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hesitation while driving
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Author:  martin53 [ Mon Sep 22, 2014 11:49 am ]
Post subject:  hesitation while driving
One day my truck is driving good the next day I start to warm it up for work and it seems to have a hesitation while shifting into second and the truck starts jumping even heard it back fire. I have good spark and fuel pressure. Could it be something with the carb. Its a 78 slant 6 with a 3 speed.
Author:  wjajr [ Mon Sep 22, 2014 2:46 pm ]
Post subject: 
I vote for poor accelerator pump shot. Generally farting & popping back through the carburetor happens when A/F mix goes lean under throttle opening.

Check pump shot with engine off and choke butterfly open by looking down at throttle plate while opening the throttle by hand 1/3 to 1/2 way. One should see a nice strong squirt of gas shoot out into bore. If just a dribble, or weak stream of no doration, it's time for a rebuild kit to be installed.
Author:  martin53 [ Mon Sep 22, 2014 5:36 pm ]
Post subject: 
Seems to be squirting gas good. Stream looks perfect it started acting up a morning after we got rain. If that matters. I'm thinking just rebuild it and see.
Author:  wjajr [ Tue Sep 23, 2014 4:16 am ]
Post subject: 
Low fuel level in fuel bowl will cause drivability problems as described as well.

If the carburetor hasn't been rebuilt for some time doing so may be a good plan, and proceed from there.
Author:  Fopar [ Tue Sep 23, 2014 8:53 am ]
Post subject: 
"it started acting up a morning after we got rain"

Could be moisture under distributor cap.

Richard
Author:  nm9stheham [ Tue Sep 23, 2014 9:09 am ]
Post subject: 
Quote:
"it started acting up a morning after we got rain"

Could be moisture under distributor cap.

Richard
With the backfire (which more often than not is due to a misfiring or crossfiring ignition), this (or a similar ignition problem caused by moisture) seems much more likely than the carb. I would wipe out under the cap, and all the plug and coil wires, check for sparks arcing out of the spark plug wires or their connections under the hood at night, and see how that goes.

BTW, my son washed the car a week ago, and washed under the front fenders, and the car stopped dead a few miles later, and then ran fine after a few minutes. We figured he got some water in the ignition area on the right side.
Author:  martin53 [ Tue Sep 23, 2014 9:51 am ]
Post subject: 
I check the spark its good had some moisture under the cap and wiped it down still didn't work. My vacuum advanced isn't to strong unless I accelerate. I think I have an intake leak would that do it. Thanks for the help guys I just got my truck going a few weeks ago.
Author:  wjajr [ Tue Sep 23, 2014 1:34 pm ]
Post subject: 
Quote:
My vacuum advanced isn't to strong unless I accelerate.
No or little vacuum advance when accelerating because of vacuum drop off when throttle plates are opened, particularly when engine is under load such as driving up hill.

An intake vacuum leak probably would not effect vacuum advance if it were correctly plugged into ported vacuum source; that said source being a point above throttle plate. If your vacuum advance is incorrectly connected to manifold vacuum, that is below throttle plate, a massive leak may or may not have some slight effect of vacuum signal to advance pod at idle.

Any vacuum leak will effect idle quality. The bigger the leak the worse the idle quality to the point it won't idle without hot-foot'en it to keep her running until running on main jets at larger throttle openings and higher than idle rpm. As engine rpm and throttle opening increases the proportion of added air via vacuum leak becomes less. Think of difference between squirt gun (vacuum leak) and garden hose (main jets) and the gun's contribution is negligible once hose is opened up.

Keep plugging away at this problem you will get to the bottom of it.

The previous mention of moisture inside distributor cap is a good clue that I did not think of as there was no mention of wet or humid weather previously posted. A slight bit of dampness under cap will cause real rough idle, and poor drivability if the engine will run at all.

Wet or damp worn out spark plug wire insulation will also cause skipping and poor idle as the spark shunts off via leaky insulation to nearest ground rather than jump the higher resistance of the plug gap; resulting random non firing plugs.
Author:  63gtcv [ Thu Oct 09, 2014 6:31 pm ]
Post subject: 
Crap for gas will cause probs. too.
Author:  ValiantBoyWonder [ Thu Oct 09, 2014 11:06 pm ]
Post subject: 
Check your gas cap. I bet you got water in the gas. Buy some water remover and fill it up with premium
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