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Idle damper screw leaking


Allan Edie

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Hi all,

New here, but long time BMC owner.  

Recently rebuilt cav injection pump is leaking at the idle damper screw.  The leak seems not to be the bleed screw, which stays dry.  As far as I can tell, the leak is from the idle damper screw threads.

My question is whether the lowest nut into which the damper adjustment screw threads, I believe it is referred to as a lock nut, the one that has a sealing washer under it according to the diagrams, should seal these threads if I tighten it more than it currently is.  Is the normal adjustment sequence to loosen this lock nut prior to changing the damper screw setting?  Perhaps the rebuilder did not tighten it because he anticipated that it would need adjustment once replaced on the engine.

Thanks for the help,

Cheers,

Allan

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As timing the 1.5 and to a lesser extent the 1.8 is easy I would have it back to whoever rebuilt it. The whole damper assembly seems to be glued into the alloy on some, if not all, of those DOPA pumps and I have known more than one instance where messing with the damper has caused the glue lien to fail.

At the very least do a very careful inspection to make sure the leak is not from the steel insert to alloy interface.

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Hi Tony,

I forgot to mention, my engine is the 1.5, not the 1.8.  I am sure that the leak is not coming from the glue seam, I have run into that problem some time ago.  I have also dealt with a broken off bleed screw that the previous owner left for me.  The diesel is definitely coming from above the glue joint, most likely from the damper screw threads where they meet the top of the lock nut.

I need to know whether the design of the assembly is intended for torque on the so called lock nut to apply pressure to the sealing washer, thereby squeezing against and sealing the damper adjustment screw threads.  If that is how the thing works, I will try tightening the lock nut.  If not, one option would be to pull the pump and send it back, but that would be inconvenient due to the boat being in one place, me living in another, and the re-builder somewhere else.  If the problem is a failed sealing washer or some other issue that simply needs a part, I would prefer to have it sent to me and for me to put it in myself.  Alternately, perhaps I could remove the entire damping assembly and send it back for repair.  Any thoughts on those alternatives?

Thanks for your prompt reply Tony, you are a very generous with your support of this forum, and many of us are very grateful it.

Cheers,

Allan

Edited by Allan Edie
forgot to mention something
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The damper screw (the one with the bleed screw in the end) screws into a steel insert so as long as you are sensible force wise I can see no reason why you should not try to tighten the locknut a little. I would take great care not to strain that glue joint. I suspect if it were mine I would take the damper out so I could inspect the washer, possibly fit a Dowty washer if I could find one to fit and readjust the damper & tighten the lock nut. That way I would be sure there are no burrs on the sealing faces.  Otherwise I would certainly fit a new copper washer.

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  • 2 weeks later...

Thanks Tony, I will pull the damper screw and lock nut when I am out to the boat next week.  Can I assume from your comments that the damper screw can be fully removed without running into difficulty getting it back in correctly, i.e. no springs to launch across the engine room, or micro parts to fall out of place somewhere?  I'll measure the position so that I get it back into more or less the same dampening position to make adjustment easier.  Absent contrary instruction from you, I will loosen the lock nut, then back the damper screw out completely so that I can check the sealing washer setup before putting it back together.  I'll make sure that the sealing surfaces are ok, and consider whether another washer would help.  I suspect that the issue is the seal that the washer provides around the actual damper screw threads, not the seal between the lock nut and the body of the throttle assembly, so a dowty that fits might solve the problem if the washer in there now can't do the job.  My likelihood of finding one in Prince Rupert is likely zero however, but I can order on online for the next round if needed.  

Thanks again for your help Tony, I appreciate it.

Cheers,

Allan Edie

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Sorry, on holiday and the hotel library is very short on automotive text books. The 1.5 manual on

http://the-norfolk-broads.co.uk/downloads/bmc1500L-diesel-workshop-manual.pdf

Shows no springs. The only spring should be fixed around the metering valve shaft between two "washers" with a nut securing it.

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On holiday and still monitoring this site to help out - a rare fellow I would say. :)

Thanks for the manual, I had a look at it and agree that there is nothing shown that should get up to mischief, so I will pull the damper screw and lock nut to see what I can find out.  

Thanks again for your help Tony, I will let you know how I make out. 

Cheers,

Allan Edie

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