2002 Adventurer 8.1L Workhorse won't crank.

[penman39]

So I went to turn around the coach since we were leaving today. Turned the ignition to start, just a click but no starter engagement.. Push the battery boost and tried again. The coach started so I turned it around. After repositioning, I shut off the coach. Tried to start again but nothing even with the boost. Thinking the chassis battery was weak, I replaced since it was over 7yrs. old. No luck starting. I did notice that a fuel gauge went to full scale and not the normal 3/8 full postion it sits with the power off. Starter relay is not picking up, but if I remove and jumper the starter socket, the starter does crank the engine. This gizmo pictured below by Sure Power Industries blinks light 3 when turning the ignition to start, but according to Google, this is a wiper module, though why all the tranny postion lights beats me. I'm guessing that is irrelevant to my issue.

I am not have any luck finding wiring diagrams that show the starter relay circuit. HELP!!

 

[Isaac-1]

Check the engine block wiring ground strap located at towards the back of the engine.

Also check to see if yours ever had the ignition switch relay mod done, as without the mod the ignition switch is prone to burning out and causing odd things to happen https://www.nwtfc.com/wp-content/uploads/2020/04/Workhorse-Ignition-Relay-Instructions.pdf

oops never mind that second bit, as it only applies to P series chassis

 

[Heli_av8tor]

I believe that is the wiper module. It doubles as a transmission indicator for driving the chassis before the coach build.

I had to replace mine a couple years ago.

 

[Henry J Fate]

Transmission switch is a possible culprit. The other possibility is that the computer is locking the start circuit out. To reset the computer, disconnect power to the chassis and turn your headlights on. This will drain the memory in the computer and a reset will occur. 10 minutes and it will be depleted.

 

[Arch Hoagland]

Did you ever measure the starting battery voltage with the new battery in place?

 

[penman39]

Sorry for the delay in responding. I have discovered some blown fuses in the fuse block all related to the PCM/TCM modules. I will add to this thread in a few hours.

 

[John Canfield]

Hope the fuses are your problem Carl. When the problem is resolved, I'll move your thread to the Motorhome board.

 

[penman39]

So far I have blown a 20A PCM/TCM fuse that feeds the starter relay. When I put a new one in, it blew immediately. We disconnected the NSBU switch plugs and reconnected after inspecting and put a new fuse in. It did not blow so I tried a start. It would crank but not fire. I tried again but then back to my no crank condition. Rechecked fuses and found a 10A PCM/TCM fuse that feed the solenoids to tranny this time. That’s where I left it since we were still going camping, just staying with some camp mates. I am very suspicious of the NSBU switch being faulty.

 

[Henry J Fate]

There is a crank sensor that can also lock things out. I doubt if the crank sensor would blow a fuse but if my memory is still working, if the crank sensor is faulty the motor will crank without ignition. I had one go bad several years ago and to get it started, I reset the computer. The crank sensor can be seen inside the dog house and I think that the mechanic I hired to replace the plugs and wires stepped on it or screwed it up somehow whike servicing.

 

[penman39]

Problem fixed. I ordered a NSBU switch and a TCM unit from Brazels. Thankfully they had one available. They must be getting harder to obtain since the replacement came with a hefty $400 core charge. I installed the new NSBU switch and tried starting. Still no luck, however fuse #32 blew again. This circuit feeds the TCM and PCM modules. Disconnected all power sources from the coach and replaced the TCM. Restored all connections and viola' the motorhome is motoring again!!

 

[John Canfield]

Excellent Carl! I love happy endings.

Some older Jeep (2004-2006 is what I'm familiar with) parts are orphaned now. No more Powertrain Control Modules (PCM) and some of the engine/transfer case sensors are unobtainable.

Thanks for keeping us posted on your troubleshooting, I'll move this thread to Motorhomes.