Fuel pump oil weeping

[Jeff S.]

My fuel pump (NORS 4657) collects a several drops of oil after an engine run. I can't seem to locate the source by cleaning & watching, but I do find oil in the cavities of the top casting adjacent the attaching screw holes. If you look closely at the picture below, you can see motor oil in the cavity closest to the engine, front side. This picture was taken after 20 minutes of driving from a 'clean' condition. The aft cavity closest to the engine also has oil, but this does not show up in the photo.



Using a '63 shop manual for troubleshooting, it lists the pump oil seal, the plate/or pump gasket, or a hole in the diaphram as possible defects. I'd like to hope it is the gasket(s) and that the fan is blowing it around. Has anyone experieced this? Wondering if this is something that can be pushed off until fall/winter chores time.

[Joe C.]

Re: Fuel pump oil weeping

My fuel pump (NORS 4657) collects a several drops of oil after an engine run. I can't seem to locate the source by cleaning & watching, but I do find oil in the cavities of the top casting adjacent the attaching screw holes. If you look closely at the picture below, you can see motor oil in the cavity closest to the engine, front side. This picture was taken after 20 minutes of driving from a 'clean' condition. The aft cavity closest to the engine also has oil, but this does not show up in the photo.



Using a '63 shop manual for troubleshooting, it lists the pump oil seal, the plate/or pump gasket, or a hole in the diaphram as possible defects. I'd like to hope it is the gasket(s) and that the fan is blowing it around. Has anyone experieced this? Wondering if this is something that can be pushed off until fall/winter chores time.

Most likely a worn piston seal. If that is the case, the oil will be coming from one of the weep holes. Two ways to verify this:
1. Wipe pump thoroughly, run engine and carefully watch weep holes.
2. Removal of pump will find pump housing full of oil.

Not serious unless excessive, and/or coupled with a perforated diaphragm!
Check your fuel pressure.

[Stuart F.]

Re: Fuel pump oil weeping

Jeff;

Guess that's the problem with having such a clean engine, you notice things like this.

Given the location, it almost appears as though it could be migrating past the mounting bolt threads. Did you use any thread lube or sealer on these bolts? (not that you should or need to). The fuel pump cavity doesn't usually see a lot of oil, mostly that which comes down the push rod. In fact, many blocks still have the tapped hole clear into the cavity from the front of the engine which was used for the original passenger car motor mounts, and various power equipment brackets through the years. If open and clear, it can be used for a tool (spring loaded bolt) which is used to lock the pump rod in position when removing/replacing the pump.

Looks like you will have to remove the pump and certainly follow the Service Manual Trouble shooting to locate the source. Just thought I'd mention the bolts to cover all bets.

Stu Fox

[Jeff S.]

Re: Fuel pump oil weeping

Joe
This pump has <900 miles on it from NORS condition. Is the piston seal made of rubber? If so, perhaps the decades of shelf time have caused early failure. I will try to set up for observing the weep holes with a dental mirror or something.

Stuart
I know I used thread sealant on the plate attaching machine screws -- don't recall if I did on the pump mounting hardware. I thought the pump mount females were blind holes not requiring sealant(?).

[Stuart F.]

Re: Fuel pump oil weeping

Jeff;

Believe you may be right. It's been a while since I changed mine.

Follow Joe's advice. He's our expert.

Stu

[Joe C.]

Re: Fuel pump oil weeping

Joe
This pump has <900 miles on it from NORS condition. Is the piston seal made of rubber? If so, perhaps the decades of shelf time have caused early failure. I will try to set up for observing the weep holes with a dental mirror or something.

Stuart
I know I used thread sealant on the plate attaching machine screws -- don't recall if I did on the pump mounting hardware. I thought the pump mount females were blind holes not requiring sealant(?).

Jeff,

Most, if not all modern gasketing/sealing rubber products are Buna-N Rubber, this Nitrile-Butadiene material is gasoline resistant and ethanol tolerant. The old style rubber parts were neoprene, not buna-n rubber compounds, and will not tolerate modern fuels as well as the buna-n.
If your pump has low hours, then it's unlikely that the oil seal is damaged, unless it was cut during insertion of the diaphragm stem. Also unlikely.
Another fact, is that the old style diaphragms and pulsator cover gaskets were cotton reinforced neoprene. The upgraded components SHOULD BE nylon reinforced buna-n. Somewhat thinner, but much stronger and fuel compatible than the old material. The reinforcing mesh is still visible when viewed edgewise, although it is NOT white, like the old cotton!
Much more likely scenario is a leaky valve cover and/or pump mount bolts or pump plate gasket. If that's the case, no probs! Again, even if oil appears at the weep holes, that's just an annoyance, because, as Stu stated, there is very little oil in that area anyway.