oil pump - new vs. old

[chrisfa1]

So,

How do I tell if an oil pump is worn out? I picked up a new one but, I can't feel or see a difference.

I guess maybe I jumped he gun thinking the oil pump was the cause of my low pressure.

It's stays at 40 at start up, but drops like crazy as soon as the engine warms up. hangs right around the red, sometimes dropping into the red.

it's a 258 engine. Do I just need thicker oil?

[Gawdzilla.]

Chris, go to autozone and get an aftermarket oil pressure gauge. Hook that up and see what it does before you do anything else.

[Crazy_Jeepman]

Thicker oil may help, but if the gauge is correct it most likely is bearings. Cam, rod or mains.

[tgreese]

Cheaper than Autozone is Summit's generic mechanical oil pressure gauge for $22 or so. That plus shipping should be about $30.

If the pressure is too low at hot idle, you can run straight 50wt plus STP for a while. All you need is 10psi/1000RPM. If it doesn't make bad noises, you can baby it - keep the revs down. IMO 258s shouldn't be run over 4500RPM ever, even in prime shape (long throw, cast crank).

hth :cool: Tim

[ January 19, 2004, 03:48 PM: Message edited by: tgreese ]

[chrisfa1]

Thanks. Yes, it doesn't make any noise at all. The engine really sounds good.

But, I've also already taken out the oil pan. smile.gif So, since the oil pump was only 40 bucks, should I just put it in anyway? Or take it back? What would you do?

[tgreese]

How do you know that the oil pump makes no difference if you haven't installed it? The TSM should have some measurements you can do with a feeler gauge. If you were to rebuild, you'd routinely replace the pump and not worry about it.

[ January 19, 2004, 04:32 PM: Message edited by: tgreese ]

[tgreese]

Chris, if you don't have a TSM (Jeep technical service manual), I'd recommend that you get one. The diagnostic chart for low oil pressure say 1) low oil level, 2) oil excessively thin due to dilution, poor quality or improper grade, 3) oil pressure relief spring weak or sticking, 4) oil pickup tube and screen assembly has restriction or leak, 5) excessive oil pump clearance, or 6) excessive main, rod or camshaft bearing clearance.

Here are the two pages about the oil pump:
http://www.nmr.mgh.harvard.edu/~reese/oilpump1.jpg
http://www.nmr.mgh.harvard.edu/~reese/oilpump2.jpg

The TSM will also tell you how to check and replace the rod and main bearings.

hth :cool: Tim

[chrisfa1]

Thanks,

Hey one more question. Do I have to drain the oil to change out to a mechanical oil pres guage?

[tgreese]

Nope - when you shut the engine off, all of the oil will drain back into the pan. Just remove the oil pressure sending unit and screw in the new fitting.

The stock oil pressure guages are notoriously inaccurate. Good luck - no bad noises is a good sign! :cool: Tim

[ January 20, 2004, 06:51 AM: Message edited by: tgreese ]

[chrisfa1]

Cool Tim, Thanks. You always make me feel better.

Here's what happened yesterday w/ the new oil pump. I went ahead and put it in, then put 10w-50 motor oil in it, and took it for a drive. great pressure, according to the stock gauge. This great reading lasted for about 30 minutes, even on the freeway. Then, in like the last 2 blocks before I got it home, the gauge took a dive all the way to the bottom! I mean below zero.

Still no knocking and the motor runs the best I've ever seen (only had the jeep 6 weeks)

Anyway so, today I'll put in the mech. gauge and hope for the best!

[mtn goat]

good luck, I hope it works out...

[chrisfa1]

Well, I can't get it! I can't seem to get a wrench on the oil sensor to take it off an install a mechanical. But, I found a wire hanging around and reattached it to the top of of the sesor assembly?? Anyway, the guage came back to life so, whatever. I guess I'm happy for now. I'll figure the rest out another time. I just can't seem to get in there. Hopefully I have the right thing!

[Brin M.]

Check the terminal that goes on the sensor. Sometimes the get spead and loose when they sit on the sensor shaft, falling off going over a good bump. Squeeze it back together with a pair of pliers until it gets loose again, or do the sane thing and go with a mechanical gauge.

[tgreese]

The sending unit has a hex shaped area that's between the sending unit body and the threaded end that screws into the block. Use an open-end wrench, 1/2" I would guess.

Here it is in the center of the picture:
http://www.nmr.mgh.harvard.edu/~reese/opsu.jpg

[ January 21, 2004, 08:10 AM: Message edited by: tgreese ]

[Sbonley]

Make sure the oil pickup tube from the pump is in the right place. That is how I killed my 258 motor. The previous oil pressure was not a problem, the sixes do that. The pressure drops at idle (not to zero though) and climbs with rpm. Mine lasted 160,000 miles that way. Then I was replacing gaskets and decided to replace the oil pump. I didn't get the pickup in right. The presure was good on the road but dropped to zero at idle. I kept thinking I would fix it but it ran fine and made no noise, so I never got to it, for a few thousand miles then major rod knock and that rod went through the side of the block.

[chrisfa1]

UGH:

Well, Now I'm frustrated because the truck won't even start now. Just out of nowhere.

Yesterday, I started it up fine. Then a few minutes later tried to start again, and that's when the trouble started. It just cranked and cranked and cranked. I looked under the hood and found one of the two green wires from the coil (i guess) had fallen off. So, I reattached it. And it started.

Then I shut it off and started it at least 3 more times that afternoon. Then last night, nothing but cranking mostly. It fired up once or twice but ran very slow for just a few seconds, then died. This time, there were no detached wires. And I still can't get it going. I hope this is a random coincidence, and not anything related to my dumb oil pump project :(

Maybe I'm not cut out for this!

[ January 21, 2004, 10:50 AM: Message edited by: chrisfa1 ]

[tgreese]

Sudden no-go or no-start has to be fuel or spark. It's easy to check ... ask if you need help.

[chrisfa1]

I do need help, I'm totally new!

I've HEARD before of taking out a spark plug and watching for spark. But, don't know the details or safety involved there.

I do SMELL fuel, I think.

Also, I just noticed that when I crank it, the gas pedal drops to the floor, and stays there even after i release the ignition. Is that normal? Maybe I just never noticed.

Thanks tim.

[tgreese]

Ok, fuel. Look down the carb to see the accelerator pump squirt gas into the venturi. To do this, you'll have to take the top of the air cleaner off, prop the choke plate open with your finger, and then move the throttle open and closed. Just grab the linkage where the throttle cable connects to it and move it over its full range. Do this with the ignition off.

Spark. If you have an extra spark plug, pull one of your plug wires and push it onto the plug, then lay the plug on the engine block where it will be well grounded and where it will stay put and it won't catch anything on fire (don't touch it during the test!). If you need to, hold it in place with a stick or something else well insulated (not pliers or a screwdriver). Key on, crank the engine and look for a fat, blue spark across the electrodes. You can use one of the plugs from the engine if you don't have an extra plug.

Missing spark or fuel? Get back to us.

Sounds like the throttle return spring is broken or came off. The pedal should'nt move on it's own unless you have electronic fuel injection (EFI).

[chrisfa1]

Ok tim, thanks

I'm probably not going to mess with this again until Tuesday or so. So, I'll be posting again then!

[ January 22, 2004, 08:34 PM: Message edited by: chrisfa1 ]