Worth Repeating

[DaveNY]

Well I've read and heard it before but I had a Problem with TDCO and Other Issues that popped up all of a sudden. Every thing pointed to stepper motor or the pump moved by itself? Too cold to stay in garage and check things out,so I started to chase codes all over the place.Two days ago I just took it upon a whim to clean the battery terminals.Volt meter went from 14 -15volts But to my amazement the truck ran great even it had set a p1214 with the light on.Hooked up the scanner "AE" and cleared code. next morning hooked up scanner and everything went back to normal.I thought I was heading for a new pump but she runs great and all indications that was the big problem. CHECK THEM CABLES!!

Dave

[Robyn]

Bingo

Thanks for bringing this up again.

The way that these trucks battery cables are set up there can be an issue between the batteries with one getting charged and one not, and it not being apparent right off.

Poor grounds at the batteries, block etc, as well as the positive connection can drive these things NUTS, including the owner.

The factory cables with the crimped terminal ends can look great but be total trash deep in the core of the wire strands.

Once the cables get some years on them, they are totally suspect for sure.

I had a ground cable that was less than a year old (parts house replacement) and there was ZERO connection between the battery and the block.

Cable had corroded internally at the crimped ends

The best solution is to use good Welding cable and solder on the loop ends and use batteries with threaded stud terminals or Optimas and use the top terminals with marine stud type adapters.

Anything to get away from the crimped terminals that corrode.

Once the cable is fully soldered to a loop end, it's pretty sound.


Another place to be vigilant of are chassis and body grounds.

SADLY, many of the harnesses ground to screws under the dash in the area of the A pillar, and the batteries ground to the front fenders.

Best on a rig with time on it to get a ground to the firewall, which is all welded into the structure, where as the fenders have paint and bolts and can be subject to corrosion at the joints.

Ground the body to the frame, the engine to the frame, the batteries to the engine, frame and body.

Sounds like a lot, but just a couple straps can take care of it.

Another spot to pay attention to is the main engine harness plugs.

Spray each plugs connectors with electrical contact cleaner then assemble.

The engine harness (connects all the sensors and the IP to the main chassis harness)

Be sure to spray the two main gang plugs where the engine and chassis harness join.

The stuff under the dash at the ECM and such are or should be fine since they are in the cab and away from moisture, dirt and such.

Butttttttttttttttt, in the event of an issue, never beyond being suspect.

IMHO
Many of the PMD issues as well as other driveability problems with the 94+ 6.5 can be electrical connection related.

Poor grounds can cause current feedback and high amp draws in places that just don't tolerate it well at all.

The wires that feed the PMD are very small, especially the +++ power wire.

Small wire size cause issues, and then add time, corrosion and the amp draw goes into the twilight zone, or the voltage simply goes away.

Yessssss, a real PITA when something gets hinky.

I spent a day going over all the stuff under the hood on the Dahooley after the 4 year sojourn.

Sprayed and cleaned all the connectors, grounds etc.

Missy

[jrsavoie]

I run a few extra 10 ga wires - usually soldered in one eyelet.

I run one to the stud with all the grounds at the back of the engine.

One to the battery box bolt that you have to remove the battery to get to.

Another to the frame by the starter.

I also add a ground from the heater blower to the dash mount bolt, just inches away

I sometimes add one directly to the IP where the little wire goes and to the remote PMD

I use Kopr Kote on all connections. It seems to be working for me. So I just keep doing the same

[Robyn]

Good grounds, tight clean 12V connections.

With this, life will be good. :D

Our members who live in areas that use SALT :eek: can have myriad issues as the nasty corrosive stuff gets into everything, and eats away at stuff.

Just a tid bit

Install a HEAVY DUTY relay (Ford Starter relay) and connect the wire that comes from the ignition switch to the starter to the relay to activate it, and then run a wire from the Bat + to the relay and then on to the small stud on the starter solenoid.

This takes a huge load off the ign switch and also keeps the voltage supply in the ign harness higher.

The solenoids on the 6.5 starters draw a bunch of amps, and over time this will sack the ign switch.

The little relay takes very little, plus the relay being wired close to the battery provides full battery voltage and lots of amps.

