H/W Single Oil Pumps

JBP650 · Post by **JBP650** » Mon Mar 13, 2006 1:57 pm

Can anybody please help me with a pump that does not 'Suck'?
Following a complete rebuild of a 1951 model 18, I came to the exiting bit when the engine is kicked over for the first start up.
After (eventually) running for a few minutes I became aware of a pool of oil eminating from the engine breather but none returning to the oil tank.
On inspection it was found that the engine was retaining the oil in it's crankcases. ie pump delivery OK but scavaging not OK.
Oil will only start to appear in the tank filter when the oil in the crankcases rises high enough to flood the suction line, by which time I'm panicking!!
Stripdown of the pump (engine insitu) followed on 3 occasions with special attention paid to the end caps and gaskets. The pump was changed for another good condition 'used' one, the oilways were prodded with wire and blown through with air (no obstruction in the suction lines)The pump housing checked for damage (none) and the pump clearances in the housing checked (no excessive clearance)
The sump plug was checked for clearance with the suction line - OK

Has anybody had a similar experience and can offer any advice to overcome this problem - I would be most grateful for all replies.
Thanks for reading about my problem.
Kind regards
John

Biscuit · Post by **Biscuit** » Mon Mar 13, 2006 2:27 pm

Have you tried running the engine without the oil filter?. Examine the top of the filter, is there an excessive overlap of the felt?, if there is cut it back as short as possible.

Don Madden · Post by **Don Madden** » Mon Mar 13, 2006 4:19 pm

Do follow other tips, such as the oil filter obstruction. There are a couple of problem areas that trip up the unwary. The rear oil pump cap must be sealed to hold a vacuum for a portion of the plunger stroke until it uncovers the suction port sufficiantly. The suction port from the sump is drilled from near the drain plug to a point high in the case, where it intersects with one drilled through the pump bore a a sharp angle. I have found portions of gasket material, the notorious silicon sealer, etc. trapped at the junction. Probing with a wire will not detect the obstruction. I use two long extension drills, manipulated by hand only, up both drillways simultaneously. If the port is clear, you can feel the two bits contacting each other. If not, twirling them by hand will fish out the offending material. Air pressure can be used if plugs are made that span the gap from bottom of sump to drillway and/or one made to fit the pump bore. Appropriate drillways must be provided in either in order to provide a path for the air. Pre-'64 short stroke engine cases are complicated by a variation of the above with a short drillway near the inlet cam bush plugged by brass connecting the other two oil passages. Please try the tips & report back to us. Cheers, Don.

JBP650 · Post by **JBP650** » Mon Mar 13, 2006 5:41 pm

quote:
Have you tried running the engine without the oil filter?. Examine the top of the filter, is there an excessive overlap of the felt?, if there is cut it back as short as possible.

Thanks for your very prompt reply. Yes I have tried with filter top nut and 'tophat' removed - but no oil except as described when crankcase level rises.
Best regards
John

JBP650 · Post by **JBP650** » Mon Mar 13, 2006 6:06 pm

quote:
Do follow other tips, such as the oil filter obstruction. There are a couple of problem areas that trip up the unwary. The rear oil pump cap must be sealed to hold a vacuum for a portion of the plunger stroke until it uncovers the suction port sufficiantly. The suction port from the sump is drilled from near the drain plug to a point high in the case, where it intersects with one drilled through the pump bore a a sharp angle. I have found portions of gasket material, the notorious silicon sealer, etc. trapped at the junction. Probing with a wire will not detect the obstruction. I use two long extension drills, manipulated by hand only, up both drillways simultaneously. If the port is clear, you can feel the two bits contacting each other. If not, twirling them by hand will fish out the offending material. Air pressure can be used if plugs are made that span the gap from bottom of sump to drillway and/or one made to fit the pump bore. Appropriate drillways must be provided in either in order to provide a path for the air. Pre-'64 short stroke engine cases are complicated by a variation of the above with a short drillway near the inlet cam bush plugged by brass connecting the other two oil passages. Please try the tips & report back to us. Cheers, Don.

