TAMD41 A _ fuel regulator leak help

[MD99]

Hi folks, I wonder if any knowledge out there about a fuel leak I have from the hollow ( vent) screw on my Volvo TAMD 41 A fuel regulator. This is item 49 on the exploded parts view.

I changed the rubber diaphragm and it stopped the leak at idle, but higher revs will leak again .

Any help appreciated .

Located in Chatham, UK.

[skipperpete]

Originally Posted by MD99

Hi folks, I wonder if any knowledge out there about a fuel leak I have from the hollow ( vent) screw on my Volvo TAMD 41 A fuel regulator. This is item 49 on the exploded parts view.



I changed the rubber diaphragm and it stopped the leak at idle, but higher revs will leak again .



Any help appreciated .



Located in Chatham, UK.

You did quite well to replace the boost control diaphragm, did you make or buy the service tool to release the diaphragm from the control link?
You should not be getting fuel leaking out of the boost control vent and one reason for it happening could be a blocked fuel return line to tank so maybe run a return to a container rather than the tank.
Just a thought !
Pete.

[MD99]

Thanks Pete I will look at the fuel return line at next opportunity I get to go to the boat and report back.

re taking off the diaphragm : The short round metal shaft the diaphragm is attached to has flats at the top , not visible at first but you can get a thin open ended spanner on this ( eg a bicycle spanner ) and then easily undo the nut holding the diaphragm; it is sandwiched between two penny washers.The shaft sits inside a spring and so needs a but of pressure to hold it down while re doing the cover bolts ( 3 only) .

[DougR]

Changing the diaphragm in the aneroid should have no effect on a fuel leak from the breather, unless it wasn’t really fuel leaking but was oil instead.......

-The chamber above the diaphragm should be completely free of liquid with the possible exception of a little oil which might be leaking past the turbo seals. Changes in turbo boost pressure are felt in that chamber which move the diaphragm up and down.

-The chamber below the diaphragm is also normally free of liquid, and the volume of that chamber expands and contracts in response to the movement of the diaphragm. The air normally in that chamber moves in and out breather #45 in response to the volume changes. If the diaphragm had a split in it you might see some oil leak out the breather.....assuming there was some oil above the diaphragm.

-The area of the pump below the top cover is full of fuel and is normally isolated from the upper chambers by an O ring.

In your parts breakdown, parts # 4,5,6,7,8,23,&25 consist of the linkage that are moved by the diaphragm in response to boost increase and decrease. Their locations on the drawing are distorted...they really reside in the left side of the top cover, and #23 &25 are below the cover residing in the fuel. Pin#8 resides in a drilling that passes from the fuel chamber into the area below the diaphragm, and it is sealed by O ring #6. If this O ring develops wear, it will allow fuel to move from the lower section of the pump into the chamber beneath the diaphragm, and thus out the breather.

Besides having an external lift pump in the fuel system, there is also an internal gear pump within the injection pump which changes the internal pump fuel pressure. As the RPM goes up the pressure increases and this operates the injection timing piston and also ensures good injection chamber filling. It’s this internal pressure change that is probably causing the lack of leak at low rpm but leak at higher rpm.

It’s possible that a blockage in the fuel return line, as mentioned by skipperpete, could be causing some leakage as a result of pressure buildup in the injection pump, and that’s easy to check. My experience with blocked fuel return lines is frequently associated with excessive fuel injection and smokey exhaust. You might also check the return fuel banjo bolt on the injection pump. It normally has a restricting orifice in the bolt, and if this were blocked it might also cause a pressure buildup and subsequent leak.

Hope this helps...

[MD99]

Hi, thanks for suggestions.

As diagnosed by the forum DougR it was likely to be a simple O ring in the lower half of the pump.

The end result was get pump off boat ( took 1 hour, inc taking the water pump off too, just 2 bolts, and all the fuel lines) and take to a car diesel pump expert.

I used Essex Diesel in the UK, who knew all about Bosch VE pumps such as this, even 1987 vintage. They took it apart and cleaned it and changed all the usual seals.Then pressure tested it on a bench jig and it performed almost as original spec.Cost £250 including all parts and vat; can be a bit less than this but this pump needed a lot of cleaning inside.

Re fitted to boat ( 1.5hrs) and with help of a marine mechanic and special tools needed to re set the static timing. Once fuel rail bled with all injectors cracked off - started easily and ran high revs with NO leaks and more responsive to the throttle. As soon as lock down eases more in the UK and marinas welcome visitors again I will be out on the river Medway and Thames Estuary to do a proper load test. This engine did not achieve WOT rpm and of course the max boat speed was lower than it should be.Thanks folks.