Mep-003 low oil pressure

[DMont]

I just bought it last week. Cleaned all the fuel system up and got the fuel pumps working. Changed the oil and it cranked right up but doesn’t have but 16 to 18 pounds of oil pressure.
I tried a different gauge hoping the gauge was bad but it read exactly the same. It takes a while for the pressure to come up.

Could it be the pressure relief valve or is the oil pump and bearings just wore out? It runs good. Don’t hear any knocking. Where do I go from here?

 

[rickf]

How many hours are on it? And what color is it? Reason I ask the color is to see if it was in the sandbox. If so it may be sandblasted. I have heard of some that came back minus air filters and the engines were worn out due to sand inclusion. Many other horror stories from there. I think maintenance has gone to crap in the later years.

 

[DMont]

It’s got 1216 hours on it. It does have the desert paint on it. The air filter that’s in it looks good but like you say who knows what it’s been through. I’m just really bummed because it’s all there and makes good power and runs great just not much oil pressure. I didn’t give but 400 for it so not a huge loss. I’m just wondering could it be the oil pressure relief valve?

 

[rickf]

How did the oil look that came out? Besides black, any gummy stuff or chunks. Or excessively thin from diesel fuel? Try putting straight 40 weight in it and see if that brings it up. If it does then you are probably looking at bearings.

 

[DMont]

The oil that came out was just real black. It seemed about the right viscosity. I don’t think it had any diesel in it. The oil filter didn’t have the spring in it so I found one that seemed about right that I put in there. I don’t think that’s the problem but I’m wondering now. I started it before I changed the oil to warm it up and it was the same so I don’t think the filter made any difference. I will try some 40 weight when I get to town again. Maybe some STP too? I put 15-40 Rotella in it when I changed it.

 

[rickf]

I would skip the STP, I am not a big fan of oil additives. Modern oils are well equipped with all that is needed. I did a rather large test for a very well off gentleman I maintained a fleet of old vehicles for and we came to the conclusion that the additives did no good at all over the factory oil package and did damage in some of the cases.

The fact that he did this with old and expensive engines was both impressive and scary since I was the guy doing it!! And the one who had to rebuild the damaged engines. None of this was any cost to me, I actually got paid very well and worked out of his mansion.

Note, STP is a fantastic engine assembly lube. But it does make holing onto tools kind of hard and at the end of the day the parts washer is jam packed with all of the tools from the days work.

 

[DMont]

I’ll just do straight 40 weight and see what happens. The oil pressure relief valve wouldn’t be stuck open some way would it?

 

[Ray70]

On that motor I've never seen a bypass valve get stuck, but anything is possible. The problem is that it is located under the flywheel on the back of the engine, not easily accessible. Try the oil 40W first and see what happens. A little usage may free things up if it is stuck, but I think it is unlikely on that motor.
Depending on how you double checked the pressure originally, you may want to adapt a mechanical gage down close to the oil filter adapter, just to rule out a collapsed oil feed line to the gage or clogged fittings etc.

 

[DMont]

That’s what I was going to do is hook a gauge to the low oil pressure shutdown port but I’m going to have to get some fittings to hook it up there. I don’t think anything is stopped up but who knows.
The low oil pressure switch is new so I think whoever had it was having trouble. It runs as soon as it starts without holding the starter on so I’m not even sure the low oil pressure switch is working right.

This is my first mep generator and I’m still figuring it all out. I do know the line that goes to the gauge is open. I’ve cracked it open at the gauge and oil pours out.
Thanks for all the suggestions.
I’m just hoping that there’s something I’m missing here but it’s probably not good. I’m going to get some 40 weight oil and put a load on it and see what happens. I’ve only had a electric heater on it so far.

 

[DMont]

Can you just drop the oil pan without too much trouble on one of these? I’m just wondering is the oil pickup stopped up.

 

[DMont]

Just a FYI on the fuel pumps. Mine were totally gummed up so I took them off and took them apart to clean them.
I couldn’t get the pistons out of them so I used compressed air on the top port to push the pistons out.
I blew a little too hard and shot one piston and spring across my shop like a bullet. I spent the next two hours looking for the spring and finally found it.

Make sure you put a rag or towel over the bottom of the pump to catch them.

 

[rickf]

I keep thinking about the spring you mentioned in the filter. You had good pressure before you added the spring? It has been a while since I had one of these apart but isn't that spring in there to hold the filter seal to the block? If it was not in there then there would not have been any filtering of the oil and that may be your problem.

Circulation of unfiltered oil for a long time took out the bearings and now you seal the filter up and put a little resistance in the oiling system and there goes your line pressure. OR, is it possible to put that spring in wrong and restrict the oil flow? Best to check that out before running it too long and especially before loading it.

 

[DMont]

No it had the same pressure before I changed the oil. I was going to run it some before I changed the oil but didn’t because of the low oil pressure.
As soon as I got it started the first time the oil pressure was the first thing I looked at. I let it run a few minutes tapping on the gauge hoping it was the gauge and then decided to kill it and change the oil.

When I took the filter off it didn’t have the spring or the other thing that goes at the end of the spring. I forget what they call it. I found a spring off an old weed eater trimmer head that fit perfect. It makes the filter protrude probably a half inch past the can. Seemed about right so I put it in there.

The oil pressure didn’t change though after changing the oil. You’re right about it not filtering right the way it was and it may have been that way for a while.

I did read somewhere that a lot of people have had the springs missing in theirs too. I’m headed to town to try to find some 40 weight oil and try that.

 

[Guyfang]

Open up TM 5-6115-585-34.
Turn to page 7-19. (PDF page number 125)
go down to para. 7-13.
Start reading until you hit para 7-14

 

[Ray70]

Removing the "Pan" is not a simple task. You will have to disconnect the motor mounts and a few things and lift it up off the frame to be able to drop the pan and access the pickup screen. Not a real big deal, but not as simple as just unbolting the pan and dropping it down either.