Idle cut off solenoid

wqqdster · Post by **wqqdster** » Thu Mar 12, 2015 7:34 pm

Since putting my wife's '78 Spider back on the road it has developed an annoying symptom. When it's cold and on the choke it runs fine. When it's warmed up it's okay but has a quick little stumble when lightly accelerating. Before it gets fully up to temperature it will pop back through the carb when accelerating.... if I let up it stops popping, if I floor it it stops popping. I rebuilt the carb, cleaning out all of the ports and jets, set the float level and gave it a general going over.

I noticed that when tuning it up I had to turn the idle screw quite a ways out to get it to idle. Today the idea of that solenoid being flakey occurred to me.... I pulled the solenoid out and it went click, click when the power is applied but when the engine is running and I unplug it..... nothing happens, the car continues to idle away.

Could this be causing my popping? The solenoids aren't cheap so I don't want to buy one if that won't help my problem. The Fiat parts site says this valve is for idle and progression....

Thanks for your thoughts!

vandor · Post by **vandor** » Thu Mar 12, 2015 9:02 pm

I think you may have 2 problems. The popping is from a lean condition, vacuum leak, carb not jetted right, choke coming off too soon, etc. If the engine does not die when you unplug the solenoid then it's not idling on the idle circuit. The primary AND/OR secondary throttle plate may be partially open, and/or a vacuum leak.

Do check that when you are opening the throttle there is a good flow of fuel from the accelerator pump squirter.

So Cal Mark · Post by **So Cal Mark** » Thu Mar 12, 2015 10:58 pm

your solenoid has probably had the pintle cut off. It will still click but won't cut off the fuel flow through the low speed jet. It sounds lean on transition, the low speed jet may be a size too small

wqqdster · Post by **wqqdster** » Fri Mar 13, 2015 12:10 am

The car ran fine before being parked so I can only assume that the jetting is correct. It sounds like it would be worth taking a chance to replace the solenoid.

Thanks!

131 · Post by **131** » Fri Mar 13, 2015 1:21 am

wqqdster wrote:The car ran fine before being parked so I can only assume that the jetting is correct. It sounds like it would be worth taking a chance to replace the solenoid.

Thanks!

Waste of money if it's not your problem. At idle, disconnecting the solenoid the engine should die. If it doesn't, either as Mark said the rod has been cut (which I did on my last car), or as Csaba said, it's not idling on the idle circuit. Check the end of the solenoid rod, it should be machined to a point, but not sharpened. With the body grounded, apply 12v to the connector, the rod should move a cm or more. If it does, and the solenoid clicks when installed, but idle isn't affected when you disconnect power, you need to consider other issues first.

wqqdster · Post by **wqqdster** » Fri Mar 13, 2015 1:33 am

131 wrote:Check the end of the solenoid rod, it should be machined to a point, but not sharpened. With the body grounded, apply 12v to the connector, the rod should move a cm or more.

With the unit out of the carb it makes a clicking noise but I don't see anything moving.

So Cal Mark · Post by **So Cal Mark** » Fri Mar 13, 2015 1:59 am

take the jet from the end of the solenoid, then you can see the pintle

wqqdster · Post by **wqqdster** » Fri Mar 13, 2015 11:11 am

Thanks, didn't know it could be disassembled.

Idle cut off solenoid

Idle cut off solenoid

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