I have been restoring a flood truck since last December, the water line was a couple inches into the cab. The vehicle runs and drives, I have since gotten a salvage restored title and it is my daily driver. 
 

Through all the many fixes on my vehicle I have had some creeping intermittent boost drop/dead pedal/bucking surging mostly when moving from lower speeds. When I am heavy on the accelerator it seems to be much less apparent.

 

I have put at least 200 hours into the truck this year and have had many components taken out and reattached so anything is fair game when it comes to explaining the issues I am dealing with.

 

The main question I have, and the issue that I am trying to solve is the loss of power on application of the accelerator. What is causing this? Is my VP44 dying, do I have alternator noise, do I have bad grounds or power supply issues? Do I have a dying APPS?

 

I have a thread running on turbodieselregister cataloguing a good chunk of the work I have done on this vehicle, but I will sum it up here because I don’t know if linking to other forums is acceptable.

 

This truck has the following aftermarket modifications, 

 

FASS Signature series lift pump (previous owner)

Edge Juice w/ Attitude (previous owner)

Airdog Draw Straw kit (I did this, to fix the fuel supply issues caused by having the in-tank fuel pump still in line with the lift pump)

Jasper Transmission w/ “low stall triple clutch torque converter” (previous owner)

Some unknown suspension lift with kyb struts (previous owner)

 

Projects I have tackled in restoring the truck:

Rebuilt starter (this was the main thing I had to do get this truck running)

Rebuilt hvac box and installed Geno’s garage cabin fresh filter kit.

Removed all carpet and sound deadening material

Fuel issues (air in fuel line, fuel restrictions From in tank fuel sender)

Replaced all u joints

Replaced ball joints at knuckles

Replaced 

Vacuum line leaks

Cleaned front axle tube and carrier housing

 

I currently have the batteries out and I am navigating some of the wiring with a focus on grounding points. I am using electrical cleaner on all the dirty battery harness elements, it’s not EXCESSIVELY corroded anywhere but there are some spots that don’t look great. I’ve had to do some cutting of wiring at terminal connectors to expose clean copper (in the past). 
 

There is a single ground wire that is attached to the firewall above the trans dipstick that I can’t seem to recall where it was attached to before I did the work to this area as part of removing the hvac box.
 

I don’t know if this disconnected ground is contributing to my pedal issues. Is this a PCM case ground of some type?

 

Did the issues with my lift pump and fuel sender cause the start of VP44 failure?

 

 

 

Edited June 29, 20204 yr by diesel_rob

Have check3d formany trouble codes? They might help guide us. If it was a flood I would check electrical connections and the battery cables. All your problems could be hardware or just electrical. These truck are very picky on the DC power you feed them. I you have excessive ac voltage they will do crazy things. I have been thru everything you just not all at once. With exception of a failed VP the rest of mine were all electrical.

I haven't used the multimeter on the truck yet, other than when I was having issues with the previous set of batteries. There were codes when I was initially starting the truck, the fuel pump circuit was throwing codes, but that's it. I currently have the E-brake light on and the one next to it on. The batteries are out so i don't remember which other indicator is illuminated but it's not major. I haven't looked at the codes recently but my Edge Attitude has a maintenance code readout so I can easily check later today.

 

I busted the terminal that connects to the heater grid wires at the positive terminal of the driver's side battery so I have to fix that, and locate where the firewall ground goes then I will start everything up again and check.

 

Reading some of the posts on here, and checking the wiring diagrams has me wanting to test the AC/DC voltage across my alternator.

Edited June 29, 20204 yr by diesel_rob

1 hour ago, diesel_rob said:

Is this a PCM case ground of some type?

That is exactly what it is.  Attach it to the PCM by way of a case mounting screw.

Remove the EDGE nd see how it drives.

Check your alternator AC voltage should be less than 0.03 volts at idle with no load.  

Do a W-T ground mod and PCM ground wire fix along with a protective fuse for the alternator/PCM.

Edited June 29, 20204 yr by IBMobile

10 minutes ago, IBMobile said:

That is exactly what it is.  Attach it to the PCM by way of a case mounting screw.

Remove the EDGE nd see how it drives.

Check your alternator AC voltage should be less than 0.03 volts at idle with no load.  

Do a W-T ground mod and PCM ground wire fix along with a protective fuse for the alternator/PCM.

Excellent reply thank you for all the info.

 

I just read the W-T ground mod earlier today, I will do it as soon as possible.

 

What type of fuse for the alternator/PCM? Is there a write-up somewhere with more detail on this?

It is in then articles section under 2nd gen 24v, electrical. 

Very important to make sure the ECM isn't powering the lift pump. The factory lift pump power lead should only be a trigger wire to activate a relay then the lift pump runs off the batteries. This is important because excess load from the lift pump can fry an ECM. If your experiencing electrical problems now this is an important precaution.

 

Also there is an important ground for the power dist. box. It's down low on the fender in front of the driver side battery. Sometimes hidden by the wire harness running over the top of it, you can't see it right away, you have to move the small area of wire harness to see it. I kept looking and looking on both my 2nd gens. finally found it by feel and moving the wires covering it.