2001 24v Cummins High Idle Issue

[DanTheMan]

@Tractorman, I have not had a chance to test the VP44 standalone just yet, I will try it tonight and see what happens. The worn injectors possibility is starting to look more likely, especially when revving the engine up how it starts to miss and throw a bunch of white smoke. However, I noticed a thin stream of diesel spraying out from the back of the VP44, turned out to be a loose fitting to injector #4, but I tightened it back down, as well as the other 5, and they were pretty loose oddly. No more leaking, but no change.

 

@Mopar1973Man I had no idea that a worn injector could cause high idle issues like that. I have been researching for hours on end, and the only help I have been able to receive was off of your forum, so thank you for creating such an awesome helpful forum.

I am new to the diesel realm and have already learned a tremendous amount in the short period of ownership. I will look into replacing the injectors, do you have any suggestions on what to buy for stock to start? I have seen people rave a lot about the Bosch "RV275" 40HP injectors during my research, they're relatively cheap so I can just go ahead and get those and throw them in if not fixing the problem, then just having fresh injectors.

[Mopar1973Man]

I will not suggest Bosch stock or RV275 injectors. Bosch injectors are NOT pop tested as a set so they are not balanced as a set. This will void the warranty if you opt for pop testing. 

 

I typically suggest a +50HP injectors from @dieselautopower which are pop tested as a set.

[Tractorman]

3 hours ago, Mopar1973Man said:

I will not suggest Bosch stock or RV275 injectors. Bosch injectors are NOT pop tested as a set so they are not balanced as a set.

 

Each to his own on going with stock injectors or RV275 injectors, or injectors from DAP.

 

I ran my my original injectors to 303,000 miles and replaced them with new Bosch RV275 hp injectors.  The original injectors were performing just fine - good fuel economy, good power, no smoking, smooth idle, no rpm increase at idle, easy starting, etc.  I replaced them only because I thought it was time.  A friend of mine is the original owner of a 1999 truck at 293,000 miles, still with original injectors.  His engine performance is the same as mine.  Sometime in the next year or so he will replace his injectors - probably with stock or RV275's.

 

- John

7 hours ago, DanTheMan said:

I have not had a chance to test the VP44 standalone just yet, I will try it tonight and see what happens.

 

I am very interested in hearing the results of this test.

 

.....,

 

- John

[DanTheMan]

Thank you @Mopar1973Man, I found a killer deal on a set that I’m going to try anyways, just because I don’t really want to pour a whole lot into injectors at the moment. It’ll be temporary anyway as I troubleshoot and figure things out. I do also have a cheap injector tester that’s had a lot of good reviews, they’re under $100 from Amazon, it seems to work well. I wish I could find the nozzle/pin (I think that’s what it’s called) kit for these OEM injectors, IIRC, Bosch used to sell them according to several YT videos showing folks “rebuilding” and shimming them.

 

@Tractorman, I started to do the test until yet another leak had developed at the fuel filter housing, I got it fixed last night so hoping to spend some time tonight on it.

[Mopar1973Man]

21 hours ago, Tractorman said:

I ran my my original injectors to 303,000 miles and replaced them with new Bosch RV275 hp injectors. 

 

I pulled my Bosch out at 140k miles they still ran well but won't idle at specified RPM because they popped 260 bar after 140k miles thanks to Diesel Auto Power showing me injectors do not last beyond 100k miles in normal use. The bottom end spec is 293 bar according to the Dodge FSM book. For every 10 bar drop is a 1-degree advancement. Just because it's running doesn't mean it's still in tune. My Bosch stocks didn't last very long really. My RV275s even used barely lasted one year. Now Vulcan Performance +75 HP injectors barely lasted 90k miles stilled misfiring and popped at 250 bar. Now the custom-built 7x0.010 injectors popped at 320 bar huge difference in lifespan and performance. Injectors will not last very far past 100k miles without being out of specification on pop pressure.

 

Being Bosch could release a set of injectors between 293 and 327 bar and be OK. But the performance on the engine is going to be subpar once you experienced good balanced injectors (within 2%) vs 293 to 327 bar Bosch injectors you'll never go back to a Bosch.

[DanTheMan]

So here’s the verdict….

 

i went and jumped pin 7 and the one directly above it, and I heard a click. Great, I started the engine and it idles perfectly for maybe 15 seconds, then it died and it won’t restart.
 

