yanmar 2GM wont fire up unless governor at/very near WOT?

saga continues...

yesterday removed the feed pipe, sourced a 40cm short one and placed it straight on a 20lt diesel tank I have spare just in case in the e/r.
Bled the lot (not particularly well as I didn't want to smell of diesel had work to do later!), started worked fine, generator was fine drawing 1.8kW for 10-15mins. Turned off.
Went today expecting it not to fire, it did fire on the third 8sec crank session with the governor at 2.5k rpm.
With no load it was fine at 3krpm that the gen needs, as soon as the multi inverter/charger was turned on, it would drop to 2.8k rpm and obvs the charger would go offline and loop indefinitely between 2.8 under load and 3k no load.
Bet it's still air somewhere - most likely sucking air somewhere...

tbh this engine has been a right pain in the backside, but rather this than the two straight 6 turbodiesel main engines which have never missed a beat, never need bleeding, never never never...
Didn't have time to mess about will probably do during the w/e and report.
Plan to bleed the lot from start to finish extensively, replace again all copper washers / dowty ones and see where I get.

cheers

V.

PS. engine was rebuilt 3yrs ago and has only 120h since, so no I don't think it's compression/valves/etc issues.
 
a circa 5lt "day tank" which gets two 1.25in feed lines (with stop cocks) from the 1200lt tanks above it
my mistake is when I redid that to replace the 40odd yo original mild steel one, I left two 1/2in outlets one for each engine on top of that tank and added the gen pickup (again 1/2 in ) on the side and fairly low. I have another outlet to drain crud even lower. So guess I have to empty some of the contents of this day tank and see what I get.
gen to daytank is 4m 8mm fuel hose good quality 6yrs old now.

problem is that playing with diesel is messy and you end up with smelly hands and couldn't afford that during the week, hopefully I get some time to do all that over the w/e

V.
 
vas said:
a circa 5lt "day tank" which gets two 1.25in feed lines (with stop cocks) from the 1200lt tanks above it
my mistake is when I redid that to replace the 40odd yo original mild steel one, I left two 1/2in outlets one for each engine on top of that tank and added the gen pickup (again 1/2 in ) on the side and fairly low. I have another outlet to drain crud even lower. So guess I have to empty some of the contents of this day tank and see what I get.
gen to daytank is 4m 8mm fuel hose good quality 6yrs old now.

problem is that playing with diesel is messy and you end up with smelly hands and couldn't afford that during the week, hopefully I get some time to do all that over the w/e

V.
Click to expand...
Try putting cling film round each of the joints/connections and see if you can find one sucking air!
 
another update (possibly the last one???)

reverted to the main tank supply pipe, bled (with the brake needle bleeding thing I installed a month ago so no spillages), engine fired up but would need either a new bleeding session or 5-6 8sec cranking sessions to start from cold.
Noticed three days ago it was damp with fuel at the bottom of the engine mounted crappy yanmar filter. With a tissue it was clear that it was coming from the ring nut tightening the filter cup to the top. Used a wooden block and a v.light hammer and without much force managed to tighten just under 1/4 of a turn :eek:
Has started fine everyday last couple of days - e/r temps are in the thirties though...
So, looks like it was sucking air from this filter - tank level lower than yanmar engine mounted filter. I'll monitor it and see.

V.
 
vas said:
another update (possibly the last one???)

reverted to the main tank supply pipe, bled (with the brake needle bleeding thing I installed a month ago so no spillages), engine fired up but would need either a new bleeding session or 5-6 8sec cranking sessions to start from cold.
Noticed three days ago it was damp with fuel at the bottom of the engine mounted crappy yanmar filter. With a tissue it was clear that it was coming from the ring nut tightening the filter cup to the top. Used a wooden block and a v.light hammer and without much force managed to tighten just under 1/4 of a turn :eek:
Has started fine everyday last couple of days - e/r temps are in the thirties though...
So, looks like it was sucking air from this filter - tank level lower than yanmar engine mounted filter. I'll monitor it and see.

V.
Click to expand...
That sounds pretty positive, if fuel was leaking out then air was almost certainly leaking in. I think you've found the smoking gun.
 
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vas said:
saga continues...

yesterday removed the feed pipe, sourced a 40cm short one and placed it straight on a 20lt diesel tank I have spare just in case in the e/r.
Bled the lot (not particularly well as I didn't want to smell of diesel had work to do later!), started worked fine, generator was fine drawing 1.8kW for 10-15mins. Turned off.
Went today expecting it not to fire, it did fire on the third 8sec crank session with the governor at 2.5k rpm.
With no load it was fine at 3krpm that the gen needs, as soon as the multi inverter/charger was turned on, it would drop to 2.8k rpm and obvs the charger would go offline and loop indefinitely between 2.8 under load and 3k no load.
Bet it's still air somewhere - most likely sucking air somewhere...

tbh this engine has been a right pain in the backside, but rather this than the two straight 6 turbodiesel main engines which have never missed a beat, never need bleeding, never never never...
Didn't have time to mess about will probably do during the w/e and report.
Plan to bleed the lot from start to finish extensively, replace again all copper washers / dowty ones and see where I get.

cheers

V.

