• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

APP blues

T

TexR

Member
Messages
12
Reaction score
29
Bought a 1997 C3500 6.5TD just recently. Supposed to have had a good motor, lots of blow by with all the associated problems. I will be going through the motor soon but in the meantime I am fixing the small stuff. Accelerator is the next on the list. Mash the pedal and it idles up but returns to idle, mash it a little more and it idles up and returns to idle, mash it even more and it does fine. replaced the APP as I've experienced this before but this time to no avail. Any ideas out there? Thanks
 
BTW, bought the truck sight unseen off the internet. First and last time I do that! The blow by was dumping quite a bit of oil through the turbo so I vented the CDR to atmosphere and by passed the turbo. Truck has a little more spunk than before (barely) but did notice an increase in fuel economy even considering engine condition.
 
Oh my, that is sad that someone would mess another fellow over like that.
First on the list is the ground wires, located at the back of the right side cylinder head. Remove them from their mountings and shine them up with wire brush or sanding paper.
If You have a code reader, see if there is any stored codes.
 
Welcome to TTS! Glad to have ya aboard. x2 on cleaning all the PCM grounds. also check the connections on and around the IP make sure it doesn't still have that noise filter (little black box thingy) plugged inline with the optic sensor on the harness. if so pull it and connect the harness direct to the OP. for a scanner to see data and codes, if you don't have access to a tech 2, you can get a Bluetooth obd2 scanner and use some of the popular apps like car scanner and torque pro on your phone. check the data stream with the key on engine off and look for the three APP voltage readings. all three should read with a smooth transition as you slowly press the pedal to the floor. iirc APP 1 will read backwards starting at near 5+ volts and slowly drop as you press the pedal. others will chime in soon with more knowledge than me :)

oh and please post some pics. we love to see these trucks :)
 
It could also be that the PMD is failing.
Check to see if it is still mounted to tje injection pump or if it has been relocated to a different position. If it has been relocated, there will be an extension harness hooked to the IP harness right near the injection pump.
If it has not been relocated, might check with Leroy Diesel or Quad Star tuning and get one of their flight systems PMD relocation kits. The one with the 6’ harness will reach to a location behind the front bumper.
 
Thanks for the quick responses! I still need to check the grounds but in south Louisiana, we're having a serious cold front, bout 39 LOL! so I'm staying warm. Truck has a new IP and relocated PMD. Haven't ran codes yet but am intrigued with being able to check codes on the iphone. Back Soon!
 
You need to get a scanner on it to look for codes and read PID data. That's the first place to start on any electronically controlled diesel engine. If that doesn't point you in a specific direction then test the fuel supply pressure and volume. Also look for air in the system by putting a clear hose on the return line.

Also you guys can save alot of time by voltage dropping the grounds. If its under .5v then they don't need cleaned. I like to load the system by starting the truck with my meter in min max mode. If it goes over .5v then its worth cleaning them and retesting.
 
In addition to echoing the comments to get a live PID reader / monitor, have a thought about that sight-unseen deal...



While understanding the regret with this purchase's outcome, no need to completely avoid future remote purchases. Consider taking a look at escrow agents and paying the extra fee for them to collect the title in advance. And prior to engaging the escrow agent, have a good contract which clearly details the vehicle's conditions to include all warts and details the escrow agent's role. There are plenty of sample contracts available for free download, so just find one (or more) that work and modify accordingly.

A benefit to using the escrow process is that it allows for X days (buyer and seller will need to agree on the X's value) for you to inspect the vehicle once it arrives at your location. If everything (within reason) matches the seller's claims, then tell the escrow agent that all is good and they send the money to seller, and the title to you. If the vehicle does not match the contract's narrative regarding the vehicle's condition and you are not willing to deal with the discoveries, tell the escrow agent (*BEFORE* the inspection window expires) that you are rejecting the vehicle which in turn prevents the seller from getting the money.

And back to that contract comment, having a good contract which details both the vehicle's condition and the escrow process (including reasons for possible rejection and that the seller will need to pay for return shipping) will scare-off many sellers looking to hide their baby's warts and force a little more honesty. Then again, am sure there are sellers whom will try to get away with it anyway, but at least with an escrow agent in the middle, the seller will not get your money and now they have to deal with recovery of their pile-o-warts ;)

And toward the money flows, with an escrow agent in the loop and an allowance for X days of inspection, this removes the need for a down payment to claw-back in the event of a rejection. As part of the escrow process, the buyer must send the *whole* purchase amount prior to the vehicle moving or the title starting its transfer, so there is plenty of skin in the game at this point.
 
Brake question for you. Had a bad ABS unit, mushy pedal and the works. Replaced it with a salvage yard unit since GM is so high priced. Got back brakes now. Had to adjust them up only to get the feel of a warped rotor. These are drum and doing the same thing. The drum, shoes, wheel cylinder and hardware is all new and it still vibrates hard when stopping. I replaced the drums and upgraded the shoes all still being under warrenty from OReilly's. Just drove it and doing the same thing. Shoes are oriented correctly and the hardware is installed according to service manual. Anyone been here before? Im a pretty fair mechanic having grown up in the business and having had my own shop but seems like I'm falling off wagon here with this truck....
 
When I mash in the ebrake I get the same results. I don’t get the feel through the steering wheel suggesting a warped front rotor nor can I get a feel through the brake pedal do the the violative shake when I apply the brakes. Should’ve mentioned this at first. Sorry.
 
You must log in or register to reply here.
Back
Top