Old PB100 VM Diesel Issues

GGM63

New member
We have an older PB100 with a four cylinder VM engine. It starts fine when plugged in and struggles when not.
When it is not plugged in, you get a lot of smoke and it stumbles. After a couple of tries it might turn over.
Im assuming that it is a glow plug issue and plan on checking them individually.
My question is if the plugs are bad, where can I find replacements?

Also, does anyone have manuals and/or a wiring diagram?
The model is a PB 100 DR
The serial number is wkk8130001013879.
Thanks
IMG_4463.JPG
 

PJL

Well-known member
When you say it might turn over after a couple tries is it cranking but just not starting?

Glow plugs are easy to check. Put a volt meter on them while the glow plug light is on. Assuming that's how it works. If you have power then disconnect the wire going to each plug and use your ohm meter on them. The resistance should be very low. Like single digit ohms. Hopefully it's just bad glow plugs. Could also be weak battery not letting it crank fast enough or low compression.

I had a 6.2 Detroit engine that refused to start unless it was shot with ether. Checked the glow plugs. Only 2 out of the 8 were working.
 

alryA

Active member
Nice to have you here with us GGM63! Sorry to here you have starting grief with that VM engine. I can't add anything smart for you...
 

GGM63

New member
PJL: Yes when not plugged in (running heater) it cranks and does not start. It is getting fuel and the batteries are brand new.
From the way it is behaving, Im pretty sure one or more of the plugs are bad. I can check them with an ohm meter.
Im just having a hard time finding a source for parts for the VM.
Thanks
 

GGM63

New member
The plugs are getting power when the glow plug light is on. I have not removed rail to test w ohm meter.
 

PJL

Well-known member
What exactly is a VM engine? I thought the PB100 used a Mercedes diesel.
 

alryA

Active member
What exactly is a VM engine? I thought the PB100 used a Mercedes diesel.
VM Motori S.p.A. is an Italian diesel engine manufacturing company which is wholly owned by Fiat Chrysler Automobiles through its subsidiary Fiat Group Automobiles. VM headquarters and main production facilities are located in Cento, in Emilia-Romagna, Italy.
Parent: Fiat Chrysler Automobiles
Geographic scope: Italy
https://en.wikipedia.org/wiki/VM_Motori

A PB150 I operated 15 years ago had that motor. Loved the way it sounded.
 

Red130

Member
Have you gotten around to checking the glow plugs? Valve adjustment is another possible issue, in addition to compression and battery mentioned above. On the OM617A engine in my PB130D I found one of the 5 GP's burned out, replaced it and found it started better at temps down to about 20 or 25F, but not noticeably different at temps below that. Then the next summer I changed oil from 15w-45 to 5w-40 syn, adjusted the valves, improved my battery cables, ran a solvent through my injectors (this"purge" is a thing on the old Mercedes diesels, seems like snake oil but i got a lot of gunk out) and now it starts at 15F like it used to start at 25 to 35F, although there are some weird non-repeatable things like sometimes it wants lots of fuel when starting, other days it doesn't. Below 15F I still like to be plugged in if possible.

EDIT- Just remembered, that summer I also replaced the other 4 GPs. So I can't say for sure which of those things helped the most, but collectively it was a big improvement.
 

GGM63

New member
I did test the plugs. In the vehicle w a test light and removed and tested with multimeter. Resistance off the charts. All four are dead.
When I removed the plugs they are 11v Bosch on a 24v system. Is this screwy? Im looking for new plugs now, not much luck finding Bosch plugs 18v-24v that fit. Any suggestions?

Batteries are good and fully charged. Leads could be better and should be replaced.
 

Red130

Member
If they put GPs from a 12v system into a 24V circuit they won't last long. If you can't get new plugs from someone like vmengineparts.com or if their shipping it too high to North America, likely you could get them from PB in Reno. PB will charge 2x for them, but once you have the part number you can order from anyone next time.
EDIT: vmeningeparts.com is not the one. I think the European outlet that PB people talk about for VM parts is in the UK?
 
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jo5

Member
Some cold start system used a fast start system where they used a 6 volt glow plug in a 12 volt system( example)
They used a relay that only left them on for a short time if you bypassed the relay you burned them out
If you bypassed the relay and used them manually you had to replace the glow plugs with the system voltage ones
Need to see what system you have and act accordingly
Service manual parts book our knowledgeable person would be a good place to start
 

Red130

Member
Some cold start system used a fast start system where they used a 6 volt glow plug in a 12 volt system( example)
They used a relay that only left them on for a short time if you bypassed the relay you burned them out
If you bypassed the relay and used them manually you had to replace the glow plugs with the system voltage ones
Need to see what system you have and act accordingly
Service manual parts book our knowledgeable person would be a good place to start
Might be worth checking the relay timer?
 

PJL

Well-known member
I worked on a slightly militarized version of a Chevy truck with a diesel engine. Has a 24 volt starting system. 12 volt glow plugs. It used a large resistor unit to drop the voltage from 24 to 12. Maybe your PB has something like that? What voltage did you see when you tested it?
 

GGM63

New member
When I checked, it was 24v and change at the glow plug rail. There was only power when the glow plug switch was manually engaged. Im not sure if there was ever a timer in the circuit. The glow plug spec is Bosch 0250200070. This is a 18v plug for us in higher voltage system.
The only source right now is the local PB dealer and they are crazy expensive. I have looked everywhere , including europe (eBay) anyone have any source ideas?
 

DAVENET

Bronze Member
GOLD Site Supporter
The Freightliner system doesn't bring it up, but knowing other Bosch numbers, try searching with their number sequencing (adding in the correct spaces) - 0 250 200 070
 

GGM63

New member
Have searched cross reference sites with every combination of spaces, dashes etc. spoke with Bosch "discontinued". Not very helpful.
 

PJL

Well-known member
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GGM63

New member
Yes, I ordered a set of those (N75). Im just a little concerned because they are about 5mm shorter on the working end than the original. think this is an issue ? and the time to get them delivered is kind of a pain
 

PJL

Well-known member
5 mm isn't very much. I think as long as the voltage, thread size and pitch are the same you should be ok. Hope this helps.
 
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