lpdsn
New member
And it's still failing? Where is the take off from the can? Before the primary filter or before the lift pump?
Yanmar 3GM30F Baffling Diesel Problem - Chapter 3.
- Thread starter BobnLesley
- Start date
And it's still failing? Where is the take off from the can? Before the primary filter or before the lift pump?
jdc
Well-known member
When I had an air leak it caused irregular running but didn't stop the engine completely, whereas the fuel blockage - which makes for more of a vacuum so also encourages air leaks - stopped the engine even wih no load. But whatever it turns out to be, best of luck and I hope you resolve it soon.
vas
Well-known member
do you really need the priming bulb? can you eliminate it for testing?
BobnLesley
Well-known member
Half a step forward and a new run-time record at least:
After reading last night's suggestions I went first for just re-starting the engine, which'd been stuttering/fuel starving on shutdown last night: It did start, ran OK for perhaps thirty seconds and then stuttered and died - strike 1!
I next rigged a jerry can in the companionway and gravity fed from that through a new flexible hose which also didn't have a priming bulb; with 3-4' of head it easily bled the system, the engine fired easily (as always) and ran faultlessly for four hours. I'm hoping from this that I can discount any problem with injectors, injection pump, secondary filter or the pipework between?
Having beaten the run-time record I carefully lowered the jerry can to the saloon floor where I estimated that the fuel draw-off point was just below the level of the mechanical pump; it continued to run fine, though that was for only another 15 minutes as I felt it perhaps wasn't proving much? Whereafter I carefully lowered the tank into the bilge and sat it atop the fuel tank - this was where it was yesterday, though today I had a new hose and no priming bulb within it's length. In addition, I secured the pipe so that its high-point was perhaps 18" above the level of the mechanical pump, this I hoped would reflect the lift-height required to bring fuel from the original fuel tank and if it ran happily, indicate that my problem/air-leak? was within the length of the replaced hose, or more likely the priming bulb? Sadly that wasn't to be, the engine ran for perhaps another 20-30 minutes before stuttering, a return to saloon floor level got it going again, but once I lowered it back down, the stutter/failure quickly reappeared.
Logic says that the mechanical lift pump whilst working is perhaps not doing so as well as it used to and is now only providing 98 or 99% of the fuel necessary to run the engine, hence it runs for a while but eventually starves, the variance in how long that starvation takes to occur being due to the engine speed I've been setting it at. Conversely, I've tried running the engine using another/similar mechanical lift pump and an in-line electrial pump too and suffered exactly the same problem; it seems unlikely that all - the electric one especially - aren't strong enough? That said, it will be around 4' from the bottom of the fuel tank to the level of the mechanical pump, so perhaps toward the limit with a mechanical lift pump even when brand new?
I would like to hear any fresh/revised comments & opinions based on today's results, but am now thinking along the lines of perhaps installing a small day-tank in the cockpit locker to gravity-feed the engine from, which I can hopefully top-up from the main tank (via the primary filter) using an electric pump?
After reading last night's suggestions I went first for just re-starting the engine, which'd been stuttering/fuel starving on shutdown last night: It did start, ran OK for perhaps thirty seconds and then stuttered and died - strike 1!
I next rigged a jerry can in the companionway and gravity fed from that through a new flexible hose which also didn't have a priming bulb; with 3-4' of head it easily bled the system, the engine fired easily (as always) and ran faultlessly for four hours. I'm hoping from this that I can discount any problem with injectors, injection pump, secondary filter or the pipework between?
Having beaten the run-time record I carefully lowered the jerry can to the saloon floor where I estimated that the fuel draw-off point was just below the level of the mechanical pump; it continued to run fine, though that was for only another 15 minutes as I felt it perhaps wasn't proving much? Whereafter I carefully lowered the tank into the bilge and sat it atop the fuel tank - this was where it was yesterday, though today I had a new hose and no priming bulb within it's length. In addition, I secured the pipe so that its high-point was perhaps 18" above the level of the mechanical pump, this I hoped would reflect the lift-height required to bring fuel from the original fuel tank and if it ran happily, indicate that my problem/air-leak? was within the length of the replaced hose, or more likely the priming bulb? Sadly that wasn't to be, the engine ran for perhaps another 20-30 minutes before stuttering, a return to saloon floor level got it going again, but once I lowered it back down, the stutter/failure quickly reappeared.
