Car dies suddenly

[bob hughes]

Mike

Without reading the replies I have cut to the chase. I had a similar problem and it was to do with the low tension cable from the coil to the dizzy, the connector at the side of the dizzy was hanging on by a thread to the wire - if even that much, put a new wire in and that was it.
Hope that this helps.



Bob

 

[Michael Oritt]

I realize that I am the guy with the questions here and some of you who feel the issue is fuel-related may think me either a know-it-all, a hardhead, an ingrate or a fuel-issue denier. Due to the failure mode I have felt pretty certain that fuel is not the issue but to keep an open mind I just performed a test:

1. While driving at 60-65 mph in 5th gear (about 2500 rpm's) I switched off the fuel pump (again, I have a double-headed SU with an ON-OFF-ON switch located just behind the driver's seat).
2. I kept a constant throttle and speed and it took about 15 seconds for the engine to begin to falter and another 10-15 seconds before it began to die and became unresponsive to the throttle.
3. Before the engine died entirely I turned the fuel pump ON and within two seconds the engine was running fine and I accelerated back up to 60-65.
4. I repeated the above test twice--using each of the fuel pumps--with the same result

From this I cannot construct a scenario under which the engine would die INSTANTLY from lack of fuel whether due to a restriction on the supply side, a failed or failing fuel pump or a clogged vent. If I am missing something I am happy to be corrected.

MEANWHILE: While I was driving I reconstructed in my mind Monday's experience and I began to wonder why the car did not restart between the time that the engine died and point where I reached the side of the road with the ignition still on, but did restart after a very short delay--about 30 seconds the first time and perhaps 4-5 minutes the second. If the issue is, for example, an intermittently failing ignition key or power source TO the coil I would expect that the engine would have come back on even before I reached the side of the road.

Many listers have suggested the MSD coil to be the culprit, that it is overheating. A number of others point to the ballast resistor which is supposed to protect the electronic module from too much voltage. While I am loath to replace more than one component at a time, since the issue--whatever it may be--seems to have gone dormant since Monday I don't want to spend a lot of times driving the car waiting for a failure to occur, so I will replace these two items and see what happens.

I don't want to waste everyone's time and bandwidth with further speculation until I have something further to report and I again appreciate all of the suggestions and thoughts.

 

[bob hughes]

Michael

I had to wait up to 5 minutes each time before I could restart the engine, certainly not seconds. I can not explain it, it it just happened.



Bob

 

[red57]

Michael,

For what it's worth, I agree with your fuel diagnosis and I was thinking electrical too - seems too quick/sudden for fuel.
I think you have thought it through well and I agree your fuel pump test pretty well eliminates fuel supply issues.
Chasing intermittent problems can be very frustrating - just 'cause it's working now, does that really mean we fixed it?

I know from my RV experiences that some modern electronics are very fussy about the voltage they will operate on and will sometimes shut themselves off (for self preservation) if they sense less than the voltage they require.
So, as strange as it sounds, the battery story may be applicable - theoretically with enough amperage the starter might turn the engine but be less than 12v and therefore the ignition module saved itself??

Trust me, I am very weak on electronics so the above is just speculation. Looking forward to your results.
Dave

 

[John Turney]

I doubt it was the battery. In the MG story, the car died while idling, which means that the generator is not putting out enough voltage to charge the battery. British cars are known for having the headlights dim when coming to a stop as the voltage decreases. You were driving at highway speed, so your generator/alternator would have maintained adequate voltage. Also, you were able to easily restart after a minute.

 

[RAC68]

John,

It is also not uncommon for a battery to fail and not deeply recharge in 1 or more cells. Given the use of gear reduction starters and the lowering power draw, it is possible that a battery could start a car but as a result, have less then the necessary power for the electronic ignition. I agree that the power needed to operate a points triggered car is not much but I am not aware if the unit Michael is using is not sensitive to having a minimum level of power that a faulty battery can fall below.

Just my conjecture,
Ray(64BJ8P1)

 

[aero3113]

Got ya, my reply is what happens when you read through a post to quickly. LoL

 

[Deleted member 8987]

Generic.
If fuel supply, the float bowls will deplete and poor running just before it quits.Sometimes you have to be sensitive to the changes.

Coil? Maybe, but usually when they go they go, or heat up and will NOT restart until they cool off.

Ignition? Yeah. Wire that flexes in the distributor?

But:

Experience, did auto electric for part of my income for a long time. First thing I would look at is ignition switch. When things get worn, doesn't take much. Car quits, turn the key off, right? Turn the key on and hit the starter and it starts?

Wires to switch. Inline plugs and connectors getting weak (Prince of Darkness does not only apply to lighting).

Me? I'd be adding a light (temporarily) from ground to power in to coil, stick light on dash in view, or even under wiper blade. Drive it. If the car quits and the light goes out, you have eliminated coil, distributor...and pointed into primary side.

Just a thought.

 

[John Turney]

.... Me? I'd be adding a light (temporarily) from ground to power in to coil, stick light on dash in view, or even under wiper blade. Drive it. If the car quits and the light goes out, you have eliminated coil, distributor...and pointed into primary side.

Just a thought.

A very good thought!

