I'm thinking this is carburetor related

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m3a1
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I'm thinking this is carburetor related

Unread post by m3a1 » June 18th, 2019, 10:28 pm

Ok fellas. A buddy of mine has an A1. He bought with what turned out to be a problem motor which was duly replaced by the fella who sold it to him, Unfortunately, in the swapping of the motor, his freshly rebuilt Zenith carb went out with the old mill and the "new" motor got put in with another Zenith. He says it has points ignition and it starts with no problems so I'm rather sure the timing is spot on. The guy that provided the truck and replacement motor says the engine has had a valve job.

The issue is that the truck will try to stall after hard acceleration (as though it is suddenly starving for fuel.) It starts right back up again as though nothing happened but the problem will repeat itself regularly whether the engine is hot, or cold. Plugs look normal (no indication of a lean condition). I was thinking the carb's float was sinking or set improperly. We got into it and found a perfectly normal and properly set float. Carb appears to have been rebuild not too long ago. I looked over the vacuum lines. Everything was right and tight, though I did not fiddle with the PCV valve.

The truck has a fully renewed fuel system, fabulously clean tank and there appears to be solid fuel delivery all the way up to the carb.. While we were looking it over, I noted the idle was rather high and when we turned it down something else became apparent. The truck's idle would lower itself almost to stalling and then run back up to normal and then repeat the process. I'm still thinking this is a sick carburetor. Am I missing anything?

Cheers,
TJ

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raymond
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Re: I'm thinking this is carburetor related

Unread post by raymond » June 18th, 2019, 11:25 pm

Accelerator pump diaphragm :?:
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svramselaar
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Re: I'm thinking this is carburetor related

Unread post by svramselaar » June 19th, 2019, 5:15 am

hi

if the condender from the ignition is bad
the engine revs at idle mormal and wil not turn good at higher speed it looks the same if the carburator is clocked

george

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muttguru
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Re: I'm thinking this is carburetor related

Unread post by muttguru » June 19th, 2019, 5:25 pm

.....and if the fuel system has been fully renewed, make sure that the filler cap is a VENTED cap with the valve in the OPEN position.
Ken
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m3a1
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Re: I'm thinking this is carburetor related

Unread post by m3a1 » June 20th, 2019, 4:37 pm

Cap is vented (and open) and it'll run even at higher RPMs but grudgingly, meaning even at higher RPMs, you can feel them rising and falling.

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Re: I'm thinking this is carburetor related

Unread post by rickf » June 20th, 2019, 6:56 pm

I have seen some really bad caps and rotors come in from overseas marked as NOS, some are so bad they do not even fit the distributor. A lot of them are misaligned and break off the tab on the rotor.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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