390 Just Dies!!!
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390 Just Dies!!!
My 1976 F150 390 ddied five times in the first five minutes I drove it and then not again on a thirty minute drive. It doesn't die when I come to a stop or let it idle even though it seems pretty rough. It dies when I am cruising at 50 or 55. It doesn't sputter or seem to be missing very badly, and then it just quits like someone threw a switch, so I put it in neutral and start it back up while I'm still rolling at 40 or so, then put it back in drive and just keep driving.
Any ideas?
It also doesn't start everytime just right, I will turn the key and it just won't catch, but if I turn the key back off and try again, it usually starts right up. It has a brand new battery and plenty of juice.
Any ideas?
It also doesn't start everytime just right, I will turn the key and it just won't catch, but if I turn the key back off and try again, it usually starts right up. It has a brand new battery and plenty of juice.
Logistics Pro
Joined: Feb 2000
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From: Sun River St. George
Sounds like you may have a short in the switch (ignition or neutral start). But the first thing I would suspect is the ECU and next the pickup in the distributor. Lastly the coil. Good luck and post back, we like to see how these come out!
Senior User
Joined: Oct 2001
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From: Las Cruces USA
Over the years (older than dirt), the most common problem I have run into on these "mature" trucks is a poor connection at the coil.
The most unexpected was the ignition switch. The wipers in the switch were apparently worn, plus the tabs on the rear that held the swich together had weakened with "maturity", allowing the rear section of the switch to separate a bit from the metal case. This created a condition where the truck would not start some times. Cycling the ignition switch off and on would "cure" the problem. This usually occurred while I was looking for some other cause.
And, of course, driving down the road was an adventure in itself. I never knew when the engine was going to die. But I did know that it would be the most inconvenient and dangerous place that could be found at the moment.
It was so random and erractic that I was a long time noticing the connection between the switch and the "must kill engine" syndrome. Once I woke up and replaced the switch, the problem went away. That was almost a year and a half ago. No ignition problems since,
Off the walll idea, but you might consider it.
OldFords
bad attitudes
The most unexpected was the ignition switch. The wipers in the switch were apparently worn, plus the tabs on the rear that held the swich together had weakened with "maturity", allowing the rear section of the switch to separate a bit from the metal case. This created a condition where the truck would not start some times. Cycling the ignition switch off and on would "cure" the problem. This usually occurred while I was looking for some other cause.
And, of course, driving down the road was an adventure in itself. I never knew when the engine was going to die. But I did know that it would be the most inconvenient and dangerous place that could be found at the moment.
It was so random and erractic that I was a long time noticing the connection between the switch and the "must kill engine" syndrome. Once I woke up and replaced the switch, the problem went away. That was almost a year and a half ago. No ignition problems since,
Off the walll idea, but you might consider it.
OldFords
bad attitudes
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Update: Drove it home last night without a hiccup. This morning same thing but a little worse. Died a couple of times later in the trip and a few times this trip were accompanied by a backfire and a little black smoke.
Is backfire an indication of the problem or just a side effect of dying at 55mph?
Switch sounds like something easy I could try. Thanks.
Is backfire an indication of the problem or just a side effect of dying at 55mph?
Switch sounds like something easy I could try. Thanks.
Logistics Pro
Joined: Feb 2000
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From: Sun River St. George
Don't get ahead of yourself! Do the "check all the connections" first, use electrical connector cleaner in the spray can, then replace the ECU, Distributor, and lastly the ignition switch. This is an ignition problem! You just gotta find it!
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I will definitely check the connections before I replace anything. Just didn't have time last night (MNF).
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More Turbo
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From: manson
strange
Mine doesn the same thing once in a while...I can be driving 5 or 55 mph..doesnt matter..I loose electrical and everything shuts down. Well, I shouldn't say I loose everything because I don't know but it just stops...kick her in to neutral, hit the key and she is running again. Haven't had time to track the problem down yet. And yes, the backfire is amusing! Great fun for scaring the heck out of friends 
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Help!
Well, I checked the ignition timing (first time I've ever done that). Was set at 10 degrees, engine sticker says it should be at 16 so I did did the "turn the distributor thing" (that wasn't fun, burned my hand numerous times) and got it set to 16. Now it runs worse than before.
My book and the sticker made mention of RPM setting but I don't have a tach on my truck so how can I tell. Does it really matter? Personally I think my truck idles a little higher than it should (the sticker said 650 RPM). Should I put the ignition timing back to the old setting.
Also it is hard to gauge which setting is best while I am turning the distributor because it changes so much once I put the vacuum line back on.
My book and the sticker made mention of RPM setting but I don't have a tach on my truck so how can I tell. Does it really matter? Personally I think my truck idles a little higher than it should (the sticker said 650 RPM). Should I put the ignition timing back to the old setting.
Also it is hard to gauge which setting is best while I am turning the distributor because it changes so much once I put the vacuum line back on.
Post Fiend
Joined: Sep 2004
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From: Near Fresno, California
Idle speed should not change when you put the vacuum line back on - are you plugging the line when you take it off? Otherwise may cause a vacume leak and your engine will idle too fast.
Also, if you have vacuum in that line at an idle, the line is connected wrong. Some carbs have two bibs, one has manifold vacume, the other does not. You do not want this line connected to stright manifold vacuum.
Also, if you have vacuum in that line at an idle, the line is connected wrong. Some carbs have two bibs, one has manifold vacume, the other does not. You do not want this line connected to stright manifold vacuum.
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The vacuum hose to the dizzy definitely sucks when at idle. I plugged it when setting the timing, got the 16 degree mark and the pointer lined up, tighten dizzy bolt, reattach the vacuum hose to the dizzy and the idle picked up everytime and moved the timing mark about twenty degrees to the advance side.
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From: Floriduh
There is part of your problem. You need to attach the vacume line to a different bibb.That line should not have any vacume to it until you give the engine some gas. And, the ignition switch isnt such a bad idea either. I would replace it before the ECU as it is definatly cheaper. Always replace the cheapest stuff first.