yanmar 2GMF air in fuel problem [again!]

[jwfrary]

Vas,

Could you check the lift pump isn’t leaking?

Perhaps take it off pressurise it in a water bath and see if any leaks are present ?

Change the o ring on the filter housing? - I have one housing spare which came off a scrap engine if you want it for cheap.

Are you having to bleed the injector lines each time? If so I’m wondering if a nozzle is sticking allowing air in the go injection pipes so your not getting fuel in. It’s a theory!?

 

[RichardS]

Vas,

Could you check the lift pump isn’t leaking?

Perhaps take it off pressurise it in a water bath and see if any leaks are present ?

Change the o ring on the filter housing? - I have one housing spare which came off a scrap engine if you want it for cheap.

Are you having to bleed the injector lines each time? If so I’m wondering if a nozzle is sticking allowing air in the go injection pipes so your not getting fuel in. It’s a theory!?

I think the original problem has been sorted.

Richard

 

[vas]

thanks,

yes, original lift pump issue solved by removing and fitting a blanking plate
new electric lift pump fitted, you know the pulsating ones, integral non-return valve on it theoretically should work fine as it's only been in use for a couple of months and in that period generator has been used for 3h in total, mostly starting tests, five ten min work, stop, repeat next day sort of thing...
And anyway el.pump is only working when cranking, not needed afterwards seems that high pressure pump is happy to suck fuel from almost 4m of 8mm hose to the tank, not complaining.

New o-rings in filter housing, thanks for the offer, but seems that it's OK and not leaking! If I was to change that I'd fit a separ5/2000 same as main engines so I can have a spare if something nasty happens and I'm stranded with one engine.
No, will start after 3 max 4 10sec cranking sessions, no need to bleed anything.
Maybe I'm asking too much, but I feel that it would fire faster if pressure wasn't dropping.
haven't touched the injector lines since the refit of the filter, so shouldn't really be that, although I'll probably remove the injectors and have them measured/tested just in case as well...

I'll fit a stopcock before the el. lift pump on Monday, run the thing and when stopped will turn it off and see if pressure still drops.
If it does, and since there's no sign of diesel, I'll start suspecting the high pressure pump. But that was removed and checked/measured/serviced a few months ago for good measure. Further oil level is not increasing, diesel is not around the high pressure pump, it cannot just vanish!



cheers

V.

 

[jwfrary]

thanks,

yes, original lift pump issue solved by removing and fitting a blanking plate
new electric lift pump fitted, you know the pulsating ones, integral non-return valve on it theoretically should work fine as it's only been in use for a couple of months and in that period generator has been used for 3h in total, mostly starting tests, five ten min work, stop, repeat next day sort of thing...
And anyway el.pump is only working when cranking, not needed afterwards seems that high pressure pump is happy to suck fuel from almost 4m of 8mm hose to the tank, not complaining.

New o-rings in filter housing, thanks for the offer, but seems that it's OK and not leaking! If I was to change that I'd fit a separ5/2000 same as main engines so I can have a spare if something nasty happens and I'm stranded with one engine.
No, will start after 3 max 4 10sec cranking sessions, no need to bleed anything.
Maybe I'm asking too much, but I feel that it would fire faster if pressure wasn't dropping.
haven't touched the injector lines since the refit of the filter, so shouldn't really be that, although I'll probably remove the injectors and have them measured/tested just in case as well...

I'll fit a stopcock before the el. lift pump on Monday, run the thing and when stopped will turn it off and see if pressure still drops.
If it does, and since there's no sign of diesel, I'll start suspecting the high pressure pump. But that was removed and checked/measured/serviced a few months ago for good measure. Further oil level is not increasing, diesel is not around the high pressure pump, it cannot just vanish!



cheers

V.

 

[jwfrary]

To be honest that’s not abnormal GM starting performance when it’s cold!

To rule that out you could hot air gun the intake minus the air filter! prior to start attempt. If it’s the same then it’s fuel if not it’s just temperature!

 

[vas]

Jon,

e/r temp this afternoon was 20C
but true, it seems to have improved over the previous week with ambient in the tens.
I'd really like to keep fuel pressure on the filter constant when stopped and not dropping 1bar in less than an hour though.
I'll look into it a bit more and report back. Frankly not much I can do, not allowed to use the boat, am kind of allowed to visit the boat so that's what I'm doing

cheers

V.

 

[vas]

hopefully the last time I report/close a yanmar 2GM starting thread in here...
Following a month onboard, generator hasn't missed a beat, starts everytime on first crank and in less than 3secs.
Only extra thing I ever did was going around the 2 circlips securing the el.lift pump hoses and tightening them a bit more. Looks like it was leaking eversoslightly (well sucking a bit of air) through that.
Mind ambients in the e/r are not lower than 30C throughout July, but confident that the issue is sorted, vedrict:
internally (most likely) leaking stock lift pump, replaced with el.pump only running during cranking.

cheers

V.

 

[vas]

me again!

since this thread showed all the steps I took over a period of time in debugging the 2GMF starting issues, I think it's right to give another instalment to that. Wont dare say final, but probably is

right, so end of Sept 2021 was onboard for half the month with diesel level in the tanks being quite low, as in 10-20cm lower than the lift pump and 30odd from the HP pump. Would only start after 3-4 cranking sessions :-(
so a few months ago decided to add an extra digital solid state relay on my custom geny control box and program my arduino to run the lift pump throughout the time engine is running - Remember, was only running the lift pump for as long as engine was cranking (simply wired in parallel to the starter solenoid!)

Amazingly (well, maybe not) with tank almost empty, generator starts on 2-3sec crank even after two months of sitting there doing nothing (removed the exhaust elbow for a modification)

So, seems to be:
- yes check lift pump, may be failing, leaking to block, leaking back to tank
- if replacing lift pump with an electric one, you MUST run it throughout the time engine is running (although even with an almost empty tank, if it would fire, it would work fine with the lift pump disabled)

hope I wont return back again on this...

cheers

V.