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View Full Version : Fuel Pump Help needed


steve.barnett71
04-16-2018, 09:56 AM
Just picked up a 1960 M38A1. It is very solid with no rust. I bought it in non running condition. I am starting to dig into the obvious things to see what it will take to get it up and running.

It looks like the previous owner may have intended to install an electric fuel pump. The main fuel line routes directly to the carb and does not attach to the fuel pump. Also, from my very little knowledge of these pumps it appears to me that the vacuum and pcv lines are hook up to the wrong part of the pump.

I am attaching a picture, any guidance on the proper connections would be great!
LarrBeard
04-16-2018, 10:23 AM
I don't think this is an M38A1 fuel pump. See the attached image of an original M38A1 pump.

Someone swapped something on your vehicle....
gmwillys
04-16-2018, 10:31 AM
The fuel pump on you A1 will work, but as you already figured, the vacuum lines are attached to the fuel portion of the pump. The diagram that LarrBeard provided will get you heading in the right direction.

Welcome Mr. Barnett.
steve.barnett71
04-16-2018, 11:00 AM
Thanks for the replies guys. Yes, it is an aftermarket pump. Since I no longer need the vacuum can I go to a single action pump? How would the PCV routing work out then?
gmwillys
04-16-2018, 12:56 PM
The quick and dirty answer is, yes you do need the PCV hooked to a vacuum source.

http://www.cj3a.info/tech/pcv.html

Willys employed a closed PCV system because of the lower speeds that are typically traveled in a Jeep. The lower speeds would not allow for a traditional draft style crankcase breather, (of that era) to be utilized. The PCV valve that Willys uses does not close off completely, except for if a backfire were to happen. With that being said, do you have to have the vacuum source at the fuel pump? No, if you tap into the vent line to the air cleaner, then that should give you enough vacuum to keep the PCV working properly. The extra vacuum created by the fuel pump was used mainly to run the windshield wipers. To have the fording capability, it was easier to have the PCV hook into the vent line, to where it could be controlled via a shut off valve, then to plumb it into the intake manifold, as a civilian model was. The theory is that if you shut down the flow of vacuum via the shut off valve, the system would then pressurize itself with the PCV system, keeping water out of the engine.