BMC fuel bleeding issue

[Ripley]

Hey looking for some advice, currently servicing our bmc engine which has 3 old fuel filters fitted that I've replaced, got 3 new ones on there and started bleeding the system which was going fine as normal for the first 2 filters, then the final 3rd filter I can't seem to get any diseal to come through (got the bleed screw open and the manual injector pump is working but can't get any fuel to come through) tried taking the filter off and putting back and there doesn't seem to be any obvious issue stopping it from getting through after the 2nd filter which bleed successfully. Anyone got any troubleshooting advice or ideas on what the issue might be?

[Onewheeler]

The only stupid question is the one that doesn't get asked... I suppose you have turned the fuel supply back on? I know of someone who didn't, he got a surprising distance before the engine stopped!

[Ripley]

No worries ahahah yeah thr fuel supply is on good. Worth mentioning maybes that the diseal in this particular filter before I replaced it, was black in colour when I took the old filter off 

 

 

[Bee]

Yeah, black is not a good sign. To get it running take the filter off, fill it full with clean fuel, screw it back on, try to start the engine, If no luck try again but loosen a pipe to an injector and see if anything comes out, it really ought to. If it does fire up then run it for a good 10 minutes and check for leaks around everything you have touched. After that you can drain the fuel tank, clean it and refill with nice new fuel ........

[Ripley]

Okey thanks will give it a shot filling the filter up a bit first with fresh fuel, appreciate the advice alot

[BEngo]

If the third filter will not bleed I would want to check that the pipe to it was actually able to deliver diesel, especially if the previous contents were black.

So what moves the fuel from the tank to the filters?  You write about a manual injection pump.  Is this the lift pump?  Are the filters between the tank and the lift pump or between the  lift pump and the injection  pump?

 

Some pictures of the fuel supply system might help.

 

N

[Tony Brooks]

As might the model of engine because on a 1.5 or 1.8 it would be almost impossible to fill the filter off the engine and then refit it (3 separate parts sealed by O rings.) The 1.5 and 1.8 do not normally have a bleed screw as such on the engine filter.

 

3 filters is unusual, usually a water trap, that may contain a filter, and the actual engine filter. Photos may help.

 

For clarity in the future few engines have a manual INJECTOR pump, I assume that you mean lift pump.

 

Typically, your third filter will be the engine fuel filter and that is fed directly from the lift pump. The vast majority of BMC lift pumps have a strainer under the lift pump cap (and sediment trap). In view of the black diesel, have you cleaned this. If not then when you take the cap off on no account take the rubber sealing ring out f the cap. They tend to swell, so if you do you may never get it back in.

 

I think your first two filters may well bleed by gravity, but the third one usually needs the lift pump, so this may indicate a lift pump problem. Loosen the inlet pipe and see if diesel leaks out, it should unless you have a fuel tank lower than the engine. Repeat on the outlet, but this time use the priming lever, again fuel should leak out. Then go to the filter inlet and repeat. That should give you an idea where the problem is.

 

[Tracy D'arth]

Black diesel? Are you sure its not the engine oil filter?

[Tony Brooks]

Just now, Tracy D'arth said:

Black diesel? Are you sure its not the engine oil filter?

 

That would explain "three filters" and not getting any fuel to it, but he did mention a bleed screw that would not normally be on an oil filter. I think we need photos.

[Ripley]

18 hours ago, Tracy D'arth said:

Black diesel? Are you sure its not the engine oil filter?

Yeah it's definitely a 3rd fuel filter not an oil filter, now thinking it might indeed be a lift pump issue as the other 2 are gravity fed 

19 hours ago, Tony Brooks said:

As might the model of engine because on a 1.5 or 1.8 it would be almost impossible to fill the filter off the engine and then refit it (3 separate parts sealed by O rings.) The 1.5 and 1.8 do not normally have a bleed screw as such on the engine filter.

 

3 filters is unusual, usually a water trap, that may contain a filter, and the actual engine filter. Photos may help.

