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Car dies suddenly

Michael Oritt

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Yesterday morning I went out for a drive and after about five miles the car suddenly died. There was no rough running, sputtering or missing leading up to it—the car simply died. I coasted to the side of the road and after about 30 seconds since the key was still on I pushed the start button. To my surprise the car started immediately, revved freely and idled smoothly. A bit perplexed I decided to drive on to see what would happen now that I was paying close attention. The car accelerated smoothly and ran fine for about 1/2 mile and then it died again in the same manner as earlier. I shut off the key, popped the hood and examined the ignition system. Everything seemed fine—all spark plug leads were firmly in place as was the lead from the coil to the distributor. The power wires to the coil were tight and the harness/connector to the distributor (see below) seemed fine.


After scratching my head for a couple of minutes I got in the car, turned on the ignition and pushed the start button. Again, the car started right up and ran normally. With fingers crossed I headed for my shop/garage, about ten miles away and got there without any further event. Though the problem did not seem to be fuel related I decided to verify that this was not a fuel delivery issue. I have a double-headed SU fuel pump wired to a switch mounted just behind the driver’s seat which allows me to switch between pumps as well as turn the fuel pump off. While I was running the car at highway speeds it ran perfectly on either pump and when I selected the “off” position it slowly lost power as I expected it to—but in no way like it had suddenly twice died 15 or so minutes earlier. This indicated I was not dealing with a fuel issue but rather something related either to the ignition system or to the primary wires that run to it.


This morning I dove a bit deeper to try and diagnose the problem. The car has a Mallory Unilite ignition system tied to an MSD coil which has been in place and performed faultlessly for a number of years. I removed the distributor cap and everything appears to be okay, at least visually. The interior of the distributor was clean and dry as was the cap, leads, carbon contact, optical reader, etc. Mallory specifies the use of a ballast resistor in the lead from the power source to the coil and with the engine fast-idling I tested 12.5 VDC to the resistor and about 5.5-6 VDC out of it and at the positive coil terminal.


I have a large low-oil pressure light that is mounted in the dash in place of the original overdrive switch. It is wired from the ignition switch through a 10 psi normally-closed switch mounted in the oil pressure gauge sender line and then to the light. I point this out because both times when the engine shut down yesterday the light immediately came on, from which I conclude that the ignition switch itself is not the source of the problem. And though I did not remove the ignition key switch the wires to and from it seem tight and intact.


So my question is: What do I do? I hate to throw parts at it without finding something that appears to be defective but I don’t know where to start any further tests, etc. I also don’t want to simply wait for the issue to happen again. BTW over the weekend I drove about 150 miles with no issues whatever. Beyond installing four new plugs last week I have not performed any work related to the ignition system. All suggestions/questions welcome….
 

roscoe

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It sure sounds like you have an intermittant open either in the coil or the ignition module. The plug wires are not likley (unless it is the center wire on the coil) as you had a complete shutdown, also nothing like runnng with low fuel pressure or one or two bad spark plugs. Have you carefully checked the wire connection on the positive side of the coil (assuming neg. ground). Perhaps a bad crimp or a little corrosion? It is one benefit to having a condenser and points that the troubleshooting is a little more "in the open". Was the carbon button in the dist. cap ok? Have you checked the primary and secondary coil windings for proper resistance ( I just can't think of anything else to say)? You are correct to scratch your head as getting a normal restart by only engaging the starter with no components cooling off or being poked and prodded is kind of strange. Please let us know if you figure it out.
 

LarryK

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Had this happen when a coil got hot. Restart fine then wham. If coil is clean of oil, check by touching coil to see if it is hot. Also, had the same problem, but with wires to coil becoming loose on running hot, by being brass or aluminum would cool down enough that a quick restart was possible. Resistor wire could be vibrating and cause a quick kill too.
 

Gliderman8

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Could you possibly have a clogged fuel filter? Easy enough to change and rule it out.
 

Healey Nut

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Check your battery switch if you still have one , over bumps it maybe opening the contact ?
 

John Turney

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Agree it's not fuel. It's also not a single cylinder, so it's not a plug or plug wires, and probably not the cap or rotor. If it were the rotor, it wouldn't restart. I doubt it's the battery switch, your oil light came on and they usually show up as not letting the starter run. I think roscoe is closest.
 

aero3113

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I had this same issue with a 71 Karmann Ghia. Turned out to be a parts info label that was floating in the tank. Every once in a while the label would be sucked to the pickup (screen was missing) and cause the car to stall. I would turn the ignition off and then it would start right back up. I found the label when I took the tank out to clean it. Once the label was removed, no more issues.
 
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Michael Oritt

Michael Oritt

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All--

Thanks for the input thus far. BTW I should have mentioned in the original post that I did away with the B/W coil grounding wire long ago and replaced the original problematic switch with a high-quality marine unit that has plated brass innards.

With due respect to those who suggested that fuel might be involved I am certain that is not the case. As stated, after the second shut-down while I was driving to the shop I conducted a test of the fuel system by shutting off the double-headed pump while driving at 55-60 mph and, as I expected, the car began to miss and lose power slowly as the fuel bowls emptied, then immediately sprang back to life as soon as I switched either of the pumps on.

