I installed a brand new High output oil pump on my 351 M. I started the engine and everything appeared fine. I drove the truck about 6 blocks and it died. The engine was turning over but when I pulled the distributor cap the rotor was not turning. After some difficulty I was able to pry the distributor out and the pin was fine, the gears seemed fine. I as able to look down the hole with a light and I could seem the cam and crank turning as the engine was cranked. Anyone have any ideas of what would make a brand new Oil pump sieze like this? Am I missing something? Any thoughts would help, I plan on putting in a new pump next weekend but would hate to go through the same thing again.

Thanks for the space.

 

Did you prime the pump first? Was it the right oil pick-up for the oil pan? Did you change oil pan styles? These are the only things I could think of.

 

Here's the answer:

You replaced the oil pump because the stock one did the same thing, right? Well, the valve stem seals are breaking up, going down the block into the oil pan, and getting around the intake screen and finally stopping your oil pump, shearing the distributor drive pin, and causing an immediate stoppage to your rig.

You need the valve stem seal replaced (all 16 of them,) and you need to pull the oil pan off the bottom and clean out all the broken bits of plastic down there. You need a new oil pump screen. (Available from Ford) You need to take the oil pump apart and get all the plastic out of it, then reassemble.

You can do this (replace valve stem seals) yourself by inserting a rope into the cylinder while the piston is down in the bore, and then rotating the engine until the rope holds the valves shut. Then you can get the springs off with a valve spring compressor, and then replace the seals. This takes quite some time to do all eight cylinders.

Or you can remove the heads and have them redone entirely. (Valve job)

Or you can take the truck whole to the repair shop and have them do the whole thing $$$$$$$$$

After you get it fixed, however you fix it, take the oil pan off about a week after it's running again, to make sure all the bits of plastic are flushed out of your engine. My truck has a 3" lift, I can remove/install the oil pan in less than 20 minutes now, without jacking the truck at all.

fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George

 

Oh, about the pin, it probably is sheared, just heat locked on there so you can't spin it by hand. If you put it in a vise, you can probably spin the drive gear right off with a pair of pliers. Then you can remove the broken pin. You have to buy new pins from Ford, and they are only sold in 6 packs.

There is really no way for the oil pump to lock up and the pin not shear. That is why the distrubutor rotor won't spin. If the pin and gear on the cam and distributor are ok, the roto must spin. Unless the drive rod for the oil pump broke in half (not likely)

fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George

 

Thanks for your imput, I checked and you were right the pin was seared. I then checked the pump by putting a socket on it and it was bound up a little but broke free and seems to be turning fine now. What do I do? The heads I just had done and replaced the oil pump/timing chain while I was there. Is it possible that the new pump/timing chain somehow was just "too much" for the old sear pin on the distributor causing it to go???
I am thinking I will get another distributor from a junk yard and see what happens. What are your thoughts?

 

Reman distributors are less than $30 from Autozone for the 351M/400/429/460 (yeah, they all have the same distributor) Junkyard ones tend to stick in the block due to corrosion between the alum distributor and the iron block. Use antisieze when you reinsert yours to prevent this for happening to you. I would recommend pulling the oil pan, and seeing if anything is in there that shouldn't be. Also check your oil screen and if it wasn't replaced, replace it.

Also take apart the oil pump and see if anything is still in there. It's pretty easy.

Now the bad part. When I was having my problems with the oil pump, many people told me that a HD oil pump would tend to blow out the shear pin. I was thinking of putting on a HD oil pump when mine first siezed. I stuck with the stock oil pump, and haven't had any problems for over a year now that I changed the valve stem seals. Also from what I understand, too thick of an oil can cause premature breakage. Just use 10W30, maybe 10W40 if you live in Florida or the Desert Southwest. The Ford shear pins are the only hardened ones, I would recommend getting the pin from Ford. I could blow out a shear pin from a parts house (like auto zone) in no time. The Ford one lasted much longer, even when my oil pump was sticking.

fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George

 

Thanks for your help. I did as you recommended and bought a new distributor from Autozone... about $50.00 bucks (small price to pay if it works). I changed the oil and ran a magnet through the oil (No metal!). Dropped the new distributor in but now the motor does not want to run......? It was purring like a kitten prior to the pin breaking. Any ideas? I can get it to run but it runs REALLY RICH and a lot of white exhaust. What do you think? Thanks again for your help.

 

I believe that most distributors purchased at a parts house are merely assembled, and need to be set up by somebody who really knows how to set the advance curve.

BBT

 

The parts the jammed up my oil pump were plastic - so a magnet would not pick them up. Something to think about.

As to the running poorly, did you just drop the distributor in where the rotor was when you finally opened the hood. If so, chances are the rotor is not in the right position. The wires could be one or two off, and the truck still run from arcing over. Try moving the distributor around while the truck is running and see if moving it one way or another helps it run better. Seems it took me about 4 hours to get mine where I liked it. I did the timing by ear, as the marks on my engine are nonexistant. Also make sure the vacuum line is hooked up to the right place.

Hook up a timing light to the engine and make sure you get advnace when you rev it up to check the distributor. I could do this, even with no marks.

To totally eliminate the new distributor, get a shear pin from Ford and reassemble the old one and stick it in. If the truck runs a lot better, then back to the Zone.

Also, when you put in the new distributor, you used the white paste stuff on the connection between the distributor and ignition module? If not, the poor connection could cause poor running.



fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George

 

Once again I thank you (seems like an every day thing!) I will go back to auto zone and try to get my core back and try that with the pin. I am thinking it MUST be the new distributor as it ran so nice with the old one (pretty sure I have it correct). Big brown truck comments are well taken.... I dont know how to set the advance so I'll try to recover the old one. If I cant get it I guess I will call a shop. Thanks for all your help.

 

I have a 351w everything is new in motor have siezed two oil pumps within 800 miles has great oil pr when it was running 50-60 psi the motor is built I run a high vol meling pump does anyone know what the problem is Thank you HELP.

 

The suggestions in this thread are where you need to be looking. Did the pin shear when the pump locked up? (By the way, this is the wrong forum; there is a separate Windsor forum, and this thread is 7.5 years old).