Problems with idle after new injection pump installation

[M&H]

I had a new injection pump installed on my 1.5 bmc. Since then, the idle speed's been erratic. At times it's dropped so low the engine's cut out. I've adjusted the idle speed screw on the pump to which puts it up to about 600rpm (I think - the guage isn't that accurate), but after things have warmed up the idle increases significantly, possibly 1000rpm.

 

Any ideas what could be causing this, and possible solutions?

 

RCR installed the pump and I've had the engineer back - but his only suggestion so far has been to play around wtih the adjustment screw.

[pete.i]

Possibly the bleeding process hasn't got all the air out of the system.. BMCs can be a bit of a pig to bleed fully. There is a Whilton Marina video on You Tube which goes through the process. This is purely a guess on my part because I have had similar problems with my BMC1.5 and bleeding the engine, eventually, cured my erratic tick over speed. Someone with a bit more knowledge will, no doubt, be along shortly wih some more suggestions. In the meantime heer is a link to that vid.

 

[Tony Brooks]

Personally I would not advise any DIY boater to touch the bleed screw the spanner is on. Especially as they have not got another spanner preventing the head of idle damper from turning. By that I do not mean the locknut that is against the turret of the pump.

 

Was any other work done like fitting new filters? If so I would want to check all the seals are on correctly and not twisted. I would also be looking very closely at the way the filter centre bolt is sealed, especially if its one that ostensibly uses an O ring. If so also fit a soft washer.

 

Anyway I thought the BMCs were supposed to have an idle of 600 RPM or more.

 

 

If this "drops so low the engine cuts out" mainly occurs upon shutting the throttle then the idle damper needs adjusting because the governor is overshooting the idle position and is reducing the fuel supply too much.

 

 

.

[RLWP]

BMC 1500 is 500-600rpm according to the manual

 

Richard

[M&H]

BMC 1500 is 500-600rpm according to the manual

 

Richard

 

Just to clarify. I set the idle in the 5-600 range, as per the manual, but it slipped down to a slower rpm.

 

It hasn't done this since I last tightened the screw a couple of days ago, though, so that particular issue might be sorted now. Maybe.

[M&H]

Thanks for the advice, Pete and Tony.

 

I'll give the system another bleed and see if that makes a difference.

 

I haven't changed filters since I started having problems back in October, when diesel was diluting the oil - hence the new injection pump.

 

Excuse my ignorance, but what is the 'idle damper'? Is that what I'm calling the 'idle adjustment screw', or is this the nut for bleeding the pump at the top - as in the video?

[Tony Brooks]

Excuse my ignorance, but what is the 'idle damper'? Is that what I'm calling the 'idle adjustment screw', or is this the nut for bleeding the pump at the top - as in the video?

 

 

The bleed screw in the video sits in the top of the idle damper screw and that in turn has a locknut against the top of the pump "turret". I very much doubt that you altered this unless you did it by accident when you bled the top of the pump (as per the video).

 

The idle adjusting screw is either a thing like an old carburettor mixture screw with a spring around it set at an angle in the pump "turret" or one of the pair of ling hexagon screws that sit either side of the throttle lever. The maximum speed one should be covered with a tin can thing and lead seal, so its the other one.

 

I explained how to adjust the idle damper in another recent 1.5 thread but it is is not slowing down too much or stalling only when close the throttle it is not likely to be the damper adjustment.