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Carb issue I think

D

David67

Active Member
So I was driving on the freeway yesterday and when I went to speed up in 5th gear my car starts to sputter. It's fine in every other gear when I get the rooms up.

I'm thinking I got junk in the carb because I don't drive it as much as I used to. Probably need to rebuild it.

I'm going to drive it next weekend when I have time but should I be looking at something else?

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It's a good place to start, but if it's junk in the carb you would think the problem would be there all the time. That said, I once had a tiny leaf in one of the fuel bowls which would move around.

Also had a capacitor in the distributor which would break down under load. Ran fine up to 50 mph then would start to playing up.
 
Hard to diagnose from your short description but it sounds more to me like a fuel pressure or volume delivery issue. May be more about the pump than the carb.
 
Horseplay said:
Hard to diagnose from your short description but it sounds more to me like a fuel pressure or volume delivery issue. May be more about the pump than the carb.
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I noticed it when I was getting on the freeway and I put it into 5th gear then I was trying to get up to 75 mph is was just not going anywhere. Never had this issue before. When I was on the street, the idle wasn't as smooth but it was fine going through the gears.

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For starters, 5th is an overdrive gear which is likely .67 or so to 1 which is NOT designed to facilitate acceleration. It's for cruise and economy. That said, if you were stepping into it and got nothing aside from the gearing it could be a power valve issue but in 5th engine vacuum may not have been right to really actuate the power valve circuit.

I'd take it out again on normal surface streets and pay attention to how it behaves at normal throttle, hard acceleration etc. and note how it responds. Do you have a fuel pressure gauge hooked up? Electric or mech fuel pump?
 
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What carburetor make and model?
I still run an OEM 4200 on the D-code and ran across an anomaly that presented mostly after sitting and, after much diagnosis, ran it down to the CA ethanol laced fuel chewing away at the carb and presenting little particles to the emulsion tubes in the main venturi assemblies and idle/part throttle circuit and introducing resultant lean conditions at part throttle cruise and acceleration. Pop the lid, pull out the main venturi assemblies, clean the passages, flush the idle circuit, 10-15 minutes, back to normal. As a control, I tried a load of clear fuel from the local station in Oregon, no problems. It's the gas.

There can be many possibilities in the carburation and Ignition systems. Easy enough to hook up some test gear and run it down. Particulars would depend on the type of equipment in use, carb, ignition, etc. Could be electrical too, never know, I've seen such anomalies show up under load in top gear and not before. Happens.
 
When it happens a few seconds after a (hard) acceleration , its fuel starvation. Probably the pump or a restriction in the fuellines.
When you accelerate in 5th , you demand torque and torque means fuel .
Look into the carb while the engine is running and look if you see 2 jets of fuel squired into the carb when revving the engine.
Like Terry said , acceleration pump could also be the problem but it would happen also at lower rpm/load.
IMHO.
 
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