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Fuel pump


damonleslie

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Hi. I have a bmc 1.5 that recently cut out after eractic revs from the engine. Bled the system but unable to start it. Looks like I have air escaping from a bolt on top of the fuel pump, there is a thread with a big bolt at the bottom of the thread and a smaller one slighter higher and then a small nut right on the top. I tried to remove the bolt as was told it may just be an o ring that needs replacing. The bolt turns but doesn't seem to come out, also that whole bit that the bolt goes through has slight play. Do I need to remove the small multi spline bolts that hold it in place and if so what tool do I need?

I'm stuck as to the best way forward and live aboard so really want to get it running.

Any advice would be much appreciated!!

20200907_153250.jpg

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The image is far too much of a close up to see much but it looks as the whole governor assembly is loose on the top of the pump body. If the stop or the throttle spindle is leaking then you may have to remove that screw but not if the spindle is not.

 

It sounds to me as if the thread in the pump body has been stripped and it is just the similar screw on the other side of the "turret" that is holding the governor assembly in place. The governor housing is, I think, normally sat on a gasket and if your "turret" is moving it can't be making a very good seal.

 

However the pump body runs under transfer pump pressure so a leak at that joint would be more likely to leak fuel but may allow fuel to flow back to the tank under gravity when the engien is off. This may airlock the pump.

 

You say you bled the system - exactly how did you do this? Many people don't know the full procedure.

 

When these pumps suffer fuel starvation the engine will rev up and down all on its own so have you checked the filter and water trap(s) for water and fouling? Have you drained or sucked any build up of water from the tank? Have you dipped the tank to ensure you have at least six (6) inches of fuel left?

 

 

 

 

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I emptied the water trap and put a small amount of deisel back in. I also changed the fuel filter. The steps for bleeding the system were done after.

 

First I primed the lift pump and undid the nut on top of the fuel filter until the air was released and fuel was flowing then tightened it up. Next I undid two injectors and again pumped the lift pump until air was released and fuel flowing and then tightened them back up. 

 

The leak is coming from under the biggest nut of the spindle on top.

 

I've added a new pic and circled the spindle I am referring to. 

The arrows indicate where there is slight movement.

 

What do you think?

 

Just checked the fuel tank and I have 4 inches of fuel which amounts to about 16 litres 

20200907_161047.jpg

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Years ago I had a problem with a bmc 1.5 where the speed varied continuously at random, regardless of the control setting. Turned out to be fuel starvation as a result of the inlet filter to the fuel pump being blocked, which in turn was caused by failure of the element in the main fuel filter allowing crap to get through.

Replacing the main filter was straightforward. We simply cleaned the pump inlet filter very carefully. Cleanliness is absolutely essential when working with the fuel pump, and it should really have been done by a specialist on the workshop bench. But we got away with it, crouched in the engine bay of a cruiser stormed boat.

 

Why does fuel starvation cause random speed variations? The engine is hydraulicly governed. The incoming fuel is pumped into a chamber which has a fixed orifice which bleeds excess fuel back to the pump inlet. The pressure in this chamber varies with engine speed, and is used to control the amount of fuel injected into the cylinder. With fuel starvation, there's no pressure buildup, so the governor assumes the engine is running too slowly and injects more fuel. This causes the engine to rev up, the pump runs faster, and manages to suck some more fuel past the blocked filter. Pressure now builds up, and so the engine slows down.

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7 minutes ago, damonleslie said:

I thought I needed a special splined socket.

What size spanner would I need? Idon't have anything small enough.

Sorry, don't know the exact size, its around 7 0r 8mm I guess, 12 point ring spanner or 12 point socket but most this small are only 6 point.

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1 hour ago, damonleslie said:

I emptied the water trap and put a small amount of deisel back in. I also changed the fuel filter. The steps for bleeding the system were done after.

 

First I primed the lift pump and undid the nut on top of the fuel filter until the air was released and fuel was flowing then tightened it up. Next I undid two injectors and again pumped the lift pump until air was released and fuel flowing and then tightened them back up. 

 

The leak is coming from under the biggest nut of the spindle on top.

 

I've added a new pic and circled the spindle I am referring to. 

The arrows indicate where there is slight movement.

 

What do you think?

