Engine Dies when De-accelerating

[wildcard]

71 F100 with a 300 I6
I had this problem a few weeks ago and now it's back.
This morning on my way to work, 40 miles, when I let off the gas and pushed the clutch in to make a left turn, It just died. No spitting, sputtering, lights dimming or any warning at all. I pulled over,shut the lights off and turned the key off. Tried to start it back up and it finally rolled over about 3 times reeeal slooow and that was it. Sit there about 1o - 20 seconds and turned the key again and it started at the first bump of the key. Lights were bright, engine running fine, volt meter in dash showing 13.8 volts.
4 miles down the road, right turn, same thing. My first thought was something was getting hot like a breaker and resetting. So as soon as I stopped I grabbed the flashlight and raised the hood. I felt the regulator, battery and connections, alternator and starter solenoid. All were cool to the touch. Got back in and bumped the starter and it fired right back up. All same as before. When I stopped at the guard gate, I put it in neutral before I got there and kept the engine revved just enough to keep it running. When I got to the parking lot it acted just fine.
On the way home I ran the lights on bright and the heater fan on high just as they were this morning. NEVER had a bit of problem.
IF it does it tomorrow I'm going to feel the ign. switch and the coil. If they're not warm either, I plan to get the battery and alternator checked Friday.
Does anyone have any idea what might be causing this ? I would rather fix the problem than just throw new parts at it.

[Cipher43]

i know my bronco had a similar problem to the dyeing at odd times and it ended up being a wire on the solenoid being loose. It would run until you turned right and hit a bump then it was dead.... wouldn't start back up sometimes and would others.

[basketcase0302]

I think your on the right track with the coil and having the battery load tested. I'd also check the timing as this is a classic symptom of too far advanced timing.

[wildcard]

Thanks for the input. It ran fine today but I'll check them all tomorrow and let you know what I find. If anything.
Is there any way of checking the coil or does it have to be replaced ?

[basketcase0302]

wildcard on Thu Dec 13, 2012 6:49 pm
Thanks for the input. It ran fine today but I'll check them all tomorrow and let you know what I find. If anything.
Is there any way of checking the coil or does it have to be replaced ?

Yes, you can ohm the primary side of it, and I believe there is a way to also check the secondary side. Seemed like there used to be a tutorial on it here somewhere?
And you can also crank it up after dark and watch for the fireworks. The last one I had go out was shorting across the manifold, (from the primary + lead) and barely visible in daylight.

[wildcard]

Well, so far everything checks out ok. Didn't get the battery tested because AutoZones people couldn't get their battery tester to work. But I still haven't had anymore trouble out of it.

[wildcard]

Well last night it went from bad to worse. At first it would idle fine and run fine at the in-laws. On the way to my daughters it was feeling kind of sluggish.
Went to leave there and it would start and run good but as soon as I took my foot off the throttle it would die. By the time I got home, I was hoping I would'nt have to call someone at 2 AM.
This morning it sounded like it was running on 2 cylinders. Or trying to anyway. After scratching my head and checking different things, I tried pulling plug wires to see what was actually firing. Only #s 3 and 6 seemed to be firing. I went and got new plugs, wires, and dist. cap even though I had only recently replaced it all. No difference.
So I start adjusting the timing with no luck. Pulled the distributor to check the gear and shaft. No problem there. So now I get the timing light to reset it better and discover the plate with 0 and the graduations is gone. It was in the shop recently to get some gaskets changed and apparently they removed it and never replaced it. So now I have to try timing by instinct and blind luck. Finally get it to crank but it's still running like crap.
An old mechanic friend came over and he determined the vacuum advance isn't working. He pulled the vac. line and it pretty much smoothed right out. We plugged the vacuum line for right now and got the timing adjusted close. But it still has a miss.
So, my questions are :
Is there any way of getting the timing really close other than by feel?
Will replacing the dist. solve a lot of my problems including the miss?

[wildcard]

OK, I seriously have considered taking the truck to the salvage yard and go buy a new one with a warranty.
I had to replace the distributor at Christmas. I'm pretty sure the timing is set as close as can be possible without a light. New points, condensor, plugs. distributor cap, battery, coil and wires. All gaps are set correctly and double checked. AND IT STILL DIES WHEN STOPPING OR SLOWING DOWN !!!! And just started doing this all at once.
It always starts back up with just a bump of the key. Idles fine and runs down the road fine. So I'm assuming it is not an electrical problem.
I'm thinking maybe a fuel problem. The pump has almost 200,000 miles on it. Could this be a worn out pump maybe ?
I am getting disgusted with this . But not nearly as much as my wife. So we may end up bumpless if I can't fix this.

[69Ford]

I had a simular problem only I have an automatic. The truck sat for years and when I first got it running it would stall letting off the accelerator. Replaced the fuel pump and added a fuel additive to the tank. It took about a hundred miles
but runs fine now. I realy don't think I needed the pump.

[sargentrs]

Vacuum leak or carb needs a rebuild? Since you've done all that ignition work that's where I'd look next. Have you tried spraying ether around the intake, carb and brake booster to see if the engine revs up or hooked a fuel pressure gauge up to check pressure to the carb. Sounds like she's starving at low rpm or vacuum required conditions.

[basketcase0302]

like Randy said about spraying to test for a vacuum leak, (especially around the intake where the4 I6's are known for them). You can also test your fuel pump pretty cheaply, but I'd throw one on it if it has 200K miles on it!
https://www.google.com/search?q=300+ci+ ... =firefox-a

[sargentrs]

Btw, do you have a power brake booster? A bad diaphragm in one is a "hidden" vacuum leak.

[wildcard]

All manual, I sprayed ether around the carb base, Nothing there. It done fine on the way home today.