401 wont crank

[82Waggy]

I had a brand new one that was stuck due to casting debris and machining flash.

Make sure the plunger drops all the way in so that the point on the end touches the far wall, and that it is free to move easily back and forth without the spring. If it won't bottom and fall out freely without the spring you need to ream out the plunger cavity to the proper diameter and get rid of all the garbage.

[guffey24]

I had a brand new one that was stuck due to casting debris and machining flash.

Make sure the plunger drops all the way in so that the point on the end touches the far wall, and that it is free to move easily back and forth without the spring. If it won't bottom and fall out freely without the spring you need to ream out the plunger cavity to the proper diameter and get rid of all the garbage.

so what you are saying is that the plunger should slide in and out easy, I get that part

If I am under my Jeep and slide the plunger up in the hole it should freely fall back out?

If that is the case, the plunger I have fits real tight and will not come out on it's own, when I push it up in there, with or without the spring it stays and does not come out on it's own

[1980_Cj7]

I'd work the bore a little, real slow and by hand, with some real fine emory paper on an appropriately sized drill bit. Go slow and do lots of test fitting. Check and make sure the plunger is smooth too.

[82Waggy]

I had a brand new one that was stuck due to casting debris and machining flash.

Make sure the plunger drops all the way in so that the point on the end touches the far wall, and that it is free to move easily back and forth without the spring. If it won't bottom and fall out freely without the spring you need to ream out the plunger cavity to the proper diameter and get rid of all the garbage.

so what you are saying is that the plunger should slide in and out easy, I get that part

If I am under my Jeep and slide the plunger up in the hole it should freely fall back out?

If that is the case, the plunger I have fits real tight and will not come out on it's own, when I push it up in there, with or without the spring it stays and does not come out on it's own

You need to pull the filter adapter off the timing cover to be able to see what I am talking about and to clean it up properly. I assumed you already had it off. If you have never done this, get a copy of the TSM before you attempt it as the pump gears will come out too and you will need to remove and replace the old gasket properly.

If you try to machine/clean the filter adapter while it is on the vehicle the chances are you will release all kinds of chunk into the engine that may tear things up.

[jeepsr4ever]

Your probly much better off getting a new updated oil filter adaptor than trying to deal with a bad/grooved one. I am sure we can find a *Flat one.

[guffey24]

Your probly much better off getting a new updated oil filter adaptor than trying to deal with a bad/grooved one. I am sure we can find a *Flat one.

I will take mine off again, and see what it looks like, and I am guessing that this is the one I would need to replace it with

http://www.bulltear.com/catalog/prod...roducts_id=135

[jeepsr4ever]

Yes that is the replacement

[guffey24]

alright guys I got everything fixed for now, took the oil filter adapter off and cleaned the whole thing real good, installed a new gasket

also installed a mechanical oil pressure gauge

I am in Fuzz's good range now

70 psi cold and 25-30 PSI when it warms up

thanks for all the help

[mika01]

Plungers should not be larger than .561. The hole it goes into is actually a precision bore that should be held pretty close to .5625 or 9/16". We ream the 626 and the 534 oiling plate holes out to .563 when they are being made here in house. I am suspecting you may be bypassing your filter. Whats the scoup on your oil filter adaptor?...is it new or used and what is the date code on it. Pre 1988 means oil filter bypass...1988-1991 means no oil filter bypass. Some 1987's had it either way. Maybe you forgot to put your bypass back in if was dis-assembled.

Wow this was quite a revelation for me. I just fired up my 401 which had a 75 timing cover with oil filter adapter and was getting about 12 psi cold. Once I read this I scavenged an oil filter adapter from a 89 and voila 50 psi cold!
Thanks for info MC never would have guessed it!

[Holeshot]

I also have seen a bunch of stuck plungers.