'61 Fuelie Suddenly Running Rough

[Larry B.]

The other day I ran my 283/315 and noticed it was idling 100 rpms more than normal and running rough when hot. I tried dialing in the idle and mixture with no success. The engine is running very rich as you can smell the unburned gas. Only thing I did recently was remove the fuel pump drive cable, lubricate and re-install. Car is in tune and has a Pertronix 1 with Flamethrower coil which has been in the car for 7 years and trouble free. What trouble shooting steps should I follow? Thanks

[Jerry G.]

Re: '61 Fuelie Suddenly Running Rough

First thing I'd check is for a sticking choke. The combination of rich and higher idle points that way.

[Tom P.]

Re: '61 Fuelie Suddenly Running Rough

And a blown cranking signal valve (first thing I'd look at). Clamp off the rubber hose between the line and the valve and see what happens.

[Jim L.]

Re: '61 Fuelie Suddenly Running Rough

And a blown cranking signal valve (first thing I'd look at). Clamp off the rubber hose between the line and the valve and see what happens.

I agree with Tom. Check the cranking signal valve. The symptoms you've described are consistent with a failure of this part.

Jim

[Larry B.]

Re: '61 Fuelie Suddenly Running Rough

Jerry, How do I check to see if the choke is stuck? Do I look down the air meter? Seams to run a little better when at operating temperature but still very rich.

Tom, I believe the FI does not have a cranking signal valve. It has an electric primer button. See photo. Let me know if it has one.

[Larry B.]

Re: '61 Fuelie Suddenly Running Rough

Tom & Jim, I pinched the line as seen in my picture and when I do so it stumbles until I release it.

[Tom R.]

Re: '61 Fuelie Suddenly Running Rough

And a blown cranking signal valve (first thing I'd look at). Clamp off the rubber hose between the line and the valve and see what happens.

I also agree with Tom and also would check for any vacuum leaks. I had one at the cranking signal valve connection and it exhibited the exact symptoms you described. Fixed the leak and all is well now.

[Tom P.]

Re: '61 Fuelie Suddenly Running Rough

You're right, the cranking signal valve circuit is GONE! A previous owner has obviously removed it.

This is what it would have looked like. The valve screws into the side of the plenum (where the plug is on yours). Then a T-fitting (instead of an elbow like on yours) would be screwed into the top of the main diaphragm cover with a steel line and a rubber hose connecting the steel line to the valve.


This is the enrichment housing. If the diaphragm inside of it is cracked or ruptured, then manifold vacuum cannot pull it over to the lean position and it would allow a full time rich mixture.




There is a rod coming out of the back side of the enrichment housing which is connected to a lever (ratio lever). During idle or normal cruise conditions, that rod SHOULD be pulling the lever (AWAY from the plenum) and hard up against the lean stop. If that rod is not pulling the lever during idle, that may be your problem (the below picture shows the lever up against the RICH stop).

[Larry B.]

Re: '61 Fuelie Suddenly Running Rough

Tom, Great pictures..learning something here! The lever goes from rich when shut off to be what appears to be full lean when running. There is some fuel residue and smell by the area of the lever. Below is a picture of the lever with the car running..hope you can see it if you zoom. Can't find any vacuum leaks. Can the diaphragm still be bad if the lever moves to lean? Is there a way to check to see if the choke is stuck. The fuel is so rich it gives me a headache!! Could I have re-installed the drive cable wrong when I took it out a few days ago. Seemed to go in and screwed up easy. What should I check from here?

[Jim L.]

Re: '61 Fuelie Suddenly Running Rough

Larry, your enrichment diaphragm is working properly. Regarding the pump cable, it doesn't have any bearing on the rich condition.

The priming circuit has my attention. If the priming solenoid is somehow remaining energized after you start the engine, the engine will run nauseatingly rich at low RPM. On your car what activates it? Can you verify that it receives power only during engine cranking?

Another condition that will result in an overly rich mixture is any failure of the needle and seat to close when the bowl fills with fuel. This could be due to debris at the needle/seat area or a failure of the float itself. You noted fuel residue in the area of the ratio lever. Anywhere else?

Regarding the "choke", yours is working properly (or at least not the cause of the problem) if the ratio lever is being pulled forward against the economy stop. If the choke were on, the ratio lever would be against the power stop (towards the rear).

Jim

[Larry B.]

Re: '61 Fuelie Suddenly Running Rough

Jim, The priming circuit is activated by a push button switch. On a cold start, I turn the ignition key to the on position, push the button in for several seconds and start the car. The car smooths out a bit after getting up to operating temperature and idles at about 800-850. Still smells very rich. Idle is not perfectly steady and bounces up and down a bit. Don't know if that is normal for the Duntov cam.

[Jim L.]

Re: '61 Fuelie Suddenly Running Rough

Jim, The priming circuit is activated by a push button switch. On a cold start, I turn the ignition key to the on position, push the button in for several seconds and start the car. The car smooths out a bit after getting up to operating temperature and idles at about 800-850. Still smells very rich. Idle is not perfectly steady and bounces up and down a bit. Don't know if that is normal for the Duntov cam.

Larry, some questions:

From your description of the starting procedure, you must have an electric fuel pump.... true?

The priming circuit is a modification someone has made to your FI unit. Are there any other modifications?

What happens to engine idle if you push the priming button while the engine is running?

How does the engine run once the car is moving? Any hesitation when you step on the accelerator? Any black smoke?

Does the idle mixture screw have any effect? I. E. if you screw it all the way in (closed), does the idle mixture lean out any? Does the engine stall (it should)?


Jim

[Tom P.]

Re: '61 Fuelie Suddenly Running Rough

Jim,
Notice that fuel bypass line (at the fuel meter inlet) ala 57-64/65 FI units. We got some kind of hybrid FI setup here!
I'd have to see/examine this unit/setup in person to make an intelligent diagnosis. Sorry, I can't speculate any further.

[Jim L.]

Re: '61 Fuelie Suddenly Running Rough

Jim,
Notice that fuel bypass line (at the fuel meter inlet) ala 57-64/65 FI units. We got some kind of hybrid FI setup here!

I see this modification frequently on racing units and occasionally on street units. It's not my favorite modification for several reasons:

1. This mechanism must be manually activated. In contrast, the factory CSV operates automatically (and can be made to be reliable when backed up by an electric valve).

2. When used with an electric fuel pump, as I suspect is the case on Larry's car, inattentive use of the priming circuit has the potential to flood the engine (at a minimum) or fill a combustion chamber with fuel, risking a hydrolock situation.

3. Most implementations are done without any thought given to mechanical support of the solenoid valve and are generally lacking in craftsman-like details.

I've reversed this modification on many units and advocate doing so to anyone who has it on his/her FI unit.

Jim

[Joe M.]

Re: '61 Fuelie Suddenly Running Rough

Some versions of the pertronix require the key be turned on for a couple of seconds before starting the car.

Pertronix coils have a reputation for failure.....

FI units were dumped for problems other than FI problems...

Try a new coil?

Could be dirt.