Oil leak at fuel pump

andrew honychurch · #1 03-08-12, 19:57

OK, so a bit of a weird problem has arisen on the T16. Basically, I have oil being emitted out of the fuel drip hole in the bottom of my mechanical fuel pump. As it happens , its quite a lot, enough to make it un reasonable to drive and foul up my engine bay floor. It does not do it until the engine is thoroughly warm and driving reasonable hard.

On the T16, there is an oil relief valve on the oil cooler circuit, and on mine there is a very professional looking mod which takes oil from the cooler return circuit and feeds it directly back into the oil filler/breather tube directly above the fuel pump . This could be responsible for jetting oil directly into the fuel pump sump, but I doubt it as its meant to flow directly down the fuel pump pushrod tube and back to the sump.

This is very confusing, and at present I am looking at crankcase pressure , oil relief valve, cooler relief valve malfunction. I did a quick Google and found that there has been some problems associated with ensuring that there is clearance on the pushrod so that it doesn not cause a cause a crack in the fuel pump housing . Anway, any thoughts are as always much appreciated as at present I am somewhat baffled.

Lynn Eades · #2 03-08-12, 23:05

The relief valve shouldnt be bypassing, unless you have a blockage( or partial blockage) in the cooler circuit. Maybe the valve is in need of adjustment. Check the spring ball and seat. There is an adjustment proceedure in the U.C carrier book, which may well be the same.
Another angle; some a.c. type mechanical pumps are fitted with a neoprene type gasket that allows little more than the arm to poke through, at the mounting face. This would help by acting as a baffle.
Maybe you can add a drop tube to the return, so that the oil flow goes down past the pump, before it exits the tube.
Is the crank case ventilation at the sump clear? (if it uses that system)
Does it have a PCV valve and is it functioning?

andrew honychurch · #3 03-08-12, 23:14

hey Lynn, some great ideas here. intestingly I did notice that the oil cooler was not getting as warm as previouly. Also noted that the engine oil pressure was getting lower when warm. So maybe there is a blockage in the cooler which has caused the oil to get very warm and be redirected through the return valve. This valve exits , as I said, back into the oil filler tube just above the fuel pump, so maybe its part of the problem. The oil relief valve is in a large brass housing which has been soldered shut. I would have to brake this to take a look and there are no instruction in the T16 manual on setting this up. There is a thermost in the oil cooler circuit which could be failed closed but I think it would still allow flow if it has.

By the PCV valve, do you mean the crankcase breather valve as on a Jeep? If so, yes it does have one of these and I have not checked to see whether it is working, having never looked at one, I assume it can be disassembled? Any instructions on how to check it if indeed this is what you are referring to?

Lynn Eades · #4 03-08-12, 23:35

Yes the pcv valve can be unscrewed. It has a piston (valve) and a spring in it. back then , there were all the same. Note the arrow on the body showing flow direction.
The cooler bypass cap is soldered on. underneath is a screw plug that loads the spring against the ball. this is adjustable.

andrew honychurch · #5 04-08-12, 09:45

I am going to check the PCV first thing this morning. I am a bit reluctant to disturb the oil relief valve, but of course I can check whether this is allowing oil back down the filler tube by looking down the filler tube itself when the engine is running. Will report back. thank

andrew honychurch · #6 04-08-12, 19:55

ok, pulled the PCV and cleaned it not really a problem.

However the oil is flowing continually out of the relief valve into the tube directly above the fuel pump. Hence the problem. Broke the seal on the relief valve and checked it , all good. Turned it two extra turns, which stopped the flow but put the engine oil pressure up to 80 lbs!!!! Broke for lunch and a think. Back on it tommorrow. Maybe the oil cooler is plumbed incorrectly and restricting the flow??/

Edit; there are two fleible pipe that then join onto the steel pipes upto the cooler. If I was half asleep when I assembled it I may have crossed these, but I would think I have checked this was correct at the time. More confusing is the T16 manual which shows the relief valve on the side of the crankcase opposite to mine. In other words, it may be that good old British Army have assembled my engine with the relief valve on the return pipe not the outlet pipe.....Not sure what effect this would have until I can sit down and think about it. so to be clear, my valve assembly is on the pipe on the clutch housing/crankcase nearest the outside of the engine, whereas in the book it appears to be on the union nearest the middle of the engine......Would it matter?? Must do surely