I agree with those who point towards a problem with the ignition system. I simply want to ID an issue as definitively as possible and fix that rather than, for example, changing the coil--or the distributor cap or the module or the rotor--and then hold my breath waiting for something NOT to happen. If the problem is in the ignition switch or the supply wire to the ballast resistor and the coil I will hopefully be able to detect resistance with an infra-red thermometer while the engine is running. I am also hoping to contact someone with a Sun distributor tester (or the like) who can analyze the distributor's performance under simulated load.

More as it happens.....and thanks again.
 

LarryK

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Coil has an independent test in the lgnition section of book, doesn't have to have load to test, wires can be check with an ohmeter tonsave money.
 

Bob_Spidell

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I've heard the so-called 'sports' coils have been faulty, but the OEM one my BJ8 has 205K miles and a dent and is still firing. The coil--unless it's one of the 'sport' ones--would be my last guess (there's really nothing to them, unless it's oil-filled and leaking). Yes, rotors usually fail outright, but I can imagine one going intermittent, and the distributor cap would be another suspect. Intermittent short to ground is most likely; maybe in the ignition switch?
 

vette

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I also agree that I think it is ignition. The unfortunate thing about aftermarket electronic ignitions is that it is usually near impossible to trouble shoot them. I believe you have something in the electronics that is opening due to heat or vibration. Can you pull the distributor and put in a points type just for test. If you can, you might have to run it with the points for awhile to prove the point. (no pun intended). On my '70 Vette I have a Crane Module in the distributor. I carry in my spares box a complete original points distributor in case the module ever quits. In my Healey I carry every part for the points style distributor and in the last two years I have had to swap out the condenser twice and the rotor once to get home.
 

dklawson

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I agree with those who suggested checking the ballast resistor and checking the carbon brush in the dizzy cap. I hate spending money on would-be fixes.

I have a number of tachs at my disposal. Were this my car I would wire one up so I could see where the problem is. If the tach keeps working when the car dies, I would look at the dizzy cap and coil high-tension wire (components after the ignition module). If the tach dies immediately when the engine dies, I would look at the ignition module and power from the ignition switch. Since you are running an Mallory ignition the tach test may not be possible or helpful. You will need to review how voltage sensing tachs can (or cannot) be connected.
 

pkmh

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I had the same problem on my BJ8. I noticed one of my connections to the ignition coil was broken, though it never looked it. Just another possible cause to look into before spending money on parts.
 

mgtf328

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Happened on my MG once. Found the tank wasn't venting. Easy to check in the driveway. When the car stops take the fuel cap off and listen for the air rushing in.

AJ
 

RAC68

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Hi All,

As I see it, it is either a loose connection issue or an ignition component that has developed a heat-related failure. Since diagnosing a heat-related flaw in an ignition component requires more knowlecge and technological assists then I posess, I would focus on a wiring disconnect.

My initial thought sides with the Healey Nut and would be initially focused on the battery switch. Since the car engine stops without prior engine sputter or fault indications and power is still fed from the battery to keep all else going, I would look to the switched-on battery cut off's security ignition grounding wire being disconnected from the switch and bouncing around until it makes body connection and grounds the ignition. After a short respit, the pre-bent wire settles down and moves away from the grounded surface it came in contact with and the engine can be restarted.

Although this is a well publicised happening that many of us have experienced, it is not uncommon for us to check every other issue before getting around to looking in the boot. Should this not be the cause of your problem, I would still investigate other possibilities of loose car/engine ignition wires that may have come loose as a result of car jostle and, when at rest, return to their pre-bent original point to remake contact.

Good luck and all the best,
Ray(64BJ8P1)
 
Last edited:

aero3113

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Michael, I understand the fuel pump test you did but that doesn't rule out debris in the tank floating around and blocking the pickup at certain times. Also as mgtf328 said, check the vent.
 
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Michael Oritt

Michael Oritt

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Aero--

Thanks for the suggestions and that scenario has actually happened to me in the past.

I do not mean to seem argumentative but the symptoms of no or not enough or bad fuel is a fairly rapid but not instantaneous falling off of engine power--perhaps over 10-12 seconds, usually coupled with a lack of or no response to the throttle pedal. I am talking about a RIGHT NOW engine failure--no miss, no cough, no hesitation, etc.

And to really thicken the soup read this post that was forwarded to me by Peter C:


https://www.mgexp.com/forum/mgc-forum.48/mallory-ignition-v-s-battery-electrical.3909372/
 

HEALEYJAG

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Aero--




Thanks for the suggestions and that scenario has actually happened to me in the past.

I do not mean to seem argumentative but the symptoms of no or not enough or bad fuel is a fairly rapid but not instantaneous falling off of engine power--perhaps over 10-12 seconds, usually coupled with a lack of or no response to the throttle pedal. I am talking about a RIGHT NOW engine failure--no miss, no cough, no hesitation, etc.

And to really thicken the soup read this post that was forwarded to me by Peter C:


https://www.mgexp.com/forum/mgc-forum.48/mallory-ignition-v-s-battery-electrical.3909372/




Not quite buying the"battery" issue..Think his problem will reappear after awhile...
 

RAC68

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Hi Michael,

WOW. The post you referenced from Peter is something I would never have thought. It also sets me up for the purchase of a battery as my 12 year old Optima is not taking a deep recharge even at the 10 amps setting on my charger. Now, I don't have a Mallary ignition but do have a Crane Electronic Optical ignition and don't want to see if my Crane and Optima will replicate Peter's experience.

How is your battery?
Ray(64BJ8P1)
 
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