This one has got me stumped. Can anyone assist?

S

SteveM

Member
Messages
43
Reaction score
1
Location
Australia
My CS has developed a problem that has got me beat. I can't find anything close to answer in a search of past messages so I'm wondering if anyone has experienced the same issue.

The car starts and idles happily. It drives for a few hundred metres then cuts out. All lights in the dash are gone, all instruments and of course the engine. If I turn the ignition switch of and back on I get all lights and instruments, the motor easily restarts, it runs for a second or so and then the car experience complete death again. I can repreat this cycle endlessly - or until I run out of battery.

While I'm waiting for the tow truck to come and collect it, (this time I can't push it back up the hill!) I wondered if you guys could provide some guidance.

Regards
Steve
 
My first guess would be the ignition switch contacts. The ignition switch energizes fuses 6 and 7 in the "On" position. These two fuses send power to most of the dash. brake lights, reverse lights, horn, wipers, ignition, main lights (and then all lights), and the load shed relay for the electric windows.

When this happens will the horn honk? What, if any, electrical stuff works? Try placing a meter on fuse 6 or 7 when it fails. You may actually se voltage but I suspect it will be low.

As a short term remedy you might try disconnecting the battery, removing the lower plate (4 screws) on the steering column, and then push hard on the back of the ignition switch (little black plate with 4 wires) while turning the key all the way on and off a bunch of times. This may help to burnish the contacts enough to make the work again for another few days or 30 years. It is also possible that the switch is starting to come apart like BarryG's. Fortunately they are common (pretty sure anyway) with the E3 and probably a few others.

Then again I could be all wrong.
 
Thank you. I'll give it a shot but ...

I wonder why the engine/electrical dies so quickly after reaching operating temperature when the car idles when cold and drives well as it approaches that operating temp. That and the fact that it restarts with full electrics for a second or so.
 
I guess I didn't think this through completely. This makes is a bit less likely to be the switch if it is operating temperature (I was going on the 100 feet thing). However, not much happens electrically when the engine gets warm and it definitely sounds like you are losing power to the ignition circuit which is powered directly from the switch. I'm wondering if there is some circuit that starts pulling too much current when warm?

Do you think it is a function of the engine being warm or is it a time that the engining has been running ?

A few other ideas:

1. The ignition coil may be getting warm and shorting internally. More than likely this would blow a fuse.
2. My car was doing something like this and it turned out to be a condenser whose insulation was breaking down when warm and shorting the coil secondary. This took a week to track down
3. The coil ballast could be defective (this would just cause the car to stop and unlikely to effect other electrics).

Again, based on your description, the key to this problem I am pretty sure lies in the circuits on fuses 6 and 7. It is still possible that the switch contacts are resistive (age and oxidation) making them slowly heat up when current is flowing and then eventually going open circuit. This would be more time related than engine temperature related through.
 
In the L-Jets 635 there was a "Combo Relay" that powered the fuel pump and the ECU, among other things. If this was old and tired, the heat of the energized coil would cause the relay to open thereby killing the engine (not the whole car). THere may be a similar issue with one of the relays. I would start by looking at the electrical diagram and finding all the parts and connectors that are common tot he things that are losing power. If there is a relay in such a position in the circuit, I would replace it.

S
 
Electrical woes down under

It would help if we had a fair understanding of the condition of your car, including the state of arrested corrosion.

I have a couple of thoughts similar to jh’s relay related suggestions. It may be that one small issue triggers the rest of your problems. For example, if the coil overheats and shorts out (weak winding, cracks, bad ballast resistor, etc.) your engine will obviously not run. A loose wire from coil to distributor or even a condenser wire, as jh alluded to, may also cause a shut down.

