Cummins diesel engine runaway rpms! Why is this happening? 🤷

So I'm running my 98 Dodge ram 3500 truck, with the Cummins 5.9 diesel engine down the interstate and suddenly, out of the blue it's stuck at 2200 rpms and won't idle down. Here's what I've found out so far.

[@bain5872]

As an electronics tech, my thinking would be to save the expense of an ECM, I would build a voltage regulator using a LM317 and with this, limit the input voltage down to 5 volts. I would think this should correct the voltage input issue. The parts for this build would be less than 5 bucks. You would need a small plastic parts box and cut the input wire and install the regulator in that one line. You would also need a ground in the box for regulator reference. It's a cheap fix and I'm sure it would work as the ECM is processing the output of the TPS correctly. However, this is a cheap fix and the best fix is a new ECM.

[@WagsAutomotive]

Thanks, that's an interesting option. But there could be other issues with the ecu as well. But I had no way to know that since it was running at 2200 rpms sitting still. Maybe I could have but a resistor in series to cut the voltage down as well? IDK. 🤷

[@bain5872]

@@WagsAutomotiveIn the end the right thing to do is replace the ECM. The resister option you mention wouldn't work to well as the ECM will pull current through the resister and would constantly change the voltage drop as you pressed the accelerator pedal. This would cause a very erratic output signal. I do hope you have it repaired by now.

[@WagsAutomotive]

@@bain5872 Well, I did replace it. If you watch part 2 you can see the result. Not what I expected....

[@maddawgnoll]

My dad's p pump went crazy one day. Neither of us had experienced anything like it. Key out, runaway. The rpms just kept climbing. In the panic of not knowing what to do, i crawled under and pulled the fuel lines. Nearly caught fire and i was told that i saved the motor. Pump i ruined the fuel pump and the mount on top of the tank. I now know... choke the turbo. But this isn't quite the same kind of runaway as you're showing

[@WagsAutomotive]

Ya mine didn't max out on rpms. Guess I'll see if it fixes it? 🤷

[@jaybrunner-ji3lt]

Throttle position sensor needs to be adjusted Apps

[@WagsAutomotive]

@@jaybrunner-ji3lt actually it was bad. I had to replace it under warranty. 😁

[@brentschuler2795]

My problem I had 5 years ago was that Cummins computer on the side of the engine from this very same issue but just started this video and six months after I was driving and the engine still ran perfectly but the sensor in the injection pump was stuck can’t remember what the code was but replacing the pump took the code away but went through hell doing all the testing from blue something can’t remember but had me unplug the connector on the injection pump and put 12v to one spot and ground the other spot and the truck would start and idle perfectly

[@WagsAutomotive]

Yep I saw that on his website. But he thought the ecm was bad, so we'll see if he was correct.

[@brentschuler2795]

PCM failed because of loss of communication with the ecm on the computer on the firewall on the passenger side which is where the information gets sent to your dash cluster

[@WagsAutomotive]

Ok. I was told it was the PCM so I'm replacing it? 🤷

[@stephenwest798]

AI, when ecm's get a mind of their own. Who knew?

[@WagsAutomotive]

I didn't! 😁

[@samuelrock5809]

Junk

[@WagsAutomotive]

😭😭😭 Hater! 🤪

[@MrMatt8478]

Your attitude is junk