no oil pressure

[Hollis]

I just did a complete engine rebuild on a T0-20 it has the Z-120 continental Gas engine, however I did replace the oil pump, The engine started right up and ran smooth after complete rebuild, I let it run for about 30 seconds 2 different times and it is showing 0 lbs oil pressure, does anyone know how long the engine should run after start-up before the oil pressure starts? I dont want to hurt the new engine by letting it run too long, i did check the oil pump , I took the plate off the oil pump and looked at the gears all gears looked ok, but there was a little backlash in the to gears inside the oil pump, any Ideas what my cause it not to have no oil pressure? should I just let it run longer? or does the oil pump have to be primed or something? thanks

 

[Hollis]

I meant I did not replace the oil pump or put a kit in it... sorry

 

[Jerry/MT]

You can check for oil flow by removing the fitting from the block that goes to the gauge and seeing if you have oil there. Don"t start the engine, pull the plugs out and crank it with the starter to see if you have oil at the gauge tapping.
Some times there is a leak in the oil pick up tube and the pump won"t prime if that is the case. Check the pickup tube for cracks, damaged seal, loose fit to the pump, etc. Did you put some oil in the pump to help it prime? A little backlash in the gears is probably normal on thses things. It"s a pretty sorry oil pump. If you used assembly lube whe you put the engine back together you won"t damage the engine by running it for a half a minute.

 

[Hollis]

Thanks jerry, oil pickup tubes are fine I have redone the whole(compete rebuild) engine with a complete over haul, all ready disconnected the the fitting at the block, nothin, no pressure with engine running or turning it over with out starting it, pick up tube is fine, even checked the tube to make sure it wasn't clogged

 

[Hollis]

I have only ran the engine for 30 seconds wated 15 min and ran it another 30 seconds

 

[Bob (Aust)]

Does that engine have an oil pressure relief valve? If so, is it stuck open?

 

[Hollis]

how can you tell if it is stuck open? thanks

 

[Grits]

Hollis, you are depending on the gauge for your diagnosis: is there any chance it is bad? If you unscrew the gauge connection from the block, you should get some oil squirting out of the hole if you"ve got pressure and just a bad gauge. Maybe cover the hole or something so it doesn"t make a huge mess. Also, on mine, I hear quite a bit of oil raining down to the pan just after it is shut off. Hope it"s a bad gauge - cheap and easy fix...

Cheers!

 

[Anonymous-0]

Most engines drive the oil pump off of the bottom of the distributor drive .
Pull the dist. out , and make a shaft that will fit down thru the hole , and fit into the oil pump shaft . Hook a drill up to the shaft , and turn it in the direction that the dist. shaft rotates . This should pump oil .
Have you left a soft plug out of a passage ?
Did you install a gasket incorrectly , so as to plug the oil pump oil passage ?
Did you install the spring back into the pressure relief valve correctly ?
Good luck

 

[KSTractor]

The oil pump on the z129 engine runs off the timing gear on the front of the engine and is part of the front main bearing cap. I think the z120 is the same so you will have to take the pan off to get to it try forcing oil into it where the oil pickup tube connects to the pump.

 

[Hollis]

what would be the best way to force the oil into the pick up tube?

 

[Jerry/MT]

If the pick up tube isn"t sucking air the only conclusion I can come to is a stuck open relief valve or a bad pump. The relief valve is on the pump.

 

[Hollis]

how can u tell if it is stuck or not?

 

[Bob (Aust)]

Hollis. Sorry, I can't help you - never seen a Continental engine in a tractor. (All Ferguson tractors in Australia are UK built with Standard engines.)

Jerry is suggesting the oil pressure relief valve is on the oil pump?

But I had a Continental aircraft engine drop to zero oil pressure in flight - twice!! The problem was eventually traced to a few glass beads (from bead blasting at overhaul) in an oil gallery, which stuck the oil pressure relief valve open.

Bob in Oz

 

[gshadel]

To build on the previous posts, your engine should build pressure within about 3-4 seconds. Check your gauge as others have said. Your Z120 oil pump has a built-in pressure relief plunger and spring that is held into the side of the oil pump by a setscrew. Oil pressure pushes against the spring, when it exceeds about 25 psi (for a good spring), the plunger is pushed back far enough that the oil escapes back into the pan, ie. releves pressure.
If that plunger is stuck/cocked back in the open position it will not build pressure. You can pull the set screw on the side of the pump and pull out the spring & plunger to clean & inspect without pulling the pump off the #1 bearing.

