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Broken down, is it the fuel pump /lift pump


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Hi All,  BMC 1.8 sherpa marinised  engine

I was confident enough today to take the boat out without fear of engine problems etc, alas it it didnt  work out that way.

In total I travelled about 4 or 5 miles, never more than at tickover speed, it's the first time the engine has worked in over 18 months.

Anyway , I was quite happily tootling along and I got to a nice open straight so I thought I would open the throttle just a little bit more,( and I do mean just a little bit more), engine note changes slightly with the throttle , all seems good. Happy as Larry I was!

Then revs go higher, then lower then I think something is wrong, so I moor up. The engine starts again and dies in approx 2 minutes, have I run out of fuel, after checking tank again ,I've  got at least 3/4s of a tank.

What can it be I scratch my head, air lock in fuel not likely or I wouldn't have got this far, filter blocked ? Don't know, will check to see if plenty of fuel going in filter, should i open a union? No i think.

I press the lift pump a good 4 or 5 times, plenty of pressure there I think, try to start it. It's just firing but not starting up.

Got a can of easy start even though the engine is still warm / hot. Engine fires up no problems, a bit noisier but it's running and settles down quite quickly to normal tickover. 

It now runs for a good 2 or 3 minutes 

Then revs then go up quite a bit and it dies soon after.

Lift pump again, easy start squirt again, it fires up again no problems me thinks it's just some airlock in the fuel some how, then the engine dies again in 2 or 3 mins following erratic revs  without touching the throttle again.

So then loosen 2 injector fuel pipe unions so I can see fuel coming through whilst cranking the engine. Nothing visible whatsoever,

Could it be the fuel lift pump not doing it's job, is that why when I've pressed and primed it the engine runs for 2 or 3 mins. 

Then if I don't prime the pump it won't start and sounds like no fuel.

I do believe that the 1.8 sherpa bmc  actually self primes and runs without to much trouble and the cut out is a solenoid on top of the pump activated on the key.

 Advice needed , what to go for 1st, does anyone have any experience of what to do next.

Thank you keith

 

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But to avoid loosening an injector union some/all vehicle engines have a bleed screw on one of the injector unions on the injector pump.

 

I agree its almost certainly fuel and a filter change or at least remove, clean up & refit as it seems you are on the cut would be the first stem. Remember there is a good chance the lift pump may have a strainer under its cap.

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  • Hi RLWP,  strictly speaking I know it doesn't self prime on its own, but what I mean is it doesn't take much to get the fuel to flow is my understanding.

If you've got no air at the filter and you've got 2 injector unions just loosened off the there is no need to worry about the cav pump.

At least that's how I understand it. Regards keith

Edited by Karen Lea Rainey
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Hmm. Unless its a CAV DPA pump I have not ever worked on I can not agree with that. They can be a pig to bleed.

 

I agree you do not need to use the bleed screw on top of the turret holding the stop and throttle lever but I would always bleed from the screw on the side of the cylindrical part of the pump body.

 

Given a good battery I suppose the transfer pump may eventually purge the pump body of air but at a cost to battery and starter but its not worth it, bleed on the side of the pump followed by the injector unions should be easy and work well

Edited by Tony Brooks
  • Greenie 1
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5 minutes ago, Karen Lea Rainey said:

Thank you, will work on dismantling the fuel filter first,  try for a clean up first, then bleed system.

Will report back on situation tomorrow night now.

You may well have/should have a filter/water trap between tank and lift pump. If you have one then that one needs cleaning as well.

 

Edited to add: if cleaning does sort it  so you can get back to base please change the filter(s) and it may be a good idea to pump whatever is lurking in the bottom of the tank out.

 

That is three places to clean:

 

1. Water trap/filter between tank &  lift pump.

2. Lift pump strainer.

3. Main engine filter.

 

I will not go into the strainer in the DPA pump until it is made an almost certain candidate for problems.

Edited by Tony Brooks
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Two things, you say the engine speeded up a bit then died, that can happen if you run out of fuel, but you have plenty you say so maybe its sucking in air? dry off all the unions then with a fingertip just see if theres a little drop of diesel leaking out after a few minutes. Secondly, Easystart. you say it started but a bit noisier, that noise is all the innards shouting NO! at you.

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You say plenty of pressure when manually using the lift pump.

 

After a few strokes there should be NO resistance once the fuel pressure is up.

 

If there is still pressure it could well be the fuel pump or it is sucking air in between the tank and the pump. Check your tank vent is not blocked.

The 1.8 will speed up as it runs out of fuel in the injection pump, it throws the governor out.

CAV injection pump is NOT self priming at all, you need to bleed the nipple on the body and at least 2 injectors.

Edited by Boater Sam
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Nice dirty picture, 

Just rushed back to the boat to turn down stern grease, quickly took off the filter, looks like rusty dirty sand if you asked me, the diesel was a strong dark colour with some small black bits of sediment floating aswell. I cleaned up the bottom case before the picture was taken but it was just as dirty

Regards keith

20180620_222153.jpg

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12 minutes ago, Karen Lea Rainey said:

Nice dirty picture, 

Just rushed back to the boat to turn down stern grease, quickly took off the filter, looks like rusty dirty sand if you asked me, the diesel was a strong dark colour with some small black bits of sediment floating aswell. I cleaned up the bottom case before the picture was taken but it was just as dirty

Regards keith

20180620_222153.jpg

Thats actually not too bad, would expect to see a small amount of red sediment on top of the filter. How bad was the stuff in the base/bowl? However I suspect you can still have a blocked filter even if the top is clean. Is there another filter? is this the first or second one?

 

.................Dave

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There is only the one filter on the feed in, apart from the small mesh on the top of the lift pump, which I will check tomorrow,

I collected the diesel in a jug when undoing the bolts. There were at least 6 pieces of black crud / rusty black specimens in the jug, to suggest a size of them, some were as big as a small matchstick, like they may have come off the rim or seal of the filter.

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There is a sediment compartment beneath the little filter in the lift pump which will need blowing and cleaning out. The black nits could well be bits of sealing rings, if so air might be being drawn in where the bits have come from. Looks like you could do with another fuel filter just after the fuel tank, ''Agglomerator type'' which separates water out as well as pre filtering the fuel.

Edited by bizzard
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The lift pumps cam operated lever might might be worn and developed a lot of free play and not delivering enough fuel, despite the hand lever working ok. If the pumps outlet pipe is slackened off or removed and the enine turned over fuel should gush out in strong spurts.

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8 hours ago, bizzard said:

There is a sediment compartment beneath the little filter in the lift pump which will need blowing and cleaning out. The black nits could well be bits of sealing rings, if so air might be being drawn in where the bits have come from. Looks like you could do with another fuel filter just after the fuel tank, ''Agglomerator type'' which separates water out as well as pre filtering the fuel.

Personally I would rather it was a sedimentor that has no filter but still separate the larger bits of muck and up to 80% of the water, The engine filter should agglomerate the rest of the water. A decent sedimetor will hold a lot more stuff than  an agglomerator and is far less easy to block.

 

Personal preference though.

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To my inexpert eye that filter looks pretty grim. What does the diesel smell like? if it smells wrong then I would try to run the engine from a container of clean fuel after changing the filter. If it runs ok then you have horrible stuff in the fuel tank. I would carry on with your cruise topping up the temporary container and leave the fuel tank for a project, having had a sludgy fuel tank nightmare I think you have to get into the monster and scrape the rusty sludge and crud out. Fingers crossed.

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