*help* truck won't start

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98-k1500-z71

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please bare with me as i try to paint the best picture that i can. truck is a 1998 gmc k1500 5.7L 350. a few days ago i was driving and noticed the ABS light disappear (which is usually on) and then the Brake light would come on and then went away and the ABS light came back and then they were both on.....you get the idea. so the next day i was driving and the same thing happened. i got home and parked the truck. went out a few hours later and the truck wouldn't start at all. (i have no idea if the lights flickering on the dash are realted to why the truck is dead but wanted to give all the info). battery has 12.4 volts. all the lights worked. so i pulled the starter and tested it and it was dead. put a new one in and still nothing. all the fuses look good. swapped the AC relay and starter relay-still nothing. used a multi meter on the starter relay prongs and with the key on it had 5.4 volts and when cranking 4.1. on a side note my third brake light and taillights come on with the running lights but only the third brake light illuminates brighter when the brake pedal is pressed. i don't know if that is related or not. i'm thinking this is a ground issues somewhere but i am obviously here because i haven't figured it out the last two nights after work. thank you in advance
 

GMCTRUCKS

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Check what voltage is going to the starter post coming from the battery and some months back my starter was giving me problems so I ran a wire from the starter solenoid to the inside of my truck then I ran it to a momentary switch then to my fuse box well when my truck didn't want to start I would just put my key on the start position on the column and hit the button I put on and my truck would start right up.

Well I was thinking when my truck wouldn't start I was able to hit the button which does turn my truck on but that same day I put on the switch my truck never gave me a problem starting it with the key all I can think is when I put on the additional wire for the switch it must have made up a good connection on the stock wire I wish you luck one last thing years ago I replaced the whole wire coming from the battery to the starter it was the small wire coming off the positive cable it had green acid inside the wire I mean from one end to the other which in turn wasn't putting out the correct voltage to the starter.
 

98-k1500-z71

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that's some good info thank you for that! i just did some more multi metering and the battery is at 11.7 volts from sitting for a few days now. with the key on the starter is at 11.7 volts as well so that's good. the problem seems to be that the slots where starter relay is goes is only getting about 5 volts with the key on.
 

Stephen

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My 96 C3500 with 7.7L had a similar problem but without the warning lights. It turns out the plug for the starter relay had a pin that had over heated and melted the plastic around the connector and the associated pin on the relay. I took a needle nose pliers and closed up the connector on the plug & have not had any problems related to that. I did need to replace the battery cable to the starter on 2 occasions. The end that connected to the starter has a copper connector and the copper was a dull, not shiny, color indicating that it had been subjected to high temps either from internal or external heating. Both times the starter would not spin but all the lights & accesories would work.
 
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