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Hi all, new to the community, just picked up my first L-Body car, an '85 Omni with a VNT engine among other mods. Just caught my fancy and I couldn't pass it up, so I'm still learning quite a bit about the car.

Long story short: On the way home from purchase, it died on me. Bit of quick diagnostics, the upgraded melling oil pump gear and distrubutor drive gear on the intermediate shaft ate each other. Got it all back together and she started and ran fine on the first crank. This included a new oil pump, new pickup, intermediate shaft, intermediate shaft bearings and seal. Couldn't have been happier.

Noticed a small oil leak, so I thought the pan needed to get tightened a bit. Did that, then on the next start it immediately blew the oil filter gasket out. Behaving just like the drain-back valve froze shut, so took that apart, and it looked and operated fine, so just cleaned and reinstalled with a new filter/ oil. Same thing. Started, and immediately blew the gasket and was puking oil out the filter seal/ distributor base (shortest distance to pump outlet.)

Pulled the oil pump and inspected, pulled the intermediate shaft to check bearing alignment and seat, pulled the check valve again and everything looks absolutely perfect, no visible blockages anywhere. A friend thinks I spun a main, but even without knowing the oil flow diagram, I can't believe believe one main would block 100% of oil flow.

Seems likely to me it's positive crankcase pressure since it blows immediately when it fires. Crank without fuel/ spark and it doesn't leak oil or seem to be building oil pressure anywhere, but where would it be coming from? Can't be blow-by, it's instantaneous, and it wouldn't be boost coming back through an improperly timed PCV since it's at idle, Block is intact, piston's are intact...

I'm stumped. Any ideas?
 

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1,160 Posts
Hi all, new to the community, just picked up my first L-Body car, an '85 Omni with a VNT engine among other mods. Just caught my fancy and I couldn't pass it up, so I'm still learning quite a bit about the car.

Long story short: On the way home from purchase, it died on me. Bit of quick diagnostics, the upgraded melling oil pump gear and distrubutor drive gear on the intermediate shaft ate each other. Got it all back together and she started and ran fine on the first crank. This included a new oil pump, new pickup, intermediate shaft, intermediate shaft bearings and seal. Couldn't have been happier.

Noticed a small oil leak, so I thought the pan needed to get tightened a bit. Did that, then on the next start it immediately blew the oil filter gasket out. Behaving just like the drain-back valve froze shut, so took that apart, and it looked and operated fine, so just cleaned and reinstalled with a new filter/ oil. Same thing. Started, and immediately blew the gasket and was puking oil out the filter seal/ distributor base (shortest distance to pump outlet.)

Pulled the oil pump and inspected, pulled the intermediate shaft to check bearing alignment and seat, pulled the check valve again and everything looks absolutely perfect, no visible blockages anywhere. A friend thinks I spun a main, but even without knowing the oil flow diagram, I can't believe believe one main would block 100% of oil flow.

Seems likely to me it's positive crankcase pressure since it blows immediately when it fires. Crank without fuel/ spark and it doesn't leak oil or seem to be building oil pressure anywhere, but where would it be coming from? Can't be blow-by, it's instantaneous, and it wouldn't be boost coming back through an improperly timed PCV since it's at idle, Block is intact, piston's are intact...

I'm stumped. Any ideas?
Maybe take the oil filter check valve out clean/inspect. that's the threaded part that goes in the block.
 

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1)Have you checked actual oil pressure?
Your issue may be oil pump relief valve related.
Oil Pressure Specs
At Idle - Above 4 PSI
3000 RPM's - 25 - 80 PSI
General rule of thumb is 10 PSI for every 1000 RPM's.
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Best...
2)Is the PCV System functioning properly?
a)Is engine vacuum present at the PCV valve itself?
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3)Is there any oil in the Airbox?
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4)Is there any blowby from the oil fill opening with the cap off and engine running?
5)Are there any signs of sludge buildup on the oil cap, in the valve cover?
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6)
Are there any signs of water in the oil?
a)The oil color will turn Tan/Yellow/White.
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7)Is there any oil present in the charge piping?
 

· Old School Hot Rodder
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Jan, I was thinking about this one myself, having seen a Mustang with a 390 blow a Fram HP1 filter clean apart on the starting line at our (then) local drag strip. If it almost instantly blows when the engine starts, could it be a bad head gasket/cracked head allowing combustion gasses into the left front head bolt area. Maybe try disabling #4 injector and removing #4 plug and start the engine. If the filter survives, then head removal would be indicated.
 

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For info. purposes, I always eliminate the anti-drainback valve.

It's actually a restriction to oil flow but that's not the issue either way.

More likely, the oil pump pressure relief is stuck in the closed position.

Thanks
Randy

Here is a post by a Chrysler Engineer on oil pump installation:


Intermediate Shaft / Oil Pump Indexing

For those who have ever had intermediate shaft or oil pump gear devastation, there is a method to improve gear meshing and component longevity.

As much as we'd like to believe that these components are precision machined to strict standards, they unfortunately are mass produced components with a wide quality acceptance band.

This means that the journal, gear tip, and tooth cutting processes for both components in addition to oil pump gear centering on the shaft and the distributor hole machining in the block can all amount to a noticeable uneven mesh, between the components.

This can be observed during the engine assembly process as variation in the rotating effort required to turn the intermediate shaft sprocket upon installation in the block.

This is typically caused when 'minor' non-concentric high spots on the oil pump gear are aligned with high spots on the intermediate shaft.

