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MG MGB Technical - Testing an oil pump?

67 BGt with an original 5 main fresh rebuild professionally assembled. Initially couks not get oil pressure. None. First time I ended up being unable to work up pressure, so I thought i was not getting the pump primed.

The machine shop has a nice pot oiler I borrowed and hooked up to the shop air and pushed through 4-5 quarts of oil into the block at about 90 pounds of pressure through the oil gauge line filling and lubricating the whole system including the filter and cooler. Tried again and no pressure as I could not get a drop out of the gauge port on the block or the big cooler line directly behind it. Pulled the pan to confirm the correct 5 main gasket was installed and it was. Dumped oil into the rear cooler line and spun the engine backwards to fill the line again and buttoned it back up....Nada, no pressure. I am now both perplexed and not happy that I did not check the pump which was replaced when rebuilt. They do about 10 MG engines a year and have done many over the years. Lots of good assembly lube used and oil went everyehere when I used the oil pot under pressure including the filter, rockers and sump.

What else should I be looking at besides the pump itself at this point. How does one check an oil pump to determine if it is at fault? Appreciate any thoughts or experience. I am stuck. Thanks
R Stegs

Are you sure the oil pump drive shaft/gear is in there? And the pressure relief valve and spring?
There parts are known to fall in the cleaning tank, residing there forever more.

FRM
FR Millmore

Fletcher. I would assume, if he removed the sump and states: "Pulled the pan to confirm the correct 5 main gasket was installed and it was.", that he would have noticed if the pump's drive gear was not there. I have more question, in my own mind, about how he knows that he has the correct oil pump gasket. Especially, since all of the symptoms he describes have, as their most common source, the use of the incorrect oil pump gasket.

But, I had not thought about someone not installing the oil pressure relief spring and plunger. That, too, would give the same symptoms--but I have never seen it happen before.

Les
Les Bengtson

Here is a link to an illustration of the two gasket types:

http://www.chicagolandmgclub.com/driveline90/0693/tech.html

I hope it will come up as a "hot link" when submitted. If not, you can either copy and paste or go to the Chicago Land MG Club website and check through their tech articles.

Les
Les Bengtson

Les -
"Assume" is how these things happen!
Having met both situations on other people's work...
But I could still ask if the timing chain is there.

FRM
FR Millmore

"pushed through 4-5 quarts of oil into the block at about 90 pounds of pressure through the oil gauge line filling"

Did you have a gauge on this? Or simply know that whatever you were using to push the oil through is *capable* of developing 90psi? And at what flow rate? If the former then unless the flow rate of your oil is significantly more than the engine pump, which is pretty prodigious in its own right, then there can only be a problem in the 'circuit' through the strainer, pump, etc. to the oil gauge tapping i.e. the engine pump isn't generating any flow.

If *no* pressure is being generated by the oiler, simply flow, then the engine pump could well be pumping oil, but it is escaping back into the sump before it can develop any pressure. This could be from any number of causes like a crack in an oilway, drilling plug not missing etc.

If you didn't actually measure the pressure using the external oiler, then I would see if *that* generated any actual pressure, or simply flow.

Did you try turning the engine *backwards* with the external oiler connected? That should fill the oil pump and the circuit down to the strainer with oil.

Perhaps the simplest diagnostic step is to disconnect the gauge at the block, crank the engine, and see if any oil comes out. No flow, then the problem lies back through the pump. Some flow but no pressure, then the flow is escaping somewhere it shouldn't. And you have tried another gauge, haven't you?
PaulH Solihull

Regarding the oil pump gasket, I'll add this. If you look at the wrong gasket when it is placed on the block, it looks believable that it is correct. It fits the studs, and it goes around all the holes in the block. If you place the wrong 3-main bearing gasket on the 5-main bearing pump, it becomes apparent that it is incorrect because it does not go around all the holes on the pump.

I made this mistake. With the engine upside down on an engine stand, it looked okay. In my defense, the head gasket set that I had only contained one oil pump gasket. The set had been opened before shipping to provide a different head gasket, so I guess the correct one was accidentally pulled out then.

Paul, if I'm understanding it right, he did crank and get no oil with the pressure gauge port open:
"Tried again and no pressure as I could not get a drop out of the gauge port on the block..."

Charley
C R Huff

Forget the oil gauge fitting - undo the rear cooler line from the block and pump oil in the rear fitting till it reaches the top.

