Yanmar 2qm20 not starting troubleshooting

[charliehows]

well done thesauvage, I'm chiming in a bit late on this but I'm glad to see a classic old engine wont start thread solved without the usual kneejerk resort to pulling apart lift pumps and injector pumps, tho' you were on the verge of fiddling pointlessly with the injectors before you actually checked the cheapest, easiest and most common cause of these sorts of problem, the fuel lines. I spent a year sorting through a medley of recurring fuel air leak problems with my 2qm20 and it was actually running quite well when i first got it, so let me warn you to check the following; the fuel tank taps, fuel filter connections and bleed screw, bleed screw seal on injector pump, seal on lift pump, seals on secondary filter and its bleed screw, vibration damping on the fuel lines to injectors - if there isnt any make some.
get all these things bullet proofed and you'll have years of trouble free running from a 2qm20. good luck.

[bony]

Originally Posted by thesauvage

OK, I'll re-bleed the fuel lines, just to make sure:

I found with my old 2qm15 starting problem that the Yanmar fuel pump was taking too long to bring the fuel up to the injectors each time I tried to start it.

I believe it was due to the length of the fuel line. At 7 feet it was too long so with the engine not running fuel would drain back down the hose and the fuel pump had trouble bringing it all the way back. I solved this by fitting one of those rubber squeeze bulbs into the line near the engine just before the fuel pump. A couple of squeezes on the bulb brings the fuel right up to the pump under pressure and the engine now has no trouble starting.

[Michael Cobbe]

One thing that can cause that is a loose solenoid.