M38A-1 Fuel pump problems

[stinsonb17]

Having trouble with the fuel pump (repro) on my M38A-1. I installed a new fuel pump on my jeep which hasn't been run in 15 years. It cranked easy and ran smooth. Then I switched it off and cranked it again. It ran smooth at idle, but it popped and skipped at a higher RPM and the oil pressure went to zero. I switched it off and checked the oil and found that it was contaminated with gas. Is it a problem with the new fuel pump or what?

 

[armytruck63]

It sure sounds like the pump diaphram is torn or has a hole in it. The fuel pump is still pumping some gas, but not enough to feed the engine at higher RPM's. It is also pumping or leaking gas into the crankcase.

You'll have to replace the fuel pump (again) and change the engine oil and filter.

 

[Bob H]

Check the float in the carb too.

 

[RodUSMC1962]

Get that oil and filter changed asap,gas eats bearings.

 

[820jeep]

Are you putting on a Double pump ( Fuel pump and Vacum pump) or a single pump ( fuel only) ?

 

[stinsonb17]

Thanks for info

Once again I removed the #@&* fuel pump, changed oil, took fuel pump apart, and found the diaphragm was neither holey nor righteous. I have decided to order an original pump that someone smarter than I rebuilt. I ordered a rebuild kit for my original pump and after I redid it, the stupid thing blew air bubbles back in the tank. Once again, I ask you, what did I do wrong? Would any of you believe I was a mechanic for 15 years? (small engine mostly 2 cycle).

 

[armytruck63]

Is the line between the pump and carb blocked? If you unhook the line at the carb and crank, does gas spurt out? Just some thoughts here...

 

[820jeep]

Any news on the fuel pump problem?

 

[Sir Mech]

If it is blowing bubbles back in the fuel tank it sound like you might have gotten the fuel hose's backwards. The out hook to the in and the in to the out or the pump is running backwards some how

 

[Amer-team]

If you have any rubber lines in the fuel line setup, they could be failing and collapsing under pressure, which causes a variety of poor running problems.

Also did you change your oil before you put the new pump on, so that you know it was the new pump and not leftovers from seapage from the old pump?