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Author Topic: Ignition Vacuum advance problem (I think?)  (Read 2603 times)

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Offline Dubv

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Ignition Vacuum advance problem (I think?)
« on: September 02, 2016, 09:17:34 PM »
I was driving  home a couple of weeks ago and I had been having intermittent issues on the Eagle where it would die...and I had thought it was a fuel issue, but after thinking I had run out and only being able to put 6 gallons in the tank, and then seeing plenty of fuel coming out of the fuel line...scratched that idea.
Finally the car died and would not restart...had it towed home.  The way it was having intermittent issues, my immediate thought was the ignition control module, so I replaced the box...no luck.  I then moved on to the ignition wire from the coil to the distributor...no luck.  I then replaced the coil.  Still no luck.  I could get the car to start and run for a bit, but once it kicked down off high idle, it would run for a bit, then die...and then wouldn't run unless I raced the engine.  I disconnected the vacuum line at the distributor and lo and behold it will run.  Idles a little low since the vacuum is leaking, but it will run.  When I hook the hose back up, it kills it almost instantly. 
So the question is, is there a valve somewhere in this vacuum line that is failing and if so, where is it located and how do I repair it?  Any thoughts would be much appreciated!

Offline amcfool1

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Re: Ignition Vacuum advance problem (I think?)
« Reply #1 on: September 03, 2016, 12:05:25 AM »
hi, sounds like a timing thing. check, or have your timing checked. When you pull the line of the dist, the vacuum leak should speed up your idle, not slow it down. the vac advance may be bad. Also, what year is your Eagle? 80, and 81-83, and 84+ are very different critters. Also, the Carter BBD idle tubes are known to clog up, easy fix for this, drill 'em out to .032". VERY CAREFULLY!! good luck, gz

Offline Dubv

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Re: Ignition Vacuum advance problem (I think?)
« Reply #2 on: September 03, 2016, 11:28:10 AM »
My Eagle is an '84.  I had the timing rechecked when I had the car in for service maybe 6 months ago.  The problem came on kind of gradually to reach the point its at now.  Something could be clogged somewhere I suppose?

Offline AMC of Houston

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Re: Ignition Vacuum advance problem (I think?)
« Reply #3 on: September 03, 2016, 03:42:48 PM »
I second the idle tube problem (AMC had a Service Bulletin on it).  You have to pull out the idle tube plate (the 2 hollow screws you see under the choke flap).  Then drill out the bottom "pinched" area of the tubes to .032 (.030 works if that's the only bit you can easily find).
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
'73 Jensen Interceptor
'86 Audi 5000 Turbo
'98 Aston Martin DB7
'09 Nissan Titan
'10 Nissan Maxima

Offline Dubv

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Re: Ignition Vacuum advance problem (I think?)
« Reply #4 on: September 04, 2016, 06:04:54 PM »
So the vacuum seems very strong, if I take the hose off of the distributor it will run fine, unless I put my finger over the hose and then it will kill it unless I throttle up the engine.  Does this sound like the idle tube issue?
Everything on the distributor itself seems ok.  I found the two screws you all mentioned, but wanted to confirm this sounded like the correct symptoms before I missed with them.

Offline AMC of Houston

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Re: Ignition Vacuum advance problem (I think?)
« Reply #5 on: September 04, 2016, 08:52:31 PM »
The idle bleed thing makes the carb run too rich at idle; so pulling off a vac hose leans out the carb a bit and will offset the rich mixture a bit, hence running better with the hose off.   One usual check for the idle bleed issue is to look down the carb while its idling, and see if you see drips of raw fuel coming from the venturis.   You see drips; you have a problem.
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
'73 Jensen Interceptor
'86 Audi 5000 Turbo
'98 Aston Martin DB7
'09 Nissan Titan
'10 Nissan Maxima

Offline Dubv

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Re: Ignition Vacuum advance problem (I think?)
« Reply #6 on: September 04, 2016, 08:57:58 PM »
Got it, I will check for the drips in the morning.  Thank you for the ideas!

Offline amcfool1

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Re: Ignition Vacuum advance problem (I think?)
« Reply #7 on: September 05, 2016, 01:04:35 PM »
hi, so you have an 84! count yourself either lucky or cursed, you decide. Me too. Is your car still basically stock? ie not too badly "hacked"? This was AMC s last series of motors, and the technology involved was/is  pretty impressive, if a bit of a PITA to understand. OK, heres the short version. What you have is a very early attempt at computer control of the engine. It works very well IF, big IF!, you have all the sensors working and still in place. In 84+ Eagles, the distributor does NOT send a spark to the motor. The computer does. The distributor just sends a signal to the computer, which then does it's thing. (btw, the computer is behind the pass.  side kick panel, and is still available for about $105. from anywhere) Essentially the distributor acts like a "crank trigger" in more modern motors. The computer also controls the carb, telling it to lean/enrich the mixture, again,  depending on inputs from about 8 sensors. The good news is, believe it or not, most of these sensors are still available. I just brought my 84 back to life, and the only sensor I could not find is the knock sensor. The red one just under and in front of the carb on the intake. But that is basically a small microphone, and is still OK. You also MUST have the wiring and the vacuum system hooked up and functioning. THERE IS NO OTHER WAY!! Its a computer!, and computers are "stupid", ie, they only know what they are told, and react accordingly. It took me roughly a year to bring my 84  back, more reading and research than I care to remember, but man, does it run smooth now! New computer as well. Runs like it just left the showroom! You can put a glass of Pinot on the valve cover and it will not shake it off! Smooth!  AMC engineers really knew what they were doing. Since they are no longer around to help us, we need to know and understand our cars.
good luck, gz

Offline Dubv

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Re: Ignition Vacuum advance problem (I think?)
« Reply #8 on: September 05, 2016, 07:18:58 PM »
Well, let the car run with the vacuum advance hose disconnected this afternoon and didn't observe any drips down the throat of the carb.  Good news/bad news. 
The car does not run great with the vacuum advance hose disconnected, but it will run.  The engine dies in short order if I either attach the vacuum advance hose again or if I cover the end of the hose with my finger.  The way the motor dies it really sounds as though its an electrical/ignition problem as it will stumble very abruptly..as if there is spark/no spark and then die.
It has the new electronic control box, new coil, new wires...I guess there could be a problem in the wiring harness on the distributor itself ( I don't think thats sold seperately...but the distributor isn't hugely expensive).
This is just weird.

Offline Dubv

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Re: Ignition Vacuum advance problem (I think?)
« Reply #9 on: October 23, 2016, 12:23:32 PM »
Just wanted to give you all an update here...
So after a lot of trouble shooting by my mechanic and I, it turns out the issue WAS the distributor intermittantly failing.  To add to the confusion my gas gauge is also not reading correctly once it gets below a half a tank so running out of gas was also a problem once.  Knock on wood, seem to have it solved.  Also put in a new radiator to boot to replace my very tired, patched, rusty one. Thanks for all the ideas.

Offline amcfool1

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Re: Ignition Vacuum advance problem (I think?)
« Reply #10 on: October 23, 2016, 01:14:33 PM »
good deal!, glad you got it running again. gz

 

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