Not your average vp44 question

[Dieselinmyblood]

First time posting but I’ve reading and gaining from this site for quite some time . Thus the title of this post. I’m really struggling with my truck and I’ve read just as much as I possibly can. My background (just so no one is afraid to through anything complicated at me) is 10 years of diagnosing and repairing medium and heavy duty trucks and now about to reach my 5th year of being a shop manager.

 

Sorry this might be long winded. My 99 is a fairly new purchase and it wasn’t acting up when I got but now it’s getting terrible.

 

The two main issues are : when I first leave my house and start driving it will (only once or twice) loose power but it’s not the same dead pedal every one else describes. The truck doesn’t die and will rev up in response to throttle input. It’s just very low power and slow to respond. After it works that hiccup out I’m fine for a bit but eventually the truck does start dying . And yet again it’s nothing like I’ve read about. It’s a standard so with it still in gear and rolling down the highway, literally all I have to do is cycle the key and it’s rolling on full power like nothing happened. It has never not come back to life and when it happens somewhere where I do have to restart it, it fires instantly back up. Everything I’ve read says it dies completely or is incredibly difficult to restart . I’ve checked just about everything that I know of or have read about. I installed new batteries due to one of mine actually being bad. No change. Trying to be lazy and hoping it was something simple I changed the apps. No change.

 

The truck has never had a CEL. I even forced a CEL to make sure that part was functioning. The wait to start light functions completely normal. Sorry I’m bouncing around I just wanna to give as much info as I can .

 

Another thing is that while test driving it down the road to try and diagnose it with my scanner, as soon as the truck dies my scanner gets kicked out and says no communication. The scanner attempts to reconnect and if I cycle the key it reconnects and functions fine until the next time it dies. Also when running the scanner shows that the vp44 is claiming to only be getting 12.1-12.3 volts. I haven’t back probed it yet to test while running with a meter but I have unplugged the pump and checked the power and ground and it was within .01 of the batteries.

 

Sorry I know that’s a lot and there’s still more that Ive done but I know there are some very expienced people on here and hoping someone can help. That’s why I joined this one. Definitely a lot more info and a lot less “how do I roll coal” nonsense. 

Edited May 28, 2019 by Me78569

[Me78569]

do you gauges die on the dash when the engine turns off?  

 

sure sounds like the ecm or pcm is shutting off.  

[Dieselinmyblood]

No they don’t . At least not the times I pay attention to them . I do my testing on a 75mph farm road so I have minimal traffic and time to look at the scanner, fuel pressure gauge and dash gauges . Lol but i feel panicked when it happens to grab as much info as I can . When it’s dead but rolling in gear I had rpm still and oil pressure. I’ll test again ASAP and try to focus on all of it . But I agree, I know it’s not ever certain but I swear my pump can’t be bad . That’s why I finally asked here because I’m stuck between some expensive items or possibly a cheap wire fix . How does the CCD and PCM tie into the ECM ? I understand what they all do but I don’t see how for instance the PCM can wig out the ECM. 

[dripley]

When my oe VP gave up it was very much as you describe except it did not try to die. Down on power and I could restart the truck while moving and it come back. No hard restarts either. I am a manual also. Mine would blow blue smoke when this would happen. Never tripped the CEL either, but I also never checked it for codes.

 

The scanner loosing touch with the truck, maybe ECM, dont know. @Me78569 would know that better than I would.

[Dieselinmyblood]

Ya that’s what has me so confused ... mine doesn’t seem to have low power . It seems to act like a typical stock truck when it’s running. Also no smoke from tail pipe . That was one thing I looked for a lot in the beginning of this . Air in fuel will smoke a pump pretty quick . I wish the data link made more sense on these to me . I’m actually pretty decent with the j1939 can bus on heavy duty trucks . 

[Me78569]

what bus are you reading when it losses communication?

[kzimmer]

2 hours ago, Dieselinmyblood said:

as soon as the truck dies my scanner gets kicked out and says no communication. The scanner attempts to reconnect and if I cycle the key it reconnects and functions fine until the next time it dies.

 

I think this is the most important clue.

 

4 minutes ago, Me78569 said:

what bus are you reading when it losses communication?

 

I'd like to know this as well. Does a plain old cheapo OBD2 scanner lose connection, or is it the j1939 bus, etc.

[Dieselinmyblood]

I’ll go check in a second . What’s ironic is that my cheaper scanner shows me which data link it successfully connects to but my solus just tells me which key it’s using . 

