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MG TD TF 1500 - New engine rebuild - no oil pressure.

New crank, bearings, cam, rings, valve job..... y'know the drill. Oil pressure before rebuild was 60# dependably.

Oil pump got new gears. The original pressure valve was cleaned, inspected and re-installed. The proper oil pick-up gasket was installed inside the case, and the passage through the crank gasket was properly aligned.

On cranking, no oil pressure. A 10 second run, zero oil pressure. Oil filter empty. I won't run it again like this.

I dropped the oil pressure valve and the cavity was dry. I could see the gears and gave it a crank - the gears are turning. I primed the pump through the prime cap several times and filled the oil filter.

I've seen cars sitting for 20 years start and run just fine.... I'm missing something. What?


My experience is that it takes about 25-30 seconds of cranking to begin to see oil pressure in a newly assembled engine. I hope that your "10 second run" wasn't with the engine running. Bud
Bud Krueger

From Moss Motors: "Donít ever just install a new oil pump right out of the box. There are two easy methods of insuring the oil pump will create the seal needed to pull oil in on initial start up. The first method is to pack the oil pump full of Vaseline. Vaseline will create the seal needed for vacuum to draw in oil. The Vaseline will then be quickly dissolved into the oil. The second method is to use engine assembly lube and lube all the moving parts. The goal here is to sufficiently coat all moving parts so when the pump spins for the first time vacuum is created to draw the oil into the pump and then push it through the system."

TW Burchfield

I wonder if I can pump vaseline into the gears through the pressure valve opening?

I plan to use the crank handle to ensure that I do have pressure before I use the starter motor, initially without spark. Once pressure is again confirmed then & only then will I try & turn her over. Overly cautious? Probably. But I've been waiting for 45 years so a little bit longer really isn't going to matter. I've also heard that Vaseline is a good way to prime the pump. Good luck Mitch. Cheers
Peter TD 5801
P Hehir

Seal off the breather tubes in the tappet and rocker covers and then pressurise the sump via the dip stick hole. I used a blow gun connected to my compressor but an adaptor to a foot pump will do. This pushes oil up into the pump. And yes Vaseline in the pump gears does help.

Good luck

Jan T
J Targosz

Its a very common problem and the above solutions should all work. I don't like putting Vaseline into the engine oil, so my alternative (copied from others) is to use a cheap pump up garden sprayer. Remove the spray head, disconnect the engine pressure gauge capillary, and find a fitting to connect the two (an old fuel pipe connector does it). Then fill the pump with engine oil and pump into the engine filling all the oil galleries down stream of the pump. Reconnect the oil pressure gauge, and remove the rocker box cover, then crank the engine by hand until oil is seen spurting from the rockers. Then start the engine and you will have pressure.
Dave H
Dave Hill

The last time i had this problem on a TR6 ehm... I was told to fill the pump prior to assembly with Graphogen. This is stuff like black butter and does not run out of the pump. you then get instant pick-up/pressure. does no harm to the engine long term
E I Buckley

remove the priming plug above the pressure control valve. Fill with oil and push down the ball valve with a small driver to allow oil to the suction side of the pump while turning the motor with crank handle. You will see the oil pass through the pump. This will fully prime the pump. Put the plug back in and wizz up the motor (plugs out).
Ray TF 2884
Ray Lee

What style pump? On early pumps, remove the top output oil line, fill the pump with oil, rotate the engine backwards a bit which will suck oil into the pump. Repeat several times. George
George Butz

I had a similar issue after a recent rebuild. I filled my oil can that has a pump action with engine oil. I used this to fill the oil filter unit and then pumped oil into every oil plug I could find. Then having removed the spark plugs I turned it over on the starter motor. I had the rocker cover off and after a while I could see the oil circulating from several points on the rocker shaft.
Then ran engine with fuel and got good oil pressure - job done !
Mel Pascoe

Packing the oil pump gears with Vaseline (petroleum jelly) is a good step - but- do not rotate the engine backwards or you will break the seal and have an air pocket. I can not imagine that I can crank the engine over by hand fast enough to develop initial oil pressure. Peter, you must have fantastic arm strength. Bud
Bud Krueger

Bud, The backwards deal only works with oil, you are correct it won't with Vaseline or grease in the gears. I have successfully done that a couple times. George
George Butz

When I build an engine I use a pressure pot and fill the engine through the outlet for the oil pressure gauge.
K-mart have a small plastic pressure pot to spray various liquids for less than $10.00.
Doing it this way you can even see the oil oozing around the rockers.
One other problem can be the oil gallery between oil pan and block.Gasket can completely block that hole.
Sandy Saunders

Rocker arm shaft right ways around? Assembly lube where needed, etc?

Do like the TC owners do, to ensure oil is in the pump gears prior to any cranking after an oil change (usually not needed) or after the car has been sitting a long time, pump or engine work/rebuild, or after the PRV has been removed for whatever reason, etc. After filling up the filter with as much oil as possible, then remove the supply line to the pump (top of pump). Find a good fitting funnel type thing and stick it in (either direct into pump body or into supply line end- removed at filter, whatever is easiest). Put in 4th gear, add a few ounces (3-4?) of oil to the funnel and push the car backwards until the pump draws the oil in from funnel. Don't push too far and let it suck in any air! Re-attach line and crank some with ignition switch off, or just start it. This method should be just as effective as the vaseline method on a rebuilt/new pump. Some crank with ignition off and valve cover off, to visually be sure oil if flowing up top prior to starting.

The pressure tank method has been around, and some swear by it. I don't see why the pressure method would necessarily prime the pump? Maybe it does prime it, but I prefer knowing a few ounces of oil have been drawn in by the pump itself.

D mckellar

Success. I turned the rear tire in reverse and primed the pump.

I ran it for 20 mins at 2000 to cndition the lobes/tappets. It sounds great.

Driveway trials start tomorrow.

And Bob's your uncle. More than one way to prime a pump.
Bruce Cunha

This thread was discussed between 07/03/2017 and 09/03/2017

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