 

[Michael Oritt]

TOC--

While i promised to shut up I want to reiterate one fact which I think militates AGAINST the culprit being the ignition switch or wiring to it:

As stated, I have a low oil pressure light mounted in the dash, powered from the ignition switch through a normally closed switch that is spliced into the oil pressure gauge sender line. The switch opens at 10ps or more. I distinctly remember that in both instances where the car suddenly died while I was driving the light was on when the car died, which tells me that there was 12VDC to and from the switch, and suggests that whatever killed the engine must have been downstream of the switch/light: The ballast resistor, the coil and/or the ignition module or wire to it.

What do you think?

 

[Deleted member 8987]

I read that. And, not knowing off hand the AH switch wiring, seems a lot of vehicles have several leads off the switch to do that.

Unless you are wired for power to the hot terminal of the coil, all you may be able to discern is you have power from where you have connected.

ANY of the wires and Lucar connectors between where your low oil switch is wired and coil. Light on coil terminal will either eliminate all that or point you to distributor/module/coil.
Since it's so fleeting, heat must be a minor player here. But who knows.

I remember later MGB's with those stupid factory ignition modules screwed under the coil. Best fix was a tow rider on your insurance policy.

 

[John Turney]

TOC,

The early AH ignition switch is a simple on-off affair. There is a separate "start" button.

 

[Deleted member 8987]

Remember, too, backfeed from generator can keep some stuff functional....maybe not ignition. But you have no idea, so if you stick a light in (maybe more than one) to sort of determine what quits.
Has to be a hard enough failure with clutch still engaged it won't restart until you stop and....cycle the ignition switch while scratching your head.

But, parts stores make a lot of money from folks replacing things without knowing what is actually wrong.

Let's see...coil, ignition module, distributor, then plug wires and plugs....and it still quits on a dark and winding road.

Doesn't bother me any. I have stock in auto parts stores.

 

[Bob_Spidell]

Well, I just HAVE to be a contrarian. I've had numerous fuel pump failures, some documented here, and until the last one there has always been some stumbling, intermittency, etc. beforehand. The last time, on the highway between Bishop, CA and Tonopah, NV the car stopped running, instantly, and with no warning. I don't know why--maybe both float bowls emptied simultaneously--but that's what happened.

 

[pdplot]

What about our old friend vapor lock? I had a Corvair that died a couple of times and then started normally after a few minutes. I also had a VW Beetle that died twice from bad coils but they would not restart.

 

[Dandare]

As roscoe said in post #2 I would be suspicious of the coil to distributor HT laed (wire)...I am presuming they are not copper core with that ignition?

This fooled me for weeks on an unrelated vehicle with Bosch HE ignition which did the same thing. After replacing module, pick up coil, ignition coil and so on (including fuel pump!) it transpired that failing to check the the HT leads first was my big mistake!

This coil/dist lead breaking down can kill the engine dead and restarts moments/minutes later.

Danny

 

[Michael Oritt]

At the end of post #22 I said I would be quiet until I found something worth reporting. I may have found the culprit today.

Rather than replacing parts on a wholesale basis without learning what was the cause of the car's suddenly stopping my hope/goal was to find a component/connection in the ignition system that appeared to be defective. This morning I started at the key switch and it tested fine. I then moved to the ballast resistor whose task is to reduce voltage to the MSD Blaster 2 coil and the Unilite ignition module. I wanted to check the ballast's value with an ohm meter and because of where it was installed--just above the starter on the inner face of the passenger toe box--I could not get the probes to the contacts, so I removed it to check it on the bench. When I unscrewed the bolt that held it in place a piece of its innards fell onto the floor of the garage! (See thumbnail)

The Mallory 700 resistor, which along with the Unilite, has been in the car for 10-12 trouble-free years. It is supposed to have a value of 1.5 ohms. On examining its remains on the bench I could see that the coiled wire appeared loose at one end and when I checked its value I got readings that were all over the scale. Luckily I had a spare ballast on hand--this one actually made by MSD and matched to the blaster coil--so I installed it in place of the old unit (see second thumbnail). I'm "cautiously optimistic" that I found the issue but of course that will have to be borne out by experience.

My wife likes to ride in the Healey and we like Richmond VA, which is about 125 miles from home. The route down US 301 will keep us off of interstates, so we're heading down there in the morning for an overnight trip. I'll be bringing along a multimeter along with a spare coil, rotor and Unilite ignition module, wire and connectors, etc. Hopefully all will go well. Fingers crossed....

 

[roscoe]

Have a great trip. Sooo nice to find the culprit. You have your dual, selectable fuel pumps, spare spark plug rack and I'm certain a boot full of likley spares. You could add a second balast resistor and wire them through a switch in the cockpit. Switch over every 9 and 1/2 years and you should be good. I'm not sure you can set an alarm on your smart phone that far ahead and I know I'd forget where I hid the switch.

 

[Michael Oritt]

Yes, sorta like wearing two condoms in case the first one falls off.

 

[Michael Oritt]

I am back in Maryland from having driven down to Richmond after replacing the damaged and suspect ballast resistor. We drove about 275 miles total at speeds up to around 70 mph as well as around town. Car ran fine--no miss, no cough, no sudden stopping. Of course, it is impossible to prove a negative--that is, that the damaged ballast resistor was in fact the issue but it does add up. In any case this trip's success restores much of my confidence in the car.

Thanks to all for your input, patience and support.