Car goes dead while driving but starts back up

jeffgrice · #1 (**permalink**) 08-05-2018, 05:17 AM

Hey Gang,

Need some pointers on what possibly could be causing this problem and where to start looking.

I have a SPF Daytona Coupe with Roush 427sr and Mass-Flo Throttle Body FI (fox based ecu).

On the way home from a long flawless drive yesterday the motor died 4 times in about 10 miles. All about the same interval from each event.

Here's what would happen:

While driving the motor would die in an instant.
The tach plumeted immediately
No coughing...dead
All electrical was still functioning

Each time I would hit the starter and the motor would fire back up. I would say it took more cranks than usual and stumbled upon start.

BUT ...

Then would run fine for a few miles until it happened again.

When I got home I started/stopped the car a bunch of times each of which it started fine.

Here's what I have checked:

I can hear the electric fuel pump
The fuel pressure regulator shows the set pressure
No codes thrown from the ECU
While running I fiddled with the key to see if vibration would kill the motor - nope

Any thoughts on what this could be and what to check?

Thanks in advance!

Jeff

bobcowan · #2 (**permalink**) 08-05-2018, 09:47 AM

Usually when it just dies like that it's electrical. Probably ignition. Based on time interval, I would guess that something is getting hot, and getting ready to fail.
Probably not the coil, though. They usually don't fail like that.

jeffgrice · #3 (**permalink**) 08-05-2018, 10:22 AM

Quote:

Originally Posted by bobcowan

Usually when it just dies like that it's electrical. Probably ignition. Based on time interval, I would guess that something is getting hot, and getting ready to fail.
Probably not the coil, though. They usually don't fail like that.

Bob - I think you nailed it when you said...looks like something is getting ready to die...

So this morning I pull the car out, check all connections and decided to start and then move wires, connections looking for an issue.

It started and before I could crawl out of the car it died. This time permanently. Would not restart. The ECU light on the dash that illuminates when the key is on indicating the ECU is working is not illuminating.

So I think it is the ECU that failed.

Thanks for the input.

Jeff

twobjshelbys · #4 (**permalink**) 08-05-2018, 10:26 AM

Check ground esp on fuel pump. If you have a fuel cutoff switch make sure it is ok. My Lucas switch depends developed a flat spot that tripped on bumps and killed the car on the freeway. I jammed a toothpick to keep it away from the trouble spot

bobcowan · #5 (**permalink**) 08-05-2018, 11:02 AM

Quote:

Originally Posted by jeffgrice

So I think it is the ECU that failed.

Thanks for the input.

Jeff

Do you have a relay for the ECU? I would check that first. Make sure the ECU is getting power. ECU's almost never fail - sometimes, but it's rare. Relays, fuses, fusable links, etc, often fail.

520SC · #6 (**permalink**) 08-05-2018, 05:41 PM

The fact that the ECU throws no code when the engine dies points to loss of power to the ECU. There's no code for that. So, there's a good chance you have a loose power connection to the ECU.

spl310 · #7 (**permalink**) 08-09-2018, 08:07 PM

Are you by chance running an MSD unit?

torre44 · #8 (**permalink**) 09-01-2018, 05:08 AM

i had same issue for years. turned out to be ford duraspark issue, replaced & never had problem since.

Jaydee · #9 (**permalink**) 09-02-2018, 12:23 AM

You could run a test light across the coil and have it sticking out the bonnet whilst you drive, if it goes of then you have a power problem. After that run a high tension wire from the coil out of the bonnet and put it in a clear tubing and have a small gap and run another wire back into the dizzy. That will let you know if the spark is dying. Then you can do the same with injector signal using a led test light.
Intermittent problems can be a pain. I remember years ago A vehicle wouldn't start when it was cold, but ok as the day warmed up. I put the ignitor in the freezer and it failed.
Good luck.
JD

Danr55 · #10 (**permalink**) 09-02-2018, 10:08 AM

Check the fuel filter. A running engine will require more fuel than the filter can supply if it is plugged. After you shut the engine down, the filter will refill and supply enough fuel for a short run or a restart. Then when you hit the pedal, you suck the system dry again. If that doesn't do any good, check the fuel pump.

