OM606 lift pump re-assembly

[SilverSaloon]

hi

i have reassembled my lift pump but i'm now concerned whether i've done it correctly....

i have serious vaccuum now in the tank and the fuel is getting sucked back in.... i wonder if i've fitted the non return valves in correctly.

how many loose non return valves are there in addition to the one "sealed" in the outlet port? 1 or 2?

i have fitted one loose one to the end where the outlet port is. should i of put it where the inlet port is i wonder....?

see attached diagram and let me know which one is correct, A, B or neither?! i'm not convinced by 'A' anymore, as i cant see how the loose non return valve at that end really does anything.....

Its currently assembled as A and once i get it started it does seem to run ok, but due to the tank vaccuum all fuel has gone by morning.

cheers

derek

 

[SilverSaloon]

here are all the new reconditioned bits (not sure whether there were 1 or 2 "loose" non return valves)....

can someone let me know the correct way to re-assemble as i am sure the non return valve went inside the part 2nd from left and that sat by the inlet port, rather than the outlet port i currently have it in.

 

[Number_Cruncher]

There are only 2 one way valves - one at the inlet, and one at the outlet. The both "point" the same way with respect to the fuel flow direction - i.e., they will let fuel flow into the inlet, and out of the outlet.

These pumps pump on the return stroke - it is the spring which does the pumping, not the pushrod. All the pushrod does is to return the plunger to the start position.

The strength of the spring effectively determines the pump's pressure capability. In normal use, the plunger doesn't actually move very far down its stroke towards the injector pump body before the pushrod pushes it back to its start position.

In your shoes, I would;

a) check that fuel is being returned properly - there's either a sprung ball vale or an orifice in the banjo bolt on the fuel *outlet* from the injector pump which might be stuck or blocked.

b) check your tank venting system - IIRC, there's a pipe and rubber shroud which dangles by the side of the tank - check that pipe.

c) check to see if anything has been blocked by, ahem, alternative fuel and its products.

Funny how you and Olivier have lots of bother with your fuel system - it's a complete mystery to me! ;-)

 

[SilverSaloon]

hi

i am sure there was two "loose" valves you know.... one was at the inlet end and one at the outlet end..... i could be wrong but i remember putting two in and compressing the spring to re-assemble it all. then i slipped and everything sprung everywhere and i only found one "loose" valve.

so as everyone i have spoke to since says there is just the two (1 loose, 1 sealed) i fitted it back together as i show in diagram A.

however, i just found this diagram on the internet, which is a very similar lift pump design, but with the 2 loose valves + 1 sealed....

note "check valves" A B and C. A is a loose one at the camshaft
end... B is the sealed unit and C is the "missing" one that i HAVNT FITTED.

It is definatly returning to tank as i ran the car from two bottles, one with diesel in and one empty and it filled the empty one gradully using the return.

i also drove about 3 miles yesterday with the car running from the main fuel tank... car ran well once going, car was able to start again fine too straight away and when still warm, until i left it overnight.... now all fuel has gone from the pipes. hence my concern over the non-return valves - could one misplaced (ie in diagram A vs B) cause the fuel to run or even be sucked back to tank?

 

[Number_Cruncher]

If the pump is pumping at all, then, it's OK - if you had any seals or valves missing, it just wouldn't pump. If the tank isn't venting, then, the vacuum will draw fuel back to the tank through even the tiniest leak at the engine end. In extreme cases, the tank crushes.

 

[Dieselman]

The way you have it looks correct, the valves should be towards the exit side of the pump.
As long as the seals are sealing well no fuel should drain back to the tank, but if there really is a vacuum this may defeat the integrity of the seals.

Try running with the filler cap loose so no vacuum can build up.

 

[chizzel89]

I'm having lift pump issues too (funny that). It is fine with Derv, but anything thicker and it just doesn't deliver enough fuel at high rpms. It used to, but it has got worse. I've changed all filters and blown the feed line back to the tank with compressed air until I heard it bubbling away in the tank- no improvement.

I contacted a trusted diesel specialist in order to get a rebuild kit, but they've only sent me a basic kit.
In order to get what I want out of the pump I think it's going to need more new parts (namely a new spring and one more NRV).

Here's an exploded diagram they sent with the parts, with an X on the parts they've supplied. They also sent me a gasket (not on the diagram).

I take it I now just need the spring and one more NRV (they're both the same part number, just fitted different ways?).

Thanks in advance.

 

[Olivier]

You defenitly need the spring, this is the spring that does the sucking/ push action, see Number Cruncher post.
And the other non return valve is encassed in the bolt, its a whole thing, it costed 11 quids last time I did it.

 

[SilverSaloon]

yes 225 is a whole unit with a sealed NRV in it. see the big shiney part in my photo vs the original parts.

 

[chizzel89]

Cool. Thats cleared it up then. I just phoned them and he said 225 was the other NRV which I needed. He's going to phone me back with the full price for 225 and 18. Hopefully be able to rebuild this pump before I need to drive to manchester again next sunday!

 

[Olivier]

The NRV was about 11 quids... I think the spring was about 4, don't remember exactly tho.