It runs, but oil pressure issue

Wayne64 · Post by **Wayne64** » Fri Dec 12, 2008 11:31 am

The weather has been bad for this old cripple but I did up the distributor yesterday and installed it today. I only pulled one plug and checked the gap as I just wanted to hear it run after my carb rebuild and electric pump change. It fired right up and settled into a fairly decent idle without even timing it yet or adjusting the carbs mixture. I thank everyone so far. I started it without my glasses on and looked at the fuel gauge and saw 30 psi , after a few minutes I saw I was looking at the wrong gauge and the oil pressure gauge showed zero or close to zero. I shut it right down and will have to hook up a mechanical gauge where Charles told me to in another post. My question is I read somewhere in a search that the pump should be primed? Pray tell what is that all about? The only pump I used to prime after it's winter nap was my 47 Indian Chief and that priming was only for the return part of the pump.

Post by **Cal_Gary** » Fri Dec 12, 2008 12:50 pm

An oil pump that hasn't been immersed in oil needs to be primed (to remove the air) in order to move the oil. Some guys use a spare distibutor shaft down the distributor mount attached to a high speed drill to spin the oil pump internals. I've never tried this on mine-some of our M-vendors please weigh in on this one with their expertise....
Gary

Wayne64 · Post by **Wayne64** » Fri Dec 12, 2008 2:14 pm

Gary what you are referring to shouldn't work on the Dodge as the oil pump is geared to the cam. I do what you are referring to, when I do a first start up on SBF or SBC V8s as the distributor has the driven gear and I'm looking to pre fill the oil galleys and get some oil in the hydraulic lifters.

DaveO · Post by **DaveO** » Fri Dec 12, 2008 4:49 pm

I primed the pump on my 230 according to the book, and while the engine was still in the truck. By the time I was done, there might still have been some oil in the pump. It's a messy business.

I prime the pump on the jeep engines (a very similar set-up, and notorious for zero pressure after pump re-installation) with assembly lube. Whenever I have the pump out, I pack the pump intake full o' grease, turn the shaft in the proper direction, then pack in some more. Voila! Nearly instant oil pressure/prime.

I haven't tried it on the Dodge, but I don't see why it wouldn't work.

Good luck to you...

Wayne64 · Post by **Wayne64** » Sat Dec 13, 2008 7:54 am

Breathing easier now. I pulled the sender and added about a 1/2 quart of oil, installed my gauge and fired it up. I'm showing about 40 psi at an idle. Now I question did it need the prime? or is either the sender or gauge bad? Is there a Ohm's test for either? BTW, it started right up at about 15 degrees with the wind chill and got the heater to start putting out BTUs

HingsingM37 · Post by **HingsingM37** » Sat Dec 13, 2008 4:54 pm

Wayne,

How long did you run it for? 40# OP at idle seems a bit high to me. If I recall it should be about 25# at idle and 55-60 at high end with the engine warm. I could be wrong here but thats what I recall reading in my manual.
I have always went with a mechanical oil pressure gauge on my engines. They are simple to install and available in the size to fit the M37 dash. Then you don't have to worry about electrical snafus

Wayne64 · Post by **Wayne64** » Sat Dec 13, 2008 5:35 pm

David, I didn't run it up to fully warm. But after it ran for a short while I had my son watch the gauge while I brought the RPMs up a bit. He said the OP didn't increase. I won't pass judgment yet on maybe a oil pump problem till it gets some run time at full temp and an oil change.

Rich · Post by **Rich** » Sun Dec 14, 2008 9:06 am

Wayne 64
I had a problem with the oil pressure in my truck. It had 30 lbs at idle when I put the truck in gear and moved it just slightly it went to 0. Take it out of gear it went back to30lbs. The trans had nothing to do with it, but I took out the oil pressure sending unit cleaned the inside with break clean blew it out and put alittle oil from my oil can in it and 30 llbs when I drive it up and down my road. This truck had been sitting for over 10 years. All I did was change the oil rebuild the carb and fuel pump Renue the fuel tank, clean and replace fuel lines and rubber vent lines, as wellas the whole brake system.

Rich Szklany

MSeriesRebuild · Post by **MSeriesRebuild** » Sun Dec 14, 2008 10:12 am

Rich wrote:Wayne 64
I had a problem with the oil pressure in my truck. It had 30 lbs at idle when I put the truck in gear and moved it just slightly it went to 0. Take it out of gear it went back to30lbs. The trans had nothing to do with it, but I took out the oil pressure sending unit cleaned the inside with break clean blew it out and put alittle oil from my oil can in it and 30 llbs when I drive it up and down my road. This truck had been sitting for over 10 years. All I did was change the oil rebuild the carb and fuel pump Renue the fuel tank, clean and replace fuel lines and rubber vent lines, as wellas the whole brake system.

Rich Szklany

I'm not clear on what you are saying about your oil pressure reading in the above post. If you are saying it simply stays on 30 PSI all the time, you still have a problem. Generally speaking, oil sending units are not repairable. It would be wise for you to hook up a known good mechanical type gauge at an oil galley port. This should reveal true readings. Once you know the real story on oil pressure, you can replace the original type components with new parts. If you then get comparable readings with readings you got from the mechanical gauge, you can have good faith that you are getting an accurate reading.