blocked.

 

[djawahir]

While you're at it, you may want to blow compressed air through your charcoal canister to make sure it isn't plugged up.