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Old 09-24-2020, 10:52 AM   #1
chuckwp
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Default No Oil Pressure While Cranking

So, I am working on a 38 Flat Head that has not run in quite a while.
I got to the point of putting oil in it and cranking it to see if I have oil pressure.
This is not my car but, a project car I am working on. The history is sketchy but, I do know the engine has run in the past couple years. It has other things before it can drive but, for now I am just trying to see if it will run.
No oil pressure is evident in that there is no oil coming through the feed hose to the filter. The hose is not blocked or clogged. I have not cranked it long-less that 30 seconds.
Is it normal to be slow on building pressure or, do I have a cavitation problem?
The oil is VR1 20w50 so, it should have good cold pressure. The engine does have compression. I left the plugs out to increases cranking speed to help the pump prime. It is a 12 volt system.
If it is normal to have low cranking pressure, I will try a longer crank. Maybe it just has to run to get the pump to start moving oil. Suggestions?
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Old 09-24-2020, 11:58 AM   #2
deuce_roadster
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Default Re: No Oil Pressure While Cranking

Do you have a mechanical gauge on it? If you are cranking it with the switch in the off position the stock gauge wouldn't be in play. I would try it again, I don't think those stock oil filters get a lot of oil when just cranking it..
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Old 09-24-2020, 12:15 PM   #3
chuckwp
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Default Re: No Oil Pressure While Cranking

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Originally Posted by deuce_roadster View Post
Do you have a mechanical gauge on it? If you are cranking it with the switch in the off position the stock gauge wouldn't be in play. I would try it again, I don't think those stock oil filters get a lot of oil when just cranking it..
Mechanical gauge. Again no oil coming out of the hose that goes to the filter housing which it connected to the one and only oil pressure port on the back of the engine. The gauge and the filter supply hose attach at the same point so, if no oil to hose, no oil to gauge.
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Old 09-24-2020, 01:07 PM   #4
JSeery
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Default Re: No Oil Pressure While Cranking

Is this a by-pass filter?
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Old 09-24-2020, 01:23 PM   #5
marko39
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Default Re: No Oil Pressure While Cranking

On my 39 engine,I had to crank longer than 30 seconds to get pressure. Crank for 10 secs. And give it a rest for a few mins. Eventually I got 25 psi. but mine is 6 volt and was using a 12 volt batt. Just make sure your starter doesn't get too hot.
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Old 09-24-2020, 01:27 PM   #6
chuckwp
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Default Re: No Oil Pressure While Cranking

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Is this a by-pass filter?
Yes. I had an earlier post about the drain back holes in the tube and it was determined this was an early design with one return hole in the center tube and no restriction in the feed line.
With the filter out of the housing and cranking the engine there is no oil coming out of the line that feeds into the filter housing and no pressure on the gauge which is mechanical and t'd into the same port as the feed line for the filter.
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Old 09-24-2020, 02:23 PM   #7
19Fordy
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Default Re: No Oil Pressure While Cranking

I wouldn't be surprised if you don't get a pressure reading until engine fires up.
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Old 09-24-2020, 02:55 PM   #8
rockfla
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Default Re: No Oil Pressure While Cranking

"IF" its been sitting a long time, I'm with 19Forty and it "may" take a few before the oil pump will pick-up "prime".


Question for the higher "pay grade" than me......Can you "reverse" prime the oil pump??? By that I mean pull the fitting at the back of the block and start pouring fresh oil down the hole at the back of the block, letting it soak in and prime it with oil from that direction???? Just a thought???
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Old 09-24-2020, 03:23 PM   #9
alanwoodieman
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Default Re: No Oil Pressure While Cranking

you did pull all of the spark plugs? did you put oil in the spark plug holes? use a 12 volt battery to turn it over the engine, worst case scenerio is to pull the oil filter line coming off the boss at the back of the engine and pour oil into the pump to prime it. I just did a 38 that has been sitting for over 30 years!
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Old 09-24-2020, 05:09 PM   #10
chuckwp
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Default Re: No Oil Pressure While Cranking

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Originally Posted by alanwoodieman View Post
you did pull all of the spark plugs? did you put oil in the spark plug holes? use a 12 volt battery to turn it over the engine, worst case scenerio is to pull the oil filter line coming off the boss at the back of the engine and pour oil into the pump to prime it. I just did a 38 that has been sitting for over 30 years!
Yes to oil in the cylinders. It is a 12 volt system.
Gong to go with the try and start it with a close eye on the oil pressure gauge.
If that fails can try pouring oil into the oil port.
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Old 09-24-2020, 07:29 PM   #11
flatjack9
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Default Re: No Oil Pressure While Cranking

Some times it does take a while to get pressure. When it primes you should easily get 20 - 40 psi. Keep trying.
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