Hello, Thanks for having a look at my post & question. I recently bought a 2000 7.3 with about 220K on the clock. I've had it about a month but don't drive it much.

Once a few weeks ago I started the truck with the AC on high and did not wait for the GPCM to cycle before cranking her up. The *service engine soon* a.k.a MIL came on. I checked the code at the local parts store and the truck stored P0682. GPCM fault. I read many other have had this failure and ordered the part while I was getting some other stuff from my Ford parts supplier. While I was waiting for the part to arrive I pulled the plug off the GPCM and used some WD-40 on the terminals and put it back. A few drives later the light went out. I know this means the truck no longer had reason to store the code and extinguished the MIL. I also know it did not fix it's self but left the old GPCM in and assumed I had improved a connection at the GPCM by unplugging and reconnecting.

Took my first road trip last week to UT from the west coast. During my road trip last week the MIL came on again, I've not been able to pull codes yet but I'm worried I may have heard detonation during my drive home. I'm not a diesel mechanic by any stretch but I am a pretty good sports car mechanic. Not sure if I was making up noises in my head but if it were a gasser I'd say it was detonating. I know it is possible for a Diesel to detonate but not sure why a stock 7.3 would? I did accidentally fill-up with bio diesel in Las Vegas (beware Sinclair is Bio Diesel only) but it wasn't until I was in UT I had the MIL come on. Only once did she ever start remotely rough and cleared up right away.

Have you had any similar experiences? I guess I should check the GP harness before anything else but I'm really concerned it may have been detonating.GPs should have no affect once it's going right? It seemed to rattle almost like a light ball peen hammer on a steel workshop bench at part load. I know it did it at 2200 and other engine speeds too. I never listened to the motor before with such concentration as I did on my first long road trip and then not really until the way home.

Water temp never went above 210 on the hottest day with 5000lbs in tow.

Otherwise the truck was flawless, we picked up a camping trailer in LV and with (dreaded) Bio fuel got 10 MPG with the good stuff got 11.5 when towing, unloaded I was getting 14.5 MPG.

Anything you guys know about detonation in a 7.3 I'd like to hear, maybe it's nothing but would hate to burn a piston or crack rings.

Thanks in advance,

T

 

Scan for codes when you get a chance and let's see what you get.
The glow plugs don't have any effect on the engine once it's started and slightly warm.
It's not possible to have pre-detonation unless you have a leaking injector or the calibration has been changed. A leaking injector is usually very very noisy....more like a sledge hammer sound.

The ball peen noise you describe sounds like injector knock...or commonly known as 'cackle'.

Since you have a GPCM....you may also have the type of calibration that stores freeze frame data. If you can get your hands on a quality scan tool such as AE or Snap-On etc, then the freeze frame data may be a really helpful clue. Most bargain scanners can't read the more detailed and IDM specific codes so be advised that you may not actually be getting all the stored codes....

 

I agree with S&B. And, not waiting for the WTS Light to go off doesn't "hurt" anything unless the engine is cold and below 50*F and even then the probability is low.

There are many possibilities which (based on your description) could contribute to faults and the MIL activation. Look for changes in fuel mileage and performance decreases as they are often noticeable change on Diesels. Other indicators are its ability to start within a few revolutions both cold and warm. Fuel Pressure Under a Load is also a great help in eliminating numerous probabilities.

If you plan on keeping the truck I would also suggest AE or a Twin Scan II as a minimum to monitor and/or troubleshoot. AE allows for KOEO / KOER Testing, Buzz-Testing, activating EBPV, FFD, and much more. Twin Scan II is also OBD-II Based but doesn't allow access to PIDS, GEM's, BCM's etc.

Retrieving DTC's alone often do not provide the required information to determine what the "problem is". My 99 will continuously report a wiper motor issue and 4x4 switch issue which it has no issues with either as I have checked each circuit and both are within OE Spec. It has done it for the past 177,000 miles.

Just a note: If you're moving wires and wiggling harnesses be aware that the PCM's will last the life of the Truck. But, they are fragile! I ALWAYS make it a rule the customers keys are in my pocket when I leave the cab. $500 at a time will break one of the practice of doing those things. I've contributed at least once to a new PCM.

As for the biofuel... You'll definitely want to change the fuel filter at 15k (sooner if your that concerned). May also want to add some anti-algae additive, Diesel Kleen, etc. for a tank or so before changing it - not that's there algae; just to reduce the possibility of something sludge or growing related.

Hope this helps in some way.

Tom

 

Okay so, pulled P0683 which I think I misquoted in my original post and was the original code, the text is the same as I recall glow plug control module fault. Wiggled wires tried to clear code code would not clear - un plugged module plugged it back in code would not clear made me think wiring. Then I plugged in my new module and the code was gone event though I didn't erase it.P lugged in the old module Code is gone not sure why the code cleared but I've not used this scan tool before and I was trying to clear it maybe just got confused don't know, also could be it's just not cold enough here to require glow plugs that's why the fault isn't reoccurring may have to try and start it on a cold morning here over the next few weeks.