When the solenoid is struggling to pull in and hold, the heavy contacts in the solenoid can and do start to arc, and then the power to the starter motor proper starts to head south.

Soon or later the contacts reach a point that they are carbon'ed badly and the motor starts drawing waaaaaaaaay to many amps.

This also leads to the starter running slower and the engine starts harder too.

Also with the large amp draw, everything else that depends on a good power supply to start the beast suffers too.

The ECM can see low voltages and this in turn ends in a death spiral for the entire starting cycle.


Get that solenoid in fast and hard and hold the contacts tight.

GM did us no favors in the wiring department, and time/duty cycles just makes it all worse.

Missy




Missy

[jrsavoie]

I also do the battery bolt mod. I use stainless 1 1/4" 3/8 16 tpi Allen screws instead of the OEM style battery bolts.

I use 3 stainless metric washers that fit inside the rubber on the cable ends.

For some reason I like the rubber left on the ends of the cables.

I have at least one bolt left to change on the 1995 Tahoe. Daughter had troubles a couple days ago. Went to her house and stripped the remaining battery bolt. Ended up at Napa buying another because it was 25 miles closer than driving home for an Allen screw and washers.

I should have throw some extra stuff in before I took off. Could have saved myself a few bucks

[jrsavoie]

Good grounds, tight clean 12V connections.

With this, life will be good. :D

Our members who live in areas that use SALT :eek: can have myriad issues as the nasty corrosive stuff gets into everything, and eats away at stuff.

Just a tid bit

Install a HEAVY DUTY relay (Ford Starter relay) and connect the wire that comes from the ignition switch to the starter to the relay to activate it, and then run a wire from the Bat + to the relay and then on to the small stud on the starter solenoid.

This takes a huge load off the ign switch and also keeps the voltage supply in the ign harness higher.

The solenoids on the 6.5 starters draw a bunch of amps, and over time this will sack the ign switch.

The little relay takes very little, plus the relay being wired close to the battery provides full battery voltage and lots of amps.

When the solenoid is struggling to pull in and hold, the heavy contacts in the solenoid can and do start to arc, and then the power to the starter motor proper starts to head south.

Soon or later the contacts reach a point that they are carbon'ed badly and the motor starts drawing waaaaaaaaay to many amps.

This also leads to the starter running slower and the engine starts harder too.

Also with the large amp draw, everything else that depends on a good power supply to start the beast suffers too.

The ECM can see low voltages and this in turn ends in a death spiral for the entire starting cycle.


Get that solenoid in fast and hard and hold the contacts tight.

GM did us no favors in the wiring department, and time/duty cycles just makes it all worse.

Missy




Missy

Not to be totally stupid, but could you post a detailed parts list, with mountable relay sockets. I seem to have a lot more problems figuring things out anymore.

[trbankii]

Basically, you’re taking a starter relay from a Ford truck, which looks like this:

http://www.thedieselpageforums.com/tdpforum/attachment.php?attachmentid=2918&d=1423328479

And wiring it into the setup like this:

http://www.thedieselpageforums.com/tdpforum/attachment.php?attachmentid=2919&d=1423328479

Of course, you have two batteries, so for the diagram you’re just taking the positive cable off the passenger side battery. The OEM wiring is basically the “thin” red line from the battery to the ignition switch then directly to the starter. You’re adding the “heavy” red line from the battery to relay to starter and splicing the relay into the existing “thin” red line to control the relay. So the power to the starter is going through the “heavy” red line - plus taking a much shorter path from the battery to the starter.

[jrsavoie]

Thank you much

[trbankii]

Glad to help!

[Robyn]

Thats it, RIGHT ON :):D:)

Best $$$ to spend.

This will really help the ign switch and starter life.

Just unhook the small wire from the stater solenoid, clip the eye off, butt splice in a 112 gauge wire and run to the relay.

No need to mess with the heavy cable to the starter, just leave stock.

Add an extra #10 wire from the relay to the starter control stud (small one) and another #10 from the battery + to the relays other heavy terminal.

The only wire you need mess with on the starter is the little one.

Banki
Thanks for sharing the Schematic.

Missy