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I bought a rebuild kit for the mechanical fuel pump on my 61 Olds 98, 394 because it was leaking oil near the bottom of the pump. There was no fuel smell, just oil. I figured it was time for a rebuild. I recently threw the kit in, about 2 months ago if that, and at first, there were zero leaks. But within the past 2 weeks, I noticed oil around that cavity at the bottom of the pump. Anyone know why / how / where oil would leak from a pretty newly rebuilt fuel pump with new seals and valves and rubber? Fuel pump. The cavity behind that steel 3/8 fuel line is where I suspect oil coming out of. Leakage outlined. Suspected leak area?
I don't know how the camshaft is designed on a 1961 Oldsmobile 98, but I know the mechanical fuel pump lever/arm rides on generally an eccentric of the camshaft - the motion of which drives the mechanical fuel pump. Since the camshaft (eccentric) is oiled during normal engine operation I suspect the only manner oil would get to the mechanical fuel pump is via the opening of the mechanical fuel pump where the lever/arm protrudes into the engine & rides on the eccentric. Since I don't know exactly what the innards of the mechanical fuel pump look like (I'm sure it's sealed internally to keep only fuel from entering/exiting):
(1) I'd suspect something faulty in the innards of the fuel pump (I've never rebuilt a mechanical fuel pump); or,
(2) The gasket used to mount the mechanical fuel pump to the engine is defective, or not secured correctly.
If you put a small bottle of UV dye (~$6-7$) in your oil and let the engine run to operating temperature, you'll find the location of the leak in a heartbeat - even Ray Charles could see it. They sell the dye at any automotive parts store along w/ a small UV penlight to visualize the dye.
Make sure the fuel pump isn't pumping fuel into the crankcase.
Hardware as in the mounting bolts for the pump / gasket to engine block? I used blue removable Loctite for that. I did not use Loctite on any other screws on the fuel pump. What's the quickest way to test for fuel in the oil? The oil doesn't smell of gas, but is there a more reliable test?
I'd just keep an eye on the oil level on your dipstick when you drive the car. Loctite on the hardware assembling the pump may help prevent fuel leaks.
A couple of problems I ran into when I rebuilt mine and what I found initially from the first time I had to rebuild it.
Where you see the oil is the location for the internal weep holes to exit in case the oil seal that seals the diaphragm shaft fails. Did you peen the oil seal ring and add a couple of drops of oil to the seal during the rebuild? Was the kit you used a fairly new one that uses ethanol resistant rubber parts? Did you preload the diaphragm when you tightened down the screws?
A couple of problems I ran into when I rebuilt mine and what I found initially from the first time I had to rebuild it.
Where you see the oil is the location for the internal weep holes to exit in case the oil seal that seals the diaphragm shaft fails. Did you peen the oil seal ring and add a couple of drops of oil to the seal during the rebuild? Was the kit you used a fairly new one that uses ethanol resistant rubber parts? Did you preload the diaphragm when you tightened down the screws?
I did not peen the seals over, nor did I add oil to them when assembling. The kit was the ethanol resistant kit and looked pretty darn new. I did preload the diaphragm. But I will have to disassemble I think and peen those oil seal rings. I'll start there I suppose.
Thanks Art
I was in a rush this morning and forgot to add what I had found with mine was one of the valves had popped out and that oil seal popped out too.
Here's a link for a rebuild that's similar to your's but has the extra pump feature. He goes over the details pretty well and shows how to do the preload just in case you had any doubts about how you did it.
Don't feel bad about having to do it over, mine is leaking again too.
Thanks for that Art. I found one of the valves maybe not seated all the way. I replaced one because I did have a spare. Made sure to seat them nice and tight. Used Loctite on the hardware as well. Started her up and let her run, no leaks so far. I will go back and verify a bit later after my hi temp gasket muck has a chance to cure on the pump to block surface
June 17th, 2024, 02:22 PM