When the engine dies or starts to die, it may have a tendency to shutter or jerk - even just a little bit. This, in turn, may exacerbate a weak ground. The negative ground cable, from the battery to the body is a laughable affair where a little unnoticed corrosion may go a long way to making it seem like you have a perpetually wimpy battery - despite the battery being fair dinkum. Another area of concern may be the cable from the battery positive post to the starter. Despite their advanced age, these cables have a tendency to look great but harbor all sorts of copper sulfate. If you have any doubts about the electrical connections in your car, pull each off, wire brush or emery cloth them so they are shiny and reconnect. A coating of dielectric grease or another corrosion retardant is never a bad idea. Even if this does not correct your problems, it will provide peace of mind and eliminate some possible causes. I find that when I do this I inevitably find other areas that need attention.

My overall point is one thing may be the cause of the stalling, and the act of stalling may bring on the shut down of other components.

I can empathize with you in that I had another car with an infrequent tendency to misfire and occasionally stall - after the car was washed and only if the car made a low speed left-hand turn. For some reason, the stalling did not happen when it rained, but only after the car was washed and usually dried and polished! It was obvious the moisture had something to do with it, yet we repeatedly hit the engine compartment with a virtual fire hose induced tsunami and could not repeat the results. I actually replaced the ignition system including much of the wiring harness to no avail and found the only true “cure” was to cover all electrical connections with dielectric grease and to stop washing the car. (Instead we only dried it!) In retrospect, I believe there may have been a micro leak near the windshield that may have gotten under the dash wiring. I looked many times and it seemed the only moisture I found was my sweaty brow.

Good luck and please follow up with your successful remedy.
 
Thank you all for your ideas and suggestions. It's why this forum is so indispensible (thanks Dan)

Hopefully jhjacobs was right and its related to the ignition switch. I've just tried starting the car again now that its cold and I got the same results - it starts cleanly, runs for a second and then dies. But jhjacobs suggestion got me thinking of an unrelated issue that I'd read in an initial search for possible solutions.

As we know, the ignition lock has two positions. Position 1 switches everything on (so you get dash lights etc), and position 2 fires the engine. The ignition appears to have a sprung arrangement on the key so when you release it after engine start, it returns to position1.

in an related post, someone suggested that if you hold the key in position two for a length of time, you can force an electical circuit to stay open(!). So mindful of the cost of a new starter motor and ring gear, I tried this option.

Held the key in position 2 and bingo, the motor kept running.

Put it in gear and drove away. Released the key after 10 seconds (it returned to position 1) and the car kept running.

So the next step would appear to be looking at those electrical connections in the ignition switch.

The car is a zenith-carbed, 4 speed (that had been converted from an automatic), very good condition, repainted, reupholstered, mechanically excellent. I'll upload some photos for you into the gallery in the next hour.

Once again thank you and I'll let you know if this solves the problem.
 
The E9 (and E3) ignition switch design is baffling to me. The starter is driven by a relay but the switch "ignition" setting actually provides considerable current directly to many systems. Even the "Acc" position powers the radio directly which could easily be 2+ amps! A "reasonable design" would have included a relay in this path instead a direct switch connection. The amount of current a switch must pass will have a direct impact on how long it will last; each time it engages and disengages there will be arcing and contact fatigue. Now that I have pondered this one I think I'll bypass my switch with a relay since my steering column and under-dash area are dismantled (and my harness if far from virgin). Who knows, maybe it will last another 35+ years!
 
electrical short

I had exactly the same problem with a 1977 320i. It turned out to be an incorrect battery was grafted into the car rather than the correct one. It was not fastened to the battery tray and would short to the hood during acceleration or the first turn I would take. A bmw specializing shop identified it for me.

I also had a similar experience with a 530i. Turned out to be a combination of severly corroded bonding, or grounding leads for the block and distributor as well as a failing condenser in the ignition system. The battery ground cable was also very corroded.

Good luck with it,

Cheers

Flywulf
 
A quick note to fill you in on the solution. The metal collar that holds the plastic insert (containing the wiring) into the base of the ignition switch had separated from the insert. This lead to intermittent electrical contact.

Simply replacing the ignition switch and contacts has solved the problem.

Thanks for your suggestions.

Cheers
Steve
 
You must log in or register to reply here.
Back
Top