Logic says that the mechanical lift pump whilst working is perhaps not doing so as well as it used to and is now only providing 98 or 99% of the fuel necessary to run the engine, hence it runs for a while but eventually starves, the variance in how long that starvation takes to occur being due to the engine speed I've been setting it at. Conversely, I've tried running the engine using another/similar mechanical lift pump and an in-line electrial pump too and suffered exactly the same problem; it seems unlikely that all - the electric one especially - aren't strong enough? That said, it will be around 4' from the bottom of the fuel tank to the level of the mechanical pump, so perhaps toward the limit with a mechanical lift pump even when brand new?
I would like to hear any fresh/revised comments & opinions based on today's results, but am now thinking along the lines of perhaps installing a small day-tank in the cockpit locker to gravity-feed the engine from, which I can hopefully top-up from the main tank (via the primary filter) using an electric pump?
lpdsn
New member
I think you said in post #1 that the lift pump was replaced. Does this mean they are both faulty? Maybe worth trying an in-line electric pump too but that just feels like treating the symptoms.
Maybe worth seeing if you can get a vacuum guage from some local motor factors or by post. Mine's just a cheap boy racer style one and cost €7.
jdc
Well-known member
If you're thinking it's starvation then the amount used by the injectors will be a very strong function of load. Does putting it in gear (even 'tho you're tied up or at anchor) make it fail much sooner? If not, then it casts some doubt on your theory of lift pump not being man enough.
incidentally, how sure are you of the secondary fuel filter's seal?
incidentally, how sure are you of the secondary fuel filter's seal?
jfkal
Active member
Secondary filter at the engine still clogged? I can run my 3GM with a closed fuel cock at the tank for 15 mins easily. Tough to find the problem with so little consumption.
lw395
Well-known member
I'm not sure which is more useful, a vacuum gauge or a pressure gauge.
By now I'd be wanting to check fuel pressure at the inlet to the injector pump.
So, at the very least a T piece and some means of seeing fuel spurt out or not.
If you put a clear filter in the line from secondary filter to injector pump, with a small air bubble in it, you should see the bubble shrink as the lift pump pressurises it?
I don't know the supposed output pressure of the lift pump but I bet it's at least 1 bar. Could be 3 bar so you might want to be prepared for the filter to fail!
A couple of years ago I pressure tested some cheap ebay inline fuel filters at 5 bar and they were OK FWIW. But you might not want to trust the brittle plastic sort only intended for gravity fed carbs....
There comes a point where you just have to check the pressure at every point in the system.
BobnLesley
Well-known member
Thanks for you perseverence, you're the one ray of hope I can see in this out of the way corner of the world; the 'official' and only mechanic here seems to know less about diesel engines than I do!
I will check for a blockage at the secondary filter and also the filter housing's seal - there is a rubber ring-seal on the bowl and that's one item which I haven't changed, though why should either of those cause a problem when the fuel's being pumped/lifted, but not when gravity fed? I will also try to obtain a vacuum gauge, though I can't see how I'd be able to install a pressure gauge or clear filter/air-bubble between the secondary filter and injection-pump as that's a rigid copper line, not a hose; if I damage that Yanmar pipe I may be suck here forever waiting for a replacment!
As to 'loading' the system, I've generally been running at 1/2 - 2/3 revs with the engine in gear pulling against the docklines, that was the case for both the gravity feed and pumped-feed experiments yesterday. I do have/have tried an in-line electrical pump, but that too failed; hence my reservations as to the problem 'definitely' being with the mechanical lift pump; a chap I chatted to last night suggested that I might also 'run a finger' over the mechanical pump's cam-shaft to feel if there's excessive wear in that? Both my mechanical lift pumps are used and I am now down to the one which I suspect is the weaker of the two, the threads for the inlet banjo-bolt having stripped on the better one (were they already weak/potentially leaking?) so today's task will be to switch the top covers on both to make the best of each.
Keep the suggestions coming, I'll report back what I achieve. Thanks again, Bob.
I will check for a blockage at the secondary filter and also the filter housing's seal - there is a rubber ring-seal on the bowl and that's one item which I haven't changed, though why should either of those cause a problem when the fuel's being pumped/lifted, but not when gravity fed? I will also try to obtain a vacuum gauge, though I can't see how I'd be able to install a pressure gauge or clear filter/air-bubble between the secondary filter and injection-pump as that's a rigid copper line, not a hose; if I damage that Yanmar pipe I may be suck here forever waiting for a replacment!