 

Just checked the fuel tank and I have 4 inches of fuel which amounts to about 16 litres 

20200907_161047.jpg

 

OK as you say you can turn the 12 point screw and it won't come out it is as Tracy and myself thought. Its stripped and its probably the pump body so it needs to go away for repair.

 

2. So you missed a vital step out and that is to bleed the low pressure side of the injection pump. You do this just like the filter but at the hexagon you have arrowed on the side of the pump. keep going for at least 30 seconds after you think all the ait is out. If it is leaking there you need a new soft washer under the head. Then you loosen the injector pipes at the injector and spin the engine until the loose unions spit or drip fuel. If the unions will not drip then go back to the injector pump and loosen the SMALL hexagon in the larger screw head right at the top of the pump on the loose bit. Hold the larger hexagon with a  spanner. Then bleed from there and when done repeat the engine spinning.

 

3. Be very wary about trying to stop the leak under the lower nut on the idle stabilisation adjuster. Its another soft washer but to change it you need to unscrew the whole thing and that will require you to readjust the idle stabilisation. You need a manual. Never get heavy handed in this area with spanners because the bit the idle stabiliser is screwed into is typically glued into the housing and amateurs often rip the whole lot out of the housing. 

 

4. Four inches of fuel may not be enough.

Edited by Tony Brooks
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1 hour ago, damonleslie said:

Initially I thought it was the fuel filter but it wasn't even dirty, I changed it anyway. I haven't the inlet filter. The main problem seems to be the leak from the spindle on the top, plus the housing it goes into has play in it. 

All together now - oh yes you have!

 

It is under the large hexagon that forms part of the fuel inlet union on the pump. Be very careful and ultra clean using lint free cloth if you intend to have a look at it. |its a little nylon cone but below it is a spring loaded valve. I think there are two springs in there. 

 

I don't think the fact the housing you circled in the diagram is leaking has much to do with the rough running and non-starting. I think you have not bled it properly and may not have enough fuel in the tank. Once you get it running the leak might cause erratic response to varying loads etc. but I doubt it will stop it running.

 

Edited to add:-

 

You will probably have a strainer with a sediment trap below it under the domed cap on the lift pump and these can clog.

Edited by Tony Brooks
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Just one thing I'm not clear on: 

"you can turn the 12 point screw and it won't come out"

Do you mean the spindle on top with 3 nuts (the larger nut at the bottom) or the smaller splined one on either side?

 

Thanks for all the advice and info, I really appriciate the help!

I will read through it again and make some notes.

I've had the boat since April and the engine has always run without problems. It was last week for the first time when it cut out.

I'll go through the steps and see if I make any progress.

Thanks!

 

 

 

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16 minutes ago, damonleslie said:

Just one thing I'm not clear on: 

"you can turn the 12 point screw and it won't come out"

Do you mean the spindle on top with 3 nuts (the larger nut at the bottom) or the smaller splined one on either side?

 

Thanks for all the advice and info, I really appriciate the help!

I will read through it again and make some notes.

I've had the boat since April and the engine has always run without problems. It was last week for the first time when it cut out.

I'll go through the steps and see if I make any progress.

Thanks!

 

In your first post you circled a photo of the 12 point screw that holds the governor assembly onto the pump body. I thought this, the only one in that photo, was the one that just turned and would not come out.

 

Now you seem to be talking about the set of nut and screws right in the top of the governor housing.

 

I now have no idea what turns and but won't come out and what has "slight play".

 

Please clarify.

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Yes sorry, it was a bit muddled. I now understand a bit more.

 

The governor assembly has slight play. I thought maybe that the 12 point screw needed tightening but wasn't sure what tool I needed.

 

The leak seemed to be coming from the large nut at the top of the housing. This is the one that turns but doesn't come out.

 

20200907_195559.jpg

Edited by damonleslie
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17 minutes ago, damonleslie said:

Yes sorry, it was a bit muddled. I now understand a bit more.

 

The governor assembly has slight play. I thought maybe that the 12 point screw needed tightening but wasn't sure what tool I needed.

 

The leak seemed to be coming from the large nut at the top of the housing. This is the one that turns but doesn't come out.

 

20200907_195559.jpg

 

Right, so it is the splined 12 point screw in the first photo that turns but will not come out. That suggests the thread is stripped and a sit is in alloy its probably the pump body that is damaged.

