Ignition Cutting Out

thehackmechanic

thehackmechanic

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I'm trying to get this '73 CS (US spec, auto converted to 4-speed, desmogged, Webers), running right. It'll rev up to a certain point, then stumble badly, like something is cutting out. The distributor seems to be functioning -- I marked TDC and the 22 degree ball with White Out, and at idle it's pretty close to TDC, and at about 1800 RPM it's pretty close to the the 22 degree ball. It's a 002 dizzy with a vacuum advance and retard. The retard isn't hooked up. The advance is hooked up to the port at the base of one of the Webers. The dizzy plate moves when I suck on the advance line, but I have to suck really hard.

Most of that is neither here nor there, because I was trying to reset the timing when I noticed that the cutting out and stumbling and dying was correlated with the timing light no longer flashing -- a damned good smoking gun that the ignition is cutting out.

The points look fine. I reset the gap and it's still doing the same thing.

This is a car that's been off the road three or four years, and was not driven much for several years before that. The coil and plug wires look original, the cap, rotor, condenser, and points look recent.

Condenser? Coil? Or should I just throw a Pertronix at it?

--Rob
 
Might be a stretch but my 2002 is cutting out at speed and when I disconnect the tach wire at the coil it is fine. I can drive 20 miles and then it happens and reocurrs. I replaced the tach as the wires looked fine but now I will replace the wire. Loose condenser can also be a problem, any stray ground will cut the ignition.

Chris
 
I would replace the coil, add a pertronix, and change the plug wires. And as Chris says, check the grounds.

thehackmechanic said:
I'm trying to get this '73 CS (US spec, auto converted to 4-speed, desmogged, Webers), running right. It'll rev up to a certain point, then stumble badly, like something is cutting out. The distributor seems to be functioning -- I marked TDC and the 22 degree ball with White Out, and at idle it's pretty close to TDC, and at about 1800 RPM it's pretty close to the the 22 degree ball. It's a 002 dizzy with a vacuum advance and retard. The retard isn't hooked up. The advance is hooked up to the port at the base of one of the Webers. The dizzy plate moves when I suck on the advance line, but I have to suck really hard.

Most of that is neither here nor there, because I was trying to reset the timing when I noticed that the cutting out and stumbling and dying was correlated with the timing light no longer flashing -- a damned good smoking gun that the ignition is cutting out.

The points look fine. I reset the gap and it's still doing the same thing.

This is a car that's been off the road three or four years, and was not driven much for several years before that. The coil and plug wires look original, the cap, rotor, condenser, and points look recent.

Condenser? Coil? Or should I just throw a Pertronix at it?

--Rob
Click to expand...
 
thehackmechanic said:
Condenser? Coil? Or should I just throw a Pertronix at it?
Click to expand...

While a Pertronix is certainly a worthwhile addition to any coupe, I wouldn't install one yet. The problem could be in the coil, condensor, or even low tension wiring. If the electronics in the Pertronix get a "dirty" power feed or coil load, it might fry the circuitry.

I would begin by swapping in another coil/condensor/points from your bin of spare ignition parts.
 
thehackmechanic said:
I'm trying to get this '73 CS (US spec, auto converted to 4-speed, desmogged, Webers), running right. It'll rev up to a certain point, then stumble badly, like something is cutting out. The distributor seems to be functioning -- I marked TDC and the 22 degree ball with White Out, and at idle it's pretty close to TDC, and at about 1800 RPM it's pretty close to the the 22 degree ball. It's a 002 dizzy with a vacuum advance and retard. The retard isn't hooked up. The advance is hooked up to the port at the base of one of the Webers. The dizzy plate moves when I suck on the advance line, but I have to suck really hard.

Most of that is neither here nor there, because I was trying to reset the timing when I noticed that the cutting out and stumbling and dying was correlated with the timing light no longer flashing -- a damned good smoking gun that the ignition is cutting out.

The points look fine. I reset the gap and it's still doing the same thing.

This is a car that's been off the road three or four years, and was not driven much for several years before that. The coil and plug wires look original, the cap, rotor, condenser, and points look recent.

Condenser? Coil? Or should I just throw a Pertronix at it?

--Rob
Click to expand...

Rob,

My CSi does the same thing and I'm running a Pertronix. Previous owner said it stuttered occaisionally when he owned the car. When the top end was rebuilt this past summer the mechanics replaced everything that would lead to that condition. I am thinking of replacing the alternator, voltage regulator and cleaning grounds.

