Little to no oil pressure

Mark

FIATFREAK
One of my Scorpions has developed an issue with little or no oil pressure at startup. It was sporatic at first, happening after the car sat for several hours; but not always. It got to the point when once the pressure didn't come up. I was able to prime the pump by removing the spur gear and then it ran fine. However, the problem persisted. So I dropped the pan and disassembled the pump, but everything checked out fine. I refilled it with a 5w-30 instead of the 20W-50 I have always run, thinking that might change the behavior. At first it seemed to, but the other day the oil light came on at a stop light within only a few minutes of travel. So, I devised a mechanical gauge to verify the low pressure and it confirmed only a few pounds at idle. So, once again I dropped the pan and replaced the pump with a known good pump. Still no pressure. My next and last step prior to pulling the engine is to prime the pump as before. Any ideas what might be happening?
 
What i posted on Lancisti...

I think you have either a stuck or bad pressure relief spring or a bad bearing. Oil analysis (which comes up on the Vanagon List from time to time) would be able to confirm a bearing due to metallic contamination of the oil. Could also be a bad oil galley plug etc.
 
Low Oil Pressure Causes

Low oil pressure can be caused by many factors...

It could be caused at the source by an oil pump that is worn with wide clearances, has a failed pressure relief spring, has poor sealing between the pump body and the engine block, or is being starved for oil by a clogged sump pickup.

It could be caused at the point of lubrication from badly worn bearings with way too much clearance, allowing the oil to flow with a lot less restriction, thereby preventing pressure from building up.

It could be caused by a failed oil galley plug, either in the block or the crankshaft, also preventing pressure from building up.

It could also be caused by a restriction in the oil system, where the pressure is dropping across the point of impeded flow, before the oil pressure sending unit, perhaps inside the oil filter. I would check inside the camshaft housings to confirm that oil is circulating such that it is filling the top of the engine as expected, and if not, then replace the oil filter to rule out a possible simply cause.

Beyond that, further engine disassembly may be required to confirm the exact reason why the oil pressure is too low.
 
!

It's wierd that it's inconsistent. Usually mechanical defects are consistent. Either gradual, or sudden, but once it breaks it stays broken.

Something might be drifting in and out of spec. But it seems most likely that the pressure bypass valve is getting jammed open. Sometimes it seats when the engine slows down, other times not. If it jambs open, you won't have any pressure at low engine speeds.

It's a wierd problem that I've never heard anyone else complain about. :hmm:
 
Update

So I decided to "prime" the oil pump by removing the bevel gear and using a tool I made a long time ago:
B65C09E8-0151-455A-BA40-4F65653449E3-2271-000003B591E3AB4E.jpg

It fits onto the end of the oil pump and I turn it with a drill. My mechanical gauge registered 20 psi. I started the car and had excellent oil pressure, but some weird issues:

Listen to the snapping noise at 6-12 seconds into the clip. Also, watch the pressure drop and recover at 14-23 seconds. (Lots of background noise from my exhaust fan.)
Not sure what to make of it, but I'm convinced there's something abnormal going on that will require pulling out the engine to fix.
 
Possible Incorrect Oil Pump/Gasket?

Hi Mark, does this car have a 1756cc engine? You mentioned changing the oil pump, and there are early and late 1756cc engine designs, which use different oil pumps, the gasket between the oil pump and the engine block is different. Is it possible that the oil pump, the gasket, or both may not be the correct parts for your engine? I think the wrong oil pump can be installed, but the holes do not line up, which may prevent oil from flowing in the direction that it needs to in order for pressure to build. IIRC, the Scorpion 1756cc engines actually use the same oil pump body as the 1995cc engines (but with different sump pickup than the Fiat 124/131 engines) which has the same hole pattern as the late 1756cc engines, and so they use the late 1756cc and 1995cc oil pump gasket. Something else to consider as a possible cause.
 
Mark Have a look at this first befor pulling the motor

This is from a friend:

This happened to me 3 times and to many others I know .
On all of the situation I found out just to be caused by the failure of the
bypass valve to open inside the OIL FILTER. They were with FRAM filters installed

No one mentioned to replace the oil filter first. better with the known functioning used one "just for checking.
A new filter might have the same result.

Often times when someone comes to me with low oil pressure complain ends up with just replacement of the filter.

(I curse the use of the disgusting FRAM oil filter).

Since I am not a member of the forum, please do suggest this to Mark immediately before he disassembles the engine.

Thanks !

Check this first and don't use Fram!!
 
Also, possible that the aux shaft fuel pump cam hit# 2 con rod causing a problem?

Regardless, the fuel pump cam on the end of the aux shaft should be cut off, hole drilled and tapped for a 1/8 NPT plug and plugged if a mechanical fuel pump is never used.


Bernice
 
no oil pressure!

I'm encountering something similar, but more severe. When I last drove my '77 Scorp #1792 in July, it ran great. Put it away until a month ago. It has twin Webers, so it takes some cranking to fill the float bowls. I noticed that the oil pressure warning light never went out.

The engine started, but I kept it at a very slow tickover, hoping the light would go out. It didn't, the pressure gauge didn't budge, and the rod bearings started making noise. I shut it down. Today, I replaced the Fram with an Italian made o/f, removed the oil pressure light sender and cranked it over. Absolutely nothing came out - zero oil pressure!

What could happen so suddenly? Having read the rest of this thread, I'm wondering if the pressure relief valve spring broke while cranking the cold engine? Winter weather temperatures permitting, I'll be removing the oil pan in the next few weeks to see if I see a cause.

Is there anything else I should be looking for? I hope the rod bearings are okay.

Thanks and Happy New Year!
Rob
 
Check The Oil Pump Shaft

Hi Rob, it's possible that the end of the oil pump shaft, that inserts inside the drive gear at the auxiliary shaft, may have snapped. If you remove the cap on the engine block, you can remove that gear to check.
 
no oil pressure!

Thanks for your reply Dave.

Thanks to Gregory Smith over on Lancisti.net, I cranked the engine over with the oil filter off and spark plugs removed. It began pushing oil out the filter boss, so I reinstalled the filter and got oil pressure on the gauge (and the light went out). Reconnected everything and it started and ran just fine.

I've owned a lot of vintage imported cars over the years, but never encountered anything like this before.

Afterwards, I treated the car to an oil change. :)
 
One more its, to check. The aux shaft to oil pump coupler gear has internal splines. These do wear and can slip causing a problem like this.

The gear can be removed using a magnet or long grippers after the block dizzy cover has been removed.



Bernice
 
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