ECM or something else?

[Ihasfip]

Hi guys. New here. Been around these things for a long time, but don't know Cummins like you guys do. I come from the rockcrawling world, and know a lot about LS stuff, and worked on lots of different diesels over the years, but not lots of cummins stuff beyond 12v.  I need some help. Have a few issues on this cobbled together hooptie. 

 

Bought this truck as a tow rig, as my Bil's buggy will fit on the rear and it can tow my crawler behind it. Supposedly it was running and driving and then wouldn't start one morning. Tried and tried to get it but couldn't. Had some "diesel mechanic" diagnose it as a bad VP44 due to codes etc. Removed it and then he couldnt afford to fix it so listed it.

I bought it. Put a new Thoroughbred VP44 on it. New RV275s. New injector tube seals. Resealed oil pan, timing cover, tappet cover. Sumped the fuel tank. Deleted the metal return line and T from the VP44, and replaced with AN lines and Banjos to AN. Bought big nice battery cable kit with all the engine/chassis grounds etc. 2 new 31-5 18wheeler/tractor batteries. And a new starter. Cracked open injectors 1 - 3- 5 and got it to start up. Closed injector lines. Ran great. But couldnt get them to quit seeping after you drove it. And it would get progressively harder to start after it sat. Bought a new set of aftermarket lines (not the cheap ones, but ones with good reviews) and they sucked and didnt fit at all. Ended up pulling a set off another running engine I have here and put them on. I have got all but 1 injector line to quit leaking. It will weep a little after you run it and turn it off. Enough to get damp on the head around the line. Ive held my mouth every which way, assembled him in every different order, and this time with this one just barely weeping is best I have been able to get. I get 17 psi key on engine off. And 14i-15sh at idle running. Air dog runs constant with key on but is interrupted during starting as I read was the correct way to do it. 

 

Another piece to the puzzle is the tach only works for first 5 seconds when you start it and then it goes away. But I can plug in my ancient snap on scanner and see RPM, codes etc. I found out when doing that, that the vin in the ECM shows to be a 2001 model with a manual. I have another 98.5 truck and I swapped the ECM to this truck and the vin in it is a different 2001 with an auto. Truck runs same with both of them. Just one has codes for trans. I changed crank sensor behind the starter (with an oreilly one, not a cummins...I know I know...but don't even think its bad). Also sometimes the WTS light is delayed or doesn't come on, which I believe points to a dying ecm. So reflashing to the correct tune for this truck likely wouldn't even fix it completely. So is a repaired ecm with correct flash the fix?

 

Heres where it gets more interesting. You can park it overnight. Try and start it and crank and crank and nada. Doesnt matter if flat ground/up hill or down. But you can roll it like 10 ft and pop the clutch and itll fire right up and run smoothly. Not like it has a bunch of air in the lines. It also will start up with the starter fine after that. But the longer it sits after you turn it off the harder it is to start. I cannot find any leaks what so ever except the one weeping first injector line. I have put air to return side and get no wet spots or anything at any of the connections and itll hold 20 psi no problem.  Is this one weeping injector line enough to make it not start after a few hours of sitting? I have an old tractor that leaks from about everywhere and it starts almost as fast as a cummins normally does... 

 

So couple different issues, just not sure what is causing what. So thats where I am at. I have a buddy and his uncle that have like 40 old cummins trucks and such around his place. His uncle been obsessed with em since the 80s and has parts coming out his ears. And they are stumped too. 

 

He is getting his breakout box today and checking the vp44, it is brand new, but...it is a vp44.

 

Sorry for such a huge first post. Thanks for any help you can give. 

[Tractorman]

1 hour ago, Ihasfip said:

Heres where it gets more interesting. You can park it overnight. Try and start it and crank and crank and nada. Doesnt matter if flat ground/up hill or down. But you can roll it like 10 ft and pop the clutch and itll fire right up and run smoothly.

 

Have you push-started the truck with the same results BEFORE you tried starting the engine with the starting motor?  If not, the engine may have coincidentally been ready to start during the push-start.