The stutter is like a temp gauge in an 02 with a bad ground...sporatic random jumping.
 
Other E9 considerations

A stumble can be fuel related as well as spark. I'm working on a similar problem today.

Remove and read your plugs. Old school I know, but my car gets used infrequently, so a lot of choke especially this time of year can add to the problem. The car hummed (I had tuned it the day before, timing and carb adjustment), went out on the freeway and then stumbled badly. Got home, pulled the plugs, fouled, with fairly new plugs.

It would run, but low idle 5-600. But just not go over 3000 rpm. One bank of cylinders were just not responding. What else had I done? I put a quart of oil in. Fast. Was there enough oil that pooled around a valve? Maybe. I won't go dumping in oil like a Jiffy lube any more.

Pulled the carb top, checked everything, cleaned the jets, etc. Nothing realy there, fuel level; check, blocked idle jet, no. For you FI guys- cold start, leaking injectors, loose wiring and grounds,etc.

What else? Well, after idle, more fuel get used ( either FI or carbs) was that enough to push the plugs beyond working? When accelerating FR goes way rich, Definately. Kill a set of plugs, yep.:shock:

Don't really hear these problems on newer cars- they run lean and hotter.

Oh yeah, my battery died too. So I guess I'm good for another 5 years. So check your voltages.

That's my story. Happy holidays guys!
 
adawil2002 said:
My CSi does the same thing and I'm running a Pertronix. Previous owner said it stuttered occasionally when he owned the car. When the top end was rebuilt this past summer the mechanics replaced everything that would lead to that condition. I am thinking of replacing the alternator, voltage regulator and cleaning grounds.

The stutter is like a temp gauge in an 02 with a bad ground...sporadic random jumping.
Click to expand...

Erratic engine operation (flat spots, missing, hesitation and stuttering) can often be traced to traditional ignition faults, including dirty points, improper plug gaps, a distributor rotor that is defective (badly worn/corroded) and possibly the wrong size, (this includes the rev limiting style rotors) and defective condenser and coil. However, your fuel injected model may be suffering from a fuel delivery issue.

Given the age of these cars, off the top of my head, you have a fuel injection wiring harness that could be a problem. Trigger contacts could be contaminated. Throttle Position Sensor could be defective or misadjusted. Potentiometer could be showing its age. Fuel pressure regulator could need replacement or adjustment.

Interestingly, it is commonly presumed that a test for ECU function is if the engine will run. However, it can function poorly or outside of some unknown “minimum tolerance limit.” (This is the factory’s pronouncement.) When this occurs, the suggested remedy (aside from replacement) is to increase fuel pressure.

For starters:
http://www.e9coupe.com/forum/showthread.php?t=4781
http://www.e9coupe.com/forum/showthread.php?t=3546
 
Forgot to add that the car has brand new NGK plugs in it.

Again, the smoking gun symptom is that, using a timing light, when the car stumbles when I rev it, the timing light stops flashing. If I put the timing light on the wire from the coil to the center of the distributor and rev it, it stays lit, indicating spark is heading into the distributor but not making it out.

Disconnected tach wire, no change.

Swapped the coil, condenser, and points from the spare parts box, no change.

Swapped the plug wires with my other E9, no change.

This would all tend to isolate the problem to the cap and rotor. I'd drive up to Bavauto and grab them but they don't have them in stock.

This car has small-bodied 002 dizzy. My other E9 has E12 electronic ignition with the big-boddied dizzy that came along with the L-Jet retrofit, so I can't quickly swap dizzys without also dragging along the electronic modules.

I would've sworn I had another 6-cylinder distributor around, but I sold it along with the rest of the original D-Jet stuff -- another indication that, if you sell any part, eventually you will regret it.
 
I've cleaned up the cap and rotor and see nothing amiss in terms of cracks or carbon tracks. The spring contact in the center of the cap looks fine.

The ignition seems to be cutting out on all cylinders -- that is, when I put the timing light on each plug wire and idle the engine, the timing light is solid, but when I rev the engine and hear the car stumble, the timing light flashes irregularly or cuts out all together. The stumbling behavior was the same when I swapped plug wires with my other E9, so plug wires don't seem to be the culprit.

