No Oil Pressure. HELP!

[JohnM15]

I just bought this M15-20 flat bed and previous owner told me that it was running a year ago. So I got thing running, but no oil pressure. I removed an oil galley plug and oil squirts out when running. I attempted to remove the oil pump but it must be captive by a clip or something inside the engine. I did remove the non-driven pump gear and it looks OK. Hand turned the engine to make sure the driven oil pump gear turned, OK. I mounted a known good gauge on the oil galley, still no oil pressure. I removed the oil relief valve, cleaned it up and re-installed it (PIA). Still no oil pressure. My next thing to try is what you say I should have done in the first place, Replace the oil...

Is it possible that the oil pump pick-up tube is plugged up?

Before you all faint, I never run the engine more than 10-15 seconds and some oil is making it to the bearings...

Thanks,
John

[PackardV8]

I'm not a Commander expert. However, on any engine where I suspect an oil pressure problem, I remove the distributor, fabricate a driveshaft and turn the oil pump with a variable speed 1/2" drill motor. Using a loyal minion to operate the oil pump on command, you can check every possible orifice and not risk bearing damage.

jack vines

[BobPalma]

I just bought this M15-20 flat bed and previous owner told me that it was running a year ago. So I got thing running, but no oil pressure. I removed an oil galley plug and oil squirts out when running. I attempted to remove the oil pump but it must be captive by a clip or something inside the engine. I did remove the non-driven pump gear and it looks OK. Hand turned the engine to make sure the driven oil pump gear turned, OK. I mounted a known good gauge on the oil galley, still no oil pressure. I removed the oil relief valve, cleaned it up and re-installed it (PIA). Still no oil pressure. My next thing to try is what you say I should have done in the first place, Replace the oil...

Is it possible that the oil pump pick-up tube is plugged up?

Before you all faint, I never run the engine more than 10-15 seconds and some oil is making it to the bearings...

Thanks,
John

John: If the part of your writing I highlighted in red is true, you have oil pressure, period.

Is the engine making any funny noises? Knocking?

If it is relatively quiet and you have oil "squirting out when running" as you report, there is a problem in how the oil pressue is getting reported, not whether or not it is developing oil pressue. BP

[rockne10]

Brake hoses can collapse; so can oil pressure sending hoses; obstruction in the sending line?

[jclary]

If you have taken the oil pump loose, it is possible that you have dumped enough oil out to cause it to lose its prime. Whatever you do...make sure you re-fill the oil pump with oil to prime it after you re-assemble it on the engine. If you do not have a shop manual, stop working on it until you get one.

[JohnM15]

Thanks for all the responses.

The gauge I mounted to the oil galley is connected through a few copper fittings, no rubber hose.

I primed the oil pump by squirting about 10oz into the mechanical dash oil pressure gauge hard line.

I don't believe that oil pumps move much volume and thus it doesn't take much of a restriction decrease to drop the pressure (i.e. worn bearings...). I'm guessing that the pump is pumping but the engine (God forbid) passes more oil that the pump can produce...

I plan to drain the oil and drop the pan next. Check the pickup tube and some rod bearings.

The engine does make more noise than I expect and does not blow smoke (the owner claimed that it blew smoke). No oil pressure, no smoke.

Thanks,
John

[jackb]

before all that, try packing the oil pump full with Vaseline and start it......make sure you are taking your readings from a pipe plug on the oil pump (if there is one), or from a galley plug closest to the pump ....not a bad idea to pull the pan and check all while underneath....GL

[jclary]

One additional note about low oil pressure. Does your engine have an oil filter? If it does, how about checking the brass fitting where it is screwed into the oil gallery. Make sure it has the small restriction hole required for correct "back pressure" to keep the oil pressure up through the system. If it has been replaced with an ordinary fitting, it will increase flow through the filter but dump the pressure.

[JohnM15]

I drained and replaced the old oil with some straight 30 SAE oil. Ar idle the pressure is 20lbs and revving the engine did not increase the pressure. The engine was a lot quieter. After the engine warmed up a bit the pressure dropped to near zero. So I guess the answer is that the bearing are trash, time for a rebuild. My guess is that the original owner must have effed the bearing a year ago when he resurrected this beast from a 30+ year hibernation. I was hoping to rebuild the engine at a later time when I got more comfortable with restoring the whole truck, but I now need to make a decision whether or not to continue fixing the thing up...

Thanks everybody for your help,
John

[ozarkman]

John,
Have you checked the compression?
If not, I would to see if it's good. If it is, then maybe you could get away with just replacing the main and rod bearings. They're not expensive, and if you do it yourself you don't have to pay the machine shop. If you don't mind working on your back, you might be able to replace the bearings without pulling the engine. You can pull a main cap or 2 off and check for scoring, and the same on the rods.
I would do it if the compression was good.

[JohnM15]

I did check the compression. All cylinders are between 70 and 80 pounds. With oil squirt in the cylinders the compression increased maybe 10lbs. Expected a greater increase, maybe some of the exhaust valves are slightly burnt... I thought of just an "in car" bearing swap but might as well do the deed and do it right... I have experience rebuilding engines. The key, from my perspective is to find a good machinist/machine shop to do the work I can't or can't do well (bore cylinders, true block/head, hot tank/clean...).

Thanks,
John

[gordr]

John, before you tear that thing down, get a second opinion. Find another car hobbyist, or even a regular mechanic near you, and have them repeat your oil pressure and compression checks. It's possible the low readings you got are the result of a bad gage, or even faulty technique. I wouldn't expect an engine with low compression due to bad valves to be so uniformly low; some cylinders are nearly always worse than others. And if they were uniformly low due to bad rings, then adding oil should have netted you a much bigger increase. That compression test is unusual enough that it bears repeating by a different instrument in the hands of a different operator.

It'd probably be a good idea to perform a valve adjustment, and re-check the compression afterwards, too. If a previous worker uniformly set all the clearances too tight, that could cause the low compression you are seeing.

Point is, before you commit to something expensive and irreversible, try the cheap and easy things first. You might get lucky, but even if you don't, at least you can be content in knowing that the overhaul really was needed.

[JohnM15]

Gordr,

Good points! You are right about the compression tests. I had to put the thing back together, I was using the gauge on some other application... Also, I was looking at the manual I just received and it indicates that the compression to be in the 105 lb @150 rpm neighborhood, not far from my 70-80 lb range. Any idea what the rpm is operating the starter?

What I probably do is to pull the pan and check several bearings. If they look good I'll continue analysis why the low oil pressure. One of the things I noticed when I disassembled the oil pump was that there was not a gasket between the pump and the block and none between the pump body and the cover. the pump does leak but not much so I thought that it was not an issue for now.

I think the only reason I want to jump to a full rebuild now is that I am concerned of running the engine and doing more damage that I would regret (bearing freeze, throw a rod, damage the crank...)

Thanks,
John

[JohnM15]

Here is the latest scoop. Bought a new compression tester and all cylinders are between 100 and 110 PSI. The spec on the Champion engine is 105 so I suspect the oil burning is from sticking oil rings.

I changed to oil with 30 SAE and got 20lbs on start up but as the engine warmed (so I thought) the pressure dropped to near zero. I have now discovered that the fuel pump was leaking and dumping gasoline into the crankcase. Now the oil pressure is near zero cold so I ordered a new pump...

John

[mbstude]

A Champion 170 6 (which is what an M15 should have) can run for many thousands of miles on 3 PSI of oil pressure. I drove one everyday with the intent to blow it up, and it was still running when I pulled it out for a V8 swap. Tough little engine.