M37 Low Oil Pressure

[M37 Weapons Brush truck]

I have a 1954 M37 with gas engine that was converted to a brush truck for a local fire department. The oil pressure has dropped and I did find gas in the oil. It has an electric fuel pump and I have put a pressure regulator on the line to keep at 4.5 psi. After a change of filter and new 30 wt oil the pressure did the same thing, ran at 40 and then dropped to 2-3 after only 22 miles. Any ideas as to where the gas is entering the system? I saw above that there is a booster pump seal but do not know if this applies to the gas engine models.

 

[dubnali]

Verify that you have the right sending unit. I had the very same problem and found that my truck had the wrong sending unit for the gauge that was in the instrument panel. Had a 120 psi gauge and a 60 psi sending unit. They used both. Replaced the sending unit with a 120 PSI and now have 70+ PSI and drops to about 40 PSI when warm.

 

[welldigger]

I have a 1954 M37 with gas engine that was converted to a brush truck for a local fire department. The oil pressure has dropped and I did find gas in the oil. It has an electric fuel pump and I have put a pressure regulator on the line to keep at 4.5 psi. After a change of filter and new 30 wt oil the pressure did the same thing, ran at 40 and then dropped to 2-3 after only 22 miles. Any ideas as to where the gas is entering the system? I saw above that there is a booster pump seal but do not know if this applies to the gas engine models.

No the booster pump is a diesel only thing. The floats in the carburetor could be sticking open causing fuel to flow into the cylinders. I'm not familiar with the old gasser trucks but I don't imagine there are too many ways for fuel to enter the engine oil.

 

[Floridianson]

I don't know much about the gaser's myself but does it have a mechanical fuel pump that could leak fuel into crankcase?

 

[welldigger]

He said it has an electric fuel pump. However, that doesn't mean the mechanical one was bypassed if it has one.

 

[Jeepsinker]

Either the pump on the block is leaking or the carb just dumping fuel. Swap it out for a multifuel and don't look back.

 

[welldigger]

It would be interesting to squeeze a multifuel into an m37. Kinda a heavy engine for such a small truck.

 

[Jeepsinker]

Oh! I missed that! Maybe one of the Detroits from a goat then...

 

[welldigger]

4bt cummins!

 

[Jeepsinker]

Detroit is a lot lighter than the 4bt.

 

[welldigger]

4bt conversions have been done in m37's many times. As far as parts availability and performance upgrades I'd go cummins and I'm by no means a cummins fanboy.

 

[foxtrk2]

just a thought if oil sending units are correct try what I did on my 63 truck I switched to rottella 15/40 oil pressure is better and stays higher while running

 

[T. Highway]

M37 Weapons Brush truck,

I would go back to square one and figure out how the gas is getting into the crankcase first.

If it is not leaking in from the fuel pump diaphragm, I would immediately look at the float height.

Bert