.03 looks like the signal wire from the computer, volvo usually supplies constant 12v power and switches by ground wire.skruving wrote: ↑29 Jan 2023, 12:50 I dug some more and followed the fuel line back to where the diesel filter sits where i found the small pump i can only assume is meant to feed the diesel heater, when measuring if the pump gets a signal i read 0.03volt before trying to turn the heater unit on and 0.06v for a few seconds as the fan in the heater unit starts and then back to 0.03v.
i also tried giving the pump 12v from a separate source which made the pump go click once and then nothing more.
assuming that something is off with the pump, and maybe also the wiring to the pump? I checked all fuses in the car that could belong to this, and none are broken.
if anyone can confirm or point me in some direction much appreciated
I'd say the pump is doing what it should. If the heater doesn't detect ignition it will shut the pump off, to prevent explosions. Its common for heaters to use an optical eye to detect combustion.
Try 3 prime cycles and see if theres any fuel present in the heater line after the pump, if not check the feed to the pump.
It might be the pump needs priming like the oil furnace pumps we have in our houses. They're designed to not syphon/leak fuel .
If theres a red button, thats probably the prime button. It will run the pump independently until fuel arrives , you can hear the pump change sound. Then try running the system.
If its getting fuel to the heater but still not firing.... check the spark generator or glow plug.
If its not firing the pump will automatically shut down.
If all else fails, buy a cheap 12v elec heater that plugs in the cigarette lighter. I used to do that on my old volvo.
Anything beats cold feet.
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