Bukh 20; no fuel from pump

Slow_boat

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I replaced injector nozzles and changed the fuel filter. I have bled the filter and fuel pump through but there is nothing coming out of the fuel pump to the injectors when I turn the engine over on the switch.

Is there something else I should be doing or has the fuel pump mysteriously died while it's been standing over winter?
 

vyv_cox

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The volume of fuel moved by the pump is remarkably small when the lever is operated by the engine, i.e. one stroke per two revs of the engine. Is there an external lever on the pump? Try pumping with that while bleeding the low-pressure side, at the filter on the engine is probably best.

I suspect there is still some air in the system. Note that if the cam driving the pump is at its highest point moving the pump external lever will not do anything and you need to turn the engine over one turn.
 

earlybird

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Take it that by engine fuel pump, you mean the HP pump.
Are you spinning the engine over with the speed control set to maximum? ie max fuel delivery.
Not familiar with the Bukh, but have you cracked open the injector pipe connections to force air out of the pipes?
 

greenalien

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There seems to be some confusion about which of the 2 pumps you are talking about - the lift pump, or the high-pressure pump that feeds the injectors.
As far as the lift pump is concerned, if you can pump the small lever underneath it and hear excess fuel being returned to the tank, that pump is probably working OK. Possible faults are either the diaphragm has become detached from the drive lever, or the lever that drives it from the cam has broken, but if the manual lever works as expected then the most likely fault is with air in the high-pressure circuit.
As far as the high pressure pump is concerned, there's a bleed bolt by the injector pipe outlets that usually needs to be cracked open and the engine spun until fuel comes out of it. If you get an air lock in this part of the system, it probably won't clear itself, you have to bleed it.
 

Slow_boat

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It's the HP pump I'm talking about, at the back of the engine. I've cracked it's bleed screw and fuel comes out and taken the injector feed pipes off the injectors and off the fuel pump and turned the engine over on the starter but nothing. I can't see how the fuel pump could have broken just sitting over winter.
 

earlybird

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It's the HP pump I'm talking about, at the back of the engine. I've cracked it's bleed screw and fuel comes out and taken the injector feed pipes off the injectors and off the fuel pump and turned the engine over on the starter but nothing. I can't see how the fuel pump could have broken just sitting over winter.

The fuel at the bleed screw is supplied by the lift pump. You haven't confirmed what throttle opening you've set. If it's at tickover setting, the HP pump might be delivering virtually no fuel for you to see at the injector pipes.
 
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Conachair

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I think this is highly unlikely so don't panic, but have you ever had a blown head gasket? I had seawater in the oil for a while in a dv20 as I couldn't get it warmed up to drain, about a year later the spring on one cylinder of the fuel pump went and the other was hanging on just, both corroded badly. Though seems very unlikely that both would go at the same time.
 

greenalien

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It's very surprising that you have fuel at the bleed point but nothing coming out of the injector pipes, and as you say, it's unlikely that the pump has failed spontaneously over the winter. Suspicion must fall on the lift pump not supplying much fuel, a collapsed or blocked fuel filter or an air lock between the lift pump and the high-pressure pump. There's a bleed screw on the top of the fuel filter housing, have you cracked that and got fuel squirting out when cranking the engine? There's also a very fine-gauge nylon filter in the base of the lift pump that can get blocked, best advice is to remove it as it's more of a nuisance than a benefit.
Next option is to bypass the lift pump and rig up a temporary gravity feed directly into the high pressure pump - bit of a pain but should pinpoint the problem. Don't forget to disconnect the inlet fuel pipe from the lift pump when doing this!
 

Slow_boat

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Thanks for all suggestions so far. I've tried turning over de-compressed on full revs, water off, and flattened two batteries with not a drop at the injector pipes.

There is plenty coming out of the filter bleed screw when I crack it open.

I know there's no water in the oil as I changed it at the end of last season.

I'm still hoping it's an air lock in the HP pump as there just doesn't seem anything to go wrong with the pump itself. If I flatten the batteries without finding the problem over easter, I'll have to pay someone to have a look, which is against the ethos of boating on a budget!

I thought I was being so clever, getting new nozzles and all. Next time, I'll just leave well enough alone!
 

Bilgediver

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I'm still hoping it's an air lock in the HP pump as there just doesn't seem anything to go wrong with the pump itself. If I flatten the batteries without finding the problem over easter, I'll have to pay someone to have a look, which is against the ethos of boating on a budget!

!



SOme Bosch fuel pumps had delivery fuel valves with harder springs and sometimes the pumps would not clear air. I have only had this happen on one of my pumps pn an MD and only on one occassion. Easy to fix. Just slcken of the delivery valve housing on the top of the pump. DOn t be overenthusiastic and whip it out and lose the bits!!!!!!!! It should only be necessary to slacken back a few turns and air will escape up the threads and allow the pump cylinder to fill. Just keep the pressure on with the lift pump. Once fuel appears then harden the housing down again.

If this doesn t work then the rack may be stuck in the stop position.

If the engine has a stop soloniod then removing this you should see the end of the rack????? Moving the speed lever you should see the rack nove!. YOu might need a small mirror or a midget for help here.
 

Taurus66

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Please check that your fuel supply line if it is rubber has not had the inner liner collapse with age or vacuum from the tank to the lift pump. Possible causes a filter blocked causing excessive vacuum , making the liner inside the hose to collapse. or just plain old age..
 

Bilgediver

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I've had a screwdriver in the hole and it seems to move against some resistance.

If the screwdriver was in the solenoid hole then it has to move in the opposite direction to that which the solenoid puts it in the stop position .The same pump on the Volvo that is moving towards the back of the engine to give more fuel. Pushing it in would be to the stop position. It should maybe move towards you. Does the rack move towards the back of the engine when the speed lever is moved to full speed.
 

Conachair

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I'm fairly certain you can take the pump out without messing with the timing. The timimg is set up inside the pump.

Though might not help you much.
 
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