It took me a few days because I’ve been dealing with some major fuel issues and I had originally thought that my new lift pump went bad, turns out that the ground wire coming off of the VP 44 connector had been snapped clean in half and I assume that is what controls the lift pump, because when I reconnected it, the pump ran and the engine fired up.

 

So I am wondering, does the VP 44 tell the lift pump to run? Because I am getting absolutely nothing.

[Tractorman]

53 minutes ago, DanTheMan said:

So I am wondering, does the VP 44 tell the lift pump to run? Because I am getting absolutely nothing.

 

The ECM controls lift pump operation.  When the engine starts, I THINK the ECM gets a continuous input signal from the cam position sensor and then the ECM commands the lift pump to turn on.  I don't think a disconnected VP44 would affect that operation - but, I don't know that for sure.

 

Are you saying that your current condition is that the VP44 is jumpered, there is no lift pump operation, and the engine won't start?  If so, does the lift pump perform correctly when you re-connect the VP44?

 

There is an internal fixed displacement vane pump (Bosch calls it a feed pump) inside the VP44.  This pump will keep the engine running (even without a lift pump) unless there are sources for air to get into the fuel lines - especially between the fuel filter housing and the VP44. 

 

When you had the engine running for 15 seconds or so with the jumpered VP44, was the engine already warmed up and displaying the high idle issue prior to jumpering the VP44?

 

- John

Edited November 2 by Tractorman

[DanTheMan]

@Tractorman, The cam position sensor has been giving me issues since I’ve had the truck. Saying a signal can’t be found, but someone already replaced it, it’s still not working. Also, the tachometer hasn’t been working either. But I did the gauge cluster test and it was fine.

 

When the VP44 is unplugged, and it’s jumped, the lift pump does not engage. Conversely, when the VP44 is plugged in, the lift pump runs continuously once I try to start it, and then it’ll start running just fine.

 

The engine was not already warmed up and high idling… I totally disregarded that. I will be performing the test again right now, and will follow up in 30 minutes or so. 

[Tractorman]

There is an angular encoder inside the VP44.  It provides many features, but one feature is a redundant camshaft position sensor.  This is probably why the engine ran for 15 seconds during your test.  I am guessing that when the VP44 is reconnected, the ECM is picking up the signal from the angular encoder and consequently turns on the lift pump.

 

- John

 

[DanTheMan]

That is incredible… Interesting. Thank you for sharing that.

 

Update: The YouTube link below shows before and after. Fortunately for my VP44, it’s working fine.. Unfortunately it’s looking more and more like my ECU is bad. However this harness is a clusterf…. I will probably be trying to source or repair this harness just to make absolute certain it isn’t the harness.

 

Every freaking part for this truck is atleast 600-1000 bucks. Harness? $800.. ECU? 600-1000….

 

 

[Tractorman]

3 hours ago, DanTheMan said:

Unfortunately it’s looking more and more like my ECU is bad

 

I watched your video.  Are you confident that you ran the engine long enough in the jumpered mode to conclude the VP44 is good?  You could jumper the lift pump to perform a longer test.  In my mind I would want to be absolutely sure that the VP44 is not the problem.

 

You are definitely right about checking out your wiring mess before you condemn the ECM. 

 

Very interested to know what the solution is going to be.  Hopefully, you will succeed - I think you will.

 

- John

[DanTheMan]

You make a good point! I fired it back up with the LP hot wired, and VP unplugged, it idles like crap but it ran at proper idle speed.

 

I will be honest, I'm seriously considering a P pump swap if the ECU is shot, because ECU is easily a grand, plus another 600-900 for a used harness….
 

It is my understanding that I’d really just have to swap the timing cover for the 12v Cummins one, and obviously gear/brackets/etc. But that’s a different topic.

 

Here’s the video showing what it’s doing.

 

Side note, I’ve been ripping this thing apart to get ready to completely redo it, basically de “mad maxxing” it. Zero rust so even if I’ve got to completely redo all the electrical, I’ve got patience to do that. I actually do like automotive wiring and making my own harnesses etc; so maybe this will be a good little project for me.

