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No Oil Pressure following some bearing swaps

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simpson

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A buddy of mine just replaced his thrust washers, main and rod bearings. Oil pump was removed and replaced in the process. He briefly started the engine but got no oil pressure on dash gauge. He has spun the oil pump with a drill and got a 50 lb reading. Anyone have any ideas what could be the problem? Is it possible to create a gap between the oil pump to dizzy drive junction when removing and replacing the oil pump?

The car is a 74 TR6.
 
Did he do all the normal stuff to be sure that the bearings were the right size like Plasigauge them?? I have seen bearings that were not within tolerances for what they were marked. And the need to match the crank since what he took off is no guarantee that's still the size required.
 
tdskip said:
Yikes.

Nothing else changed from spinning it over with a drill and installing the distributor?
Click to expand...
Nothing that I know of. I know that the rate of spin with the starter is much slower but even so one gets oil pressure then.
 
I believe that that it's possible that after the spin with the drill that the drive gear was not replaced in alignment with the oil pump's driven dog.
Waiting to hear from our friend about this, but there are indications that this step was overlooked.
 
MikeP - He just replaced the old worn bearings with new replacements. No plastigauging. He turned the crank over with each bearing replaced to check for binding etc. Seemed to be okay before buttoning it up. How would new bearings, if installed correctly, oil holes & all, cause zero oil pressure anyway? I don't understand exactly how that works. I can see how loose, worn bearings might reduce oil pressure some.
 
Hey there poolboy. I'm hoping its something like that. Its too hot and cramped under jackstands for us old guys down here.
 
simpson said:
How would new bearings, if installed correctly, oil holes & all, cause zero oil pressure anyway?
Click to expand...
I seriously doubt this is the issue, since he saw pressure turning the pump with a drill. Has to be lack of drive to the pump, as poolboy suggests.

However, if the crank had been turned to, say, .030" undersize and the bearings he got were somehow standard (box marked wrong, maybe), then new bearings could indeed cause low pressure worse than before.
 
The old bearings had no markings other than the "part #" indicating oversize. In other words no .010, .020 etc.. I believe they were original bearings that just showed normal wear and his OP was pretty decent.
I'm still waiting to hear from our friend although he says that the slight rotation of the intermeshing gears may have caused a lack of engagement between the driven dog and the slot. Seems to me that if the gear was sitting above the dog that the dizzy would not fully seat on the pedistal though. I just don't know though because I've never been in that situation.
Here's a question.
Once he got good oil pressure with the drill, how long do you think it should take for OP to register on the gauge with the engine at idle assuming the cam was working the oil pump ?
 
Plastigauge and whether the bearings are correct is a non-issue because they got oil pressure with a drill. I'd forget that path (for now - once you get the pump going and you have pressure and it's low, then you can look in that direction) It's been a while but it seems like the drive gear is located on the dizzy on a TR6. I suppose it's possible to get the dizzy down far enough for it to engage the cam but not far enough down to engage the oil pump shaft. That's about the only scenario I can see where you can get oil pressure with a drill but not with the motor running.

I'm interested in knowing the outcome of this one.
 
We will keep this updated, Rich.
The drive gear for the oil pump and the distributor is a separate gear so to speak. It's not really attached to either the dizzy shaft or the oil pump shaft.
On the bottom of the drive gear shaft is a slot for the oil pump's driven dog at the top of the oil pump shaft.
On the top of the drive gear is an off set slot to recieve the distributor shaft's driven dog..
As the drive gear is meshed with the gear teeth on the cam, the drive gear undergoes a slight rotation.
I'm hoping that the slight rotation caused a misalignment of the oil pump shaft's dog with it's home in the slot on the bottom of the drive gear.
If that ain't it, I'm out of ideas.
 
Could the pin that goes into the cam drive gear and oil pump drive shaft have sheared or fallen out? I have seen this happen on TR3s and 4s with the keyway.Just a thought.....
 
Sure worth checking. The shaft may still just be in the drive gear due to friction.
 
So that's how it all goes together. I mistookingly thought the cam drove the dizzy shaft which slotted over the oil pump tang/dog, kinda like the tool used with the drill to spin the pump. Led me to post a bunch of nonsense.
 
From what I hear, you'll be seeing it first hand in a few day's, George.. You can get a preview if you have a Haynes; see Figure 1.29 in Chapter 1
 
And for those not sure of what we are talking about, this is it. Picture #1 shows the distributor side of the gear, #2 shows the bottom of the gear where it engages the oil pump. #3 shows the gear in place and engaged to the cam #4 shows the proper gap (done with paper shims under the distributor housing plate) being set and measured #5 shows the gear in place and all set for the distributor and #6 shows the oil pump in place.
 

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Problem uncovered - the oil pump shaft got driven downwards into its press fitting inside the impeller when the oil pump was tightened down on reinstall because the pump shaft drive dog was not engaged in the drive gear slot. This shortened the height of the oil pump shaft so that no amount of adjusting or turning would get it to engage the slot in the cam driven gear shared with the distributor.

Mike (me buddy) has a new oil pump on the way from Goodparts, and will be very careful to line the OP dog up in the drive gear slot on install.

He and I thank all of you for your advice and suggestions.
 
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