Oil pressure (lack there of)

[jph0913]

I finally got my m38a1 running again after sitting for about a year, but I noticed that I was getting very low oil pressure at idle(the needle just barley moves off of the peg). I took the oil pump apart to see if there were any foreign objects in there, but it looked fine. I primed it and fired it up, but still at idle it has around 1 lbs of pressure, adn at around 2k RPMs it has about 10 lbs. As a side note, the last time it ran, the oil pressure at idle was around 8 to 10 lbs. The motor has been rebuilt and not used very much since I installed it. Any ideas on whats causing this problem? Oh its the F-head.

[javracer]

I don't know much about the F-head but, the great Late Smokey Yunick preached that, "10 pounds per 1000 rpm is good for any gasoline engine." I guess I missed alot buying a early CJ5 with a Chevy siezed 305 between the rails. :(

[jpflat2a]

Can you trust your gauge ? electrical or mechanical ? I would think at the readings you are getting, you should be hearing valve train clatter or other noises.
That being said, you need to look at a lot of things.
Oil pickup in pan, bolts loose or no gasket ?
Wow, the list can go on from there !
Good diagnostics needed here :shock:

[jph0913]

There is chatter and other knocking noises coming from the motor. The gague is fairly new, but by hearing the motor knock it kinda rules out the gauge. I'll drop the pan and take a peek. Anything else I should look at while i have the pan off?

[budtoh3zo]

can a dirty oil filter have anything to do with it? Just a idea

[jph0913]

The motor has 0 miles on it and maybe an hours worth of running. I did not do the rebuild, a local performance shop did the work. The only thing that chagned recently is the placement of the motor. I had to lower it, and shift it to the right. i did check the oil level, and it looked about a quarter quart low, but i never filled it all the way up.

[w3srl]

My flattie had a really tired L-134 in it when I bought it, and it too had really low oil pressure. IIRC, a new oil pump only cost about 40 bux and it brought the pressure up to about 20lbs at idle, and 50lbs or so at higher RPMS. Not a substitute for a new engine I know, but it may help you prolong the inevitable for quite awhile!

Just a thought; Have you checked the pressure with another guage? How about the oil itself. Have you changed it lately and made sure you have 30 or 40 weight in it? Prior owners have a habit of doing strange things to vehicles. For instance, my jeep had ATF in the T-90 so it just about ate itself to bits... :roll:

<EDIT>

Disregard my comments on the tired engine. Your last post came in before I could type in my response. :oops:

<END EDIT>

[jph0913]

I spoke with a friend of mine, and he suggested that I replace the oil pump to go with the rebuild, which does make some sence.

[Brian45]

I personally think that I would tow it over to the rebuilders and have them check it out, just a thought

[Ducks-Bass-n-Jeeps]

I just rebuilt my F-head. And the idiot light comes on at idle when the engine is at operating temperature.

:hurrican:

[jph0913]

I checked the oil pick up and it is tight and a gasket is there. But when I drailed the oil, there was a vey strong gas smell. Fresh oil and tried again, and the pressure is still low, and some knocking noises from the motor. Im running Castrol 10W30, is that too thin of an oil? Should I be running something thicker liek 10w40 or maybe 20w50?

[jpflat2a]

Where I live I use straight 30wt. This may not be suitable for colder climates. The gas odor is interesting; flooded from trying to start the engine, or maybe a fuel pump that might be leaking internally and pumping fuel into the crankcase. There are still so many possibilities, but only a few more that you would be able to check. As was suggested before, maybe a trip back to the rebuilders. If any of the machined tolerances are out of spec, there goes the pressure no matter what you do.

[timgr]

jph, I've done a little reading about the 134 lately. Maybe I can suggest something that could be of help.

- there are a few pipe plugs that have to be put back in the oil passages when the engine is rebuilt. They are shown here: http://www.film.queensu.ca/CJ3B/Engine/Rebuild2.html

- this page has some tips about oil pressure: http://www.film.queensu.ca/CJ3B/Tech/OilPressure.html Note that the oil pressure can be adjusted by changing the releif valve pressure.

- seems to me that a rebuilt engine deserves a new oil pump.

- I understand that the L and F 134 only have one cam bearing next to the timing gear, and that the other two bearing ride in the block. I'd think that this could be a problem in an old engine, and remember reading something about this problem long ago.

- usually gas in the oil comes from a fuel pump leaking into the block.

- nothing against the group here, but I'd think that the guys over on the G (g503.com) would be another good source of 134 info.

hth 8) Tim

[Glenn]

I guess you're saying the engine sounded fine, didn't knock during the original hour or so you ran it a year ago? And the oil pressure was good? When rebuilt was the block cleaned? Could be the pump, but it also sounds like something got plugged, stopped up.

[jph0913]

The engine has been flooded several times due to carb problems which have been fixed. The fuel pump is new so i doubt it is leaking. After the motor was rebuilt, it did have a knock, but and the oil pressure was a little low, around 10 to 12 lbs at idle. I dont think that taking the motor back to the guy who rebuilt it is an option b/c any warrenty has expired, and I dont want to pay someone to fix it unless I have to.

Thanks for the link Tim. The two plugs near the crank are plugged, and the freeze plug for the rear cam bore is installed. I'll order the oil pump tomorrow.

[Glenn]

On the front of the block there is an oil jet designed to spray on the timing gears. This makes me wonder if it was left out, or loose? Also, on the earlier engines the orifice was too big and caused the front main bearing (I think it was the main) to starve, so they made a jet with a smaller orifice to fix this. I don't think it caused an overall low pressure problem though. You would have to pull the timing gear cover to check this out.