Luce · #11 (**permalink**) 09-03-2018, 07:10 AM

No code and the tach plummeting faster than the engine can rev down sounds like loss of crank trigger or loss of power. Not sure what you have, but if you're running a trigger wheel and dizzy, maybe the module the pick up plugs into or the pickup itself. If it's the 36-1 ford trigger, once it misses a tooth, it's stuck for the rest of the 360 degrees and quits transmitting the timing info the the ECU.

snapier · #12 (**permalink**) 09-04-2018, 05:47 PM

I had s similar problem when I had a 69 Z/28 Camaro. Turned out to be a faulty coil. Would run fine for a little while but once the coil heated up the engine would shutdown. I could start it up again and about the same time frame the engine would shutoff. This would happen over and over until I replaced the coil. A funny thing happen after I replaced the coil the very next day a friend had the same problem on his car which turned out to be a faulty coil also...

Phx Mike · #13 (**permalink**) 09-04-2018, 09:27 PM

Similar here - also on a Camaro (70 1/2). Turned out to be the wire that grounded the base plate on the points. Would come and go depending on advance and temperature. Similarity here is that it was same symptoms as above - immediate engine stop like someone turned off the key - tach would plummet. Would crank but no tach movement. All symptoms of no power on primary (low voltage) side of the ignition circuit. Look at ECU power and ground, and ignition switch run position circuit, and coil/coil wire connection.

Gaz64 · #14 (**permalink**) 09-05-2018, 02:59 AM

Quote:

Originally Posted by jeffgrice

Bob - I think you nailed it when you said...looks like something is getting ready to die...

So this morning I pull the car out, check all connections and decided to start and then move wires, connections looking for an issue.

It started and before I could crawl out of the car it died. This time permanently. Would not restart.
The ECU light on the dash that illuminates when the key is on indicating the ECU is working is not illuminating.

So I think it is the ECU that failed.

Thanks for the input.

Jeff

This is the path to follow, the "giveaway" to the fault.

No power to the ECM, ignition relay etc, or possible ECM.

jeffgrice · #15 (**permalink**) 09-08-2018, 05:49 AM

Gang, the shop was determined the ODB1 ECU has failed. Thanks for all the input! Jeff

jeffgrice · #16 (**permalink**) 09-22-2018, 03:17 AM

Quote:

Originally Posted by jeffgrice

Gang, the shop was determined the ODB1 ECU has failed. Thanks for all the input! Jeff

And we replaced with intake/carb/ignition spec'd for my 427 SR motor. Got the car back 2 weeks ago. RUNS BETTER THAN IT EVER HAS!!

I suspect the ECU/Management system has been flaking out for the past 2 years. A couple of hints: 1) the exhaust and overall heat of the motor is cooler now, 2) prior I would get a raspy sound from the pipes at idle. No more..nice and deep rumble, 3) at idle the motor is steady as a rock.

Thanks

Jeff

rags429 · #17 (**permalink**) 09-29-2018, 10:06 PM

I had similar problem, small block 5.0--- I discovered my coil was cracked! it would run for a mile or so and then the coil would get hot -opening the crack in the side just enough to ground it out, I was in the shade with the engine running, looking at the coil when I saw a blue spark run down the side of the coil, of course it died, cooled down in a minute and started just like new---2more minutes it was warmed up and same story- crack opened and it died!! new coil fixed the problem!!

Danr55 · #18 (**permalink**) 09-30-2018, 07:42 AM

I really dislike electronic ignitions systems.

powrby4d · #19 (**permalink**) 09-30-2018, 11:28 AM

Not just electronic. I had exactly the same problem driving me nuts on my Mach 1 and it turned out to be the ballast resistor. Apparently the current draw from the aftermarket coil kept burning them up to the point that they would intermittently open the circuit.

Gaz64 · #20 (**permalink**) 09-30-2018, 06:02 PM

Quote:

Originally Posted by powrby4d

Not just electronic. I had exactly the same problem driving me nuts on my Mach 1 and it turned out to be the ballast resistor. Apparently the current draw from the aftermarket coil kept burning them up to the point that they would intermittently open the circuit.

Same here. A mate's girlfriend's car would "flatspot" really bad turning left.
Drove us nuts why the carburettor would do this, until eventually the car wouldn't start. The ballast would go open circuit on LH turns, eventually went open permanently.
New ballast solved both issues.