My 1990 7.4L is having some idle issues. This has a Rochester Carb.motor.
I started experiencing idle problems last year. Can fire up but anything below 1000 -1500 rpm stalls out.
Had carb rebuilt by a carb expert that does nothing but carbs. Changed out the electronic sensor (Thunderbolt), rotor and cap. Drained all fuel from tank (thinking that fuel was old, new fuel filter. . Still same issue.
I started the motor between each step to see if progress had been made. Nada.
When I pull back slowly from about 1500-2000 RPM no load the motor will start to stall. Pump the throttle lever and can sometimes get back to high RPM. Going back to idle the motor will hiss thru the carb like the butter fly is opening up. Possible starving for fuel??
My next step will be spark plugs (have not run a compression) and possible new coil.
I have a thought that maybe the fuel pump is not delivering at lower RPM. There is a hard line between the fuel pump and carb. so not sure how to install a pressure gauge unless I remove the hard line and build a soft line. No fuel in the sight tube from fuel pump to carb. One thing I did notice was when I pull the sight tube off the carb while running I get a vacuum on the fuel pump end. Is this normal?
Any thoughts would be helpful.
I started experiencing idle problems last year. Can fire up but anything below 1000 -1500 rpm stalls out.
Had carb rebuilt by a carb expert that does nothing but carbs. Changed out the electronic sensor (Thunderbolt), rotor and cap. Drained all fuel from tank (thinking that fuel was old, new fuel filter. . Still same issue.
I started the motor between each step to see if progress had been made. Nada.
When I pull back slowly from about 1500-2000 RPM no load the motor will start to stall. Pump the throttle lever and can sometimes get back to high RPM. Going back to idle the motor will hiss thru the carb like the butter fly is opening up. Possible starving for fuel??
My next step will be spark plugs (have not run a compression) and possible new coil.
I have a thought that maybe the fuel pump is not delivering at lower RPM. There is a hard line between the fuel pump and carb. so not sure how to install a pressure gauge unless I remove the hard line and build a soft line. No fuel in the sight tube from fuel pump to carb. One thing I did notice was when I pull the sight tube off the carb while running I get a vacuum on the fuel pump end. Is this normal?
Any thoughts would be helpful.
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