So I drove my truck to my daughters house about 6 hours away and we were hauling some stuff to the dump today. We backed into the stall at the dump site, turned the truck off and when we got back in it wouldn’t start.

Has been running great all day, and yesterday during the drive. The no-start flow chart is pointing me to potentially the chip. I’ve had a DP Tuner since about 2009 with no issues.

Truck tries to turn the engine over but there is no fuel pressure. Would the chip cause that? I also checked all fuses and they checked out fine. I’m getting ready to start checking relays but wanted any input I could get.

 

When you say no fuel pressure how do you know? How much fuel in the tank?

 

Full tank. Fuel pressure gauge (Isspro) has been reading 65+ psi all day. But with the restart attempt, it’s at 0.

Also, where is the red wire at the PCM I’m supposed to check for 12V?

 

So when you turn the key on fuel pump under drivers seat in the frame rail should come on for about 20 seconds. If it does not check fuse and if good check for 12 volts at the pump. If there the pump may have just picked today to die, it happens.

 

Not sure about a red wire at pcm

 

Fuse is good but no power at pump which explains the lack of pressure. Also no power to GPR, and when I turn the key on, no wait to start light.

from following the steps in the no-start flow chart from the tech page it looks like I may have a bad PCM. Not ideal over a holiday weekend and I have to be at work on Tuesday.

Anyone ever heard of one just dying like that?

 

Just want to make sure I understand what you've checked:

Fuel pump relay fuse is #19. That fuse is good, right? PCM fuse is #30, and can blow due to bad fuel bowl heater. No WTS light is a clue. You can unplug the fuel bowl heater/WIF sensor, replace fuse #30 and try a restart. Actually pull and reinstall the fuses when you check them. I've heard these fuses can test good on these old rigs, but sometimes not make contact unless reseated.

Great that you have a permanent fuel pressure gauge. Looking forward to having one of those again.

 

Jeff has ya going in the right direction. I've been running with my fuel bowl heater unplugged for a couple years now since it popped the PCM fuse. The connector for the fuel bowl heater is on the lower back of the fuel bowl.

 

Yup. I concur with what Jeff and Charlie said. Check for blown fuel bowl heater fuse. If blown, unplug fuel bowl heater, replace fuse and try again.

 

Keep in mind power only goes to the pump for about 20 seconds or less at KOEO. If your not watching the meter in that window of time you won't see it.

PCM's like anything can go bad but it's rare. I would double check everything like these guys said. Also there is a diode and relay in the fuse box under the hood that control the PCM. You check and see if your Getting power there.

 

Items I’ve checked so far:

-Batteries are good

-Starter is good

-Engine turns over rapidly, but no start

-No signal to GPR to turn on

-No fuel pressure

-No WTS light

-Pulled and tested every fuse under dash, all good

-Pulled and tested every fuse under hood, all good

-Fuse 22 (junction box batt feed) under hood has power coming in to it

-Fuse 19 (fuel pump motor, PCM) under hood has power coming in to it

-Fuse 24 (PCM power) under hood has power coming in to it

-PCM diode checks out good

-Bench tested relay 30 (PCM power) tested good for coil activation and continuity

-Swapped PCM relay (just in case) with blower motor relay and still same symptoms

-Disconnected fuel bowl heater plug, same symptoms

-With key off I have power at pin 30 for the relay (normal)

-With key on I have power at pin 86 for the relay (coil activation)

-When my wife turns the key on, the PCM relay activates

-Checked DPtuner chip for looseness, reinstalled PCM, same symptoms (also Tuner switch doesn’t light like normal when key is on)

-Pulled chip from PCM, reinstalled PCM, same symptoms

-Researched PCM pinouts, checked for voltage at PCM pin 55 (always hot) it’s good

-Checked voltage at PCM pins 97 and 71 with key on, it’s good

-Checked pin 24 of 42-pin connector for power with key on, its good



My conclusion, unless anyone has any other ideas, is the PCM crapped the bed. Who knows why. Maybe the DP tuner wiggled a little and shorted something or maybe it was just it’s time to die.

With all that said, does anyone know of a reputable place to get a replacement PCM?

 

https://www.dieseltechchatt.com/

 

Thanks Sous. Getting ready to check the fuel pump relay behind the radio for grins, and then I’m sure I’ll be placing an order with dieseltechchatt.

 

You might want to check the fuel inertia switch behind the panel in the passenger foot well too. Please keep us updated with what you find and how you fix it.

 

Just checked the fuel inertia switch. It's in the proper (pushed down) position. I was hoping I'd run out see it up, push it down and be good to go. No such luck.