Weird Defueling Issue, any advice can help.

[Brandon Cooper]

I have a 2000 Ram 3500 Cab & Chassis NV4500. When I got the truck, it had a P-pump converted big turbo 24v built for pulling in it, but I bought the truck and not the engine. I pulled that engine and bought a wrecked 1999 dodge 2500 that ran fine but they needed the VP44 off the engine. So I did the engine swap on this truck, pulled the p-pump motor out and put the stock 2000 engine in it. I used the ECM from the 5 speed truck I currently have and a new VP44. I put a new MAP sensor, APPS, and IAT on the engine while it was out to make things easier. The problem that I have, is that the engine goes into a "limp mode" or defuels. I know the 2000 doesn't have a limp mode. When I crank the truck, I have perfect throttle response and power, but it only lasts about 30 seconds to a minute(haven't timed it exactly) or so and then throws a P0216 code and then the truck only has about half the power. Runs great when it first starts, but then the power literally just cuts in half like you flip a switch off. The kicker is, as soon as the engine temp hits 132 with the live scanner, its like that same switch was flipped and you have instant power, to the point if you are accelerating in 2nd gear and it hits 132F the tires will bark like I just dropped the clutch. Once the engine is above 132, I can cut it off and crank it over and over and drive it anywhere with no issues at all. I could see that everyone would think vp44 computer might be a dud, but when it first starts up even cold, it has full power for the first minute or so, but as soon as it throws the 0216 code the power cuts in half. I also don't know if the ECM was tuned at some point and is defueling due to some random parameter in the tune. It's just weird how the power comes back at exactly the same temperature every time and its instant power. The truck doesn't stutter, smoke, or anything, just has half power till that temp. Lift pump is a Fass Titanium 220 with the 17lb spring and has a constant fuel pressure of 20PSI (gonna cut the spring and get that down a few lbs later.

[Mopar1973Man]

Any other error codes present too?

 

P0216 code will create timing issues. Depending on if it the timing is full retard or full advanced. I've had my last injection pump seize the timing piston at full retard and power is greatly reduced and hard knocking. Full retard will still run but the power is greatly reduced from the lack of timing. 

 

 

As stated by the Dodge FSM for the P0216 code.

Quote

Fuel injection pump operation is monitored with ignition on. DTC will set when the engine speed is greater than 300 RPM, fuel command 5 mm3/str and timing command within a certain window.

Not uncommon for a timing piston to seize up and stick. This is typically from low lubricity fuels and excessive use of cetane boosters and anti-gel. This is where the 2 cycle oil theory comes from.

 

11 hours ago, Brandon Cooper said:

I also don't know if the ECM was tuned at some point and is defueling due to some random parameter in the tune.

It wouldn't hurt to send to Auto Computer Specialist and have it reflashed to stock values to verify. 

[Brandon Cooper]

Thanks for the reply. There are no other codes present except for the one saying my grid heater is not connected, but it’s not on the truck, so I understand that. So if I clear the codes on the truck and then start it cold, it will run idle fine and throw no codes. If I try to drive it when it is cold it will run great until I get out of my driveway and normally hit third or 4th gear and then the power will instantly drop to around half power and stay that way till it hits 132F and instantly hit full power. It isn’t running bad or knocking, or really doing anything weird, just half power till 132 on the dot. Is there a chance the ECM could have been programmed with a tuner previously to defuel until it hits a certain temperature or certain parameter that I do not know about? 

[Tractorman]

Just shooting in the dark here, but what about using a resistor (if possible) in the coolant temperature circuit to fool the ECM into thinking the coolant is above 132° when you start the engine.  Might help to confirm what you are already thinking.

 

It is a rather odd situation that you have here.  Once the ECM detects a timing issue, the ECM is de-rating the engine power.  This is normal.  Just odd that it happens at a very specific coolant temperature.

 

- John

Edited February 9, 2023 by Tractorman

[Brandon Cooper]

I’ll look into that trying that next, that’s what confuses me the most. I’ve done it every single day for the last couple weeks when I get home. It’s that exact temperature every time. Even if it’s running fine and above that temp, I can turn the truck off, let it get to 116 or so on the coolant temp, it will crank, run fine for the 30 secs or so, and the start defueling till it hits 132. I’ve calibrated the apps, tried the fooling trick on the iat just to cross those off the line. I have a spare stock ECM, it’s off an 1999 automatic truck, but I know it works, I’m gonna try that this evening or tomorrow evening just to see if it makes a difference. If it does, I’ll flash my ECM with a smarty and hopefully fix something, lol. 

I’m using the OBDlink mx+ to monitor the data. 

[Tractorman]

Sounds like you are on the right path.  Let us know what you find.

 

- John

[Brandon Cooper]

Well... No luck. I tried the factory ECM and it did the exact same thing. The only other thing I can try is to swap the PCM with a factory one that I have, I really don't think that there is anything that the PCM could be causing. Does anyone know where to start with resistors to try and trick the coolant temp/engine temp to be above 132F? I wouldn't want it to be a permanent solution, but I'd like to at least test that to see if the truck operates normally. Once again, this truck had a P-Pump 01-02 engine in it, so half of the wires were not hooked up or being used at all. There's a chance I did something wrong on the install or missed a wire somewhere. I'm trying to exhaust every effort before ordering a VP44. I don't mind spending the money on a VP44 if it will fix it, but seeing as I did the engine swap with a bunch of new sensors and parts, I just want to make sure that I didn't miss anything....and yes I did clean and check all grounds, even added a few extra ones just to be on the safe side. Thank yall again for the responses!

