1995 K2500 - $1k Facebook Find

[Husker6.5]

All three sensors in the TPPS receive a 5VDC reference signal from the ECM/PCM and the resistance depending on Accelerator Pedal position returns a less than 5VDC signal back to the ECM/PCM that then uses that signal to determine the amount of "throttle" the pedal is demanding and then sends a corresponding signal to the PMD/FSD for the IP to deliver the demanded amount of fuel delivery for the amount of "go" (rpm) demanded.

 

[Husker6.5]

The TPPS is essentially three rheostats (variable resistors) mounted on a common shaft that is actuated by Accelerator Pedal movement. When they fail, is is because one, or more, of those rheostats has had either the windings wear through and an open occurs (no signal past a certain point of pedal travel), the 'wiper' has failed mechanically and no longer moves/makes contact with the windings or there is a build up of crud/oxidation that prevents the wiper from making good electrical contact with the winding, which would give that particular rheostat false/no signal to the ECM/PCM in relation to the other two rheostats in the TPPS.

 

[Husker6.5]

Thus your error codes showing two of the TPPS's rheostats reading 'High' and one 'Low' according to the OBD-I codes you posted earlier.

Out of curiosity, did your Facebook find have, or show evidence of previously having, a trailer brake controller or alarm/remote start on it? Reason why I ask is that in removing the controller or alarm/remote start, PO may have inadvertently disconnected the plug into the TPPS thinking that it was part of the controller or alarm/remote start's wiring harness off of the brake circuit (ask me how I know).

 

[Husker6.5]

Could be as simple as plug the harness back into the TPPS and she starts back up and runs! Yeah, right, we all should be so lucky!

 

[Husker6.5]

No, I didn't do that to my 6.5, had a friend with a drive by wire injected gasser who removed a non-functioning remote start/alarm system and then his truck wouldn't start. An hour with a cheap OBD-II scanner, some deductive reasoning and then cramming my fat self laying on my back into the driver's foot well to plug the harness back into the TPPS and voila, his truck started and ran!

 

[treegump]

It is always best to charge and then try to start. The elevated volts and amps from booster chargers have been doing damage for years. Sometimes the damage caused doesn't show up for months or even years

This is actually the first I've heard of booster chargers causing damage - but i suppose that makes sense.

 

[treegump]

My apologies - I meant the TPPS in my earlier posts. I didn't know there was a TPS on the injection pump.

I knew that the TPPS were known to fail because the 96 that I owned in 2009(?) had a pedal issue. I had saved the old pedal, because I couldn't recall if the pedal fixed the problem, or if that was about the time my PMD was going bad.

Anyhow - I purchased another pedal/TPPS on ebay for under $100 and that didn't change things (didn't have a code reader, so didn't know it at that time), but I also haven't changed the injection pump harness either.

I'll check the pins on the harness so as not to affect the new TPPS.

 

[treegump]

It'd be nice if I could see if it runs before the Coronavirus scare is over. Treadwright tires is having a sale and if this truck runs, it'll need tires!

 

[ak diesel driver]

FYI there is not a separate TPS on the IP. While tpps might be more technically correct I'm used to hearing it called an APP. They all do pretty much the same thing, tell the computer what the throttle position is.

 

[Will L.]

I should have caught it and didn’t. When you said tps- I thought db2 because that is the world i choose to live in. Sorry

 

[Husker6.5]

"NEW" off of FleaBay doesn't neccessarily mean it is either good if actually new, or if it is even new.

You can test each rheostat of the TPPS module with a basic digital VOM for its resistance from 'idle' through 'WOT' off of the truck. You may also have continuity/resistance issues between the TPPS harness plug and the ECM/PCM, too. As far as a new TPPS module or Accelerator Pedal assembly with module goes. I would only trust new or NOS OEM GM/ACDelco/Delphi and certainly nothing of unknown origins of manufacture or Chinese. Just MHO.

Also, battery chargers, especially in Start or Boost mode, running with Key On supply way above normal battery voltage and can fry electronics and WILL fry out 9G and 11G glow plugs if you cycle them with a battery charger in Boost or Start mode attached, it can be supplying well over 15VDC in that mode.

