Every time i used to start my motor the oil pressure would jump to around 40-50 psi. But now withing a weeks time (200 miles or so) it barely gets to 10psi on cold start ups. My question is can the oil pump fail this fast? Or could it be the sending unit going bad. I have no problem replacing the oil pump but if i dont need to then i dont want to. The PO said this motor only had 20,000 miles since being rebuilt but im not 100% thats true.
you need to geta good gauge and check the PSI right of the motor. just pull the sedning unit and screw it in there. that will tell you if you have PSI. in you do then it's in the wiring or gauge. if you dont then you have problems
low PSI is worn bearings but i've never seen them wear that fast. if the oil pump took a dump then it can go that fast. Also if you haven't been keeping up on your mainenance and not changed the oil in a LONG time. when the filter gets pluged it bypasses and can drop PSI but not usually that much
Maybe the tang on the distributor broke off or something... first.. pull the distributor and take a look at it and down the hole to the oil pump. If everything looks ok.. pull the electrical sending unit.. get a mechanical gauge and hook it up in it's place. Using a drill and a priming rod.. run the oil pump for 30 or 40 seconds..
You should be showing plenty of pressure on the mech gauge. If not.. there is some internal engine problem.
The cost of the mechanical gauge and priming rod is better than replacing a blown motor!
The prob is almost certainly either the electrical sending unit, the wiring.. or the electrical gauge though!
Well i put a manual gauge on it and...... no pressure so i ordered the rebuild kit. I just tore the pump apart and im not happy with what i have found. Theres alot of pitting and gouges in the gears and the oil pump housing isnt to pretty eithier. How smooth is the housing suppose to be? Ill post some pics up in a bit.
You should have had at least some pressure with the gears even looking like that. I still think it's some other problem. Get a new oil pump kit.. and put the gears in.. they will be nice and tight.. and you may have to take some sand paper and sand some burs off of the case. I don't think the timing cover case is shot yet.
But.. I'm going to say that there is some other problem in your engine. Perhaps a plugged oil galley or something.. because SOME pressure should result even from chewed up gears. Was the distributor engaging the pump? Did you try spinning it with a primer rod and a drill?
I didn't turn the pump with a drill because i just finally got this thing timed right and didn't want to mess with it again But i will put the pump gear back in and see if it is engaging or not. What would cause the gears to look like this other than bits of metal flying around my engine oil
Taking a closer look at that cover .. it is pretty deeply deeply scratched. I still think that the oil pressure would read some rather than none. Have you cut open the oil filter to see if there are BIG pieces of metal in there?
Yea i did and theres nothing. Im thinking maybe the old gears were just far enough gone to not be able to pull a prime after sitting? because i just changed the oil 3 days ago and it all still looks brand new so it hasn't been circulated. I took some emery cloth to the case and it smoothed out pretty good theres only one good sized gouge that i can feel with my finger nail.
Drop that new pump in and really.. prime it with a priming rod.. if you don't have one rent one. I know there is a guy on Ebay that has em for like $12. If you don't get pressure on the mech gauge after a minute or two its gotta be something else.
Was there a gasket under the oil pump cover?? you need the gasket to maintain the proper clearance for the oil pump gears. Do not use RTV, you must put the proper gasket under the cover.
In the Factory Service Manual there are specifications for the different clearances required. If you do not have a copy I can try and scan/post something from my 76 Factory Serviced manual on the 304 oil pump ?