Renwaltoys

Please excuse my amateur attempt to explain this situation. Had a rebuilt 40083 pump installed on my 65 L76 by a very experienced Corvette mechanic whom I have a lot of faith in. The pump caused fuel to spill out of various openings on the carburetor. When pressure gauge put on fuel line is registered 20 lbs. Sent back the pump back to the rebuilders (a well known firm that has been around for years) and they said it tested normal but would rebuild it again before returning it. Has anyone had a similar experience? I would like to have the correct pump on the car but the experience has left me worrying about a fire risk. Again please forgive me if this sounds like a stupid question but my mechanic seems to be at a loss as to how this could happen. Thanks for sharing your experiences, Duke

Frankie the Fink

Some of the kits have incorrect components like diaphragms and springs that produce higher pressure which will drive the needle valves in the carb off their seats....

Mechanical fuel pumps are elegantly simple...an arm that operates off the camshaft, against spring pressure. The arm cycles a rubber diaphragm up and down and individual valves on the suction and pressure side meter fuel flow - that's about it. Very little to go wrong UNLESS sloppy parts are used during an overhaul.

About 5-1/2 lbs is all you want. 20 lbs is outrageously high (and dangerous)... If you saw 20 lbs with your own eyes then don't believe what the rebuilder says - they are covering their own ***.

Now you might be in for an oil change if that fireman's hose pump spewed enough gas down your engine to wash down the cylinder walls...

Powershift

I believe the Chevrolet Service Manuals have a section on flow and pressure testing the fuel pump when just cranking the car. I would do this before the next install on your car. In my 1967 service manual it is : 6M11-ENGINE FUEL

Although not necessary, removing the spark plugs during the test will allow the engine to crank/spin much easier.

FWIW.

Larry

65tripleblack

Read my article in the Summer 2010 Restorer about how to rebuild the 40083 fuel pump.

Pressure for the hi-perf pumps should be between 6.5 and 7.5 psig @ idle. It sounds like the pump diaphragm free height was not set properly if a new diaphragm was installed on the old pump rod, or the wrong assembly was used.

If you want it done right, have Hal do it if you can't:

http://www.classicpreservation.com/f...ebuilding.html

SW Vette

Sorry to be so blunt, but I would first locate a better mechanic.

Renwaltoys

Fuel pump came back from the rebuilders after they had done it over. Installed and works fine. Thanks for all your help, Duke

leif.anderson93

All in one day?? Now, that's customer service. Seriously, glad you got her all fixed up

Renwaltoys

Thank you very much!

Frankie the Fink

It got done in one day because they knew they dropped the ball and had major liability in a dangerous situation on a fresh product. Good for you; glad its straightened out...

I learned something too....I didn't know you could even get 20 lbs pressure out of a GM mechanical pump...

Renwaltoys

Thanks so much for your kind thoughts. I think you are right in your analysis of the situation. I think they knew they screwed up. Again thanks for your concern, Duke