As to 'loading' the system, I've generally been running at 1/2 - 2/3 revs with the engine in gear pulling against the docklines, that was the case for both the gravity feed and pumped-feed experiments yesterday. I do have/have tried an in-line electrical pump, but that too failed; hence my reservations as to the problem 'definitely' being with the mechanical lift pump; a chap I chatted to last night suggested that I might also 'run a finger' over the mechanical pump's cam-shaft to feel if there's excessive wear in that? Both my mechanical lift pumps are used and I am now down to the one which I suspect is the weaker of the two, the threads for the inlet banjo-bolt having stripped on the better one (were they already weak/potentially leaking?) so today's task will be to switch the top covers on both to make the best of each.
Keep the suggestions coming, I'll report back what I achieve. Thanks again, Bob.
Leighb
Well-known member
One thought after reading the recent issue which related to the height of the temporary tank. It suggests that the built in lift pump just doesn't have enough oomph to reliably pull fuel that high fast enough?
I do know from experience that the lift pump fitted to the Beta 20 engine is only rated to lift 0.5 m, and in my boat the engine installer fitted an inline electric pump to avoid any problems as the tank was more than 1.0 metre below the lift pump. He had previously had to retrofit a similar setup to an identical type of boat which had repeated fuel starvation issues.
I do know from experience that the lift pump fitted to the Beta 20 engine is only rated to lift 0.5 m, and in my boat the engine installer fitted an inline electric pump to avoid any problems as the tank was more than 1.0 metre below the lift pump. He had previously had to retrofit a similar setup to an identical type of boat which had repeated fuel starvation issues.
Nudge
Member
Have you checked the condition of the injector spill return lines? I had a similar problem with a 3YM30 where the injectors had been removed and when the connections were re-tightened, the rose joint around the top of no 3 injector for the spill connection was rotated and the pipe was cracked (unseen). It may be that when the fuel is supplied from the high level temporary tank, the spill line is not being "pulled upon" so the "leak" is not letting air into the system..... Lower the tank and air starts to pull in from the leak.
Solved the engine stuttering problem (after 4 hours running) with a new spill return line set.
Solved the engine stuttering problem (after 4 hours running) with a new spill return line set.
vas
Well-known member
I had constant problems with the joke of a filter yanmar fit (mine is a 2GM20F on a 8KW generator)
Ended up scraping this filter (you DO need to change the o-ring often!) and replacing it with a (equally crappy but not leaking!) CAV one. This problem is gone for now, but replaced with another air leak possibly on the el. stop solenoid on the pump inlet
Anyway, since you're testing, using diesel from a tank (presumably already cleaned by having circulated the system a few times) I'd suggest you remove the filter completely and have another run, eliminating this variable.
As for installing a pressure/vacuum gauge, just remove the hard pipe get a couple of banjos, some new hose, circlips and a tee and try it.
good luck
V.
Ended up scraping this filter (you DO need to change the o-ring often!) and replacing it with a (equally crappy but not leaking!) CAV one. This problem is gone for now, but replaced with another air leak possibly on the el. stop solenoid on the pump inlet
Anyway, since you're testing, using diesel from a tank (presumably already cleaned by having circulated the system a few times) I'd suggest you remove the filter completely and have another run, eliminating this variable.
As for installing a pressure/vacuum gauge, just remove the hard pipe get a couple of banjos, some new hose, circlips and a tee and try it.
good luck
V.
BobnLesley
Well-known member
No progress today beyond removing and cleaning/checking the lift pump, secondary filter housing and all pipework to/from both, before going out to buy new copper washers, a new priming bulb and a 3m length of rubber fuel hose; 4.5 hours and seven stores later, I've finally succeeded; fecking Panama.
Contest1
Member
My pal had similar problems with his Volvo Pentan2002.
Followed all your steps. Still cut out now and then.
First thing was his son had changed the main fuel filter and left the old sealing ring in place causing air to enter.
During all the bleeding overtightened the bleed screw but thought it ok as diesel comes out here.
Bit of PTFE tape on the theads sorted it out eventually.
Couple of years of anxiety every trip caused by heavy handed tightening up.
Followed all your steps. Still cut out now and then.
First thing was his son had changed the main fuel filter and left the old sealing ring in place causing air to enter.
During all the bleeding overtightened the bleed screw but thought it ok as diesel comes out here.
Bit of PTFE tape on the theads sorted it out eventually.
Couple of years of anxiety every trip caused by heavy handed tightening up.
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