 

After a night of setting, try doing a push-start without use of the starter beforehand.  If the engine starts right away, this could indicate that there is an excessive voltage drop to the ECM or to the VP44 solenoid valve when the starter motor is cranking the engine, consequently, no fuel.  If the engine still doesn't start right away, then this is not likely a cause. 

 

As far as the one injector line that is leaking, it is not unusual a line to leak at that connection point with new crossover tubes.  Each injector line seals as a metal to metal sealing connection at the crossover tube.  The new crossover tubes may have a slightly different surface sealing area shape than the old crossover tubes.  Try loosening nearby clamps and then loosen the offending injector fitting.  As you are re-tightening the nut, try rotating the line back and forth slightly while maintaining some friction using the nut.  The objective is to grind the two mating surfaces together to smooth out any surface irregularities.  Don't be aggressive. 

 

- John

Edited January 20 by Tractorman

[Ihasfip]

57 minutes ago, Tractorman said:

 

Have you push started the truck with the same results BEFORE you tried starting the engine with the starting motor?  If not, the engine may have coincidentally been ready to start during the push-start.

 

After a night of setting, try doing a push-start without use of the starter beforehand.  If the engine starts right away, this could indicate that there is an excessive voltage drop to the VP44 solenoid valve when the starter motor is cranking the engine, consequently, no fuel.  If the engine still doesn't start right away, then this is not likely a cause. 

 

As far as the one injector line that is leaking, it is not unusual a line to leak at that connection point with new crossover tubes.  Each injector line seals as a metal to metal sealing connection at the crossover tube.  The new crossover tubes may have a slightly different surface sealing area shape than the old crossover tubes.  Try loosening nearby clamps and then loosen the offending injector fitting.  As you are re-tightening the nut, try rotating the line back and forth slightly while maintaining some friction using the nut.  The objective is to grind the two mating surfaces together to smooth out any surface irregularities.  Don't be aggressive. 

 

- John

Honestly been messing with it for couple weeks now, I am pretty certain I have roll started without trying to crank it first, just with the key on and the airdog running. I know I have tried starting with airdog on, air dog on for 25 secs and then off like factory or whatever. Makes no difference. I will find out tomorrow. Assuming snowpocalypse 2025 doesnt prevent me from messing with it tomorrow. 

 

As for the lines, I didnt change the injector tubes, and still couldnt get the original set to quit leaking. This set off the other truck I have, I got them down to just the one barely weeping after driving for a long time.

 

One injector line barely leaking like that isnt enough to make it not start that quickly is it?

 

 

D

 

Edited January 20 by Ihasfip

[Tractorman]

When I am troubleshooting difficult issues, I try to eliminate things that may contribute making troubleshooting harder.  For example:  if your fuel tank is half full or less, then I would go fill the fuel tank.  If the engine now starts easier, then you know that fuel has been draining back and drawing air into the system.  The fuel can still drain back, just not as easily with a full tank.

 

Since this is a new to you truck, have you checked to see if there are signs of fuel leaking on the banjo fitting and T-fitting on the back of the head?  A leak here will definitely cause hard starts, especially if the nose of the truck is parked up hill.

 

3 hours ago, Ihasfip said:

As for the lines, I didnt change the injector tubes

 

The used tubes will still be in a different rotational position than when you removed them.  Did you try my suggestion?

 

- John

[Mopar1973Man]

So, with your loss of prime, you will have to look at possibly replacing the injector crossover tube. The other thing is did you torque the injectors first or the crossover tubes first?

 

As for the tach. You will need to flash the ECM and PCM with the correct software to match and VIN numbers have to match too. There is dozens of versions of software which could be your problem being no VIN numbers match between the PCM and ECM. Remember the PCM is the primary controller so it can disable communication with the ECM because of software errors. 

