Overdrive Pump

[John Turney]

First, I like the new forum feature that shows similar threads when typing in a new thread title. Unfortunately, none of the threads answers my question.

OK, now with the background. Engine and transmission are newly rebuilt. The guy who did the transmission fixed 2nd gear and "didn't touch the overdrive" except to remove from the transmission and reattach to the transmission (after some difficulty). The OD was working fine before.

Now the OD doesn't work at all. Went through the electrical tests and the valve setting lever - all OK.

In shop manual section, G.7, a test of the pump is specified as: "Jack up the rear wheels of the car, then with the engine ticking over and the valve plug [#23 on Fig. G.3.] removed, engage top gear. Watch for oil being pumped into the valve chamber. If none appears than the pump is not functioning." Well, no oil appeared.

My guess is that when the guy reattached the OD to the transmission, he didn't get the pump plunger on the cam, which is on the transmission output shaft. The cam slides on the output shaft and is held in place by the roller on the pump plunger.

Question: Is it possible to get the pump plunger on the cam without separating the transmission and OD? Or separating it just enough to move the cam, so we don't have to go through the realignment of the transmission and OD?

 

[Healey Nut]

If I remember correctly you can’t reinstall the OD onto the gearbox unless the pump plunger is retracted and then released onto the cam lobe once the OD /gearbox is fully mated together , it just won’t go together the pump roller comes up against the shoulder of the cam lobe and prevents you mating the OD to the gearbox , you have to lift the pump plunger to get the OD fully together against the gearbox . ( now if you force it etc you would probably break something .
Did he possibly wire up the pump plunger to hold it retracted and forget to remove the wire ?
Did he remove the output shaft cam lobe and forget to put it back?
Do You have a pressure gauge that you can install on the OD to check the pump pressure ?

 

[Healey Nut]

I think if you remove the side cover plate/ solenoid you can look in there and see if the pump plunger is sitting on the cam lobe , simply rotating the gearbox by hand will show you if the plunger is moving up and down .
you may have to Jack up the back end of the transmission a bit to get better access .

 

[roscoe]

To answer your question yes, you can pull the oil pump and reinstall it in place.

Low oil pressure is not too uncommon but no oil pressure is curious. Mayhaps one more thing to put in your mix is that the OD pump plunger ( i.e. plunger and fork with roller) is not symmetrical on the fork end and may be installed turned around the vertical axis 180 degrees off. If you don't know this it would be possible to install it wrong. The fork holding the roller is machined on one side for clearance and not on the other. I know this because when I ran my OD for the first time it produced no oil pressure.
After much troubleshooting I finally got it out and apart and found that because the plunger was installed by the PO incorrectly it had jammed and actually bent the plunger shaft and gotten stuck in the down position. When I bought the car in boxes the transmission and OD looked pristine so I installed it as was. He couldn't "remember" if the OD had been working when he tore the car apart. The jam was tight enough so that spring pressure would not allow it to return and cam following was lost. IIRC, with the big oil drain plug out, you can see the cam and follower. Pulling the oil pump assembly out isn't a big job and if you did that you could verify whether all is well or not. The oil pump body was salvageable but not the plunger and roller. It didn't damage the OD or transmission in any other way.

If you do end up pulling the pump there is a nice little trick to reinstall it using a length of thin.020" safety wire to tie the plunger down to get the roller on the cam and the pump body in place. Cut the wire and pull it out and you're good to go.

 

[Bob_Spidell]

BTDT. Most likely, the pump drive cam is installed wrong way-round. Easy 'nuff to do.

 

[CraigC]

I'll second the incorrect installation of pump cam, with correct installation and damaged pump as a distant second.
John I have a pressure gauge if you would like to use it. Will need to pull the trans tunnel off to install it.

 

[John Turney]

Thanks, Craig. No need of a pressure gauge yet. There is no oil flow. May need it later.