Ok I made the solus attempt a connect in a different way and it backed up the other one. Both are accessing the ISO9141. That’s not something I’ve ever heard of heavy duty trucks so it’s Spanish to me . 

[98whitelightnin]

Would be nice if you had a buddy with an ecm you could borrow for a day or two.

[Dieselinmyblood]

Ya no kidding... only person I know is my dad and he’s 300 miles away 

[98whitelightnin]

98-99 will both work. Last time I "loaned" out a spare ecm, it never came back. Time to get out and make some friends

Edited May 29, 2019 by 98whitelightnin

[dripley]

1 hour ago, Dieselinmyblood said:

Ya that’s what has me so confused ... mine doesn’t seem to have low power . It seems to act like a typical stock truck when it’s running. Also no smoke from tail pipe . That was one thing I looked for a lot in the beginning of this . Air in fuel will smoke a pump pretty quick . I wish the data link made more sense on these to me . I’m actually pretty decent with the j1939 can bus on heavy duty trucks . 

That confuses me since in your first post you mention power loss. No dead pedal invoved for me either, but I did have blue smoke, not black while it was occuring.

What mods have you done to the truck?

[Dieselinmyblood]

Oh that’s my bad . I thought you meant a consistent power loss . The power loss I had was momentary . The truck is fully stock except for exhaust and upgraded fuel system to get rid the crummy stock stuff. Sump under tank, all half inch lines to a 140 Gph pump then to a fuel separator and high efficiency filter, then half inch to the pump with the little in line fitting to tap into for fuel pressure 

[dripley]

Your description in the first 3 sentences of,the 3rd fit my experience almost exactly. No dead pedal. Mine also did not die, so close to the same thing but not quite.

[IBMobile]

2 hours ago, Dieselinmyblood said:

Both are accessing the ISO9141. That’s not something I’ve ever heard of heavy duty trucks so it’s Spanish to me . 

That's just the language the truck speaks.  A lot of the European car makers use it.  I have a CRP123, my Matco reader does a better job on the Ram trucks.  

 

Well, you and I know that an intermittent problem that takes care of its self is a pain to diagnose.

 

Try this, the next time it happens on the road, with out restarting the engine, safely pull over to the side and check for power at the VP, OBD2 connector, ECM, and PCM.   You can also do a wire harness shake test with the engine running; this would help in finding a bad splice/loose connection.    

 

The other thigs to check are the auto shutdown relay, the fuel pump (VP44) relay and the grounds at the front of the engine (G125) and the ground between the left headlamp assembly and battery on the left inner fender (G100) 

[Dieselinmyblood]

1 hour ago, IBMobile said:

That's just the language the truck speaks.  A lot of the European car makers use it.  I have a CRP123, my Matco reader does a better job on the Ram trucks.  

 

Well, you and I know that an intermittent problem that takes care of its self is a pain to diagnose.

 

Try this, the next time it happens on the road, with out restarting the engine, safely pull over to the side and check for power at the VP, OBD2 connector, ECM, and PCM.   You can also do a wire harness shake test with the engine running; this would help in finding a bad splice/loose connection.    

 

The other thigs to check are the auto shutdown relay, the fuel pump (VP44) relay and the grounds at the front of the engine (G125) and the ground between the left headlamp assembly and battery on the left inner fender (G100) 

Ya my crp 123 is kinda sketchy on the 99. The solus definitely ties in better with the system . I like your idea . I’m going to leave early and drive it to work tomorrow so I can get the dash information talked about earlier and now to try your idea. 

 

Ive test driven it and pulled into my driveway once it’s acting up to perform the wire shake down test. I even pulled the little tiny cover off the pump to inspect for rubber and pinched wires . I’ll continue with this though especially when it’s acting up. 

 

I have tried putting new relays in and even new fuses. (I’ve seen to many cases of hairline fractures in the micro fuses that cause really weird stuff) I really felt initially like my issue could have been in the PDC. 

 

Ive only done a visual on the grounds for corrosion so far I need to go deeper into them . Where is the G125 ground located ? 

Oh and an easy way to check the ECM besides pulling the plug off ? I haven’t removed the cover to back probe it yet . 

[Me78569]

I think your ecm is shutting down randomly.  

[kzimmer]

On the bus he's using to communicate, what's the master? The ECM or PCM?

[Mopar1973Man]

CCD Network the PCM is Master, ECM is secondary.

 

CANBus the ECM only. No PCM data.

[IBMobile]

12 hours ago, Dieselinmyblood said:

Where is the G125 ground

Wire diagram says "front of engine" and back probe the wires/connectors..  

Always check the basics first before condemning the component.