These are from underside of Mercedes Sprinter close to fuel tank. One goes to the engine, the other to a diesel heater. I think they're too small to the fuel filters or pumps. What are they?

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  • 1
    Diesel heater? Heats the diesel, or diesel burning heater for the cab?
    – HandyHowie
    Commented Apr 19, 2021 at 7:52
  • Diesel burning heater for the cab and crew area.
    – Stewart
    Commented Apr 19, 2021 at 9:44
  • 1
    Looks like the pump for an sloppy installed aftermarket cab heater. Do you have two heaters?
    – Martin
    Commented Apr 19, 2021 at 9:55
  • @Martin Just the one heater. 2nd hand purchase. Trying to figure out how it works.
    – Stewart
    Commented Apr 20, 2021 at 5:29

2 Answers 2


My guess would be that they are electrically operated solenoid valves for shutting off the diesel when the ignition is off. Looks a bit like this in a rubber mount -

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Taken from - https://12voltfuelvalves.com/product/12-volt-multi-fuel-shut-off-solenoid-valve/

  • No way are those Original Equipment Manufacturer (OEM) components. Those screws on the heater and the orange wire bundle scream crappy aftermarket / owner add on. It sure looks like a solenoid, but why would someone add that? A pump would make a small bit of sense (say you wanted to run the heater when the vehicle is parked overnight) but that would certainly kill a battery pretty quickly. And that only applies to the aux. heater. Why touch the main fuel supply? Perhaps wacko antitheft application?
    – zipzit
    Commented Apr 20, 2021 at 15:46

if I am looking at the parts you are talking about as you have not circled them, then they could be part of the fuel return system.

  • Do diesels have evaporative emissions control equipment?
    – HandyHowie
    Commented Apr 19, 2021 at 6:51
  • @HandyHowie can you smell diesel when filling your tank?
    – Solar Mike
    Commented Apr 19, 2021 at 6:53
  • That isn’t what I asked. I was asking if they have EVAP. I can’t find any references to EVAP in diesels. Do diesels have it fitted? All references I have found say that diesels do not need EVAP due to the high boiling point.
    – HandyHowie
    Commented Apr 19, 2021 at 6:57

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