PS. engine was rebuilt 3yrs ago and has only 120h since, so no I don't think it's compression/valves/etc issues.
Click to expand...
I suspect your electric fuel pump is the problem. I found that mine was letting air in through the case. If its the cheap Facet, Chinese copy, they are really for pumping petrol. Mine has an air leak, but not as bad as the previous one
 
geem said:
I suspect your electric fuel pump is the problem. I found that mine was letting air in through the case. If its the cheap Facet, Chinese copy, they are really for pumping petrol. Mine has an air leak, but not as bad as the previous one
Click to expand...
interesting idea!
it is indeed a cheapo chinese copy pulse thingie inline pump. Annoyingly it was 50euro which I found excessive.
Of course I could buy a mechanic yanmar lift pump to replace the blanking plate I've installed in its place :rolleyes: Mine was definitely leaking and was in a sorry state...
Bet it's going to be even more expensive!
I'll see what I can find, no easy way to seal sort of this pump, is there? there's no heatshrink at this size (circa 50-60mm dia) else I'd get it wrapped 😁

cheers

V.
 
Pump part number

129301-52020​


OEM seen at € 154
compatible pumps on The Jungleweb from € 29

I have 80 mm heavy duty heatshrink, black with glue, material thickness 1,75 mm before shrinking (will increase). 6:1 shrink ratio.
Also from the Jungleweb, so it is indeed available.
 
Last edited:
vas said:
interesting idea!
it is indeed a cheapo chinese copy pulse thingie inline pump. Annoyingly it was 50euro which I found excessive.
Of course I could buy a mechanic yanmar lift pump to replace the blanking plate I've installed in its place :rolleyes: Mine was definitely leaking and was in a sorry state...
Bet it's going to be even more expensive!
I'll see what I can find, no easy way to seal sort of this pump, is there? there's no heatshrink at this size (circa 50-60mm dia) else I'd get it wrapped 😁

cheers

V.
Click to expand...
Parts4engines do a good replacement lift pump at a non eye watering price. Perhaps you have a UK visiter coming out?

Why do I occasionally forget to push the 'post' button..?. I should have posted that a day ago.
 
DownWest said:
Parts4engines do a good replacement lift pump at a non eye watering price. Perhaps you have a UK visiter coming out?

Why do I occasionally forget to push the 'post' button..?. I should have posted that a day ago.
Click to expand...
ChromeDome said:
Pump part number

129301-52020​


OEM seen at € 154
compatible pumps on The Jungleweb from € 29

I have 80 mm heavy duty heatshrink, black with glue, material thickness 1,75 mm before shrinking (will increase). 6:1 shrink ratio.
Also from the Jungleweb, so it is indeed available.
Click to expand...
You could wrap in self amalgamating tape and see whst happens.
Also, check the crappy little barbed hose connectors where they go into the pump. Mine leaked there as well
 
thanks for all the suggestions, we do have a yanmar dealer here in Volos who does reasonably priced spares, will try there next week when I'm back, and I'll probably try the self amalgamating tape solution first (as I have a couple of rolls and no use for them so I might as well 😁
Mind, bleeding the system with an el.pump is so much easier than using the crappy tiny lever (and having to turn the crank to a spot where it's got full travel and actually does something.
Re starting at WOT, I have this geny for the 7th season now, never needed to go WOT to fire up, so definitely not good, but feeling that I should get the two injectors for pattern spray testing.

cheers

V.
 
closing the thread (and hopefully not opening it again later...)
was away for a full week, this morning tried to start it, and fired up on the first 3-4secs. V. impressed tbh!
so looks all was due to air leaking in from the nasty built in yanmar filter with fuel level being slightly lower than filter assembly.
Even fired up at 3/4 throttle.
Tomorrow will try with 1/2 throttle.
Mind ambient in the e/r was 28C this morning (heatwave coming our way...) interesting to see how it will perform in the winter :)

cheers

V.
 
vas said:
closing the thread (and hopefully not opening it again later...)
was away for a full week, this morning tried to start it, and fired up on the first 3-4secs. V. impressed tbh!
so looks all was due to air leaking in from the nasty built in yanmar filter with fuel level being slightly lower than filter assembly.
Even fired up at 3/4 throttle.
Tomorrow will try with 1/2 throttle.
Mind ambient in the e/r was 28C this morning (heatwave coming our way...) interesting to see how it will perform in the winter :)

cheers

V.
Click to expand...
In my experience, it's usually an air problem.
 
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