Priming oil pump and oil pressure

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schil123
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Priming oil pump and oil pressure

Post by schil123 » Mon Dec 03, 2018 4:52 am

Hello all,

I recently replaced, with new parts, the jugs, pistons and rod bearings due to low compression. Reinstalled the engine in the mule. I now have good spark, fuel and compression. I am nervous though, because I am not getting any oil from the oil feed line to the governor. Which makes me believe I have NO oil pressure. I am running 20w 50 weight oil. Might be to thick for winter temps here in Michigan? I have always run straight 30 weight in other mules and never had a issue. I have turned it over multiple times with electric start and feel it should be enough to produce oil pressure. Prior to the rebuild I had a nice stream of oil peeing out of the governor line.

Is there a way to back feed the oil pump once the engine is mounted in the mule? Maybe the pump lost its prime. Should I run thinner oil in the winter months? I do not want to let the motor run with out knowing that oil is circulating.

Any thoughts or ideas would be helpful.

Thank you!

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Re: Priming oil pump and oil pressure

Post by muleman7 » Mon Dec 03, 2018 9:14 am

Did you fill the oil canister before installing? There is a pipe plug on the bottom of the canister and it could be used to attach a fitting that would allow you to pressurize the system.

I use Shell's Rotella T1 30 wt but live in the south. Up North you could use 10wt for the winter

If able to tow the mule put it in 2nd gear high and pull it for 5 min. Then loosen your oil line to the governor and check flow with engine running. Or remove and check while cranking the engine.

I have no info about single or multi viscosity oil as to engine life. With the modern oils available I am unable to suggest your making a mistake using either. Open to other opinions. You have an air cooled engine using a full flow oil pump and filter.

The oil stick has Mil-L-2104 stamped on it and the following sheet shows Rotella T1 meets that standard.

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Re: Priming oil pump and oil pressure

Post by Chuck W. » Mon Dec 03, 2018 10:30 am

In my experience, if you had the engine upside down, the oil will drain out of the oil pump and it will loose it's prime. I had one engine that I could not get the pump to pick up no matter what I tried. finally had to take the pump cover off and pack with light grease, worked like a charm. Every engine I work on now, I hand-pack the oil pump.
As Charles said, make sure the filter can is full of oil, and make sure you put 2-1/2 qts of oil in the engine, don't use the dip stick. Pump has to pull the oil from the pan, into the filter, through the external lines and finally to the pump, a long way and it can use all the help it can get!
Also, no oil to the hydraulic lifters means the engine may not even start, the towing suggestion may be the best option to build pressure.
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Re: Priming oil pump and oil pressure

Post by W. Winget » Mon Dec 03, 2018 11:35 am

10wt in Winter is typically the standard mil weight for oil, I have never seen a lower spec. I did see 0-20wt "Zero" to twenty weight in Walmart today (how can it have zero viscosity is beyond me)

Used Vaseline to prime an old Buick motor oil pump once that did not have pump pressure, it worked like a charm.

Most of the guys over on SS use Shell Rotella in their big mil vehicles, I've used it in all my vehicles as a standard now. I used to use Penzoil, but after a few teardowns found it to be gumming up things. Most of the Rotellas are branded for Turbo Diesel use which is a lot harder stuff to keep lubed than a standard gas engine.
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Re: Priming oil pump and oil pressure

Post by schil123 » Mon Dec 03, 2018 4:15 pm

Thank you for your suggestions guys!

I may try thinner weight oil and pressurize the system. I really do not want to pull the engine again and pack it full of vasoline. I would think that cranking it over with the starter would be enough to start pumping. I suppose I could also remove the filter housing and pump oil into the oil pump that way.

I have never heard of not using the dip stick but instead 2 1/2 quarts. It also surprises me that there is not a "pickup" tube in the filter canister.

Thanks again. I will update soon.


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Re: Priming oil pump and oil pressure

Post by Chuck W. » Mon Dec 03, 2018 7:01 pm

I have never heard of not using the dip stick but instead 2 1/2 quarts.
As you probably know by now, it is extremely difficult to get an accurate oil level measurement with the dip stick arrangement on the AO-42 engine. I don't worry about measuring the oil level, I just make sure the right volume of oil is in the pan. Actually, I think the LO says 2-1/8 qts.
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Re: Priming oil pump and oil pressure

Post by muleman7 » Mon Dec 03, 2018 8:12 pm

The Oil Line from the block to the Oil filter connection on top of the bell housing could be opened and you might get enough oil into the line and to the pump to start the siphon. This line is not easy to disconnect having only 1 end loose.

I will need to check an engine to determine if the top line is to the pickup tube in the oil pan or the pump. The brass 90 degree fitting accesses the oil filter assy. If I had to guess the circular line is the pressure side since it connects closer to the oil pressure relief valve.

The 2 lines are not easy to install with the shrouds off. Tight going with a 5/8" open end wrench. You might be able to remove both lines with the intake tube removed. That will require you to remove shrouding to get it off the head.

Again if you need to pressurize the system pull the pipe plug from the filter canister and buy fittings to adapt to a 1/8"-1/4" rubber hose and use an oil squirt can. Refill the canister with oil and if you use a 2'-3' hose you could fill it with oil and use your air compressor to force it into the housing and through the engine.

The big job you don't want is pulling the engine, clutch, flywheel, bell housing, mag, shrouding just to get to the oil pump.

Tow it first. Overfill the oil pan just to help the pump pick-up the oil easier then drain to correct level when you build pressure.

The only air gap in the pick-up passage is the o'ring around the pick-up tube at the windage tray/block and the oil tubes from the block to the bell housing and the rubber oil canister seal.

