I'm posting a problem that just got solved hoping it will help others with a 454.

My 1984 Royale with a 454 would die while under acceleration. Here's the symptons:

1. only happens when accelerating above 25 mph...runs fine under 25 mph, runs fine otherwise, idles fine, accelerates fine up to 25 mph
2. engine completely dies...has lost all electrical power...can tell this because all gauges go off...just like shut off key.
3. ONCE I LIFT MY FOOT FROM THE GAS PEDAL, the engine restarts (it has kept turning the whole time after it died since the coach is moving.) and it runs OK.
4. Sometimes, there is a whisp of smoke that comes from under the dial of the tachometer.


I thought it had to do with the fusible link by the starter. Replaced that and in fact moved it up close to the engine cover for easy access. That didn't fix it. Thought I had bad grounds. Ran new grounds from coach body to frame to chassis to engine. That didn't help.

Finally, the situation about the tachometer sending out a whisp of smoke made me think that maybe, somehow the distributor was shorting or grounding back through the tach. I looked in the distributor and it looked rough. Looked like moisture, small pieces of debris etc... in bottom.

I went ahead and replaced the distributor and it is running fine now.

Any ideas from you smarter guys?

quote:

Originally posted by K&E:
ONCE I LIFT MY FOOT FROM THE GAS PEDAL, the engine restarts

That would make me look at the vacuum advance making something inside touch something it should not be touching and causing either a short or an open.

You might suck on a hose attached to the vacuum diaphragm and observe what it does.


Pretty good on your part, changing the distributor.

I wonder if the full extent of the problem has been discovered. The new distributor got it running again, but was the problem really fixed?

What does the voltage meter say when the "lost all electrical power" situation occurs? I'd expect the battery to continue keeping the gauges operating.

I'd never heard of an automatic transmission bump starting an engine before. I thought that couldn't be done.

What this leads me to speculate is that the engine didn't really lose all electrical power, but was running at a degraded voltage level, like 6V. Maybe the engine was getting a weak spark during this event, and continuing to sputter along. Taking the foot off the gas pedal would change the vacuum characteristics of the carb and the spark advance, and maybe get things firing OK again.

Bad alternator or battery isolator at play? Any paranoia on my part will be calmed with a voltage reading of the BAT+ terminal while you are at highway speed.

The problem might have been solved with the better grounding and the new distributor.

Happy motoring,
Matt

I had a 1970 Camaro Z28 that on wet days would shut down going around left hand corners. It would usually restart and be OK until another left on a wet day.

After much fussing around I finally found one of the distributor feed wires had the insulation rubbed mostly off. Apparently it took the cornering and the wet air to get it to short to ground.

So I can't help but wonder if you have a similar situation. If so, the problem may still exist if the offensive wire is still in commission.

Your number 4. is kind of scary
Otherwise I am thinking bad ground.

quote:

Ran new grounds from coach body to frame to chassis to engine. That didn't help.

Did you run new grounds to the battery? Do you have a battery disconnect switch on the ground side?

I'm interested in any other hypothesis on the problem.

quote:

Did you run new grounds to the battery? Do you have a battery disconnect switch on the ground side?

Yes,I put in new additional grounds...that was the first thing I thought of. And I also have a master battery switch behind the drivers seat. It's a large rotary switch about 4 inches in diamer. It kills all 12 volt power.

quote:

I'd never heard of an automatic transmission bump starting an engine before. I thought that couldn't be done.

I'm like you. I thought that when the engine dies, it stops turning...but apparently it was still turning enough that I wouldn't completely loose the power steering....when it would die, it was definately electrically dead (all the gauges would act like you just turned off the ignition). Once I would let up on the foot feed, it would start running again and return to idle. It was just like you turning off the key switch and turning it back on. The thing that really caught my attention was the wisp of smoke from the tach....I pulled the dash and could not find any sign of burned wires...All I can guess is that somehow, the distributor was shorting out internally, losing the power from the battery (and all power to the ignition and accessories) and then thereby shorting the 12v lead from the battery directly to the tach wire...hence the smoke....

This weekend, its supposed to be cold and I plan on disassembling the distributor and see what it could be.

I'm hoping that if someone has a similiar problem, they will find this post and know at least to start looking in the distributor and not waste so much time in other places like I did...

quote:

Originally posted by BarthBluesmobile:

Did you run new grounds to the battery?

I like to run a ground straight from the battery to one of the starter bolts. Then a short one from the other starter bolt to the frame rail. Clean, of course.

My Kohler even became less cranky with this method.

When the doghouse is open, there is the back of the block. On the back of the head, drivers-side of the block was a bolt and I attached to this bolt, new ground cables to the frame, the battery, the body and a separate grounding cable I attached to one of the starter bolts. Didn't think of a separate one to the Koehler but that's a good idea....you're right...it's kind of cranky....but boy...it sure runs nice....

Regaurding that wisp of smoke. My old boss told me years ago about how all electrical/electronic devices needed smoke installed in them to be able to work. Don't ever let the smoke out. Once the smoke get out, you can't get it back in. Over the years I learned to believe him.
Doorman.

I am wondering if there was some mechanical interference between the power or tach wires on the HEI distributor and the throttle links on the carburetor.

With a Camaro "back in the day" I once had a tach wire short out after the insulation rubbed off, and this killed the coil in the distributor. If you had a short circuit here, I would be surprised that the coil survived.

I once installed a tach on my '81 Volvo and afterward, the car would hardly run at all. It turned out that the tach was bad and was doing something to the distributor. Took it off, (the tach) and the car ran fine.
Jim

About bump starting, when my engine vapor locked it would shut down completely, and I would just coast till it fired again. The only time it wouldn't re-start was on an entrance ramp and I didn't have enough speed up.
I also remember push starting my buddy's Austin America with an automatic. It would start at 45 mph. We didn't do it by hand!

I have also seen some cases (in old cars) with HEI being affected by tach problems. Years ago, had an intermittent miss we couldn't find. Someone noticed the missing was coincident with some slight bouncing in the tach needle. We had assumed the bounce was the result of the miss not the cause. Replaced tach, problem gone. good luck.

quote:

Originally posted by BarthBluesmobile:

I'd never heard of an automatic transmission bump starting an engine before. I thought that couldn't be done.

It depends on the transmission and the speeds involved. It worked really well with the old Powerglide and the 4 spd cast iron Hydramatic because it had both a front and a rear pump, the rear being driven by the output shaft.