lift pump experts required

[colvic987]

I have a lift pump to repair, volvo penta md7a lift pump, unsealed type.

I understand that i take the cover, gasket and a screen filter off, and the diaphram which looks like an engine thermostat spring with a rubber disc with holes around the side.

In the schematic there is a screw on left side of lift pump body does this need to be removed.

How is the best way to replace the pump innards as i dont really want to disengage the fuelpipe, but will be fitting a new gasket to engine block once the new diaphram is fitted.

And what difference should i be looking for once refitted. any other tips on repair gratefully recieved.

 

[William_H]

Lift pump

Just to waffle on and bring your post up for more attention...
I presume the lift pump is much the same as so many car lift pumps. A cam onto the cam shaft gives a push to the diaphragm on each revolution. The diaphragm is a rubber disc sealed around the edges with a spring to ensure it returns after each stroke. The body attached to the engine block is open to engine oil and has the pivot for the cam in it.
The cover which jams the diaphragm between the body and the cover has the inlet and outlet pipe attached and has flapper valves on both in and outlet. The spring sits between the cover and the diaphragm.
Outboard engines with external tank tend to have a very similar design of lift pump except the diaphragm is not pushed by a cam but rather by the pulsating air pressure of the crankcase.

Problems can occur with the diaphragm getting a hole in it but more likely the valves wear or leak.
It is often easiest just to dismantle the cover from the body. However if this is difficult take the whole body and cover off the engine block. You will not be able to remove either the cover or the whole pump without disconnecting the pipes.
You used to buy a pump service kit which replaced the diaphragm and the valves for some types. Other manufacturers may insist on selling a whole new pump.

So what is the problem? If you think it is not pumping then yes probably the valves. This may result in inability to provide enough fuel at full throttle. If the diaphragm is split then you can get fuel in the oil and of course not much pumping. What will change after service. the engine might run.
Anyway all this from memory of car lift pumps. it may not be applicable at all. In which case my apologies
good luck olewill

 

[colvic987]

I think that the guaze filter is blocked for starters, its not been cleaned since i have had the boat, as i didnt know it existed until recently.

Secondly i have had starting problems due to blocked filter, even once cleared there doesnt seem to be enough pressure to get the fuel to the injectors, its ok on tickover, but once or twice full revs have been slow to 'catch up', and have even stuttered and stopped.

The secondary filter which is after the lift pump is clear and the fuel is clean.

I have also had a slightly increased level of oil since lifting in, all this activity i have diagnosed as symptoms of lift pump diaphram and filter and the o ring at the engine block/lift pump.

So an overhaul is badly needed, after which i hope the symptoms will have been sorted.

Where are the flapper valves situated are they integral to the pump body.

schematic of pump.

http://www.volvopentashop.com/James...eDieselEngines/7742080/7742080_23/7742080_012

 

[colvic987]

If you think it is not pumping then yes probably the valves. This may result in inability to provide enough fuel at full throttle. If the diaphragm is split then you can get fuel in the oil and of course not much pumping. What will change after service. the engine might run.
Anyway all this from memory of car lift pumps. it may not be applicable at all. In which case my apologies
good luck olewill

tks for your explanation olewill, i seem to be getting most of the symptoms you are suggesting.

just one more question.

so if i'm getting leakage into the block from the lift pump, its down to the diaphram being holed or split and not from the o ring at the engine block. so the o ring might not need to be changed. am i correct on this, it is just to stop engine oil and fumes leaving the block at the mating face of the pump.

 

[2Tizwoz]

Marine parts are expensive.

Its unfortunate that you don't have an International Harvester tractor to repair as you could have used one like this.

Which these people http://www.silverfoxtractorspares.com/caseinternational-444b250b275b414bd276-fuel-pump-2556-p.asp are selling for less than half the price. £34.95.

Of course it may not be suitable as the cam operated lift arms do vary. Is yours worn and will it swap over?

I take it yours isn't a sealed type? £92.57

A replacement parts kit from keyparts is only twice the price. £73.20

On ebay http://cgi.ebay.co.uk/INTERNATIONAL...K_BOI_FarmingEquipment_RL&hash=item2c5719457a a tractor repair kit

is £8.78 plus £1.90 delivery.

The particular ebay shop sells a lot of different pumps so may be able to cross reference and provide a suitable kit or pump.

 

[colvic987]

Yes the unsealed version, £69.23 for replacement kit, o ring £1.28, total price with vat added £82.85, quite a hike in price compared with your tractor parts.

bought the parts friday.

 

[scottie]

I am sure that you will have to take it off to before you do anything check if it croaks when you use the external lever this usually indicates that it is working
When you go to check the gauze you will most likely think that the top cover is welded on as it is a ###### to remove but this can be done in place

May be worth checking e bay etc as it is a useful spare to carry
The same pump fits all small Volvo and I think bukhs. Up to the 2000 series plus the 30 & 40 engines but not 2010 etc

 

[TNT]

Lift pump

Just overhauled a VP 2003 and I think they are the same pump, as Scottie stated make sure it croaks or squeaks, this will tell you that the diamphram is OK. the screw on the side is the access to the lever fulcrum pin, worth taking out and greasing up, check that it pivots OK without jamming. The valve is a non return valve to ensure the pump is always full, the this slither of metal needs to sit flat against the plate, if there is a gap it will allow fuel to return back down and will stop the pump from pulling fuel through. If you remove the spring there is a cross shaped piece of metal that links the return spring to the arm, make sure its seating correctly when you reassemble it, it can jam at an angle. The final test is to re fit and crank the engine with the outlet pipe off, OK it will squirt diesel but it will confirm operation if you stick your thumb over it and you can not stop the diesel, the pump should have more pressure than you can stop. let me know how it goes.

 

[pappaecho]

New lift pump for my Ford Mermaid £29 quids from ASAP. Why bother in replacing the bits inside when you can get new? ( at a very reasonable price that is)

 

[William_H]

Lift pump

Hi Colvic I am gratified that my very generalised description was so appropriate.
No I would not bother to replace the body to block O ring. It is just to seal the crankcase to outside however if you remove the body then you may want to replace the o ring.
If the pump has an external operating lever then that will help a lot. Before you do anything you might want to check the engine starting after hand pumping a bit. If this fixes starting then the problem is caused by lift pump. As said it may have a poor stroke due to arm worn but perhaps not so likely. The gauze filter is likely to cause problems. However if the oil level is rising in the sump that sure might indicate a split diaphragm.
After you remove the fuel inlet and outlet pipes. You should be able to blow through the pump from inlet to outlet and also to hold a suction on the inlet pipe. There are 2 flapper valves so if you can't get a suction seal it may just be a valve. good luck olewill

 

[colvic987]

I thought that i would update you all as your help has been appreciated, i got to the boat and tried to get her started again, and as per normal run out of fuel and primary filter was emptying but not filling up, and as said before all pointed to the lift pump.

I took scotties advise and checked if the lift pump was croaking and it was, i then put my finger over the filter output line and operated the lift pump to check suction and it was ok, so decided to leave this till boat comes out of the water, and whilst i was fitting the filter back and was about to bleed the air, found that the top half of the bleed screw canister unit was devode of thread in the aluminium body, so removed the canister and bleed screw and found a longer bolt with nut and new washer, and screwed it into the lower part of the thread which was still intact, with gasket goo and ptfe around the threads, and the engine started first time and stayed that way during the weekend, so i hope the problem has been solved for now until i bring the boat out of the water.