Although, there are a few easy steps to reduce the chance of component failure and a catastrophic event should either gear shear and cause a total loss of oil pressure.

1. With the oil pump installed, Loc-tite on the oil pump attachment bolts, and the oil pump attachment bolts near snug; install the intermediate shaft

2. Rotate the oil pump housing in its mounted position to realize how much the oil pump housing can be turned to the left and right, while visually noting travel relative to the mounting bolts

3. With the level of travel determined, clock the oil pump as close to the center position that was determined by the previous step

4. Torque the oil pump attachment bolts, per the manufacturer's recommended specification

NOTE: The previous steps have minimized the chance that the oil pump is preloaded to one side of the engine block distributor/oil-pump hole because the oil pump mounting flange surface is not always 'true' to the oil pump center-line.

5. Install the intermediate shaft retaining cover without the anaerobic sealant and lightly tighten the bolts that hold the cover in place

6. With the intermediate shaft key in place, install intermediate shaft pulley

7. Rotate the shaft by turning the pulley while noting the consistency in rotating effort, throughout several rotations

If the rotating effort is not smooth and/or consistent throughout several rotations, proceed to step 8, otherwise proceed to step 9.

NOTE: If the following steps are repeated numerous times without improvement, thoroughly inspect each component for obvious signs of significant manufacturing defect and replace as needed.

8. Re-clocking the intermediate shaft

Remove the intermediate shaft pulley

Remove the intermediate shaft cover

Note or index the pulleys/shafts current position

Remove the intermediate shaft, re-clock the shaft to one/same direction, by 90 degrees

Reinstall the intermediate shaft

Return to Step 5


9. Remove the pulley, intermediate shaft retaining cover bolts, and cover

10. Complete the final installation of the intermediate shaft cover and pulley hardware per the manufacturer's recommended specifications

The above process can provide the best possible component mesh and gear loading by improving awareness to minor manufacturing variation, aligning those variations in a manner that minimizes excessive component loading, and minimize the resulting wear.

 

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Jan, I was thinking about this one myself, having seen a Mustang with a 390 blow a Fram HP1 filter clean apart on the starting line at our (then) local drag strip. If it almost instantly blows when the engine starts, could it be a bad head gasket/cracked head allowing combustion gasses into the left front head bolt area. Maybe try disabling #4 injector and removing #4 plug and start the engine. If the filter survives, then head removal would be indicated.
I had a 88 grand marquis 302 and every time you started the engine the oil filter would blow off (leaving the base) turned out the oil pressure relief valve was stuck cleaned it out and then it was fine.

And by clean out I mean I put on a K&N racing filter and ran oil flush fluid through it. Then I could go back to the crappy Walmart Fram.
 

· Old School Hot Rodder
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I personally have always used Ford filters on my Ford engines (mostly FL1A) even now I use FL500 ones on the two Flexes, truck still gets an FL1A. My 2.2L T2 in my 1985 also used a Motorcraft FL1A. Part of this was based on some tests I did in the lab I worked at years ago, the particle size in oil at a 2000 mile change was no larger the 10 microns using the then Rotunda filters on my "snake bit" 260 powered Falcon and later my 1966 Shelby GT350.
 

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I personally have always used Ford filters on my Ford engines (mostly FL1A) even now I use FL500 ones on the two Flexes, truck still gets an FL1A. My 2.2L T2 in my 1985 also used a Motorcraft FL1A. Part of this was based on some tests I did in the lab I worked at years ago, the particle size in oil at a 2000 mile change was no larger the 10 microns using the then Rotunda filters on my "snake bit" 260 powered Falcon and later my 1966 Shelby GT350.
What's your opinion on this supposedly this is real....

Maybe run one of these so he doesn't keep having filters blow off.
 

· Old School Hot Rodder
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Bypass filters, real new idea. Many engines into the 50s and even 60s had bypass filters. Mercedes-Benz used (and may still) a combination on their Diesels and some gas engines. Chevrolet only had bypass filters as an option on the 216 and 235 ci sixes, first Chevy V8s, had no filter. Even many premium vehicles had only bypass filters and they were optional. My 1955 Packard Patrician with a Packard 352 ci V8 had only a bypass filter.

Many big rigs use a bypass filter as they can be a very high level of filtration, without restricting oil flow to the bearings.
 

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Bypass filters, real new idea. Many engines into the 50s and even 60s had bypass filters. Mercedes-Benz used (and may still) a combination on their Diesels and some gas engines. Chevrolet only had bypass filters as an option on the 216 and 235 ci sixes, first Chevy V8s, had no filter. Even many premium vehicles had only bypass filters and they were optional. My 1955 Packard Patrician with a Packard 352 ci V8 had only a bypass filter.

Many big rigs use a bypass filter as they can be a very high level of filtration, without restricting oil flow to the bearings.
I once had a terrible English car called a Morris 1100. It was an unpleasant, but spacious, front-wheel-drive dog. With less power than my beard-trimmer.
I believe the 1300 version was sold in the States as the Austin America, as if anyone would fall for that bit of shitty marketing.
I digress.
The Morris I had, (a badge engineered Austin, had a constant glowing light on the dash. Orange, I recall.It certainly was bright!
I had no ides what the hell was wrong with it, as I was maybe 16, but local mechanic told me the light was to alert me that the oil filter bypass was in operation. this on a 1964 model car.
Can't remember whether that problem got sorted, as the car died in a spectacular fashion.
While legally parked on the side of the road, a truck lost a shipping container, and it squashed the old Morrie flat.
Probably the best outcome, TBH.
 
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