Visit our Popular Forums

garymcg · 05-11-2012, 08:33

Everyone

After rebuilding my Yanmar 3GM30f we bench tested it yesterday, ran it at 600 rpm and there does not seem to be any oil pressure at all. The oil pump was replaced during the rebuild. No oil is getting to the oil filter or the oil pressure sensor.

Any advice as to where we should start looking?

Thanks again

Gary

Acushla · 06-11-2012, 17:29

These oil pumps are positive displacement pumps, therefore if they are engaged and turning the oil must be going somewhere. Start by ensuring that the drive is properly engaged and the gear wheels are in fact turning. With the oil pressure sensor removed you should be able to turn the engine over with the decompression levers lifted until oil is seen at the sensor and likewise for the filter. Once this is established you know the pump is working. Then look for an open plug in the oilways such as the crank shaft bearings, head gear etc, it has to be going somewhere.

Good luck

Acushla

DeepFrz · 06-11-2012, 19:34

Maybe the sensor itself or the gauge.

foggysail · 09-11-2012, 13:18

I have seen similar problems with new oil pumps in older gas engines. The solution at those times was priming. And of course, Frz's above post could be the problem especially if the wiring was removed during rebuild and not properly reinstalled. Good luck--

garymcg · 12-11-2012, 07:31

OK, here's what we have done.

There is no electrical hooked up (engine is on the bench) so no gauges. With the compression levers flipped and the oil pressure sensor removed, we turn the engine with a large electric drill. No oil appears at the pressure sensor site, and no oil makes it to the filter. It seems that the oil pump is not primed. How do we prime it?

Thanks for you help

Gary

Acushla · 12-11-2012, 13:46

To assist the priming of the pump you can fill the filter as much as is possible before fitting and inject oil into the sensor line until it is filled. Turn the engine by hand both backwards and forwards to get the oil into the gears. When turning backwards you should see the sensor line level go down and vice versa when turning forwards. Turning the engine backwards is the most beneficial as it puts oil through the pump and down the suction pipe to the sump. Once this is established you should be good to go.

Acushla

DeepFrz · 12-11-2012, 14:05

An oil pump should never need priming as it should be submerged in oil.

NoTies · 15-11-2012, 01:27

Sorry DeepFrz but most oil pumps are above the oil level and often need some help for the initial priming

garymcg · 19-11-2012, 08:13

Acushla your suggestions did the trick, pump is primed and we have oil pressure.

Thanks a bunch!

Gary

AERICHP · 19-11-2012, 21:23

Next time pack the gears in the pump with white lithum grease

Cheechako · 19-11-2012, 21:48

Quote:

Originally Posted by NoTies

Sorry DeepFrz but most oil pumps are above the oil level and often need some help for the initial priming

Oil pumps are above the oil level...? huh? you mean with a pickup tube a few inches in the oil right?

AERICHP · 20-11-2012, 07:11

Quote:

Originally Posted by Cheechako

Oil pumps are above the oil level...? huh? you mean with a pickup tube a few inches in the oil right?

No take the pump apart and pack the gear cavity with lithum grade grease o (engine assembly lube),then reassemble it . It will always prime and save you a lot of work