[Ihasfip]

On 1/20/2025 at 7:47 PM, Tractorman said:

When I am troubleshooting difficult issues, I try to eliminate things that may contribute making troubleshooting harder.  For example:  if your fuel tank is half full or less, then I would go fill the fuel tank.  If the engine now starts easier, then you know that fuel has been draining back and drawing air into the system.  The fuel can still drain back, just not as easily with a full tank.

 

Since this is a new to you truck, have you checked to see if there are signs of fuel leaking on the banjo fitting and T-fitting on the back of the head?  A leak here will definitely cause hard starts, especially if the nose of the truck is parked up hill.

 

 

The used tubes will still be in a different rotational position than when you removed them.  Did you try my suggestion?

 

- John

Yea, I get that. I've been working on cars a long time. I have spent a lot of time with this, but some of it is unfamiliar to me.

 

I said I deleted the factory metal return line off the back of the head/from IP. I replaced it with AN lines, using banjo bolts. T's in the same location and has a new line running to the factory return port on the fuel tank. I am 99% sure these are not leaking. I make a fitting with a tire valve and put 20 psi to return side and it held no problem. Also doesn't matter if truck is sitting up hill, or down hill. Hot or cold outside. If the truck hasnt been started anytime recently about the only way itll fire usually is push starting it. 

 

We also verified yesterday that even when 20 degrees out (without previously trying to start it) that we could roll it like 10 ft and pop clutch and it fires right up and runs smooth (well smooth for 20 degrees out, but sounds runs just like the other dozen 24vs around here when it starts).

 

I am 99% sure its an issue with this PCM showing it is for a 2001 model. When I plug scan tool into another 98.5-99 model I see CKP RPM and ECM RPM. And they register both. When I plug scan tool into my truck and say its a 98 its says no its a 2001, and has a vin from a 2001 in it. It also doesnt even list CKP RPM, only INJPUM RPM and ECM RPM. Also registers no RPM on tach whilst trying to crank on top of the tach only working for 5 secs when the truck first starts and then quits. But it ALSO has a delayed WTS light, or intermittent lack thereof. Leads me to believe not only is it the wrong version of flash on the ECM, but that is also has a dying ECM possibly. Thinking I should pull it and send it to be repaired, and reflashed and go from there. 

 

As for the leaking lines. All have quit leaking except for the one. It might have even stopped, but it was cold and the truck currently isn't near an air compressor to be able to spray it off with brake cleaner and air. Like I said, it was just weeping. Only apparent around the fitting.   

 

I think I will reach out to the guys yall recommend.

 

Thanks

23 minutes ago, Mopar1973Man said:

So, with your loss of prime, you will have to look at possibly replacing the injector crossover tube. The other thing is did you torque the injectors first or the crossover tubes first?

 

As for the tach. You will need to flash the ECM and PCM with the correct software to match and VIN numbers have to match too. There is dozens of versions of software which could be your problem being no VIN numbers match between the PCM and ECM. Remember the PCM is the primary controller so it can disable communication with the ECM because of software errors. 

10-4 -Im just not sure its ACTUALLY losing prime. Doesnt exhibit symptoms of losing prime.

 

But I was going to pull the ECM and PCM and send them off to your recommended guys and have them check/flash them and go from there. At least I will know that isn't part of the issue at that point. Just yesterday was able to confirm for sure that it was showing different vins, as I didnt have another running truck where I was to compare, but compared several different ones yesterday to see. 

 

Checked all the ecms we had laying around shop and no 98.5-99 they were all like 00+ newer. 

 

Thanks 

[Mopar1973Man]

26 minutes ago, Ihasfip said:

10-4 -Im just not sure its ACTUALLY losing prime. Doesnt exhibit symptoms of losing prime.

 

Another way is the lift pump pressure constant or hang low and jump high? If the low and high problem that is a air bubble being pushed up the line to the injection pump. Currently fighting the same issue on my 2006 Cummins with long crank times but 3rd Gen has a clue with the grid heater light coming on and chiming either 5 or 10 times showing fuel rail issues. 2nd Gen's just any long cranking is loss of prime on the fuel system.

