no oil pressure rebuilt engine

[ryanbass2]

Hello all,

i rebuilt a 351w for my 81 bronco about 3 years ago. i had it sitting in a garage since then i just put the engine in and i get no oil pressure when i start it. i can manually prime the engine with a drill but it has to be at full speed to start getting pressure like 2100 rpm out of drill which would be about 4200 rpms of engine speed. at that speed i can get 40 psi of oil pressure. then i imediatly drop in distributor and start engine oil pressure goes to 20psi the drops to 0 and lifters start to make noise. /emoticons/[email protected] 2x" width="20" height="20" />

heres what i have checked so far.

pickup tube is good and gasket is there

oilpump is brand new and has gasket and releif is not stuck.

All oil galley plugs are in

all bearings are right size

dist engages rod for pump fully

oh and when i rebuilt the engine everything was replaced with new parts except for crank and rods.

i dont know what to do now im puzzeled :huh:

 

[ryanbass2]

i pulled the motor already disassembled and checked everything again. the filter is a napa gold made by wix. the way its acting i thing the flow back valve in filter is bad and thats why i get no pressure at low rpm im reassemble and change the filer and try again and o yea i use 10w-40 oil

 

[muddrivermike]

A co-worker of mine and me were just talking about the same problem a couple of days ago.I had to replace my oil pump from a problem back in dec.I had to take it off the road until it warmed up outside to do work on it,,,Anyway I have just installed a high volume oil pump which works great.What my friend said was he found out something about a huge batch of melling pumps had that went out to parts places had some kind of defect with the relief causing them to drop the pressure.The reliefs' were getting stuck open and droping oil psi to nothing.Then once you shut the engine off the relief would reset until it did it again,then you have to shut it off again..I cant confirm this,he also doesnt have a ford,he has a chevy cyclone (turbo charged s-10 pickup).So I dint know if this problem was limited to chevys or if other makes were affected also. :huh:

 

[50joe]

Found a bunch of old posts on a few other sites about that, some on the chevy motors, and a few Dodge, Nothing on the Fords though.Something about a design change that caused a TON of problems, so wouldn't be suprised if a few Ford motors were affected by it. And BTW, all the posts were from 06, which would match your time frame. Might be worth your time just to replace the pump for a little piece of mind. It's what I would do.

 

[Shadow_D]

I'd say it has something to do with the pump. I'd replace the pump first then try it again. To make life a little easier for you, put the motor on a test stand and check it before you put it back in the truck.

Next thing I would do is use a digital caliper to check the journal sizes on the crank. After that, if the problem still exists I'd replace the beerings...

 

[muddrivermike]

Found a bunch of old posts on a few other sites about that, some on the chevy motors, and a few Dodge, Nothing on the Fords though.Something about a design change that caused a TON of problems, so wouldn't be suprised if a few Ford motors were affected by it. And BTW, all the posts were from 06, which would match your time frame. Might be worth your time just to replace the pump for a little piece of mind. It's what I would do.

At least there is some kind obvious problem that is known on this not just a couple of random bad pumps.And the worst part is my high volume one is a melling from summit.So far its working perfect.Ive never seen my oil pressure gage run as high as it is now.So at least Im good for now.

 

[Broncobill78]

Couple questions, *where* are you measuring the oil pressure ? From the port right above the fuel pump or from the top/rear of the block ? In the past I've found it useful to put 2 gauges on to see what the pressure is right above the pump as well as at the top rear of the block. Also, did you by chance change/replace the pushrods ? I had a no pressure problem with a 460 I built that wound up being caused by new pushrods that were fractionally too long, they weren't letting the lifters pump up so I had no top-end pressure. Just a thought.

 

[drivingwild88]

i had a similar problem after rebuilding and switching my 89 to a carb. the gauge wasn't reading anything. turned out that i had to basically bleed the oil pressure tube that runs to the gauge. totally slipped my mind. after that it read just fine. but if you say its running a little iffy......you may have more unfortunate problems than something as easy as my problem was.