 

[Husker6.5]

TPS is '93 and earlier DB2 pump with an actual throttle cable from the accelerator pedal to the IP. The TPS's main function is to give throttle position to the 4L80E for shift points based on engine demand. What the TV cable does on the old 700R4's.

TPPS (or APP) is on '94 and up DS4-equipped that use an ECM/PCM to control the engine.

Hummers are an exception to the rule, right @Will L. ?

 

[Will L.]

Yes, hummers are a couple years behind pickups. Db2 had no turbo up through 95.
96 and up was ds4 with turbo.

the hvac systems are also like that where the years are different. They style with the square buttons in the pic are used up to 95 that I know of. The other style with 3 dials and 2 buttons is in 1997.5 and newer - idk if they ever changed after that. I dont have a pic of the 97 (and maybe 96?) where it had the dials but not the buttons.
Afaik all the hummers have same fan motor relay as trucks that the connector goes weak and burns the relays.

back to the TPS- all the 92-95 hummers have interchangeable tps and other engine parts with the 93 and older trucks.

idk the transmission years for trucks to hummers. Thats too much for my little brain

 

[treegump]

Passenger side valve cover soaked in oil

Driver's side valve cover bone dry

Dipstick shows about 2 quarts heavy on oil.

What are the chances the oil pushed past the pcv valve?

Is it possible to chance valve covers gaskets without removing the intake manifold? I'd rather see if it runs before sinking much more money into it.

 

[treegump]

Should the fuel filter housing drain be plugged? Or... Can I use the rest of the clear tube and reroute the drain to an easier access place?

Also, when I replaced the return line off the injection pump to the fuel line the fuel was shooting out!! Haha

 

[Will L.]

2 quarts overfull, that is probably why there is oil everywhere.
drain the level to proper amount. Just wash the engine and wait on the valve cover gasket.
You have to undo injector lines to remove valve cover. I say wait until it has a few miles on it because you might find more oil leaks after a bit. Could be it isn’t leaking bad, just crazy over pressurized from too much oil.

yes, cdr (pcv for this engine) is probably soaked along with your intake to the turbo.

I wouldn’t use the clear line on there too long because when the return loop leaks in 1/4”, you can easily see it by accident with the hood open.


when the drain line leaks it soaks the whole underside of the truck before you notice.
also the clear line should be 1/4” and the drain line is 5/16. Yes you NEED a drain line to a valve- thats how you get the water out if there. Locate it any where you find convenient, so long as it is below the ffm the entire way. Any uphill line can allow the water to build from that poi

 

[btfarm]

Are you sure the oil isn't half diesel fuel?

 

[treegump]

Are you sure the oil isn't half diesel fuel?

I am not sure yet. But it's awfully dark and thick to have fuel in it, I think.

 

[jrsavoie]

Are you sure the oil isn't half diesel fuel?

It's always good to have oil tested.

 

[Husker6.5]

Diesel in the oil is bad news. It indicates leaking injector(s) that wash down the oil off the cylinder wall(s) making for dry contact between the piston rings and cylinder on start up and excessive wear that leads to more blow by, really dirty, contaminated oil, even more blow by and eventually lowering compression more and more on that cylinder. Not to mention the damage that can/will be done to the rod, main and cam bearings and other wear surfaces like cam lobes, lifters/bores and timing set, too from diesel contamination.

But that is my worst case scenario. My "best educated guess" is that the overfill condition it due to the direct actions of the PO - the beastie was 'using oil' at an accelerated rate for whatever reason (leaks/burning) and it was overfilled to prevent running too low/out, below the ADD/or off the dipstick - to prevent catastrophic engine failure. Just MHO.

But yes, get it back down to normal 'Full' level and do a quick 'nose test' for diesel in the oil at the least, before proceeding further toward getting it started.

Remember, you need three things to get a diesel to start/run: Fuel, air and enough compression to heat the air hot enough to ignite the fuel (with or w/o the glow plug system while running, with the GP system to start from cold).

It may be time to think about an individual cylinder compression and leakdown test to see if lack of compression is the culprit for the lack of start/run for this beastie after verifying that you are indeed getting fuel to/out of each injector and that there is not a mouse nest anywhere in the intake from airbox to lower intake manifold (LOL) blocking airflow.