'79 F250 with a transplant 385 series 429 and C6. I have been having various issues, such as headlights flickering, gas gauge off, then out, turn signals working then not working and have replaced most of the switches. Last night I pulled the instrument cluster to check if the gas gauge is working and it is, so seems to be the sender (separate issue perhaps?). I charged my battery to full that night. I went to drive my truck the next day and could smell that electrical burning smell, but didn't initially think it was my truck. Truck started with some lag in turning over. Drove and headlights were dim, turn signals slow. After about three stops and starts while doing errands the starter seemed to lag more and more each time I finally lost all power and could not start up - a little power, then dead. I replaced a broken terminal - no go. Tried to get a jump and the battery would arc when the last (positive) jumper cable was attached (first hooked the battery from the live vehicle, then ground to mine, then hot and could not connect hot due to arcing!). Tried to connect a new battery and as soon as I touched the positive cable to the battery the starter motor kicked over without the ignition being on! I didn't try to reattach the battery so that I could take it back since it was new. Towed the truck to my brothers where it sits.


Any help greatly appreciated!! I am a relative newby and STUMPED!!

 

Check the wiring underneath on the driver's side. There are a set of wires that go from the frame to the tranny, and these have the back-up light circuit and the start circuit. If these wires get melted together, the back-up light power will cross over to the start circuit and make the solenoid kick in all the time. They run down sometimes near the exhaust pipes.

 

Thanks so much Franklin. As luck would have it I have to go out of town the day after she broke down, but this will be the first thing I try next week when I get back. Much appreciated!

 

Another thing to remember. When you are jumping a vehicle, always connect both positives then the ground on the donor vehicle then ground to somewhere on the block of your truck. A lot less likely to arc. I have seen batteries explode because of the fumes of a dead battery. Plus it doesn't take much of a spark to kill the alternator on the donor vehicle. Steve

 

So went underneath to check the solenoid. I assumed it would be attached to the starter like the diagrams in my shop manual - nope. I don't even see a solenoid??? Checked the connections and it all seems to be OK. could it be the starter relay. Could it be that something got crossed up behind the dash while I was troubleshooting the gas gauge?

I'm at a loss. Tried reconnecting a new battery again and same thing; arcing, electrical burning smell and the starter is kicking over??

Any useful suggesions would be greatly appreciated.

P.S. The starter is a Napa brand.

Thanks.

 

What happens when you take the wire at #5 off your solenoid like the picture above illustrates? Take wire 5 off and then put the bat terminal back on and see if you still have the problem with the starter turning over all the time.

 

Thanks for the response again Franklin2. I replaced the solenoid relay and the problem is fixed. Gas gauge is working too!

I have gone from perplexed to mystified! As soon as I drove the truck it simply would not shift while in drive. Park, neutral, drive, 2low, and 3low all work, but it does not shift in drive?!?

All I did was pulled the starter, the reverse switch (which Napa could find no reference for) and the solenoid relay.

How could my tranny stop working!?! It only has about 20-25K on the rebuild, is a C6.

Again. Any help is greatly appreciated!

Reno

 

To ad to my "gremlin's in the transmission" problem. I had to tow the truck to my brothers using his truck. My truck was dead due to the electrical problem, but in neutral when towed.

 

Cross your fingers and hope you have a vacuum line off. With the truck running and in park, get under the truck on the pass side and look at the pass side rear of the tranny. There should be a short vacuum line hooked to a round thing on the tranny. The round thing is the modulator. Pull this line off and make sure it has suction with the engine running. Make sure there are no cracks in the line.

I hope when you say the truck was in neutral, you mean the transfer case. If you mean the tranny was in neutral, and it's a 2wd, I hope you did not tow it far on the ground. It can damage the tranny in a short time. Always take the driveshaft out or pick the rear wheels up when towing a automatic 2wd vehicle.

 

Im new here and may be an Idiot, but how do I start a new thread/topic? Sorry for just jumping in on your convo here, I just cant figure out where to go to start a new topic. Thanks

 

It is a 4WD fortunately! I think I located the two vacuum lines. If I am correct they run out of the rear passenger side of the tranny and one ties into the radiator and the other ties into a hose that then connects to a rectangular box that looks like a small radiator situated in front of the radiator.

I checked them visually since I have to be somewhere soon. The one that ties into the rectangular box appears to have some fluid buildup around the connection between the hose and steel line.

So I better understand what could be going on what do the lines do? Are they for cooling as well as hydrolic pressure? What is the small rectangular unit?

Thanks as always.

Oh, yeah - I'll remember the towing tip for 2wd vehicles as well.

 

No, those lines you found are the tranny cooler lines. They have tranny oil inside them. Stay on the pass side of the tranny, but move more toward the rear. The crossmember may be in the way of seeing it, but it's rearward of those cooling lines you found.

There is a steel line that runs down the backbone of the tranny on top, and then there is a short vacuum line that goes from that line to the modulator.

The modulator controls the shifting of the tranny in relation to engine load. If you lightly push on the accel pedal, the engine vacuum is high, and the tranny shifts quickly up through the gears. If you push hard on the accel pedal, there is very little vacuum at the engine, and the modulator reacts to this and delays the tranny shifting up through the gears.

 

Go to the forum you would like to post in, and look at the top left side there is a blue button that says "new thread".

 

Thanks Franklin2 I did get it figured out then.

 

I must have found it by accident at the engine between the carb and fire wall(?) I found a line that was unattached and re-attached it. Drove and everything seems to be working fine - truck is basically running perfectly now (cross my fingers).

I was shocked and pleased to feel her shifting again!

Your the man Franklin2!

Reno