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Oil Pump Issues (Pressure Relief Valve?)


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First off, apologies if this is a repeat thread. I did look elsewhere, but cannot seem to find a direct answer on this pump style.

 

I have the older style oil pump (which is maybe a little odd given this is a 76'...more on that anon...)

 

It's not developing oil pressure. I've tried all the 'low hanging fruit' tricks listed in these discussions (remove filter, pour oil into pressure switch hole, crank more than you're comfortable with etc etc). Nothing worked. So, I've dropped the pan, inspected everything (pickup wasn't blocked, no other obvious signs of damage, pump turned freely without catching or any other undesirable noise) and re-shimmed the pump (chain was loose). Chain is now tight. Put it all back together, and still no oil pressure. 

 

So I've dropped the pan again, and removed the pump again (getting good at this!). Btw, my earlier fix worked- chain is still tight. Interesting point to note, oil pan is missing 2 bolts....so someone has been in here before (sidenote: is earlier style pump in a newer car commonplace?). 

 

From what I've read, it seems the oil pressure relief valve, if not set up correctly, will be a cause of pump not generating pressure. The single o-ring required (circled in red on the parts diagram below (first image)) was present. I understand the absence of this might be a common issue but it was there. 

 

Now, the second image is how the cylinder for the pressure relief valve was seated when I removed the pump. The closed chamfered end was facing up (nearest the block), while the open end was facing down towards part #24 below. The spring sat in this cylinder and then the whole thing closed up by part #24. From the parts diagram, this seems to be the correct orientation, but maybe it ain't. 

 

This is my last resort before I splurge on new pump, because if this isn't the issue, I will be one of the lucky few to have a failed oil pump. 

 

Any help greatly appreciated. 

 

 

20220907_204431.jpg

20220907_173515.jpg

Edited by BarbaratheIrish2002
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@jimk no oil pressure cranking. I'm not starting or running an engine before I see (at the very least) some oil flow. Right now, there's nothing coming out the oiling bar (after a long crank), nothing coming out the filter housing (with filter removed) after cranking or the oil pressure switch hole. If the relief valve only comes into play when there's flow, then maybe that indicates my pump is dead?

 

Btw, there's little to no sludge build-up, and I'm currently working with fresh oil.

 

Btw btw...cylinders lubricated and engine is drenched in oil from the top down during all this cranking- there's no glitter party (thankfully) in the oil pan. 

Edited by BarbaratheIrish2002
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When you say "early style pump" you're referring to the kind with two meshing gears, not the "rotary" gears as pictured in your drawing above.  If the former, did you measure clearance between the gears per the manual?  While I've not heard of one actually wearing out (and mine is fine after 227k miles) it is possible.  And check the surface of the housing on which the gears turn.  If it's scored and worn, it can be surfaced to provide a nice smooth surface again.  The above is probably not the cause, but it makes sense to check everything, especially after you've determined those hoofprints aren't horses...

 

mike

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My guess is that its not priming.  Was it a running car and the light came on that got you to drop the pan or have you been doing other engine work?  When I installed my rebuilt engine, I was surprised how long it took to prime and finally get oil to the top.  I ended up feeding oil directly into the filter intake tube, cranking until it shot out the output tube, installed a new filter, buttoned everything back up and after a few cranks, had normal pressure.  If you have the pump in your hand, others have had success packing the pump with grease until it primes.

 

 

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Seconded with Murb on the prime-

if it's completely dry, and a bit worn,

it won't always prime with starter revs.

If it's together, pump oil back down the filter housing

to get it wet.

If the pump's in your hand, take it apart, inspect it,

and grease it well.  It doesn't

have to be packed- all you're doing is sealing it up, so

that it can pull oil out of the sump.  And to do that, it has to

be able to draw a vacuum.

 

FWIW, and for future searchers, the relief valve happens after the main galley.

So it can be completely missing, and you'll still have volume, just no pressure.

It's only design coincidence that it's mounted on the oil pump itself- it doesn't need to be.

 

 

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@Mike Self thanks for pulling me up on that...I was incorrect in my description. I meant early style sprocket (3 bolt pattern, no spline as opposed to single bolt, splined version). My assumption was the sprocket type represented what style pump. I can clarify that my pump is not the mesh gear type, it is the rotor style (the diagram with my initial post was correct, the description was not!). 

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56 minutes ago, mcmurb said:

Was it a running car and the light came on that got you to drop the pan or have you been doing other engine work?  

@mcmurb I do not know, hence the precaution of going through all this rigmarole! Previous owner was an elderly lady with scant details (I think it had been her husband's car). The car all looks complete and the oil looked good when I dropped the pan. I think it's worth persevering to try get oil pressure first and then starting it, as opposed to writing it off as ruined from previous lack of lubrication. 

 

But no other engine work is taking place as of yet...

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15 minutes ago, TobyB said:

Seconded with Murb on the prime-

if it's completely dry, and a bit worn,

it won't always prime with starter revs.

If it's together, pump oil back down the filter housing

to get it wet.

If the pump's in your hand, take it apart, inspect it,

and grease it well.  It doesn't

have to be packed- all you're doing is sealing it up, so

that it can pull oil out of the sump.  And to do that, it has to

be able to draw a vacuum.

@TobyB thanks. I put some grease on the mating surfaces before I put it back in before, but perhaps I'll be more liberal in my application this time. Any particular type of grease here? 

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With the pump off I use an assembly lube in the pump to make sure it has a good seal and will prime at cranking rpm.  You can just put the lube down the feed hole (your picture right beside the pressure relief valve and the mounting bolt hole)  Turn the pump backwards to pump the lube through the pump.  

 

Are you sure it is not pumping?  try cranking (short bursts) with the filter off and see if there is any oil flow.  The oil goes through the filter 1st thing before it gets to the pressure relief valve or any of the oil galleys.  

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@preyupy I'm sure. I've cranked for 10 seconds and 30 seconds and everything in between....multiple times. Taken breaks to let the starter cool off and apply more lubrication manually to top end and cylinder...and then tried again! I removed the filter and cranked, nothing comes out. 

 

For the benefit of everyone, here's an image of the internals of the pump. If you zoom in, you can see scoring at the base just below where my middle finger is...is this normal? Would this account for pump not doing pump things? 

 

 

20220827_154232.jpg

Edited by BarbaratheIrish2002
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You might be able to attach a drill chuck (or something else that spins) to the input shaft of the oil pump and spin it up outside of the vehicle. With the pickup submerged in oil, you should be able to better observe what's happening, and if it's actually pumping.

 

Full disclosure: I've never tried this myself. Be prepared to make a mess ?

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4 minutes ago, eviction_party said:

You might be able to attach a drill chuck (or something else that spins) to the input shaft of the oil pump and spin it up outside of the vehicle. With the pickup submerged in oil, you should be able to better observe what's happening, and if it's actually pumping.

@eviction_party great idea! I've seen it done online and I think it's worth doing as next step. Might try with plain old water as I'm sure the neighbors would appreciate that better! Viscosity be damned... 

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