 

 

[Ihasfip]

39 minutes ago, Mopar1973Man said:

Another way is the lift pump pressure constant or hang low and jump high? If the low and high problem that is a air bubble being pushed up the line to the injection pump. Currently fighting the same issue on my 2006 Cummins with long crank times but 3rd Gen has a clue with the grid heater light coming on and chiming either 5 or 10 times showing fuel rail issues. 2nd Gen's just any long cranking is loss of prime on the fuel system.

 

 

No. FP is 17 key on engine off. Running is 14-15 at idle. 13-14 at WOT.  Pressure is steady. 

 

I almost bet as soon as we get the correct ecm in it will fire right up. 

Thanks

[Tractorman]

8 hours ago, Ihasfip said:

I said I deleted the factory metal return line off the back of the head/from IP. I replaced it with AN lines, using banjo bolts.

 

Sorry, I missed that in your original post. 

 

8 hours ago, Ihasfip said:

We also verified yesterday that even when 20 degrees out (without previously trying to start it) that we could roll it like 10 ft and pop clutch and it fires right up and runs smooth

 

That tells me that you are NOT having a fuel or air in the fuel issue, which is what you are already thinking. 

 

So, you could very well have an issue with the ECM / PCM as you stated, or you could be getting a severe voltage drop at the PCM, ECM, or PSG on the VP44 while the starter is cranking.  I would think that a code would be set, but not necessarily.

 

- John

 

[Royal Squire]

Could this be a starter problem since it starts so easily when rolling and popping clutch ?

[Ihasfip]

13 hours ago, Royal Squire said:

Could this be a starter problem since it starts so easily when rolling and popping clutch ?

No, it spins over as fast as any other cummins, maybe even faster. The entire starting/battery system is all brand new. I am 99% sure its ecm/pcm related at this point. Will update once I confirm.

Thanks 

[Ihasfip]

Ok so update. Sent ECM and PCM to Automotive Specialist guys. The ECM was all boogered up and had a bunch of issues. They fixed them and reprogrammed the ECM. The PCM is from the wrong year. I am uncertain what they did, if anything to it. 

 

After putting it on the truck, same issue. No start. But atleast now I see CKP RPM and CPS RPM in my scan tool like other 98.5-99 trucks I have scanned. So heading in right direction. On my old Snapon Scanner thats slow to poll, it only shows 9rpm on CKP vs 13-1400 on cps I think it said while cranking. 

 

So I am a little torn right now.

 

The timing cover on truck says 01 production date, the truck is a 98.5. Thought maybe the guy before I had it put a 01 engine/ecm/pcm in it with the 98.5 harness. He told me the truck ran fine/started fine before the IP died. Did appear to have been sitting long, and didnt look like anyone had changed ecm/pcm in a very long time. Also after I changed the IP I could usually get it to start by cracking injector lines and hitting key, or roll starting it very easily. Not sure why just barely cracking an injector line or 2 would make it instantly pop off, but assuming its same reason it will if you roll start it. Can crank till batteries go dead and it wont start. Roll it forward few feet and itll start and run perfect. 

 

I did change the CKP sensor with a cheap parts store one somewhere in the process of trying to figure all this out, so I suppose its possible the sensor is no good. I am going to verify 5v and ground to sensor, and if it checks out, Ill make sure there is a tone ring on the crank. I know there wasn't one loose or sitting in the oil pan, because I changed the gasket, but I wasn't particularly looking for the tone ring at the time, and I dont recall if there was one or not. 

 

Do all the 24v blocks have a hole behind the starter for a ckp sensor even if it doesnt have tone ring etc?Like 00 has a plug in the hole, and 01-02 have no hole at all or? Trying to figure out what we've got going on. Tired of messing with this thing. 

TIA 

[Mace]

My 01 has the hole but there is a plug in it.

[Mopar1973Man]

Might read here for more info...

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/swapping-vp44-cummins-engine-between-985-00-01-02-r429/?do=getNewComment&d=4&id=429