Joined: Apr 18, 2005 Posts: 458 Location: Rhode Island
Posted: Fri Jan 22, 2010 6:09 pm Post subject: adjusting fuel pump pressure
Has anyone successfully reduced the output pressure from an M38 fuel pump?
Mine was rebuilt by one of the vendors and runs 7.5 psi out. The carb is spec'd for somewhere 2.5-4 (from memory).
In theory the screws can be loosened and some slack put in the diaphram but has anyone actually done this?
I have some flooding problems which may be vacuum leaks from the manifold to block gasket or may be excess fuel pump pressure.
Joined: Nov 14, 2008 Posts: 91 Location: Minnesota
Posted: Fri Jan 22, 2010 8:31 pm Post subject:
Do you have the "mounting base spacer" between the pump and the block? It is about !/2 inch thick, it lowers the pressure by less action of the diaphram arm on the cam.
Did you rebuild the pump ? The diaphram is supposed to be in the down position when tightening the screws.Someone correct me if I'm wrong. I'll double check. Stick
Yes, if the pump rocker arm is not fully depressed when tightening the body screws the pump pressure will be too high.
Tom,
You should remove the pump and loosen the fuel body screws then fully depress the pump and retighten the screws. That should do it. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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