[Mopar1973Man]

4 hours ago, Brandon Cooper said:

Does anyone know where to start with resistors to try and trick the coolant temp/engine temp to be above 132F? I wouldn't want it to be a permanent solution, but I'd like to at least test that to see if the truck operates normally.

 

I think 56k ohm is 123*F if I recall correctly. So going higher in resistance from there should get you closer to that temp.

[Brandon Cooper]

Thank you! I just ordered a multi pack of resistors 

[Mopar1973Man]

Basically in the nutshell you have +5V signal from the ECM and the thermistor will vary the resistance the higher the voltage the higher in temperature. Lower resistance would give more ground lowering the voltage making the temperature read lower.

[Doubletrouble]

 If his efforts to "fool" the ecm with resistors in the twmp sensor circuit does work then great, but why would the ecm vary timing so much below that temp?

[Brandon Cooper]

6 minutes ago, Doubletrouble said:

 If his efforts to "fool" the ecm with resistors in the twmp sensor circuit does work then great, but why would the ecm vary timing so much below that temp?

I believe the problem is the VP44. It was a brand new pump that was put on another truck that ended up having way bigger issues. I know for sure it worked fine a year or so ago, but it sat on a shelf in the garage for a year. I’m pretty sure it’s the timing piston, but I don’t know. I don’t know what fooling the engine coolant temp will prove, but I’d like to see if it works, cause the truck has plenty of power and runs perfect when it first cranks and when it’s above that temp. Pretty much, this is a brand new build for me, new transmission, clutch, half the electronics. I want to drive it a little and get a list of all parts I need to make it a reliable truck for some road trips with my camper. If I can fool the truck into running right as far as the pump goes, that’s just another part I need to order. 

[LorenS]

On 2/8/2023 at 9:26 PM, Brandon Cooper said:

It's just weird how the power comes back at exactly the same temperature every time and its instant power.

This sure sounds like tune to me. Like someone set it up so at startup it runs one way (for whatever reason) then cuts power until the engine is up to temp.

[Brandon Cooper]

Just now, LorenS said:

This sure sounds like tune to me. Like someone set it up so at startup it runs one way (for whatever reason) then cuts power until the engine is up to temp.

I thought for sure the same thing, I put a stock ECM on it yesterday and tried it out, but it had the same issue. 

[LorenS]

4 minutes ago, Brandon Cooper said:

I thought for sure the same thing, I put a stock ECM on it yesterday and tried it out, but it had the same issue. 

That's what I get for posting before reading the whole thread!

This is a real mystery. I look forward to reading your updates on the matter.

[Brandon Cooper]

Thanks for the reply though, this Cummins is a whole new learning experience for me. Any help or suggestion is a good suggestion for me! 

[Mopar1973Man]

Easiest either send the ECM out to be checked by Auto Computer Specialist or heading to a dealer having it flash to true stock.

[Great work!]

These trucks add a lot of timing during warm up and extended idling.  I think it reduces the white smoke and haze. Maybe 132F is where the ECU starts pulling back the timing and your VP can match the lower timing that is being commanded. What is your fuel pressure after the filter. The VP can't advance much if it is starving for fuel.

Try some two cycle oil.

[Tractorman]

@Great work!, in his first post, @Brandon Cooperstated, "Lift pump is a Fass Titanium 220 with the 17lb spring and has a constant fuel pressure of 20PSI (gonna cut the spring and get that down a few lbs later." 

 

16 hours ago, Brandon Cooper said:

I believe the problem is the VP44. It was a brand new pump that was put on another truck that ended up having way bigger issues. I know for sure it worked fine a year or so ago, but it sat on a shelf in the garage for a year.

 

Maybe the VP44 (setting on a garage shelf for a year) has some internal corrosion (or growth) resulting in a sticking timing piston, or a sticking cam ring. 

 

When the engine is shut off, the timing piston moves the cam ring to the most retarded position by default (what I interpret from the Bosch VP44 manual).  So, it stands to reason (as @Great work!mentioned) that the timing advance requested at startup couldn't be met, consequently 30 seconds or so later code P0216 is set and the engine is de-rated until its gets closer to operating temperature.

 

So, maybe some extra lube could help, certainly couldn't hurt.

 

- John

[Brandon Cooper]

So for anyone wondering, 2.2kohm resistor sets the Engine temp at 143F so I guess it ohms out about the same as the IAT sensor.  This trick didn't work, lol. So the actual engine temp getting to 132 is causing the defueling to go away. 132F temp reading has nothing to do with it I guess. This leads me to believe that it is something mechanical and nothing to do with the electronics, so I guess I'll drive it for a while using a little extra 2 stroke and lucas fuel treatment and see if it clears up some, if not, I'll just have to order a VP44 and pray thats the problem, lol.