Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing High Idle Speed - 3000 RPM

The engine maintains a high rpm when started with no foot pressure on accelerator. (1974 Crossflow)
I hadn't started the engine for about a month until today and prior to this time it was idling at around 800 rpm - they only change I've done in the interim is to remove the one-shot oiler .

I have adjusted the idle screw at the carburetor and there is a space between the end of the screw and the plate that controls the butterfly valves so that doesn't seem to be influencing things .
I have also adjusted the throttle cable so that it there is slack in the cable .


Please see the linked [img]https://photos.app.goo.gl/gGnWEEXsxnpLHuLj8[/img] photo of the passenger side of the carburetor . Notice that the linkage does not go into the slot on the arm connected to the butterfly valves - is this correct ?
I have adjusted both the carburetor and choke adjuster screws but it still idles at 3000 rpm.

Any thoughts or suggestions as to the cause or things to try next ?

Thanks !

Yes I think it needs to be adjusted so the choke when fully open is off the fast idle cam, i.e. in that slot.

Thanks for the quick reply !

I've annotated the image, just to make sure I'm understanding correctly. The item circled should fit into the fast idle cam ? [img]https://photos.app.goo.gl/F6M3ZDkvimm8r4777[/img]

I'm a little puzzled as the solenoid (also circled) prevents what I would expect full movement of cam to allow them to connect .

This is mine in the choke off position. The choke cam is a hairs breadth away from the pin.



To be honest it looks very similar to yours.

I'd check to see if the butterflies are closing properly, and then do a check to see if there are any air leaks. I have read of a dodgy base plate causing fast idle.

Might worth getting some easy start spray, and having a spray round the base to see if there are any air leaks. Check the primary and secondary idle jets.

Mine doesn't have the idle jet solenoid - not sure if that could be faulty? Might be worth swapping in a standard idle jet to see if that helps?

Your accelerator cable isn't sticking on anything is it ensuring free play with the springs returning it to its correct position when at idle?

Is it just at start up the high revs or when at idle with warm engine, if at start up do the revs eventually drop?

Phil, thanks for sharing the picture, it's good to just see that they look so similar.


Bruce, the revs actually continue at a steady 2800 rpm after it warms up and cable doesn't appear to be sticking .

One thing we did notice this evening that, after turning off the engine, we noticed that it seems as if fuel continues to drip into the manifold as there was white smoke coming out of the carburetor (predominantly the driver's side) long after the ignition was turned off and engine stopped.

My father-in-law believes that this could indicate that the carb float is not working property and could require some adjustment - would this appear to be a likely cause ?

Yes, that is certainly a possibility and fuel should definitely not be dripping anywhere and heaven forbid on the manifold, you need to get that sorted immediately. I think the float could be stuck allowing the bowl to flood, is it a manual fuel pump or electric?

It's a manual pump. I'll focus our attention on the float - thank you

Often giving the float bowl a few taps can be enough to free off a sticky float. As it's come on so quickly, it does suggest something is stuck open somewhere - may be some crap has been pulled into the carb causing the float or butterfly to stick open.

The smoke may be a result of the car idling at 3000rpm rather than a symptom! I know when I've got my tick over up too high I get dieseling when I shut off - anything above 1000rpm can cause it on mine..