Thanks Don for your very clear description.
I have had thin pieces of wire entered simultaneously through the suction oilway and the diagonal one as per your description and can feel that they do touch. Also I have had high pressure air inserted into the oil ways and they certainly pass air OK.
My next move will be as recommended and try fishing with a thin drill bit by hand.
Do you happen to know of any instance where there has been an air leak in the suction pipe formed in the crankcase ? Possibly by internal damage or porosity ? The only way to check this is to remove the engine from the frame and split the cases. Obviously, this is a last resort.

Thanks again
Best regards
John
I certainly did not spot a

Biscuit · Post by **Biscuit** » Mon Mar 13, 2006 6:34 pm

I pass then John.

itma · Post by **itma** » Mon Mar 13, 2006 6:49 pm

I know this could be a daft question but are the pipes connected properly?
It has been known they be reversed

Don Madden · Post by **Don Madden** » Tue Mar 14, 2006 2:29 am

Not a daft question, itma. I assumed they were correct as John stated that he was getting oil to the engine. I should know better than to assume anything. Whenever connecting up the lines after removal, after putting oil in the tank, remove the front plug screw from the oil pump to bleed the line & insure the oil is getting to the feed pump. If not connected properly, no oil will flow. Another possible resriction in the return flow is the junction of the drillway from the return pipe fitting, (the upper one), & the oil pump chamber. A horizontal passage is drilled through the rear plug screw orfice, the one in front of the guide screw but horizontal. The angled one below blocks the drillway up to meet the one from the sump. With the plunger in the forward most position & the rear plate in place, you sould be able to blow air from either of these plug orfices to both return pipe & sump pickup. I have not seen a flaw in the casting cause an air leak, but the rear plate must be flat & clean with a good gasket fitted. I have seen badly damaged cases with deep scoring at joint faces.

JBP650 · Post by **JBP650** » Tue Mar 14, 2006 10:39 am

quote:
Not a daft question, itma. I assumed they were correct as John stated that he was getting oil to the engine. I should know better than to assume anything. Whenever connecting up the lines after removal, after putting oil in the tank, remove the front plug screw from the oil pump to bleed the line & insure the oil is getting to the feed pump. If not connected properly, no oil will flow. Another possible resriction in the return flow is the junction of the drillway from the return pipe fitting, (the upper one), & the oil pump chamber. A horizontal passage is drilled through the rear plug screw orfice, the one in front of the guide screw but horizontal. The angled one below blocks the drillway up to meet the one from the sump. With the plunger in the forward most position & the rear plate in place, you sould be able to blow air from either of these plug orfices to both return pipe & sump pickup. I have not seen a flaw in the casting cause an air leak, but the rear plate must be flat & clean with a good gasket fitted. I have seen badly damaged cases with deep scoring at joint faces.

Thanks you all again for your interest.
Yes - I do have the oil feeding line into the pump onto the bottom crankcase connection and the top connection back to the oil filter compartment.
I have also blown air from the return oil line inside the oil tank (filter outlet pipe) back to the engine via the feed line with the pump and blanking screws removed. There was no obstruction, proved by a considerable amount of oil blown out of the line over my overalls!)
I have previously ensured that both the rear and front end plates are true and flat by rubbing down on fine wet/dry paper on a flat surface. On Malcolm Saggers advise I also increased the thickness of the gasket on the rear plate to provide a better seal. When I last removed the end plate there was no evedence that there had been any leakage. The crankcase has no damage where the plates contact.
I did have the top (outlet) thread repaired prior to re-assembly with a screwed coupling inserted into the crankcase but I have been assured that this could have no bearing on the problem.
My next move will be to strip the pump down again(the 5th time) and go through all the procedures you kind people have suggested to me keeping everything crossed in the hope I have overlooked something.

Many thanks to you all.
Kind regards
John

Biscuit · Post by **Biscuit** » Tue Mar 14, 2006 11:50 am

John, never ever use a thick gasket on these types of items, like carburettor bodies, they are made of crap metal, and they will just bow and you will be back where you started.