Suddenly backfiring
Thread Starter
|
Cross-Country
Joined: Jul 2004
Posts: 70
Likes: 3
Suddenly backfiring
I have a 1982 F150, 4.9 300
It wouldn't start this morning, had to jump it. Get a few miles down the road and it just dies on me. Jump it again and off I go. A few miles down the road it starts shutting down and stuttering on me. I pulled over and looked under the hood to check some things but didn't see anything obvious. I closed the hood and climbed back in. I shut the door and it died, radio and all.
My wife came and jumped it again, started right up, headed home after a few miles it began back firing. She was behind me and said she saw fire and smoke come from the exhaust pipe. Tried to keep going and it got worse.
Trying to think through it all, I remembered that I had replaced the ignition module and maybe it went bad... I changed it and nothing.
I had to jump it again and managed to limp it home in first gear.
What is happening? Alternator maybe? I got bad quick.
Additional info... engine has been rebuilt professionally, plugs, wires, distributor all new.
Any ideas?
It wouldn't start this morning, had to jump it. Get a few miles down the road and it just dies on me. Jump it again and off I go. A few miles down the road it starts shutting down and stuttering on me. I pulled over and looked under the hood to check some things but didn't see anything obvious. I closed the hood and climbed back in. I shut the door and it died, radio and all.
My wife came and jumped it again, started right up, headed home after a few miles it began back firing. She was behind me and said she saw fire and smoke come from the exhaust pipe. Tried to keep going and it got worse.
Trying to think through it all, I remembered that I had replaced the ignition module and maybe it went bad... I changed it and nothing.
I had to jump it again and managed to limp it home in first gear.
What is happening? Alternator maybe? I got bad quick.
Additional info... engine has been rebuilt professionally, plugs, wires, distributor all new.
Any ideas?
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Please throw us a bone and elaborate exactly what happened when it wouldn’t start this morning.
Did the starter system get the crankshaft spinning at its normal speed, or was it slow and sluggish? Big difference in how to proceed, so please clarify.
If things were slow, as the jumpstart seemed to help, it’s very likely the battery was run down. If the charging system was not up to snuff, this could have happened over several days. Low voltage could also explain the poor running and backfiring, as the ignition system gets weaker and weaker.
Please charge the battery, a very important preliminary step for any electrical problem. After that, see if the starter system behaves. If it does, check the voltage from the charging system.
Keep us posted.
Did the starter system get the crankshaft spinning at its normal speed, or was it slow and sluggish? Big difference in how to proceed, so please clarify.
If things were slow, as the jumpstart seemed to help, it’s very likely the battery was run down. If the charging system was not up to snuff, this could have happened over several days. Low voltage could also explain the poor running and backfiring, as the ignition system gets weaker and weaker.
Please charge the battery, a very important preliminary step for any electrical problem. After that, see if the starter system behaves. If it does, check the voltage from the charging system.
Keep us posted.
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Good info, very helpful. Promise me you won't just throw parts at it. This should be relatively easy to diagnose, but long-distance troubleshooting via forum can be a very slow process.
In case it can't be fixed immediately, do you have another means to get to work? Don't want you to have to rush and load the parts catapult (Pull!) in hopes of a fix.
For a low battery, there are a few possible causes, in no particular order. Sometimes it's a combination of several:
1) Marginal battery that can't hold a charge
2) External drain killing the battery overnight
3) Bad charging system, including the alternator, regulator, wiring, and the heavy cables.
It is important to diagnose the situation correctly. For example, there's no point replacing a good battery if something is draining it overnight.
Getting a bit ahead of myself, but if the starter system behaves after charging the battery, put a voltmeter on the battery. With the engine running, you should see at least 13.7 volts. Let us know what you find.
In case it can't be fixed immediately, do you have another means to get to work? Don't want you to have to rush and load the parts catapult (Pull!) in hopes of a fix.
For a low battery, there are a few possible causes, in no particular order. Sometimes it's a combination of several:
1) Marginal battery that can't hold a charge
2) External drain killing the battery overnight
3) Bad charging system, including the alternator, regulator, wiring, and the heavy cables.
It is important to diagnose the situation correctly. For example, there's no point replacing a good battery if something is draining it overnight.
Getting a bit ahead of myself, but if the starter system behaves after charging the battery, put a voltmeter on the battery. With the engine running, you should see at least 13.7 volts. Let us know what you find.
Believe Nothing
Joined: Jun 2004
Posts: 7,516
Likes: 401
From: W. Central FL.
You've been given good advice above. Make sure the battery cables are good as well as being tight. When you get it running, tug and twist on the cables and wiring while it is running. BTW, I believe you are describing "after fire", not backfire, backfire being thru the induction system.
Thread Starter
|
Cross-Country
Joined: Jul 2004
Posts: 70
Likes: 3
Yeah, I don't plan on throwing parts at it as I know there has to be a logical explanation. Most everything under the hood is new.
I will report the findings.
I will report the findings.
Trending Topics
Lead Driver
Joined: Apr 2002
Posts: 5,338
Likes: 1,248
I guess it's obvious that when a backfire occurs that timing has gone south. If this happened suddenly the distributor could have slipped. Check ignition timing as soon as you can.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
A timing problem can do the same thing, but is more likely to pop through the intake.
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
It's obvious to me the battery is dead. So dead it will not even run the ignition system for very long. The backfiring is coming from raw fuel entering the hot exhaust system. Why is that happening? Because the ignition system can't fire the sparkplugs since it's probably running on 5 or 6v with the dead battery.
Charge the battery up overnight, everything will be good, till the battery runs down again. Step by step, you will get it.
Charge the battery up overnight, everything will be good, till the battery runs down again. Step by step, you will get it.
Thread Starter
|
Cross-Country
Joined: Jul 2004
Posts: 70
Likes: 3
Okay here are the results...
Battery tested at 11.3 volts. Jumped it and removed cables, battery was at 11.7 while it was running of course but was dropping rapidly. By that I mean it would go down a tenth every 3-4 seconds.
Checked the voltage at the alternator and it was at 11.3 and dropped to 9.3 in about 60 seconds.
Sounds like the alternator is done. I'm going to put the battery on athe charger for the night and get an alternator coming. Hopefully this is the only issue.
Battery tested at 11.3 volts. Jumped it and removed cables, battery was at 11.7 while it was running of course but was dropping rapidly. By that I mean it would go down a tenth every 3-4 seconds.
Checked the voltage at the alternator and it was at 11.3 and dropped to 9.3 in about 60 seconds.
Sounds like the alternator is done. I'm going to put the battery on athe charger for the night and get an alternator coming. Hopefully this is the only issue.
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Okay here are the results...
Battery tested at 11.3 volts. Jumped it and removed cables, battery was at 11.7 while it was running of course but was dropping rapidly. By that I mean it would go down a tenth every 3-4 seconds.
Checked the voltage at the alternator and it was at 11.3 and dropped to 9.3 in about 60 seconds.
Sounds like the alternator is done. I'm going to put the battery on athe charger for the night and get an alternator coming. Hopefully this is the only issue.
Battery tested at 11.3 volts. Jumped it and removed cables, battery was at 11.7 while it was running of course but was dropping rapidly. By that I mean it would go down a tenth every 3-4 seconds.
Checked the voltage at the alternator and it was at 11.3 and dropped to 9.3 in about 60 seconds.
Sounds like the alternator is done. I'm going to put the battery on athe charger for the night and get an alternator coming. Hopefully this is the only issue.
Lead Driver
Joined: Apr 2002
Posts: 5,338
Likes: 1,248