Edited November 2 by DanTheMan

[Mopar1973Man]

I'd never do a P-pump swap. Horrid idea being 100% of all my member that did this swap ended up buying a newer truck or just parking it. Unreliable, too smokey and a cop magnet, or the fuel milage drops off, worst case was one member sold because he had troubles keeping it running at all. Got rid of the truck. 

 

So your willing to ditch dynamic timing for fixed timing? Then willing to lose cruise control? 

 

Talk to Auto Computer Specialist and a rebuild is better price than a p-pump swap.

[DanTheMan]

I appreciate the advice, and this truck doesn’t have cruise control. Not sure why, unless the manuals didn’t have CC? Or someone removed it.

 

I will reach out to them, I’ve been researching their page for awhile I just need to contact them.

[Mopar1973Man]

Could be fly by wire like Beast. There is no vacuum motor to pull the throttle. Manual trucks in the later series 2nd Gen had fly by wire cruise supplied by the PCM. Swapping you'll lose cruise functions. Most likely you have a bad switch on the steering wheel.

[DanTheMan]

That is interesting. I actually don’t recall seeing a cruise button on my steering wheel, but I’ll have to check tomorrow.
 

This truck is the definition of electrical issues; windshield wipers don’t work, under dash harness hacked into, clutch pedal switch bypassed (I forget it’s in gear sometimes and I reach in the cab through the window to start it, gives me a hell of a scare every time) roofing screws screwed into the roof with some random roof rack and front facing light bar… 

 

Someone replaced a ball joint but didn’t align the truck, so I drove that thing home and wore that tire out… 
 

I am beginning to wonder if I made the right choice to purchase this thing for 3k, but then I think… These trucks resale around 12-14k, so if I throw 9 to 11k into it over time to bring it back, I won’t be losing money…

 

Tomorrows project is taking the entire front end apart.. Intercooler, radiator, etc and really dig into that engine bay. I’m going to remove fenders as well, just start from scratch and completely rip that harness out and rebuild it, and while all that is getting redone, I’ll send off the ECU and hope for the best.
 

I am just concerned why it runs like crap at idle with the VP unplugged, shouldn’t it technically idle perfectly? 
 

The good news is, it isn’t a 53 block.. lol

[Mopar1973Man]

Auto Computer Specialist will rebuild wiring for you.

[DanTheMan]

Good afternoon,

 

I found a few more interesting things. I am now beginning to wonder if there’s a sensor shorting somewhere causing my 5v line to fluctuate, because my intake air temp sensor is reading wonky things. Sometimes now when I start the engine, it SOUNDS like it’s returning to normal idle when the temperature holds at 70+ degrees and not showing -40…

 

Attached you’ll see the graph of my IAT sensor. When I disconnect it entirely, it still shows -40 and fluctuates, obviously not 70+ which is close to the ambient temp right now. So it is intermittently working, just acting as if something else is shorting that line

 

Also, pardon my ignorance… but what goes on the side of the block just under the ECU to the right? Someone put a piece of cardboard loaded with black RTV to cover the hole.

 

[Mopar1973Man]

53 minutes ago, DanTheMan said:

Also, pardon my ignorance… but what goes on the side of the block just under the ECU to the right? Someone put a piece of cardboard loaded with black RTV to cover the hole.

Lift pump plate. You can use a Chevy fuel pump block off plate to cover.

 

 

54 minutes ago, DanTheMan said:

Attached you’ll see the graph of my IAT sensor. When I disconnect it entirely, it still shows -40 and fluctuates, obviously not 70+ which is close to the ambient temp right now. So it is intermittently working, just acting as if something else is shorting that line

 

IAT only controls grid heater functions mostly. Below 80°F it will advance timing about 3 to 4 degrees. Then above 80°F the ECM uses normal timing. 

[DanTheMan]

Thank you for the info, I’m going to use a piece of electrical 4x4 box blank stainless plate and cut it to size and use a cork gasket behind it. I wonder why there is a hole there if it’s meant to have the lift pump mount there..

 

I am seriously at a loss here, I’m probably going to pull the entire front end apart and really get down in there to check every inch of this harness, and really look at all connections and rewrap etc. 

 

I am now doubting ECU because it idles what seems like normal for a few seconds occasionally after unplugging and plugging in the ECM to PCM harness, I’m wondering if there’s something going on inside those connectors now.

 

This truck has been interesting to say the least.