How do I troubleshoot my Ford Transit Van won’t start?

Car model and year: Ford Transit Van

Symptom: Won’t start

Explain why:

between its last start and now there has been a lot of rain and the front windscreen drain tray was leaking (via the washer hose grommet as the washer line has been drilled though the drain tray at mid height) onto the fuse box and cabling below.

The ECU reads DTC P1631 PCM main relay. The battery is fully charged and seems to try to turn over okay (but i’m not 100% sure tbh).


Experienced user’s suggestion:

Firstly I’d change the filter, fill it to the top before refitting and try again.

If there is no codes relating to the pump, then I would not jump to the conclusion that it is at fault.
Could be as simple as a faulty ignition switch, blown fuse or possibly crank sensor.

The ecu needs a good charge to run and a failing battery could be the cause of the main relay code.


What to do next:

I guess a pump failure is possible, though last Sunday when my neighbor was bleeding it diesel shot out of a loosened injector pipe with enough pressure to bounce off the cover and up onto the engine bay roof. Don’t know if that possible at the low pressure limit I’ve been told it’s at. The breakdown mechanic did successfully start it, though my neighbor only got a couple of cylinders to fire once or twice.

And I’ve spent quite a bit on the motorhome conversion so it’s worth fixing. I’ve a rust proofing scheduled for Thursday too, which also pressed me into getting a quick fix. I’d just like to not be ripped off.

I did offer one of those reconditioned pumps but the mechanic said he would only order new from his supplier to avoid warranty issues. When I pressed him about using IDS and VCM or similar to try to verify a pump failure, and ensuring that the new pump coded correctly if the auto programming failed he said he could “go online” to get it programmed. It gave me the impression he couldn’t guarantee a program of a reconditioned pump because he didn’t have the tools. That, and because he won’t tell me what simple things have been checked as part of his diagnostic procedure, makes me feel he’s chancing it.

I’m going to see about a second opinion if he hasn’t started the work. Trouble is the box on the van is very high and it might not actually be able to go anywhere else on the back of a truck.


Finally, solved!

The work was done on Friday and the van is running now. Awaiting the bill at the end of the day.

A new filter was fitted and the pump was providing fuel before it went to the garage. I was informed the pressure from the pump was low.


Thanks to @ hackmagic (

Best VCMII needed? here you can go: