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360 Chrysler wonbt idle

D

Dean Travis

Guest
I am running Carter AFB 600 an

I am running Carter AFB 600 and it will run great above 1000 rpms but stalls immediately below that. Carb issue? Ran great last year right into winterizing. Ran good on shore before launch. Stalled coming in to dock after launch. Canged all filters etc. after problem started no change.

Ideas?

Thanks

Dean
 
"Dean,

I had similar proble

"Dean,

I had similar problems last year with my 440 chrysler. It started stalling at idle ,then progressed to stalling at higher RPM's. I replaced the coil after fuel filters and it ran fine for a few weeks and started acting up again. I finally found that the ECM had melted. The front side looked fine (metal), but when you unbolt it.....the back is full of plastic and that was all melted.It is under the black electronic cover on the engine and it is about 4 inches square and has a 5 wire plug going to it. I replaced it with an aftermarket part and it still did not work. I finally ordered an original chrysler part and it has been fine ever since. If you have twin engine swap them and see if this solves the problem. It took me over a month to figure it out. I also replaced a ballast resistor that had been cooked by the bad ECM. It is a good idea to carry a spare anyway ($65)."
 
"JimCT, Captain Ed,

Thanks

"JimCT, Captain Ed,

Thanks for the responses. I am going down to the boat after work today. I have twin engines so I can swap around some things as a test. It's funny to me that I can get all my revs out of the engine but when it dies its not a stumble die its like a turn off die. Never had that type of die before. I remember having vacumn leaks where its a rough idle die. I remember someone here talking about ethenol effects on the AFB carbs. What is the symptoms of this?

Dean"
 
"Dean:

Sounds like carb flo

"Dean:

Sounds like carb flooding to me.

Try this: Warm the motor up and get it to idle by cranking the idle SPEED screw in until it does. Then turn one of the idle ADJUSTMENT screws slowly in. Did the motor slow down, or did it speed up? Repeat for the other idle adjustment screw.

If the motor sped up on either screw, the carb is flooding. If it tried to die, then the problem is elsewhere.

Note: From my experiences with these old, aluminum bodied carbs, they are the problem--especially since ethanol fuel arrived. The body of the carb gets porous over the decades and gas weeps right on through.

Came to this conclusion after rebuilding one of mine several times--and the bugger still leaked gas! Added a fuel pressure regulator to reduce the gas pressure to 4 psi, and it still leaked. The solution was a new Edelbrock Marine carb---about 300 bucks on amazon.com.

Jeff"
 
..."its not a stumble die

..."its not a stumble die its like a turn off die".
Captain Ed's diagnosis may be spot-on. Fuel starvation would likely show a stumble. Ethanol can cause all sorts of odd mischief but this one sounds electrical.
 
Had the same problem as Captai

Had the same problem as Captain Ed. My ECU was fried by a short in the wire coming off the alternator. The wire had rubbed against a sharp edge for 24 years. The ECU is a solid state sealed unit that will cost $12 at a discount big box store or $70+ at the marine store.
 
..."The ECU is a solid sta

..."The ECU is a solid state sealed unit that will cost $12 at a discount big box store or $70+ at the marine store."

And it's the SAME unit.

Jeff
 
"Hello,

Sorry to take so lo

"Hello,

Sorry to take so long to get back here. But fell and sprained my knee. out of comission for a few days. Now, Changed the ECU. Made no difference. Heres the worst part. Went to turn the idle adjustamnet screw and it broke right off even with the carb body. Rotted right through. Didn't look bad but there was a spring covering the part that was rusted. So, I can't do Fast jeff's test.

Dean"
 
Maybe time to do a carb rebuil

Maybe time to do a carb rebuild while you're replacing that idle screw. Can't hurt.
 
Changed the Carb yesterday. W

Changed the Carb yesterday. Went right to idle. Slipped it into gear. Nice!

Thanks for your help everybody!

Dean
 
"Glad to hear you finally slay

"Glad to hear you finally slayed the dragon.

After re-reading the posts here, I recall now I had the same idling problem with my 318. Re-built the AFB carb but no improvement. Long story short, the throttle shaft & bushings were worn causing a vacuum leak. What was vexing about the idling problem was that it was intermittent; rough idle for 5 minutes then smooth idling for a while then back to rough idle. $400 later (new Edelbrock carb) and the engine runs and idles like new. Who says money can't buy happiness?"
 
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