If it keeps going down you have a leak on the pump / OPR valve.

If it stays filled to the top, spin the engine backwards to prime the pump, then on the starter and oil should pump up if the pump is working correctly.

Bad joints at the oil pump / block or oil pump pickup will allow air into the pump and it will either pump weakly with lots of bubbles or not at all.
Chris at Octarine Services

Thanks gentlemen. The gasket is the one shown on a couple of sites as the correcty 5 main, as I was actually very surprised to see it.... I thought for certain that the wrong one was the culprit.

I checked for pressure at the sender unit adapter WITHOUT any line or gauge hooked up, same thing with the rear cooler line off. Not a drop. When I poured oil into the rear cooler line it seeped in very slowly and took about a cup or so to top off then bubbled a bit and settled into the line. Turned by hand backwards and then cranked and cranked with not a drop coming back out, nor the sender adapter either.

Regarding the pot oiler, I do not know how the flow or pressure works from the pot. I set the shop compresser to 90 pounds after filling the pot with fresh oil and leave the air line hooked up, then connect the oiler line to the sender unit adapter in the block and turn open the hose line allowing the oil from the pot to be pushed into the system. In observing the drawdown gauge on the pot oiler I did see that the FLOW was very slow and do not have any reference for how fast the oil should fill. It was at least a couple of minutes to fill through the small sender adapter. I do not know if that is instructive or not but it seems that I can at least eliminate blockage there as it filled the sump, the oil filter and rockers etc.

Next I am going to research the pressure release bypass and the oil pump itself. Would a missing PR give zero pressure at the sender and nothing to the rear cooler? Defective stuck versus missing? Any pressure? I will certainly pull the PR opening and have a look before I open the sump again.
R Stegs

I suppose I would be looking at the pressure regulator next also.

Here is another rather far-fetched stab in the dark:
I had a friend who ran his hydrostatic drive riding mower into his lake. After draining and replacing all the fluids, and filters, the mower would not move. He took it apart a few times and couldn't find a problem. He brought it to me and we took it apart a few more times before I figured out the hydraulic filter was wrong. He had gotten it from an autoparts store by using the cross-reference chart. It was internally checked valved in the wrong direction for the mower, so it could not move any fluid in the right direction. We put the right one on, and all was well.

Charley
C R Huff

"When I poured oil into the rear cooler line it seeped in very slowly and took about a cup or so to top off then bubbled a bit and settled into the line."
>>That indicates that the relief valve is in place and not stuck open.
Turned by hand backwards and then cranked and cranked with not a drop coming back out, nor the sender adapter either.
>>That's what Chris told you to do,and if nothing comes out the pump is not working.
I'll stick with my pump drive theory until proven wrong.

FRM
FR Millmore

As I re-read the advice I noticed an interesting clue from Les and Fletcher. When I dropped the sump to pull the pump to confirm the correct gasket, I was not really focused on the oil pump itself but I do not remember a "drive gear" on the shaft that protrudes up into the block.

I guess a simple question would be, is the shaft supposed to be topped with a gear of sorts? My recollection (wont be able to pull it again for a couple nites) is a straight smooth shaft and nothing but shaft. When I refitted the pump up into the block it stopped tight about one quarter to three eighths of an inch from being seated and I gently wobbled the pump to allow it to click (felt like it engaged) or fully seat the remainder of the short distance so the mounting studs protruded enough to allow the nuts to be tightened onto the studs. Based on what you gentlemen have provided to me, it sure seems like Fletcher's deduction regarding the pump seems most likely. It also seems to me that even if the pressure relief failed, I would still get a very very small amount of oil pushed towards the sensor adapter port and cooler line?

Your input has helped me understand the oiling system. I will let you know the outcome. The senior man at the machine shop said he was going to come out and have look once I pull the sump again because he is also perplexed and is suspect of the pump. He thought the failure of the relief valve was worth looking at but short of failure to install was less suspect.
R Stegs

