I think this boy is whacked.

Referring to the leads of the BD Cool Down Timer ~

- The ground lead connects to a verified ground.
- The + 12vdc constant power lead is connected to just that . . . . constant +12vdc (from Batt via fuse block).
- The keep alive lead is connected to the dark blue line of the truck PCM. This is verified by my '93 Dodge FSM, page 14-98. The dark blue line connects to the Ignition terminal (CAV9) of the PCM among other things (fuel cut-off solenoid included). I connected under the dash at the steering column (DB14).
- The pyro leads connect to the pyrometer device leads that came with the ISSPro gage (Amplifier box input).
- The brake lead is connected correctly to the brake light switch.

With the above, and a controller set point of 300*f:

- In park, I can raise the EGTs to say 350*f, and the controller will set (red LED illuminates). Releasing the throttle sees the EGTs drop back down slowly to 300*f and the controller LED goes out.

- Driving the truck around the block will see normal operating EGTs of about 700*f to 900*f. Bringing the truck to a stop (engine still running by way of the ignition switch/key), allowing the EGTs to drop to 300*f might take about three minutes average. In watching the temp hit 300*f, the cool down timers controller LED will go out as it should.

- If I perform the same test as above, bring the truck to a stop, and turn off the ignition key, the timers controller LED is still lit as we're still at about 400*f. HOWEVER, after about 30 to 45 seconds, the controller shuts down stopping the engine. No matter what the controllers set-point (all the way counter-clockwise to the lowest set-point), the controller shuts down the engine after 30 to 45 seconds. The EGT is WAY above the 300*f set-point. Immediately restarting the engine still sees the EGTs well above 300* and the controller immediately re-illuminates the LED.

For some reason, it appears the timer portion of the controller is over-riding the temp control after only 30 to 45 seconds regardless of the EGT.

All along, the brake pedal shutdown feature works correctly.

NOTE: The pyrometers amp is also powered by the keep-alive lead so I can see where the CDT is shutting things down.


Is it possible I'm missing something here?

 

An update,

The good folks a PDR once again stepped up to the plate and smacked a home run.

Mark agrees that boy's whacked. There gonna swap me a new one no problem.

 

Well, it's not the device itself.

I finally got around to sorting it all out (I hate automobile wiring ).

Connecting the "Keep Alive" wire to the stock blue wire that powers the fuel cutoff solenoid doesn't work. That same blue wire powers everything else related to running the truck including the PCM. Apparently somewhere around 30 seconds after shutdown the normal way, a ground is placed on the blue wire. That kills everything including any efforts of the CDT to keep things running.


Screw it!


The bottom line is all we need to do is keep the fuel cutoff solenoid energized for the cool down process.

With that thought in mind, I simply ran the CDT's keep alive wire directly to the fuel cutoff solenoid. I also placed a diode in-line with the original blue line where it connects to the solenoid.
This allows the CDT to directly control the solenoid without back-feeding to the blue line (and thus the blue line can't screw around with the keep alive wire yet still work normally).


So as it stands, the CDT is now working as it should. I'm able to have the engine shutdown automatically at any desired setpoint (in my case, 300*F). The default five minute override works, as does the brake pedal kill function.


Stupid automobile schematics!



I hope you've all been keeping up with this. Clear your desks less a piece of paper and pen. It's pop-quiz time!

 

And I thought it was a 'pop-quiz timeR'.

I followed your notes and understand the electronics... Just wondering why the blue line gets 'grounded' after shutoff? - maybe someone has run accross that.

 

Saying it's being grounded is an assumption on my part. From what I can tell about the trucks control wiring is that the PCM switches a lot of the control functions by making a ground for the given circuit (thus completing the circuit) though it appears that's not consistent with all the controls.

Keeping in mind the BD cool down timer was never meant to go on a first gen, my original thinking of how to wire it was based on how it's wired in the second and third gen trucks. That coupled with the suggested hook-up of the Howard's Cool Down Timer as marketed here in DTR all pretty much pointed to the blue wire.

The Dodge FSM shows how and where everything's connected, just not what's going on inside the PCM. I think that's what had me.

Anyhoot, I'm glad it's sorted out. Now I can button up the glove box area (that's where I located the CDT and Pyro boxes), and the Miss's can move on to fussing about something else.

 

Thanks for the info. I was curious and so I asked. Enjoy the round of getting the 'Miss's' fussing about something.

I know my wife was always sensitive to the slight smell of mildew I had in my truck because the sleeper leaked. She is glad we went through it and fixed it all up. We used to tow our trailer with a 3/4 ton van and she was not happy. All it took is one trip with the D350 and her fussing about getting rid of the trailer has all but disappeared. She even enjoys driving the rig towing the trailer!

Best to you in your next project

Rich