 

For clarity in the future few engines have a manual INJECTOR pump, I assume that you mean lift pump.

 

Typically, your third filter will be the engine fuel filter and that is fed directly from the lift pump. The vast majority of BMC lift pumps have a strainer under the lift pump cap (and sediment trap). In view of the black diesel, have you cleaned this. If not then when you take the cap off on no account take the rubber sealing ring out f the cap. They tend to swell, so if you do you may never get it back in.

 

I think your first two filters may well bleed by gravity, but the third one usually needs the lift pump, so this may indicate a lift pump problem. Loosen the inlet pipe and see if diesel leaks out, it should unless you have a fuel tank lower than the engine. Repeat on the outlet, but this time use the priming lever, again fuel should leak out. Then go to the filter inlet and repeat. That should give you an idea where the problem is.

 

Yes sorry wrong terminology on my part, the lift pump not injector pump. Got the strainer out the lift pump and gave it a clean, I think your right about it likely being a lift pump issue as the first 2 seem gravity fed. Trying your suggestion out now to figure out where the problem is 

-thank you so much for the advice

20 hours ago, Tony Brooks said:

As might the model of engine because on a 1.5 or 1.8 it would be almost impossible to fill the filter off the engine and then refit it (3 separate parts sealed by O rings.) The 1.5 and 1.8 do not normally have a bleed screw as such on the engine filter.

 

3 filters is unusual, usually a water trap, that may contain a filter, and the actual engine filter. Photos may help.

 

For clarity in the future few engines have a manual INJECTOR pump, I assume that you mean lift pump.

 

Typically, your third filter will be the engine fuel filter and that is fed directly from the lift pump. The vast majority of BMC lift pumps have a strainer under the lift pump cap (and sediment trap). In view of the black diesel, have you cleaned this. If not then when you take the cap off on no account take the rubber sealing ring out f the cap. They tend to swell, so if you do you may never get it back in.

 

I think your first two filters may well bleed by gravity, but the third one usually needs the lift pump, so this may indicate a lift pump problem. Loosen the inlet pipe and see if diesel leaks out, it should unless you have a fuel tank lower than the engine. Repeat on the outlet, but this time use the priming lever, again fuel should leak out. Then go to the filter inlet and repeat. That should give you an idea where the problem is.

 

Hi Tony

 

Looks like its a lift pump issue as you mentioned. I loosened the outlet from the pump, fuel tap on while priming the pump and only a few drops came out. Is there a part of the pump that wears out? Do I need to replace the whole pump like for like or is there anything else that may be stopping the lever from priming? Lever moves just the same as usual, no stiffness or loose feeling compared to my experiences on other bmc's.

 

Thanks for the response so far this is really helpful.

[Jen-in-Wellies]

Apologies for asking this question, but is there enough diesel in the tank to cover the pick up pipe? You wouldn't be the first...

[BEngo]

Rotate the engine one full turn and try again on the lift pump.  The pump is cam operated and if the cam stops in the wrong place the diaphragm is held up so that wiggling the manual lever has no effect. Rotating the engine turns the cam to a position where the diaphragm can move.

 

N

[Ripley]

51 minutes ago, Jen-in-Wellies said:

Apologies for asking this question, but is there enough diesel in the tank to cover the pick up pipe? You wouldn't be the first...

No worries ahah worth asking but yeah loads of diseal in there 

13 minutes ago, BEngo said:

Rotate the engine one full turn and try again on the lift pump.  The pump is cam operated and if the cam stops in the wrong place the diaphragm is held up so that wiggling the manual lever has no effect. Rotating the engine turns the cam to a position where the diaphragm can move.

 

N

Okey will give that a go, just to clarify do u mean rotate the engine as in using the ignition? 

[Iain_S]

59 minutes ago, Ripley said:

(snip)

Okey will give that a go, just to clarify do u mean rotate the engine as in using the ignition? 