The gear/shaft is a separate piece that engages the cam. It normally comes out with the pump, but sometimes sticks in the block - somebody on here recently couldn't get the cam out because the pump drive was still in place. That's how they get lost. It has a tang on the bottom that engages a slot in the shaft inside the pump proper. The tangs must align as the pump is pushed home, which it will only do at two positions. That would account for your 1/4", but that could also be some other alignment point as the pump casting goes into the block. If the pump is forced into position with the tangs not aligned, it will do evil things, as the pump may be damaged or broken, or the drive will be very "iffy".
An odd point is that there is no picture of this arrangement in the WSM, or in the aftermarket books I have, though it was pictured in the original B series WSM for the Magnette.
I had a customer 4.2 XKE once (similar arrangement) on which the factory install of the pump was out of line, and it pushed the shaft into the gear. There was just a few thou engagement, which worked (7000 miles) until the owner started the car in zero F weather, when it sheared the tiny bit of tang that had been engaged. Fortunately, she had been taught to watch the OP gauge on start up, so she shut it down, and I fixed it in her parent's driveway, no harm done.
I find all this somewhat odd, since I've put many engines together and never had a problem getting OP. I coat the pump parts with Lubriplate and fill as much of the passages as possible with oil, but I do not "pack" the pump or use a pressure fill. After all you did I would expect instant OP. While you are looking, you might want to open the pump and make sure both rotors are in there!


FRM
FR Millmore

When you are looking at the pump, check to see if it is the correct one. When I got my 68 BGT, it had suffered a recent engine rebuild. Shortly after I started driving it, the oil pressure went to zero.

When I pulled the pan, I found a brand new, but wrong, oil pump. I suppose it was for a 3-main bearing, but I don't really know. It was about 1/2 or 5/8 inch shorter where it enters the block. This meant that the pump shaft gear was just barely engaged with the cam gear.

It also meant that the pump drive shaft was not locked vertically. Since it is a bevel gear, when the engine kicked backwards on shutdown, the shaft was pulled up out of the pump and did not fall back down into engagement.

Charley
C R Huff

Here's a diagram showing the arrangement of the pump drive that Fletcher explained in words. It also shows the pressure relief valve components.
http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=192
Mike Howlett

Found it in Moss. There is only one drive gear listed for all MGA 1500 through last 1800, so the pumps must be dimensionally the same as far as the drive goes, and I don't recall any differently. Charley had something strange indeed.

FRM
FR Millmore

Perhaps off the mark but I remember a thread some time ago where an engine block clean out/rebuild had resulted in the incorrect positioning of an oil gallery plug. That is wrong gallery closed, wrong gallery left open - if I recall correctly, in the rear RHS corner of the block, just wide of the rear main. I wonder?? Perhaps worth a look when the sump next comes off.
Roger T

Well, Fletcher, the mystery deepens. I wonder what oil pump they put in if it wasn't for the 3-main brg. It was not by any means the only bad mistake they made when the engine was done, but I had given them the benefit of the doubt that at least it was an MGB pump. I guess not. The cylindrical part of the casting that slides into the block is the part that was 1/2 to 5/8 inch shorter.

Whatever it was, I suppose if one person made the mistake, someone else could make it too.

Charley
C R Huff

Mystery solved...no oil pump drive as you suggested. When I pulled the sump and pump and peered up into the block and did not see it, I was both surprised and glad to solve the issue. When I called the shop and talked with the assembler, he was contrite and
arranging for compensation. Seems the old pump was pulled with the drive stuck in it and tossed aside to the scrap bin. New pump on the bench, no drive...has to be in... no excuses he said but it explained why there was not a drive left over. I am finally glad to move on. You folks provided me with lots of help sorting through the oiling system. Fletcher, assume nothing is a good practice. Thanks all.
R Stegs

Glad to help.
Next rule: Throw nothing away until everything is finished and tested.
Actually, I rarely replace an oil pump, but
I carefully check clearances, especially on new ones. Not uncommon to find the new one worse than the old. You do at least know that the old one worked.

Charley - Can't imagine where they found a pump that fit but was not right. However, there was a change very early in Magnette at engine 1460, so maybe Austin A40/Metro had a shorter pump body, 3 main style of course. This is not well documented in the Magnette book, as it only shows the later type with the same drive gear "commencing at engine 1460" as all later engines.
Now I found a reference to a pump and drive change at that point, and the pump spigot diameter was increased so that the later pump will not fit in the earlier block, but the early pump might fit the late block but would be not located properly. Early blocks are marked "15" on the RH side, later are "1500"

FRM
FR Millmore

Glad to see compensation is coming. That drive unit lists for $80 in the Moss catalog. I hope that they have it in stock. RAY
rjm RAY

This thread was discussed between 13/09/2010 and 16/09/2010

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