1978 f250 carb issues.
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Junior User
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1978 f250 carb issues.
i was working on truck yesterday. put new plugs/gapped em, new spark plug wires, and valve cover gaskets. well after all this im quite satisfied with myself. then the truck wont start. 
so i retard the jets. get all the flooded gas out of it. it runs etc. go for a drive come back and it dies right as i pull in driveway. carb goes kapoot...... Rebuilt it, starts and idles fine now. but now whenever i accelerate in gear, it will sputter and hesitate. it didnt do this before i fixed the carburetor. i may be overlooking something but this is my DD and i really need to get it roadworthy before tommorrow.
so i retard the jets. get all the flooded gas out of it. it runs etc. go for a drive come back and it dies right as i pull in driveway. carb goes kapoot...... Rebuilt it, starts and idles fine now. but now whenever i accelerate in gear, it will sputter and hesitate. it didnt do this before i fixed the carburetor. i may be overlooking something but this is my DD and i really need to get it roadworthy before tommorrow.
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
Those are not your jets, they're your idle mixture screws, turning them clockwise gives you a leaner air/fuel mixture, turning them counter clockwise gives you a richer air/fuel mixture.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
With the truck off, look down the throat of the carburetor and pull back the throttle. You should see two good streams of gas spray against the venturis.
As MH said, those screws are for the idle mixture. Jets are internal to the carburetor. Turning the idle mixture screws all the way in will cut off the idle circuit and the motor won't run.
As MH said, those screws are for the idle mixture. Jets are internal to the carburetor. Turning the idle mixture screws all the way in will cut off the idle circuit and the motor won't run.
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any help? im still lost. i dont know names i know what im doing for the most part. just lost on this lol. or able to explain it good. it hasnt changed at all. i had something weird happen today at a light also. it was almost like my ebrake was in at the light. and it was gloing but no amount of throttle would move it forward. so i pushed clutch in gear and pulled it out and put it back in. it worked fine and went on back home. sputtering left and right. i do have a miss also, i did a compression check and im running 110psi on all cylinders. ditributor cap is still good so are the points and distributor. im thinkin when carb went out it just screwed the whole carb up beyond any repair kit. may just have to buy a new carb i guess =/
MSEE
Joined: Apr 2004
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From: Austin, TX
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Post Fiend
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From: Big Sky Country
You should have electronic ignition in a '78 unless a PO retrofitted it.
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what about it? adjustment or what? very broad. and i have 2 good streams of gas coming out when i throttle it. it doest stumble when idling only when accelerating to.
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
Like 390hog said, where on the accelerator pump lever do you have it set? you may not be getting a big enough squirt, after that i would suspect your vacuum advance is sticking but your recent work on the carb points to the accelerator pump.
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i tried all 4 settings. no difference...is there a possibility of transmission issues? i think it may be going out on me. with the incident i explained earlier i am beggining to think so. im a noobie at cars. i love learnign about em but this is beyond my reach atm. not experienced enough to diagnose this kind of stuff yet.
Freshman User
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Mine ran as you describe just a few weeks ago. I went through everything, spark, vaccum.. changed fuel pump. AFTER i changed the pump i checked out all the fuel lines. Ended up having a cracked rubber fuel line comin from the steel tank line to the pump. Changed it out, put in a filter... runs great
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
It's not the transmission because (1) those symptoms are not indicitave of transmission failure and (2) the problems only started after you rebuilt the carburetor. You have off-idle stumble, which could be due to the following:
1. Accelerator pump malfunction (unlikely since you can see it dispense fuel)
2. Timing issue (possible, yet still unlikely)
3. Float height issue (very possible since this is a crucial step of a carburetor rebuild, and improper fuel level in the bowl upon a sudden increase in fuel demand will cause a lean condition)
4. Vacuum leak (very possible).
1. Accelerator pump malfunction (unlikely since you can see it dispense fuel)
2. Timing issue (possible, yet still unlikely)
3. Float height issue (very possible since this is a crucial step of a carburetor rebuild, and improper fuel level in the bowl upon a sudden increase in fuel demand will cause a lean condition)
4. Vacuum leak (very possible).
Thread Starter
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Junior User
Joined: Jul 2009
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It's not the transmission because (1) those symptoms are not indicitave of transmission failure and (2) the problems only started after you rebuilt the carburetor. You have off-idle stumble, which could be due to the following:
1. Accelerator pump malfunction (unlikely since you can see it dispense fuel)
2. Timing issue (possible, yet still unlikely)
3. Float height issue (very possible since this is a crucial step of a carburetor rebuild, and improper fuel level in the bowl upon a sudden increase in fuel demand will cause a lean condition)
4. Vacuum leak (very possible).
1. Accelerator pump malfunction (unlikely since you can see it dispense fuel)
2. Timing issue (possible, yet still unlikely)
3. Float height issue (very possible since this is a crucial step of a carburetor rebuild, and improper fuel level in the bowl upon a sudden increase in fuel demand will cause a lean condition)
4. Vacuum leak (very possible).
i eliminated the float issue. had my friend who is 67 and owns a automotive shop check the float for me. he said it was good and height was correct. hes as lost as me. hes one who had me compression check it told me bout float and firing order. im about to go check the vaccuum. andmaybe it will be something as easy as that. but wont it run akward and idle? mine is only stumbling at acceleration in gear.