big problem....no oil pressure after 3200rpm!!!

[89frankenford]

ok so i have a HUGE problem.....whenever i get my truck up to around 3200 rpm's my oil pressure just drops completely.it takes till about 3600 for it to be 0. this is in any gear, and in neutral as well. does ANYBODY have any clue as too what or where i could start? its a really big issue for me for obvious reasons. this has been going on for about 2 months give or take. im kind of lost on this part.


oh for people that don't know

1989 f-150 4x4 5 speed 4.9L 300ci. motor rebuilt 2 years ago, oil changed about a month ago 6 quarts 5w-30 synthetic and a Motorcraft FL-1A oil filter

 

[F 150Cobra]

aftermarket oil guage or stock one? if its stock maybe its going bad

at 3200 to 3600 does it rattle? sounds likes there is no oil?

 

[flareside_thunder]

might also be a bad pump...I know I know...rebuilt last year.......parts do come defective....may also be the pump drive shaft....or...bad ground on the sending unit(if it's factory)

 

[TexasNomad]

Only thing I can think of is a bad oilpump I mean there really isn't any thing else it could be.
Well I could go Waay on a limb and say it could be sucking up to much oil and not enough is bleeding back in to the pan...

 

[Skandocious]

So the gauge is showing no oil pressure but does the engine ACT like there's no oil pressure? No oil pressure can lead to a catastrophic failure, for obvious reasons, lol.

 

[flareside_thunder]

hmmm. maybe u need a windage tray?

 

[Bricks]

Is it a mechanical gauge, or an electrical gauge?

 

[TexasNomad]

Could it be a bad oil filter?

 

[1985 Ford F-150]

Maybe the oil drive is slippin inside the pump or distributor.

 

[Bricks]

First thing he needs to do is verify the accuracy of the gauge.

The drive can't slip in the pump unless it's stripped, which it isn't or he wouldn't have any pressure at any rpm.

I suspect a gauge problem - we're just guessing until that is verified.

If it's an electric gauge, ground it and it will peg if it's good.

 

[1985 Ford F-150]

Yeah thats right if it dont sound like its runnin out of oil id leave it be. If it is an electric gauge I would also get a cluster of three and put em in.

 

[LEB Ben]

Jumping in late on this...but my guess would either be the SU or bad gauge.

 

[CowboyBilly9Mile]

Hook up a mechanical gauge that is known/proven to operate correctly and check the pressure.

 

[SuperCab]

It can't be the pump or pump drive because there would never be pressure.

If it had no pressure, it would knock like crazy, and then chuck a rod through the pan.

I vote for SU/gauge.

 

[flareside_thunder]

I think ur wrong about it not being the pump drive or pump....with increased rpm there is increased presure and volume flowing throughout the oil system........thus there could be a leak in the seal between the pump and it's mounting surface or the pickup tube and pump body which would cause this at an increased rpm.Also, it is highly possible the drive may be worn...think about it like this......you a 12 point socket on a bolt that's really really really tight...like locktight or years of abuse tight.......chances are the socket is gonna slip on the bolt/nut right?whatif that bolt/nut is less tight?It'll turn the bolt/nut easily and chances of it slipping are slight.....

 

[SuperCab]

True. We really need Travis to verify if there are no oil symptoms, ie knocking, chucking rods, seizing up...

 

[Bricks]

I think ur wrong about it not being the pump drive or pump....with increased rpm there is increased presure and volume flowing throughout the oil system........thus there could be a leak in the seal between the pump and it's mounting surface or the pickup tube and pump body which would cause this at an increased rpm.Also, it is highly possible the drive may be worn...think about it like this......you a 12 point socket on a bolt that's really really really tight...like locktight or years of abuse tight.......chances are the socket is gonna slip on the bolt/nut right?whatif that bolt/nut is less tight?It'll turn the bolt/nut easily and chances of it slipping are slight.....

At any rate until you verify the gauge, you are just guessing.

 

[89frankenford]

ok i just got back from my second job. thanks for all the replies by the way. ok so as far as i know it isn't throwing a rod, and it isnt seized haha..but in all seriousness i do believe it is knocking when it goes over 3600..im honestly not sure but i can check tomorrow and fill you in. so for now lets say it does lose oil pressure.(worst case scenerio thinking ). it is an electric sending unit(that is new when the motor was rebuilt) and the gauge is the stock ford gauge. when i rebuilt the motor it got a new oil pump and distributor(i know new parts can fail but i had to state that). the first thing i guess i am going to check is to get a mechanical oil pressure gauge on it and see exactly what kind of pressure im getting at idle and at 3600. now if that reads zero what should i look for? as for the oil filter, its been changed along with the oil and the problem is still there. ill even get a video clip of this happening too. could it possibly be something clogging part of the pump inlet filter?

 

[SuperCab]

You definitely want to avoid high revs if it's actually knocking...

but you knew that.

 

[radialarm]

Why would you want to rev a 4.9L that high? Mine sounds like it's about to explode at 2800.

It could be a bearing, my old 240 would get like that sometimes but it was worn out.