1985 4.9 issue
Thread Starter
|
New User
Joined: May 2021
Posts: 12
Likes: 0
1985 4.9 issue
Hello, I am new to Ford trucks and do wish to learn. I bought my 12 year old son an 1985 F150 with a 4.9 1V 4 speed 4x4 that needs some love. I thought he & I could work on it together and it could be his first truck. He's very excited. The truck sat for quite a while before I bought it. It's been running pretty well but this morning I decided to drive it 20 minutes to work. When almost there it began to sputter and the temperature gauge bottomed out and the fuel gauge began to drop quickly as well as the "emissions" light came on. I made it to work but am wondering what this could be. Any ideas?
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Does the truck have an ammeter or idiot light? The ammeter on these trucks is virtually useless, and typically doesn't give you much warning of low voltage. The idiot light isn't much better, and may be burned out.
I'd start troubleshooting by checking with the battery voltage BEFORE trying to start the engine. Turn on the headlights for about ten seconds to dissipate any surface charge, and then read the battery voltage. Anything below 12.6V indicates a battery in need of a recharge. If you read around 12.0, that's pretty much dead. It may not seem like much, but that fraction of a volt is huge when determining a battery's condition.
If the battery needs to be charged, do that before anything else. Don't troubleshoot with a partially depleted battery, as you may end up condemning perfectly good parts. A trickle charger won't cut it, so don't waste your time. You'll want an automatic charger with at least a ten amp output for best results.
Once the battery is fully charged (Criminy, he keeps stressing that...), test the charging system as described here. Start at the green dot, and go to the red to:
Thread Starter
|
New User
Joined: May 2021
Posts: 12
Likes: 0
So it has occurred to me that when I got the truck it needed a battery and I just threw in a deep cycle marine type battery that I had around that was in a large GM panel truck. The battery is only two years old. However, I wonder if this battery could be part of my issue?
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Possibly. Is it a straight deep-cycle battery? Or is it a combination starting/deep-cycle battery?
A straight deep-cycle is designed for long periods of low amperage use, such as with an electric trolling motor. Just a guess, but maybe 20 or 30 amps? The plates are intentionally thinner to allow deep discharge, and will warp if overloaded.
A conventional automotive battery is designed for short periods of high amperage draw, such as with an electric starter motor. A V8 starter can draw several hundred amps. The plates are much thicker.
A combination starting/deep-cycle battery is a compromise, to allow starting a big gas motor and also running a trolling motor and other low amperage loads. Think of it as a spork, which is neither a good spoon nor a good fork.
If you had a combination battery, it probably is able to handle starting an L6 without damage, but is still not ideal. But if it is a straight deep-cycle battery, it's probably ruined.
Thread Starter
|
New User
Joined: May 2021
Posts: 12
Likes: 0
It was used in a large panel truck with a lift gate. The truck was powered by a large gasoline Chevy 8.1 L V8 so I'd guess it is a combination battery. I have had it in the truck for a few days but have only driven for short trips. I wonder if it is the issue?
FTE Legend
Joined: Nov 2015
Posts: 30,940
Likes: 4,125
From: Angier, NC
Short trips may not be enough to put back in the battery what you took out to start it.
Then add the AC on maybe playing the radio and the head lights and it could be low.
If the charging system is not charging, yep AMP gauges dont read vary good and burnt bulb you would never know.
Run the test as Karl posted and go from there.
Karl when did they put "emissions" lights on our trucks or is this a Cali truck?
BTW being a 85 300 six it would have a feed back carb system is it still running the feed back system or has it been changed over to non-feed back?
If you post up a picture of the carb (dose it had a lot of wires going to it?) and the dist. (does it have wires only or a vacuum hose going to it) we can tell.
Dave ----
ps post up a picture or 2 of the truck, we like pictures
Then add the AC on maybe playing the radio and the head lights and it could be low.
If the charging system is not charging, yep AMP gauges dont read vary good and burnt bulb you would never know.
Run the test as Karl posted and go from there.
Karl when did they put "emissions" lights on our trucks or is this a Cali truck?
BTW being a 85 300 six it would have a feed back carb system is it still running the feed back system or has it been changed over to non-feed back?
If you post up a picture of the carb (dose it had a lot of wires going to it?) and the dist. (does it have wires only or a vacuum hose going to it) we can tell.
Dave ----
ps post up a picture or 2 of the truck, we like pictures
Thread
Thread Starter
Forum
Replies
Last Post