Hollis, one of the first things to wear-out on these engines is the marginally sufficient oil pump! That is the first thing I recommend people rebuild if they have low oil pressure. The backlash is a critical measure to check for wear, there is a spec in the manual, I don't recall it off hand, it is rather hard to measure because it ain't much. The gears wear on 2 planes, the gear teeth intermeshing, AND the side faces that rub against the pump case and the face plate. If any of those places are worn, oil will squeeze back through and not build pressure. The face plate has to be installed with a factory gasket, the gasket is the right thickness to build-in the proper clearence between the gears and the pump case. If the gears wear evenly - you will not be able to really eyeball the pump for wear.

As other have mentioned, check your compression fittings on the oil draw tube to make sure they are not sucking air. If you with to try to prime the pump (should not need to do this though), you can try squirting oil down thru the hole where the rocker arm bolts down.
Sounds like yo have spent a fair amount of $$$ to rebuild this engine, spend the extra $45 dollars or so and get the pump rebuild kit off this web site and rebuild the oil pump. It is pretty easy to rebuild, you will get new relief plunger and spring, gears and gasket, and bushings, and drive gear in the kit.

George

 

[Jerry/MT]

With the engine not running, the little piston should be at the top of the bore if it"s not stuck and should move freely back and forth always returning to the spring full extended position.. If it"s stuck or the spring is broken or missing, it will be at or near the bottom. It can be shimmed with washers to increase the spring tension.

 

[Jerry/MT]

I couldn"t have said it better, George! Good to see you post.

 

[Hollis]

Thanks Gearge, that info. is a big help I did check the backlash on the pump gears and the book said it was .007 to .011 and I have 3 or 4 times that think I will just git the rebuild kit and fix it right,no oil pressure was probally why it broke the rings and everything. the oil pressure gauge it had on it when I bought it, was broken, and thats probally the reason it has worn out cyl. sleeves and broke rings on the pistons and it also had dropped a valve seat too, and I bought it put it in my garage and tore it apart, and completely redid everything except the oil pump but I installed a new oil pressure guage and was going to see what kinfd of oil pressure I had and knew it wouldnt be that diificult to drop the pan and remove the oil pump and put a kit in it, so, its minor repair really and i really did use the assembly lube on everything on the bottom end and oiled everything down on the top end I pour the 1st 2 qts of oil over the rocker arm assembly before I put the valve cover back on , it sure ran nice and smooth for the 30 sec, I did run it 2 different times, but for only less than a min. so I know the has to be no excessive wear , then shut it down to investigate....Thanks for such well detailed information, it told me everything I neeeded to know, thanks again George

 

[Hollis]

Thanks to all that replied, yall have been a big
help....

 

[Hollis]

its stuck I just found that out, took out the cotter key removed the relief valve plunger and the little piston in there is stuck all the way in the top if its bore, probally the problem plus al;l kinds of sloppy back lash btwn the oil pump gears. thanks Jerry

 

[2tractors]

Are the rubber o rings inside the pick up tube in good shape? I am the last dummy to install rear main in wrong which blocked oil to top end, am wondering if all were in upside down would that block oil flow?

 

[Hollis]

no its the pump. i primed a second time and it is only showing 10lbs at 1000 rpm, ordering a pump kit i think will do the trick, thanks, no parts in wrong on this one...Thanks

 

[Fred Martin]

I bought an old pig in a poke to-20 one time, put an exhaust and spark plug wires on it and a battery. Checked the oil and put some gas in it opened the settlement bulb valve... and while I was standing along side it, turned on the key, gave it a little gas and pushed the gear shift to start. It came right to life and sounded so good I was amazed...walked around it and when I got to the other side glanced at the oil pressure gage. It said zero! I thought that if it didn't have pressure it would be rattling...took the 6" crescent wrench out of my pocket and whacked it under the dash and the gage jumped up to 30 pounds. It just hadn't been run for so long it was stuck...had to do that several times till it got used to working again. That's been about ten years ago and its just fine. Don't forget to try this! ohfred