[jph0913]

Update.. I replaced my oil pump finally, still low oil pressure, and a knock. Any ideas on what the problem could be? Im really at a loss....

[CT]

Change your oil to get any gas out it, and drive it for about an hour. The rings have not set yet. I bet it picks up oil pressure, and if it smokes, it should stop smoking

How much did an engine rebuild cost? Just wondering.

Thanks
Cliff

[jpflat2a]

A tip for the knock
one way to determine which cylinder might be involved would be to run the engine at idle (knocking) and remove 1 plug wire at a time. If it is piston, wrist pin, or rod bearing involved, good chance the noise might disappear on the suspected cylinder when the plug wire is pulled of the plug. This makes the plug not fire and reduces the downstroke pressure on the cylinder involved. If the cylinder stops making noise when the plug wire is removed, you now know which cylinder or rod to look at when you drop the pan. If bearing related, could be the source of your low oil pressure.
The rings seating/ not seating wouldn't have any effect on oil pressure.

[jph0913]

I will have to try that. I know it is coming from either #3 or #4 not sure which. What should I be looking for, the inner workings of a motor are still new to me.

[jpflat2a]

well, just trying to narrow the knock down at this point, which cylinder might it be coming from.
The engine will run rough while the wire is off, but you should also notice a difference between the wire connected and not connected.
Pull them off one at a time and gently reattach them(before you start the engine) hopefully with the engine running they will come off easily.
Don't ground yourself on the Jeep while doing this or you might get ZAPPED!

[jph0913]

CT, I have since changed the oil... I cant really run the motor for any extended period of time. I am right in the middle of the rebuild, no radiator, no pedals, no seat.... It cost me around $600 to have it rebuilt, but im not sure of the quality of the work. The guy didnt tell me that he left off the plug on the back of the cam shaft. I didnt find out that it was not there till after I ran the motor :-( , and leaked oil all over the place. But it has been installed. Will running the motor without the that cap on the backside of the cam hurt it?

[jpflat2a]

it wasn't too good for it
before you go farther, get the cooling system operational and then report back

[jph0913]

thanks Jim, i'll give a try tomorrow night.

[jph0913]

what would be a good resource to use to rebuild the motor? Other than whats on the cj-3b page.

[jph0913]

Problem found... The rod bearings are too small. There is a ton of play on all of the rod bearings... I guess I get to learn how to replace rod bearings.....

[jpflat2a]

time to take a micometer to the shaft and measure it.
Look on the backside of the rod bearings; you should see some numbers indicating what size crank they are for: .020 .030 .040 etc
regardless, time for very accurate measuring and then plastiguage each bearing

[jph0913]

I have .02 bearing in it now... But i have to go get a good micrometer, then order the bearings... Its going to be fun, cause this is all new to me, and i get a new tool :-)

[Glenn]

Glad you found the problem. Guess now you know the quality of the rebuild that was previously done. Bummer.

[CT]

If the shop that did the rebuild did a poor job, I would at least visit with the manager and let him know. Ask him what he intends to do about it?

Probally will say it is an old worn out motor and they can't stand behind thier work. But if I had a business and a customer was not happy, I would try to do the right thing.


Might ask, and see what happens. 600.00 is is alot of money for a poor job.

[budtoh3zo]

I agree with ct bring it in the only thing they can say is no for a partial refund or to fix it

[jph0913]

hind sight is always 20/20.... I should have built it myself. Im going to call that guy on monday, but i doubt that i will get any money back.

[CT]

John
If the manager of the repair shop is a good businessman, he will do the right thing.

When you visit with the shop, don’t feel the repair shop is doing you a favor for fixing something they screwed up. You paid hard earned money for a service they did not deliver. You are entitled to having it done right. An engine with a knock is not something you can jump in and drive for a 30-mile ride on a Sunday afternoon. They cheated you for not doing it right the first time. IN other words you are out $600.00 for a repair that did you no good.

Please keep us posted on your predicament. We are on your side!

Regards
Cliff

[xz3ltt]

If your still getting a gas smell in the oil, or it poor out like water when you drain the oil, its time to check the fuel pump as you may have a bad diaphram and are leaking gas into the oil.

On my "L" head, I just took apart the oil pickup in the pan and have returned oil pressure. Assume you don't have this issue due to the engine being rebuilt.

P.S. the "W" in oil rating means "Winter". the first set of numbers is only for the viscosity (ability to flow) at a certain low temperature.

[jph0913]

Final update. The rod bears should have been .050 thick, but .020 was installed. I took the crank to the guy who built the motor, and he realized what was done. He mic'd the crank and it needed to be turned (one of the rod bearings was out of round), and he ordered new bearings. I installed the new bearings and finished the motor tonight. Fired it up and no more ticking, there is plenty of oil pressure. I forgot to install the oil pressure gauge line to the motor... oops. But it ran great. Thanks guys for all the help and advise.

[budtoh3zo]

Good to hear u got her running

[w3srl]

Final update. The rod bears should have been .050 thick, but .020 was installed.

Man, what machine shop was that? Let us know please, so we can avoid it like the plague!

I know that a lot of guys areintimidated by the idea of rebuilding an engine themselves, but honestly if you can read the manual and have some common sense it really isn't all that hard. That and you get to keep that SEG forever and use it everytime you fire 'er over. ;)