Truck running rough now won't start.

[t97]

My truck has been running great for the past year but about two weeks ago it overheated on my way to work. Got it home and it ended up being the waterpump then it drove fine for a few days until my radio would randomly turn off then turn back on whIle sitting still and driving. The truck began to start working properly for a few more days until it started doing it again on my way to work. About half way to work my clock started dimming as well as the dash lights but it made it there fine. When I got out of my shift it wouldn't start just the click from the passenger side. I got a jump and it started but the lights were barely on. 15 miles down the road the truck started losing power and at the next stop light the truck was fighting to stay on and was bucking trying to get over 20. Now I have it home and it won't start again both the battery and alternator new so I know I have power .

I'm thinking my ecu went bad but I'm not sure how to check. Any suggestions? Sorry for the huge paragraph it's kind of hard to format on my phone.

[pennyman1]

that sounds like the alternator died - if it started but the lights are dim and went to nothing that is a sure sign, or a massive short. New doesn't mean it can't fail.

[ragragtimetime]

verify grounds are good...everywhere! ie-frame, body, battery. verify alternator output is occurring with multi-tester. sorry I can't help more...i'm a 1st gen guy....ecu

[t97]

I put in the alternator before I made this post but il check it again. I'm off tomorrow so il go through all my grounds and clean them up. Thanks for the suggestions guys.

[t97]

Well guys I cleaned my grounds and charged up the battery and it started right up I drove it around town for an hour and a half with no problems at all then as I was coming around a corner everything went dark and it started running terrible again. I got it into a parking lot and it finally died and when I tried to start it again it cranked once then wouldn't even give me a click when I turned the key. I got someone to bring me my battery out of my mazda and just out of curiosity I tried to jump it off and it started right up like nothing. I drove it around the parking lot and everything was fine but as soon as I got in the street it backfired twice and died. I swapped put the batteries and made it home with no problems.

Tomorrow I'm taking both the battery and alternator back to test them bUT is there anything else you think it could be? It seems weird to me that just a low battery would cause it to backfire and run really rough. If I had a short where do you think it would be to cause all of this?
Thanks in advance.

[geezer101]

Low voltage might have caused the ignition coil to break down to the point where it misfired (and running the fuel pump at too lower pressure from the voltage drop may also had an effect on it as well). Do a ECU code check on it while you're getting the charge system tested.

[camoit]

Start at the Alternator and check voltage. 14.2 = good on a charged battery. 12.5 no good. Then move to the battery. 13.5+ is good on a charged bat. Then look for ground wires between engine block and cab. With the lights on check voltage at bat and alt again. It will be lower but not much.

[t97]

I tested both the battery and the alternator today and theyou eaten fine the battery was low but it took a charge. Is there a way I can pull codes without an analog multimeter? Truck is a 91 4g64.

[camoit]

This is old school. You must have a meter with a needle. Because you are going to count the swings the needle makes. There might have been a thread on how to make an LED test light at one time.

[t97]

I bought an analog meter and according to the book everything's fine just short ticks. I did look at the 80 amp fuse connected to the positive cable and it was broken so I replaced it and it drove fine but I'm not sure if that was my original problem or if it was a result of something else because the first time it wouldn't start the link was still in intact.
Thanks guys