Oil Pressure Issues

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Apr 6, 2005
I could really use some help with an oil pressure mystery!

I changed the oil on my 1970 FJ40 (original F motor). When I started back up there was no oil pressure. Removed oil pan to inspect pump...everything looked good, nothing clogging screen, parts moved freely, no broken parts (gears etc.)

After putting everything back together and filled it back up (all 8 quarts) and removed the distributor. Ran the pump with a drill and it pumped up to 50lbs when I put the distributor back in ran fine with great pressure.

Once it sat overnight I started back up and again no oil pressure. Did the drill trick again with the same result. Pressure not a problem as long as it does not sit overnight.

Any Idea whay this is happening???
How long are you leaving it running?

Change your oil filter. Sounds like the backflow valve on it is not working and allowing all the oil back in the pan and causing the oil pump to have to prime all over again.
Left running for 10-15 minutes and took for a ride around the block.

I will give it a shot!!


I watch my oil pressure mechanical gauge like a hawk after a 2F rebuild, especially @ startup.
The distributor to oil pump tang has a tapered shoulder and it could get "unseated" with startup torque where the dizzy lockdown wasn't quite tight enough - mine did.
It made a startup noise actually, but just needed to be reseated and secured.
You might want to check that.
good luck.
Back to the drawing board.

I am gonna replace the oil pump and see what happens.........unless there are some other Ideas out there???

are you reading the pressure from the same place when you prime it and when you start it?

hows the drive on the distrib? sounds like it wasnt seated

I put mine a few degrees off the slot then turn the engine by the fanbelt with the other hand while holding down slightly on the distrib cap---that way I can feel it snick into place and drop a tad

if you spin the pump with a drill and get press it sounds all right
The distributor shaft is seated as it should be. When put back together, it runs the pump but will only pump up pressure after primed. It seems like it slowly leaks oil out of the system back into the pan and loses its prime.

I am using the same oil pressure guage while pumped with the drill and when the engine is running.

Does anyone have a good idea how the bypass valve on the driver's side of the engine works?? I am sure it is pretty simple but I don't want to mess with it unless it could be causing the problem.

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