I have a Volvo FM12 (water truck) built 1999 6 x 4 configuration. 380 or 420HP engine A good old truck it runs well. But it has some electrical problems. No tacho, no speedo. No revs. It gets to about 1/2 max revs and won't go any harder. We have checked fuses Replaced fuel filters No relevant fault codes showing Other electrics working okay. Do I need to find a Volvo truck mechanic with appropriate tools to look it over? Any ideas most welcome, thanks in advance. Michael.
What engine, is it Volvo or Volvo/Penta? There is a difference. If you can't identify the engine, maybe post a pic. Lots of resources here.
If what I found is correct, you have a D10B. It's a pump line and nozzle engine. I would start by checking fuel pressure after lift pump and check restriction at primary filter. Pressure should be no less than 3 bar/45 psi and restriction should not be greater than 4" of vacuum. If these steps don't make sense, yes, you should call a truck mechanic.
Thanks for your help funwithfuel I have posted a photo of the engine serial number if that helps. If you cant read it, it is: D12143195A We will investigate along the lines of your suggestion when we get a chance. cheers Michael.