carb troubles

[johnjoan6203]

79 midget, was running great ,then idle droped to around 600
then lost all power, checked /ubbthreads/images/graemlins/confused.gifdaspot oil had none ,i put some in an started it up,still have no power , will not go over 25mph, idle is great and smooth, just no power

 

[Mike H]

Just a guess, there is a rubber diaphragm inside the Zenith carb. Did it tear or crack?

 

[jlaird]

Has to be fuel related I should think, pump ok? Float chanbers clean? Fuel filter clean? Tank vented?

I assume smog gear is long gone. I hope.

 

[capitalcitycars]

When I had the same problem, the culprit was the filter.

 

[Morris]

I am going to put my vote on torn diaphram or vacuum leak.

With fuel starvation, typically the car will die off, then come back to life once the float bowl fills up again.

The symptoms of a torn diaphram are that the car will reach a certain top speed, and not be able to go any faster. You could drive around all day at 25 mph, but that is it. A manifold leak will produce similar symptoms. As the diaphram tear grows or the leak gets bigger, your top speed will drop until you can barely make 10 mph.

You can visually inspect the diaphram by removing the 4 screws that secure the "dome." If the dome on top of the carb is stuck when you remove the screws, gently tap it with your screw driver handle.

If that looks good, fire up the car and spray the carb and manifold down with carb cleaner or WD40. The engine idle will drop if the spray comes in contact with the leak.

If that yeilds inconclusive results, pull the vent line on the right side of the carb that goes into the canister. If your idle changes, the problem could be a clogged canister. Try driving it around with the line unplugged to see what happens.

If that doesn't work, pull your fuel line from the carb and allow it to drain into a coffee can while someone else turns the car over. It should produce a healthy stream of fuel. If it is only a trickle, check your fuel filter by blowing through it. There should only be slight resistance. If the fuel filter is fine, then the problem is probably your fuel pump.

 

[johnjoan6203]

just want to thank you guys , the diaphram was the problem.
again thank you

 

[sparkydave]

[ QUOTE ]

If that looks good, fire up the car and spray the carb and manifold down with carb cleaner or WD40.

[/ QUOTE ]

Glad to hear it was fixed, but as an FYI, carb cleaner DESTROYS the rubber diaphragm, so never spray carb cleaner into a Zenith-Stromberg.