Fast idle adjustment UK 1969 PI

[PodOne]

Evening folks

At the sorting out niggles stage.

She will start from cold well with the choke out which can then be reduced to around half and once warm will idle around 800-900 no trouble not modern smooth but I expect its normal for a 50 year old design. Checked for air leaks and the inlet manifolds nuts are all tight and a spray with ether sees no increase in engine speed.

The issue is once started she won't hold a fast idle at around 1500 while the choke is out. I have to use the pedal until I can push the choke home when she has warmed up a bit. 

The linkage is original with a Fred Millturn shaft bearings, linkages and single choke cable which pulls on a cam which then pulls the enrichment lever to the MU which works fine giving full on/off. The cam rotates against a screw on the throttle bar and is supposed to sl open the butterflies to increase the idle in line with the choke setting. Visually it does with the clearance set as per the Brown Book but won't give the desired increase in fast idle.

Reducing the clearance cranks the butterflies open but increases warm idle which cant be reduced enough even with the air bleed valve screwed fully in as the butterflies aren't fully closed.   

But are they open enough is it a simple adjustment issue? Or

Is there perhaps another reason why she won't hold 1500ish rpm? 

Any advice appreciated.

Andy

 

[JohnC]

Hi Andy,

Is it possible that the mechanism is giving full fuel enrichment but not full idle increase? For instance if, when the enrichment lever hits its stop, the fast idle cam has only rotated part way. Or if, with everything closed, the fast idle cam is already partly rotated. In both cases the cam can't achieve full travel.

I also have the Fred Millturn choke arrangement. From memory I started with the fast idle cam, getting the clearance right with it fully closed, and only connected the fuel enrichment once that was done. I can't check just now, as the car is in bits, but I seem to recall that getting both full fast idle and full enrichment was not possible. I did consider going back to the original setup. I got it working eventually.

Good luck,
JC

[PodOne]

9 hours ago, JohnC said:

Is it possible that the mechanism is giving full fuel enrichment but not full idle increase?

Hi John

Yes, Full enrichment with minimal increase in idle. From your description of how you fitted it I may have started fitting it the wrong way around. I will try as you suggest but I was hoping the fast idle to choke relationship would be progressive ie Full enrichment and 1500rpm reducing as the choke is pushed fully home to 800-900rpm once up to temperature.

It's quite a primitive set up when you consider most cars now also bring water temperature into the equation! 

I'll have a play and report back.

Anyone else any ideas?

Andy

Edited November 12, 2023 by PodOne

[marting]

Hi Andy,

Hope you are well. In the Fred Millturn kit, the overfuel lever on the metering unit is operated by the link cable attached to the fast idle cam. If you are getting full movement on the overfuel lever, the cam is rotating correctly. The CP fast idle cam in the kit has the same lift as the originals which is only about 1mm in total. This 1mm has to overcome any play in the linkages and butterfly spindles and then open the butterflies by a tiny amount. The clearance gap specified in the manual is fine when everything is new, however, 1mm of lift can be easily lost if there is play in the countershaft, linkage rods, swivel posts and butterfly spindles. As such, ignore the gap specified in the manual and adjust the screw that acts on the fast idle cam until you get the butterflies to open and close on the fast idle cam. If you have adjusted this and it is holding the butterflies open when the choke is off you have gone too far. Once this is in the zone, you then have the facility to adjust the increased revs with the amount of overfuel by adjusting the adjuster on the link cable. If you cannot get it setup correctly, let me know and I will pop up to have a look to see what’s going on.

Kind regards

Martin – Fred Millturn Parts

[PodOne]

3 hours ago, marting said:

Hi Andy,

Hope you are well. In the Fred Millturn kit, the overfuel lever on the metering unit is operated by the link cable attached to the fast idle cam. If you are getting full movement on the overfuel lever, the cam is rotating correctly. The CP fast idle cam in the kit has the same lift as the originals which is only about 1mm in total. This 1mm has to overcome any play in the linkages and butterfly spindles and then open the butterflies by a tiny amount. The clearance gap specified in the manual is fine when everything is new, however, 1mm of lift can be easily lost if there is play in the countershaft, linkage rods, swivel posts and butterfly spindles. As such, ignore the gap specified in the manual and adjust the screw that acts on the fast idle cam until you get the butterflies to open and close on the fast idle cam. If you have adjusted this and it is holding the butterflies open when the choke is off you have gone too far. Once this is in the zone, you then have the facility to adjust the increased revs with the amount of overfuel by adjusting the adjuster on the link cable. If you cannot get it setup correctly, let me know and I will pop up to have a look to see what’s going on.

Kind regards

Martin – Fred Millturn Parts

Hi Martin

Thanks for your kind offer but I'm not dragging you up north for something I've most likely cocked up!

For Info the throttle bar is OEM and the bodies etc all refurbed by Neil Ferguson albeit without bearing on the butterfly shafts and make a good seal with added Molycoat. The throttle bar has your bearing kit and link rods and there is almost no play.

I'll have a play taking on board what you have said and give you a bell if I get stuck.

Andy    

[iani]

4 hours ago, marting said:

Hi Andy,

Hope you are well. In the Fred Millturn kit, the overfuel lever on the metering unit is operated by the link cable attached to the fast idle cam. If you are getting full movement on the overfuel lever, the cam is rotating correctly. The CP fast idle cam in the kit has the same lift as the originals which is only about 1mm in total. This 1mm has to overcome any play in the linkages and butterfly spindles and then open the butterflies by a tiny amount. The clearance gap specified in the manual is fine when everything is new, however, 1mm of lift can be easily lost if there is play in the countershaft, linkage rods, swivel posts and butterfly spindles. As such, ignore the gap specified in the manual and adjust the screw that acts on the fast idle cam until you get the butterflies to open and close on the fast idle cam. If you have adjusted this and it is holding the butterflies open when the choke is off you have gone too far. Once this is in the zone, you then have the facility to adjust the increased revs with the amount of overfuel by adjusting the adjuster on the link cable. If you cannot get it setup correctly, let me know and I will pop up to have a look to see what’s going on.

Kind regardsMartin – Fred Millturn Parts

Exceptional customer service from Martin as usual, if only all traders took aftercare as seriously!

[marting]

Hi Andy,

If there is no significant play, then it should just be down to adjustment. I still do audits and training for Habasit in Elland, so I'm up and down every couple of months, so can stick my head round your door if needed.

Kind regards

Martin – Fred Millturn Parts

[Mk2 Chopper]

You set the fast idle cam adjustment screw when the engine is warm, by pulling on the cold start cable to move the cam to its maximum position and adjusting to 1800 to 2000 revs. Obviously don't also pull the enrichment lever on the MU.

Gareth