Vmac1 or 2 issue

[steeler]

Hi all. I've got a ch dump I'm working on that has a coughing/stumble mainly noticeable at idle. I have a 33 fault code. My vmac 1 book shows the 33 as injection pump speed sensor. My vmac 2 book doesn't show a 33 at all.

Now it's been awhile for me since I don't see many of these older trucks anymore. The module in the cab is a vmac 2 module, but the customer has put a different engine in the truck, that's when this issue started. Is it possible that I have the wrong injection pump because of the wrong engine? Would everything plug in the same on 1 vs 2. 

Like I said, I'm big time out of practice on the older vmacs.

[Mackpro]

Here’s the easiest way to tell a VMAC 1 from a 2  on a CH style truck .  A VMAC 1 has the engine harness plug iinto the firewall right above the windshield washer fluid jug on the passenger side of the firewall. On a VMAC 2 truck , there is a block off plate above the windshield washer fluid jug . Also  , the Econ-Vance is a lot longer on a VMAC 2  and the injection pump almost touches the air compressor, and  of course the VMAC 3 is an ETECH  style engine with the heat shielding  over the individual injector pumps 

[steeler]

20 minutes ago, Mackpro said:

Here’s the easiest way to tell a VMAC 1 from a 2  on a CH style truck .  A VMAC 1 has the engine harness plug iinto the firewall right above the windshield washer fluid jug on the passenger side of the firewall. On a VMAC 2 truck , there is a block off plate above the windshield washer fluid jug . Also  , the Econ-Vance is a lot longer on a VMAC 2  and the injection pump almost touches the air compressor, and  of course the VMAC 3 is an ETECH  style engine with the heat shielding  over the individual injector pumps 

Thanks pro. I'm not with the truck right now but I do know there is a bulkhead harness going into the firewall on the passenger side. I remember that was how I could always tell a 1 from 2, but I couldn't remember which was which.

So, sounds like a 1, so why does my module have a vmac 2 sticker on it? Didn't the 1s have an fic module?

[Mackpro]

Mack came  out with a conversion kit to replace the  two VMAC 1 ECM’s  with a single VMAC 2 ECM . The wiring harness on the engine remained the same as original. Chances are the one of the original VMAC 1 ECM’s failed and the conversion kits was installed. 

[steeler]

16 minutes ago, Mackpro said:

Mack came  out with a conversion kit to replace the  two VMAC 1 ECM’s  with a single VMAC 2 ECM . The wiring harness on the engine remained the same as original. Chances are the one of the original VMAC 1 ECM’s failed and the conversion kits was installed. 

Hmm. Interesting. Ya everything I'm looking at other than the module screams vmac 1. But I checked the vin and it is coming up as vmac2. The pump part number is correct.

I got more info on this truck. I noticed it has a new clutch and flywheel somebody else put in. I'm now suspecting they may have the wrong flywheel and the rpm sensor is not reading it.

The engine will die if I unplug the tem at the pump, but runs the same with the rpm sensor unplugged. That tells me I've got something fishy going on with the rpm sensor. It's supposed to ohm at 200-300, but I've got 180. It's a PAI sensor, I'm going to put a Mack sensor in it and see what happens.

[fjh]

I some how remember something about the fuel pump wiring is a tad different How ever im in the same boat as you ! not sure !!  The engine will run off memory with one sensor unpluged !  Same as the new engines  takes longer to start!

[steeler]

Ok after going thru it all again, I can disregard that 33 fault code. I was using a pro link and had the vmac1 cartridge in it. I hooked up the laptop and it's actually a 32, for the rpm sensor. I've eliminated the wiring and sensor, so I believe they have the wrong flywheel in it.

I don't know who was working on it before but damn, let's just say he was a hack.

Sad thing is, I'll probably never know what the outcome is. The only reason it's at my shop is because nobody else could figure it out, so the customer is going to pull the flywheel out himself.

 

[steeler]

Ok last update.....it always amazes me how you never seem to get the WHOLE story from the customer.

Anyway, now I'm told the engine (other than the injection pump) is from a different truck. Engine is a 1994, truck is a 1997. So I'm told they took an engine from a vmac1 truck and just swapped the injection pump.

This might not be an issue, I'm not sure if there are any major differences there. Either way it doesn't matter, customer picked the truck up and is going to run it till fall, then pull the transmission and check the flywheel.

Thanks for everyone's help!

[j hancock]

Call those type of folks Paul Harvey.  Eventually, you get "The Rest of the Story".