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Mike S.
Mike S., Classic Car Mechanic
Category: Classic Car
Satisfied Customers: 7499
Experience:  A.S.E. certified with 25+ years experience.
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What causes a Ford 390 to run finr whe choke is on but to

Customer Question

What causes a Ford 390 to run finr whe choke is on but to run so rough when choke goes off ot stalls. It won't re start unless you pump the gas and keep pumping to keep it running? I have put new in new fuel pump, all hosese (vacume and guel), fuel and spacer gaskets to try to fix the problem to no avail?
Submitted: 1 year ago.
Category: Classic Car
Expert:  Mike S. replied 1 year ago.

A vacuum leak. Closing the choke helps richen the fuel mixture back up some, close to normal.

Expert:  Mike S. replied 1 year ago.

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Customer: replied 1 year ago.
I knew I had a vacume leak that's why I replaced the gasketson cab an manifold and pluged the vacume ports on the manafold and cab. I wanted to know whearelse to look that can cause that problem?
Expert:  Mike S. replied 1 year ago.

Anything that could cause a too lean fuel condition, such as a vacuum leak or the vacuum too low as in the case of a high performance/ high lift camshaft or late ignition timing.

Customer: replied 1 year ago.
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Expert:  Mike S. replied 1 year ago.

Can you tell me what the intake manifold vacuum is at idle?