Not cranking...

[FHerault]

Hello,

My truck is not cranking for some days.
Since I'm working only minutes from home now, I was suspected my batteries were weak but with the boost pack nothing happened.
I had to tow the truck home and performed some tests :

- batteries fully charged : nothing
- since my starter was showing some bad symptoms and has more than 15 years, I changed it. Nothing.
- positive terminal of the starter to positive battery terminal with jumper cable and key to start : nothing, so I assume the cable is ok.
- starter signal terminal to battery positive : cranking (starter ok, so relay or wiring issue ?)
- did take out the starter relay in the fuse box under the hood (driver side). using a voltmeter I read battery voltage between pin 85 (ground) and pin 86 (12,5v when key in start position)
- I replace the starter relay with an other one but nothing. To be sure, I jumped the relay with a wire in pin 30 and 87. The fuel solenoid is acting but no crank.
- I jumped the Park/Neutral safety switch (center pin of the plug to ground) Nothing.

At that point, I assume I've missed something...

Your inputs will be welcomed.

 

[Bob4x4]

Sounds like there is a problem in the power distribution center (fuse box). There is a kit you can buy at the dealer that will bypass the problem. Or if you’re good with dc wiring you can do the same thing with generic parts and a bit of wire

 

[GAmes]

Fuse #9 is an integral part of starting. Have you checked it? How about the blue fusible link? If you can jump it the replacement is a 14 gauge fusible link, available at most auto parts stores. Theirs might not be blue though.

 

[FHerault]

I've checked all the fuses in the pdc, all good.
I've checked again the connections to the starter. The signal wire terminal was all rusted in the heat shrink tubing I decided tu cut to be sure. After cutting a lense of wire and replacing it, the truck started right away. To be sure I cut off and restarted it, but...nothing again !
I'll investigate tomorrow since it seems I've lost continuity on the wire I have fixed... Is there a device like a filter at the end of the signal wire to the starter or is the wire connected directly to the starter terminal ? Mine had, I think, a bolted adaptor to allow the connector to fit on the starter terminal, wich is to big for the connector at the end of the wire. A pic would be nice to explain, I'll see if I can post one tomorrow after work.
Thanks for the replies.

 

[GAmes]

The signal wire (brown?) might have a diode attached at the started that prevents feedback. https://www.genosgarage.com/product/lb-ss99/fuel-system-accessories-replacement-parts There is nothing there from the factory, the wire attaches directly to the stud.

 

[FHerault]

Ok, I think it's my problem. The diode might has been installed by the precedent owner more than 11 years ago and it's all corroded. I will change the brown wire between the connector near the PDC and the starter, and a new diode if needed.
I will report back.
Thanks !

 

[GAmes]

You don't "need" the diode, it is an add on for a very low percentage failure. I just installed one, for the first time, about a week ago. I would definitely delete it for trouble shooting.

 

[BigPapa]

Just in case you're wondering, the diode is put there in case your starter contacts hang up. It can be a problem when the contacts wear thin enough that they will go past each other and get hung up. If this happens it can/will burn your shut-off solenoid up, among other things, since part of it is fed by the same circuit.

 

[FHerault]

I had already heard or read about the diode but not knowing that there was one on my truck. I just did not put it in my test list...

I've connected the signal wire without the diode and the truck starts no problem now. So lesson learned : if someone has a no crank situation, have a look at that diode...if you have one !
Thank you for all the replies.