Easiest with a spanner or socket on the crankshaft. If you use the starter, the engine will often stop in the same position it started from.

[BEngo]

As Iain said.  A spanner is much more controllable than the starter motor.

 

N

[Onewheeler]

1 hour ago, Iain_S said:

Easiest with a spanner or socket on the crankshaft. If you use the starter, the engine will often stop in the same position it started from.

Don't forget to take the spanner off before trying to start the engine. This is the voice of experience 😳

[ditchcrawler]

You may be able to SLOWLY pull it round with the alternator belt it the front pulley is big enough

[Tony Brooks]

6 hours ago, Ripley said:

Looks like its a lift pump issue as you mentioned. I loosened the outlet from the pump, fuel tap on while priming the pump and only a few drops came out. Is there a part of the pump that wears out? Do I need to replace the whole pump like for like or is there anything else that may be stopping the lever from priming? Lever moves just the same as usual, no stiffness or loose feeling compared to my experiences on other bmc's.

 

 

Unless the lever mechanism has fallen apart, I would suspect valves jammed open or just possibly fallen out. Nowadays with the valves staked into the body the easiest way is a new pump, but if you take it off, split the body and look at the levers, then the underside of the top half of the body you may see what is wrong, if a load of muck has clogged the valves the patients, very soft wood spills and a fine pain brush might clear them. When you reassemble the body, hold the diaphragm right down using the priming or operating lever bas you tighten the screws.

[Rincewind]

If your pump resembles this particular shape would this be of any help?

[Ripley]

On 15/10/2023 at 15:27, BEngo said:

As Iain said.  A spanner is much more controllable than the starter motor.

 

N

Hello sorry for slow reply been away from the boat at a family funeral, as advised I was able to turn the engine round with a spanner so the cam was in a different position and then after doing that was successfully able to get fuel flowing with the lift pump by hand. Many thanks for the advice much appreciated 

On 15/10/2023 at 19:17, Tony Brooks said:

 

Unless the lever mechanism has fallen apart, I would suspect valves jammed open or just possibly fallen out. Nowadays with the valves staked into the body the easiest way is a new pump, but if you take it off, split the body and look at the levers, then the underside of the top half of the body you may see what is wrong, if a load of muck has clogged the valves the patients, very soft wood spills and a fine pain brush might clear them. When you reassemble the body, hold the diaphragm right down using the priming or operating lever bas you tighten the screws.

Have been able to get the fuel flowing with the lift hand pump now after rotating the engine round a bit with a spanner, seems like the cam was in the wrong position as suggested. Got fuel through the filters all good and successfully bled past the injector pump bleed screw. The fuel is now at the injectors but when I'm trying to bleed them with the engine, fuel is dripping from each injector with alot of air bubbles... have tried turning the engine over 4 times now both around 30seconds each attempt but still having bubbles come through out of injector unions. Is this abnormal/ how long should it take for the air to be expelled? Is it damaging for air to get this far? I'm jumping the starter of leisure batteries when necessary so power isn't an issue, just don't want to damage start motor or anything. Have heard some people use easystart for cold starting BMC's but it's not recommended much? 

[Tony Brooks]

I do not suggest that you do this, but if you took the injector nut right off and moved the pipe away a little, it is almost certain that you would just see a spit of solid fuel. As the nut is only loosened, the fuel flow draws it air, hence it looks as if there are bubbles. If you have fuel dripping or spitting from the injector unions it should start, once you tighten the nuts.

 

If you get clouds of white exhaust "smoke" when trying to start then you have fuel in the cylinders, if you only get a few wisps then you have not, so bleed again. Lots of smoke but not starting indicates lack of compression or a slow cranking speed. It might also be a partial or full glow plugs failure.

 

I would not use Easystart because doing it wrong can and does damage pistons. If you think the problem is related to heat in the cylinder then I would suggest that you play a blow torch into the air inlet while cranking (not with a plastic air cleaner housing or a paper or foam filter element - in those cases take the air cleaner ff the engine.