Uphill buck/stall 70 FJ (1 Viewer)

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Hello all! A noob to the forum, FJ's, and gas motors for that matter.

I have a 1970 FJ40, F motor with a Weber 32x36 vac secondary carb. I bought it from the PO a week ago. The first day it drove well! The second day it developed a 'buck' or stall in most any uphill situation where the motor is under load. It will idle fine all day long, and will drive around on flat and at low speed with no problems. I am thinking I am looking at a fuel starvation problem...does this sound like the right direction?

I have searched thru the forums trying to find fixes for this. I have replaced the fuel filter, checked the plugs and wires, which look to be fairly 'new'. Even removed the gas cap...none of these have solved the problem.

I checked elevations and the PO's home and mine are about 35' difference in elevation.

Any information you could pass along to this DAN would be great!
 

inkpot

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Howdy! Usually a problem at one angle only means it's a float problem. Good guess. Check/reset that and see what happens. John
 
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It sounds like fuel starvation. Look for dirt/rust in the tank, obstructed fuel lines, clogged filter, weak pump (It should pump about 8 oz of fuel in 15 seconds of cranking with coil center wire pulled). It could also be a clogged inlet filter or inlet check valve.
 
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Thanks for the info! I will check out the float next, then move on to the others.

If any body else has any suggestions...post 'em up!
 
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Had this same issue.....replaced the fuel filter and all was fine.....I know you said you replaced yours, but if a lot of crud is coming out of your tank, it may be clogged again....or there may be blockage in your lines.....blow them out, replace the filter again and then try it. If that much junk is coming out of your tank, it's time to repair/replace it.
 
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Had this same issue.....replaced the fuel filter and all was fine.....I know you said you replaced yours, but if a lot of crud is coming out of your tank, it may be clogged again....or there may be blockage in your lines.....blow them out, replace the filter again and then try it. If that much junk is coming out of your tank, it's time to repair/replace it.
I replaced the fuel filter with a see thru type in line filter (temporarily) to see if more crud was clogging it. I have only been able to drive a few miles so far (3-4) and can see no additional gunk in the filter.

From what I have been told here and from some other reading, I think it is a float problem. But this is my first gas motor in a LONG time, so I have much to learn yet...and my first gas/carb motor ever, so the learning curve will be long.
 
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I've been diagnosing and problem shooting my rig for some time now (with similar problems to yours) and, though I'm no mechanic, I'll always believe that you start with the cheapest fix first. If you're bucking, then you're dealing with a fuel starvation issue. Since you're pretty sure it isn't the filter, you may want to check the lines to make certain they're not clogged. Then you can start working your way to toward the carb. Fuel lines are cheap and, just guessing, they're probably old and should be changed anyway.

Have you done what Pin_Head suggested? If not, then step away from the computer and try all those things first......
 
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You can easily distinguish between a carb bowl fuel level (float) problem and a fuel volume delivery problem by comparing going up the same hill in first gear at 5 MPH to going up in 4th gear at 45 MPH. It takes a lot more fuel to go up the same hill at 45MPH than at 5 MPH.

If it stumbles and bucks in first gear at 5MPH, then it is a float level problem. If it doesn't, then it is a fuel delivery problem.

Unless you have fooled around with the carb float recently, I doubt that it is a float level problem.
 
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If all the fuel flow checks look good, you may want to pull the Weber apart and see what jets are installed. I just got done rejetting my 32/36 and found that the primary idle jet was way too small (had a 60) and the main and air corrector jets were off.

This is what's installed right now:
Primary
Idle jet: 90
Air corrector: 180
Main jet: 155

Secondary
Idle jet: 60
Air Corrector 170
Main jet: 170

I'm also at 4000' elevation. Hope you get it running. Fuel problems can be alot of fun.:mad:
 
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Will it buck under hard accel on flat ground?
No, it will run all day as wide open as you like on the level. And you can rev it as much as you like sitting still as well...never a problem with those.


Thanks Pin_Head I will try that out! I have not messed with the carb at all...yet

It was about 12 degrees here today so I will give your test idea a try in a few days when it warms up a bit.

My elevation here is about 2060', but I will look into the jets after I have tried some of the other things mentioned.

I appreciate all the help SO much, I know from my experience with diesels, talking a noobie thru these things can be frustrating:cheers:
 
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