The "running so rich the plugs stop firing" argument is interesting, but the plugs were installed this morning. Plus, the stumbling doesn't seem to be coming from goosing the throttle and hitting the accelerator pumps and dumping raw gas in -- it seems to be coming from slowly opening the throttle. Thus, the "running so rich the plugs stop firing" argument is, I think, less likely rather than more likely.

Ordered a new cap, rotor, points, and condenser. Looks like I just have to wait 'till they arrive and let the mystery be a mystery for a few days.
 
ign problem

Check to see if you have one of those rev limiter rotors in the distributor. They are thick down through the middle and have a band of glue down through the middle. There's a little spring inside that is compressed when the centrifical force gets high enough and acts like a rev limiter. These are common on Mercedes of that era, but I've seen them on BMW's also. The best place for those rotors is the garbage can. I fought a similar problem on a Mercedes for several days before a friend clued me in to this small problem. Good luck. Leroy
 
Sparky

Well, might read the volts going to the coil when it acts up. Resistance wire? Resistor getting hotter than normal? Jump the coil from the battery and see what's she does?

Just jumped back up on the freeway with mine.... riding down the highway.. crusing down to a show.. it's harder than it looks..... it's a long way.......:cool:
 
Voltage

Checked voltage on the hot side of the coil, and sure enough it's 2.5V with the ignition on and the engine not running, and about 3V with the engine running, but jumping the hot side to the battery doesn't make it run any better.

Brain starting to hurt from both the puzzle and the exhaust fumes... need to put this down for a while.
 
The rev limiting rotor (if you have one) would be my first guess. From my fuzzy memory, if has a "counterweight" opposite the working end, so when the revs go up, centrifugal force on the counterweight draws the working tip of the rotor inward and thus no contact with the towers on the cap.

This is rather a long shot but would perfectly explain your problem. Except that, you haven't said whether you have such a rotor. At any rate, a new one should cure it. Dunno if you want to reinstall even a new rev-limiting rotor...

Your posts indicate all else is apparently good with the system. Only other thing I could think of (not having the car in my face) would be to run the car at idle and jiggle the wires to/from the coil, inspect the cap for tracking marks, clean the cap inside and out with something strong, make sure the HT leads to the plugs aren't crossfiring.

This latter is ususally done in the dark, engine running, mist the wires and see if there are any visible sparks or listen for the snapping noise of the spark jumping where it oughtn't.

In any case, we want a full report, however brief.
 
one other thought. how much old / stale fuel is in the tank? any moisture in the tank? if it is unknown, throw it out. i have had this issue with other cars. i drained the tank, put new fuel in and all things ran much better. in FI cars, i would recommend running BG44x fuel injection cleaner thru the engine - adding it to a fresh tank of fuel.
 
No rev limiter

No rev limiter.

Will check the gas tank. I did pull the tops off both carbs and, other than a little sediment in the bottom of the float bowls, didn't see anything that elicited a EUREKA from me.

Thanks, all, for the suggestions.
 
Sparky II

With such a low voltage as you report to the coil, it might indicate that the polarity is crossed, the coil is overheating, and missfiring occurs at load. ( can't keep up)

Any number of things can contribute to low voltage at the coil such as a resistor coil in line with a resistor, etc.

Voltage to the coil ahead of the resister should be 12+, after the resistor if factory around 9.5 v to keep the points from burning prematurely.

Meter everything.
 
rsporsche said:
one other thought. how much old / stale fuel is in the tank? any moisture in the tank? if it is unknown, throw it out. i have had this issue with other cars. i drained the tank, put new fuel in and all things ran much better. in FI cars, i would recommend running BG44x fuel injection cleaner thru the engine - adding it to a fresh tank of fuel.
Click to expand...
How did you dispose of the old gas?
 
You can mix it into your car in small quantities such as a gallon at a time. I use my wife's Highlander! It won't hurt anything unless it's loaded with water, and you can always strain out any crud.
 
Bill,

i had a mechanic drain the tank as we were chasing the problem. i had already done all of the easy things - change the plugs, wires, cap + rotor, adjusted the valves, change the filters (air + gas), verified that there weren't any fuel leaks, swapped in a different afm ... and when that didn't solve it, i had the mechanic check the injection, test the fuel pump, the flywheel sensors, we went ahead + replaced the o2 sensor, and when it didn't solve it, we drained the tank + put the bg44x injection cleaner in and everything was solved.

scott
 
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