Oil Pressure Mystery!

[highcking]

So, here's the story. I acquired my '58 Roadmaster a couple of months ago. After going over the car pretty thoroughly (and finding lots of things to fix), I decided it was OK to run the car and drive it short distances. The oil pressure gauge worked and showed, as expected, fairly high pressure after a cold start and medium pressure when warmed up. A 6-mile drive to and from a gas station at 50+ mph showed no problems with the engine. After that, I started the car occasionally to move it or charge up the battery.

One day a few weeks ago, I backed it out of the garage at idle, and noticed the oil pressure gauge pegged at the low end. I thought about a gauge issue, but I started to hear valve and lifter clatter so I shut it down. So far I have done the following:

1) Dropped oil pan, cleaned the sump, disassembled original oil pump (with vacuum booster). The oil pump looked to be in very good condition - nothing obvious to explain a total failure of flow/pressure.

2) Installed a used '59 style oil pump that seemed to have almost no wear on the gears. The pump bolted in with no problem - the groove the the shaft seemed to seat easily in the fitting under the dstributor. (I assume if it didn't, you can't run the mounting bolts all the way in.)

3) Reinstalled the pan, installed a spin-on filter conversion kit and a new PH-30 filter.

4) Filled with 10w-40 oil and cranked for 10-15 seconds to get some oil pressure before starting. No pressure.

5) Unscrewed the oil filter and found it completey empty.

6) Unscrewed the high-pressure bypass fitting, found the ball and spring in good condition. (This would only kick in to keep pressure from getting too high anyway.)

7) Cranked the engine without re-installing the oil filter - nothing coming out.

8) The car will start if I connect the coil wire.

I am stumped for the moment. I think both the original pump and the replacement are good enough to generate full oil flow and good if not perfect pressure. The gauge is fine. There is no oil flowing, yet oil pressure was originally right on specs. What to look for that would yield a total loss of pressure? I am hoping it doesn't have to do with the fitting under the distributor. Obviously the distributor is working fine as the car starts and runs. I thought about a blockage - but it would take quite a blockage to resist 40-50 pounds of pressure.

Ideas?

Bill

Luray, VA

[JohnD1956]

I assume you primed the pump by either filling it with engine oil or packing it with Vaseline ( the preferred method) before installation. But that would not explain the sudden loss of pressure earlier. Did the oil pan have a lot of sludge, to the point of blocking the pickup?

If possible, I would consider holding the old pump over a pan of used engine oil with the pickup tube submerged and then spinning the gears to see if the old pump still worked. If necessary, prime the old pump by filling it with old oil too. Not that this would explain the sudden loss. But if you know it still works then the sudden loss has to be a loss of the prime in the oil pump itself. In this case I would look for a hole in the pickup tube, or a failed gasket on the pump body.

[highcking]

John - I may have slipped up. It's been many years since I had an oil pump issue. The 1958 Buick Shop Manual's section on checking/replacing an oil pump makes no mention of priming. Now that the oil pan is back on ... would it be worth trying filling up the oil filter and overfilling the pan to submerge the pump? Pull the spark plugs to spin faster? I might be able to use the method of pulling the distributor to spin - but the distributor is so far back I'm not sure I can set my drill directly over it.

The previous pump could have had a gasket failure - the gasket was in poor shape when I took it apart. That would explain a sudden loss of pressure.

[Smartin]

I would pull the distributor and manually prime it. This will tell you once you actually get pressure, since the drill will load up tremendously once it primes. It may take a minute, too.

Why did you swap to the 59 pump? I am nervous there might be a difference that is creating a problem. Did you compare the two to make sure they looked the same?

[Bhigdog]

I've never primed a pump and never had a problem getting pressure. But what I do is remove the distributor and spin the pump with an electric drill. You can feel the drill lug down when it starts pumping. I don't think you have a problem other than no prime and the relatively slow cranking RPM. ..................Bob

[highcking]

Adam - it did look the same minus the vacuum unit. Apparently the 57-58 pumps were problematic, at least that's an often- expressed opinion. I can see how the vacuum part would fail, but to be honest the oil part looks just like the 59 unit.

I would pull the distributor and manually prime it. This will tell you once you actually get pressure, since the drill will load up tremendously once it primes. It may take a minute, too.

Why did you swap to the 59 pump? I am nervous there might be a difference that is creating a problem. Did you compare the two to make sure they looked the same?

[highcking]

Bob - I plan to make a priming tool from a used oil pump shaft and do as you suggest. I'm intending to rebuild the distributor anyway.

[Caballero2]

Before you pull the distributor, make sure it is seated. The hold down clamp keeps the distributor seated and the flange on the distributor should be flush with the engine block on the left side. if not, the engine will run and the oil pump will not. I have experienced this condition. - Dan

[JohnD1956]

John - I may have slipped up. It's been many years since I had an oil pump issue. The 1958 Buick Shop Manual's section on checking/replacing an oil pump makes no mention of priming. Now that the oil pan is back on ... would it be worth trying filling up the oil filter and overfilling the pan to submerge the pump? Pull the spark plugs to spin faster? I might be able to use the method of pulling the distributor to spin - but the distributor is so far back I'm not sure I can set my drill directly over it.

The previous pump could have had a gasket failure - the gasket was in poor shape when I took it apart. That would explain a sudden loss of pressure.

I was thinking that you probably lost the prime in the pump either through a gasket failure or by sludge in the oil pan changing the flow of oil and creating a vortex while the engine was running, allowing the pump to suck air.

I do not think you can simply remove the distributor and drop oil down that hole and prime the pump. The pump has to be sealed or it would never pump the oil. But I can't recall if the pump has a separate cover or if it just bolts directly to the block without a top plate?

I do not know how best to prime the pump while it's installed and would have to study the oiling system to see if there was a place where you could theoretically fill the pump on the discharge side.

[Bhigdog]

Pump is self priming. It just takes time and RPM's.......................Bob

[Shakadula]

H, did you figure out your issue?

[highcking]

Yes. I finally pulled the distributor and discovered that the oil pump shaft was not properly engaged with the distributor shaft - which is the one being driven by the camshaft. I got the engagement right (not that easy, given the location...) and the oil pressure spun up to normal as soon as I cranked the engine. Not sure that arrangement is the best, but I doubt I'll have to mess with mine again.

H, did you figure out your issue?

[Shakadula]

Thanks for getting back to me. My issuse was stink bugs in oil pickup tube cause I had it laying on the floor of the garage for months while I rebuilt my motor. Didn't blow it out before I reinstalled it. Stupid really but live and learn. Took me days and days to figure it out.