 

The leak from the idle stabilisation adjustment has nothing to do with the screw in the paragraph above or the movement of the governor housing.

 

As I  explained before the nut on that adjustment is sealed by a soft washer but to replace it you will have to unscrew the whole adjuster and that means you may well have to readjust it so its easier if you look in the manual.

 

However I don't think any of the above problems will stop it starting once its bled. It will leak but I think it will still run. In essence you have some unrelated problems with the injector pump but I doubt any of them will stop it running..

Edited by Tony Brooks
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I think I may have confused things.

 

The first photo with the arrow points to where the fuel was leaking from.

 

On the second photo with the arrow I have circled the spindle I am taking about.

This is the part I was trying to take out. This is what turns but doesn't seem to come out. I was told it is a spindle and inside would be a small o ring that may need replacing.

Is this correct?

 

20200907_195559.jpg.2a4c2ef79ae7d53dc24078dab1e0ce03.jpg20200908_094921.jpg.935d5fee8e1d65d67f782d2afd8374d3.jpg

 

 

(I will post a photo of where the play is in the next post)

 

 

 

 

 

 

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7 minutes ago, damonleslie said:

I think I may have confused things.

 

The first photo with the arrow points to where the fuel was leaking from.

 

On the second photo with the arrow I have circled the spindle I am taking about.

This is the part I was trying to take out. This is what turns but doesn't seem to come out. I was told it is a spindle and inside would be a small o ring that may need replacing.

Is this correct?

 

20200907_195559.jpg.2a4c2ef79ae7d53dc24078dab1e0ce03.jpg20200908_094921.jpg.935d5fee8e1d65d67f782d2afd8374d3.jpg

 

 

This photo shows the part that has play, the arrows indicate the movement.

It looks like this part is fixed with the 12 point screws. I thought maybe they need tightening.

20200908_101800.jpg.bf5f11108370e2a79a842ca5a5fbcb89.jpg

 

 

 

 

 

 

 

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2 hours ago, damonleslie said:

Ok. So I dont need to take it out? Should I just tighten the nuts and see if this stops the leak? 

Also, should I try to tighten the 12 point screws to stop the play?

Sorry to go on but I really want to understand fully what needs doing

 

<Frustration on>

Go on really lash that nut where the leak is up as tight as you you can, that will stop the leak OK (because you will wrench the glued in bit right out out the pump so you will have to get a new pump).

<Frustration off>

 

As I told you that nut shoudl have a soft washer under it so tightening it is very unlikely to do any good. You need  a new soft washer.

 

You did seem to say that you can undo the 12 point screw but it won't come out. If so the pump body is probably stripped so if you do try to tighten it be very careful as to how tight you try to make it.

 

What needs doing to get it running is to ensure you have sufficient fuel in the tank (4"may not be enough) and bleed the thing properly. Then you can worry about any leaks etc. Once again to repeat myself the pump body is filled with pressurised fuel when running so the leak and loose bit are unlikely to stop it starting.

 

I can't reconcile your text with the last photo. Exactly where is the leak coming from? The throttle or stop spindle or both or the lock nut on the idle damper?

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The leak comes from the lock nut.

 

The original post did show the 12 point screw and I did mention it but I haven't tried to undo it as I don't have a tool that fits. I just thought that the play had something to do with these two screws.

 

I have no intention of being heavy handed or doing anything I am unsure of, and it wasn't my intention to cause frustration or annoyance.

I will take a look at the manual.

Thanks for all the info, albeit full of misunderstanding.

Sorry people

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The 12 point screw and its parter on the other side of the "turret" have two jobs:

 

1. retain the throttle or stop spindle on the same side as the screw.

 

2.  secure the whole "turret" assembly to the pump body.

 

There is no reason not to try gently tightening those two screws but remeber they are screwed into comparatively weak aluminium.

 

The lock nut is just that, a lock nut for the idle stabilisation damper adjustment and as far as I can remember it sally sits on a soft washer. I don't think there is an O ring associated with sealing this area because it would have to bear against a thread.  My first choice would be a Dowty, second a new copper and third by a very long way nylon or fibre. However to fit such a washer you will need to totally remove the idle stabilisation damper adjusting screw so you can put the washer on it. It would be unwise to mess with that adjustment unless you have the instructions for resettling it, hence the ink to the manual.

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