M38A1 fuel pump vacuum pressure

[WWP]

Is there a spec. for adequate vacuum pressure to effectively run NOS wiper motors from a factory rebuilt M38A1 fuel pump?

Thank you in advance!
Wally
Minnesota

[wesk]

In TM 9-8014 page page 144 all the fuel system specs for the M38A1. Just about all systems on MV's have theses listed in their operator's handbook.



[image]https://www.willysmjeeps.com/app.php/ga ... 619/medium[/image]

[WWP]

Wes,

Thank you!

We have 12 in of vacuum at idle (approx. at 500 rpm). With the pump disconnected from the engine vacuum. With engine vacuum line connected to pump, and measuring gauge at the wiper side control valve on the windshield, we have 18 to 20 inches of vacuum at idle.

Wipers were tested on my 3A and worked perfectly.

Suspected issue is insufficient flow, as it takes a period time of gauge to build vacuum. About 5 seconds to build vacuum.

Quite the conundrum.

Again, thank you in advance.

Wally
Minnesota

[wesk]

As a rule vacuum readings are lower at higher RPM's. Are you following the full testing parameters to include both 200 and 1200 RPM using a tach?