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Re: Priming oil pump and oil pressure

Post by schil123 » Mon Dec 03, 2018 9:31 pm

Just finished up playing around with the mule. I was finally able to get GOOD stream of oil out of the feed line to the governor!! Odd, but once I installed the plugs and started it, the pressure came right up!!! removed the valve covers just to make sure I had oil feeding the lifters etc. which I did!

Now it seems to run good. Kinda wants to hunt as far as the throttle goes. But if I crank up the idle adjustment a bit, it will idle smoothly and rev up nice and evenly. Wants to backfire now and then when it comes down on idle and I rev it back up. I am running the Mag at the correct timing hash marks. V to V as it should be.

Just for kicks and grins, I took a compression test on both cylinders. Both are at 80 psi, so says my Harbor Freight gauge. Now I know it is supposed to be between 110 and 120. I did take a reading last night, before I was able to get the oil pump primed and it read 110. What the hell. How could it drop so much from yesterday to today? Is my gauge malfunctioning? It runs too good and fires to quickly for it to be that low on compression!! Did I damage the rings while trying to get the oil pump primed?

I am running short valves (genset) without cylinder head spacer rings. When I torn down the engine I found it had one mule valve(intake) and one (genset) exhaust. Head the intake valve machined down to match the exhaust valve size.

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Re: Priming oil pump and oil pressure

Post by muleman7 » Tue Dec 04, 2018 8:41 am

Governor Hunting is fixed by adjusting the length of the control rod. I check a running engine by pushing on the lever attached to the throttle cable to a high engine speed 2400-3000 rpms holding it steady and observe the engine speed. If it will not remain steady [hunts] I adjust the control rod until the governor holds steady and will not hunt. When the gov throttle arm is pulled back against the low speed screw on the gov the carb low speed screw should be pulled tight against the carb stop pin.

Carb final adjustment:
1-Let engine run until it reaches operating temp 5 min Manual says 30 min.
2-Adjust the idle to as low as the engine will run 400-500 rpms.
3-Adjust the air fuel mixture screw for highest rpm. I found about 3/4 turn from closed is about right.
4-Adust engine low rpm to about 900.
5-Check or adjust air fuel mixture screw for highest rpms.
6-Reset idle if necessary.

The Manual states 900 low rpm and 3850 high rpm no load.

Caution:

I check the position of the governor throttle arm when the foot pedal is fully depressed. I do not want the throttle pedal able to apply enough pressure on the high speed set screw to brake the mount. The A5 added a throttle pedal stop using an elevator bolt and I use this to set the high speed so the arm on the gov can not put pressure on the high speed screw.

If I do not have this on the foot basket I make sure the high speed screw is not touching the control arm when the gas pedal is fully depressed.

I convert the 2AO42 genset engines to use in mules. I read about 145 psi compression on a new engine after initial run in it is 6.9 to 1 compression.

The mule 6.4 to 1 compression with the longer valves and copper head spacer new should be about 125 psi.

I do not believe you damaged the rings. If you used mule rings both compression rings are chrome plated. If you bought pistons with rings on them they were more likely genset pistons rings where the top is chrome and the 2nd is cast.

Put some time on the engine to allow the rings to fully seat then check compression.
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Re: Priming oil pump and oil pressure UPDATE

Post by schil123 » Wed Dec 05, 2018 4:41 pm

Just a brief update on last nights work.......

Contacted John Emery. Because that is who I bought the piston and jugs from. Explained to him my Compression issue. He quickly pointed out that I was not taking the compression correctly! I had the throttle completely closed when taking the compression and that would create a vacuum. He was correct because when I opened up the throttle to fully, the compression was right at 110 psi again! It never crossed my mind. I then decided to do some fine adjustments, as Muleman suggested. Seems to be running great with his instructions. I'd like to get the RPMs down. By the sound of the engine, it seems high. Unfortunately I blew out my timing gun this past summer hooking it up too my Pinzgauer, which is 24 volts!!

Thank you everyone for your suggestions!

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Re: Priming oil pump and oil pressure

Post by W. Winget » Thu Dec 06, 2018 5:24 am

"Unfortunately I blew out my timing gun this past summer hooking it up too my Pinzgauer, which is 24 volts!!"

Buy another 12 volt timing light, but hook it only to the grounded battery terminals (+/-) and you will only have 12V out of the Pinz (or any 24v vehicle) next time. :D
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Re: Priming oil pump and oil pressure

Post by muleman7 » Thu Dec 06, 2018 12:47 pm

This is one way [about the easiest place] to install an Oil Pressure Gauge this pic is for a Mechanical gauge or you could install an electric sensor in the same place.

Not the best thing to add to your mule as a mechanical gauge exposes ripping the line loose at the filter housing when traveling through thick underbrush.

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Re: Priming oil pump and oil pressure

Post by schil123 » Mon Dec 10, 2018 3:12 pm

@ muleman7

Thank you for your suggestions muleman! I have good oil pressure. The mule is running good.

However I cannot seem to get the throttle linkage from carb to governor just right, or the correct setting for the governor stops. Also were should the throttle on the carb rest when not running. Should it be almost wide open and then once it is running should the governor push it closed to the high/low adjustment stop?

Thank you

Chad

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Re: Priming oil pump and oil pressure

Post by muleman7 » Mon Dec 10, 2018 5:11 pm

Chad

With the throttle cable spring between the gov throttle lever arm and the engine block the carb throttle lever screw tip should rest against the carb idle stop pin.
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Re: Priming oil pump and oil pressure

Post by Chuck W. » Mon Dec 10, 2018 6:17 pm

Make sure you have the return spring that goes on the cable behind the front bed support cross member, item #14 below
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