Runaway accelerator

[Snizzykaliznak]

I have a 95 NA 6.5l Detroit in my k3500. For the last 3 months it's been reveing and accelerating on its own. New PMD installed, APP, fuel filter. Transmission rebuilt a couple months ago. Using a TCI ez-tcu stand alone.
Grounds clean and attached.
I know I need new thermostat. I'm a very competent Mechanic and parts are readily available. (I work for 1 of the 3 shops in town)
This thing runs fine for a few then while driving it will increase speed and RPM will redline. I can just be idling (11mph) down the road and without touching the APP it will jump to 70000 rpm and get up to 60mph in a few seconds.
It did sit for a few months. Maybe IP is sticking. I've had OBD1 35 and 36 come up with old and new APPS. Or the fact my key is broken off in the ignition is throwing everything out of wack. I'm just looking for any other ideas. If you think of something, no matter how weird please post it. Because this is a 6.5l diesel. I'm going to run codes again and go to bed.

 

[jrsavoie]

I have a 95 NA 6.5l Detroit in my k3500. For the last 3 months it's been reveing and accelerating on its own. New PMD installed, APP, fuel filter. Transmission rebuilt a couple months ago. Using a TCI ez-tcu stand alone.
Grounds clean and attached.
I know I need new thermostat. I'm a very competent Mechanic and parts are readily available. (I work for 1 of the 3 shops in town)
This thing runs fine for a few then while driving it will increase speed and RPM will redline. I can just be idling (11mph) down the road and without touching the APP it will jump to 70000 rpm and get up to 60mph in a few seconds.
It did sit for a few months. Maybe IP is sticking. I've had OBD1 35 and 36 come up with old and new APPS. Or the fact my key is broken off in the ignition is throwing everything out of wack. I'm just looking for any other ideas. If you think of something, no matter how weird please post it. Because this is a 6.5l diesel. I'm going to run codes again and go to bed.

I'd be guessing a new IP is in order. Possibly a drive by wire issue.

May be a good time to swap to a mechanical IP

 

[JayTheCPA]

X-2 for focusing on the IP.

Try the RPM test by slowly pressing the throttle to increase RPM's to 2,000, hold for a few seconds, and slowly release. Repeat 10 times (not kidding)
- If the RPM's smoothly match the throttle inputs (ie: RPM's perfectly track the throttle) on each cycle, IP is likely good.

- Indications of a failing IP are:
++ Dead spots (throttle moves, but RPMs do not change).
++ If there are variations in each cycle, such as a dead-spot or surge on one cycle, but not another.
++ RPM's surge up / down in a manner which does not match the smooth throttle input.
++ Cannot hold 2,000 RPMs for a few seconds.
++ RPM's want to run-away.

If the IP does need replacement, consider new and not reman. Have not had good experiences with reman. Last known source for new was direct from the manufacturer via a dealer.

 

[NVW]

I bought a new IP from a Stanadyne shop a few years ago, I think it has been said on this Forum New IP's are no longer being made. Electronic ones that is, there may still be new Old Stock" out there.

 

[MrMarty51]

I would first try another PMD and see if the problem persists. I had two bad Dorman PMDs in a row. The third one I installed and run the engine for a while to make sure it would start and run and then installed a new Stanadyne grey box PMD and it has not done anything weird yet.
The first PMD that went bad was doing the exact same thing that You are experiencing with Your run away issues.

 

[jrsavoie]

I would first try another PMD and see if the problem persists. I had two bad Dorman PMDs in a row. The third one I installed and run the engine for a while to make sure it would start and run and then installed a new Stanadyne grey box PMD and it has not done anything weird yet.
The first PMD that went bad was doing the exact same thing that You are experiencing with Your run away issues.

I had that with at least one gray standyne. Always check with a known to be good pmd

 

[Big T]

I have a 95 NA 6.5l Detroit in my k3500. For the last 3 months it's been reveing and accelerating on its own. New PMD installed, APP, fuel filter. Transmission rebuilt a couple months ago. Using a TCI ez-tcu stand alone.
Grounds clean and attached.
I know I need new thermostat. I'm a very competent Mechanic and parts are readily available. (I work for 1 of the 3 shops in town)
This thing runs fine for a few then while driving it will increase speed and RPM will redline. I can just be idling (11mph) down the road and without touching the APP it will jump to 70000 rpm and get up to 60mph in a few seconds.
It did sit for a few months. Maybe IP is sticking. I've had OBD1 35 and 36 come up with old and new APPS. Or the fact my key is broken off in the ignition is throwing everything out of wack. I'm just looking for any other ideas. If you think of something, no matter how weird please post it. Because this is a 6.5l diesel. I'm going to run codes again and go to bed.

“It will jump to 70000 rpm and get up to 60 mph in seconds.”

I for one want that tune.

 

[dbrannon79]

I'm with BigT on that! you must have a real beast there lol just kidding. is sounds like you have the electronic DS4 IP and it's given up the ghost.

there are no "new" electronic IP's left but only what's left of new old stock since they stopped makeing them. since you say it's already had the standalone TCM for controlling the tranny, your already half ways to converting it to the old mechanical cable operated DB2 pump which are still available new and also have a much longer life time and more reliable. we have our resident @Rockabillyrat who knows all about them and can fix you up nicely too.

 

[Rockabillyrat]

Definitely sounds like and injection pump issue. Since your already running a stand alone TCM. You have the option to replace the DS4 with a reman, or swap to a DB2. Mechanical pumps are nice and simple, but the DS4 has tuning advantages. So depending on what your power level goals are each is a good choice. A DS4 will max out at 280hp if you want more then a DB2 is your better option.