Westerbeke W30 surge and die

[fyrfytr33]

SVTatia,

Thank you for your reply. Checked the vent from the outside, it's clear. Blew into the return line no restrictions what so ever..

[skipperpete]

Originally Posted by sanibel sailor

Injectors are pressurized and open when fuel pressure reaches a specific (very high) point. If they have a bad seal, fuel leaks out, but not air in.


Surging and dying is air in the fuel. Find the leak. On a Yanmar, I had a microscopic leak from an invisible crack in the bottom of the Racor bowl. It was fine for an hour or so, until enough air collected to starve the fuel pump. I was lucky to notice the tiny stream of bubbles, or else I would still be troubleshooting that bastard.

If a needle loses its tip or sticks in the nozzle,combustion pressure will definitely enter the tip chamber and then into the leakoff pipe. This was a problem with Cummins PT injectors.... but pintle injectors will do it as well. I worked on an AQAD40 that wouldn’t even start again after shutdown and eventually found part of the nozzle missing.
Fitted a spare injector and all went back to normal.

[fyrfytr33]

skipperpete,

Lets hope it is not something that serious. Injectors are new so I don't suspect them yet.
I think the next step should be isolate, add some clear hose and pray.

I'm still hopeful someone will have had a similar issue and relate it to me.

[skipperpete]

Haha fyrfytr33 most likely not... but to solve a problem, every possibility needs to be explored and eliminated. Air in the fuel is the most likely candidate and a mechanic would do what you suggested with a remote supply and reduce the possibilities to just a few and work back from there. Keep at it, you will succeed.

[fyrfytr33]

OK, back at it.
Rechecked suction side, closed tank shut off and ran electric lift pump. Vacuum gauge reads 5" of mercury for 10 days. I don't think there is a leak there. That rules out the tank, pick up tube, fuel lines, primary fuel filter, and electric lift pump. So on the suction side that leaves the fuel line from the electric lift pump to the mechanical lift pump and the mechanical pump itself. After that I would think everything is under pressure.
So I installed a clear fuel line loop from the inlet line to the secondary fuel filter. I installed another clear loop in the leak back line to the second inlet of the secondary fuel filter.
Bled everything and got it to start, it ran for a little while then it surged and died.
This is what I found, Absolutely no air bubbles on the intake side of the filter where I would expect a leak to be. BUT... the leak back pipe was full of bubbles and kept getting worse until it surged and died. So... any thoughts on how I am getting air into the leak back pipe if it is on the pressure side of the system? I'm kind of stumped right now.

[skipperpete]

Is the injector leakoff line still feeding directly into the centre of the secondary filter? If so , try taking it off and diverting into a container and plugging the filter connection. There is still the vane pump and regulating valve on the injector pump head, that’s definitely another suction point to consider. Here’s what a dud injector can look like, not suggesting this is the problem but clarifying my earlier statement regarding the possibility

[fyrfytr33]

I didn't mention it but I did put a shorter banjo bolt in to seal and bleed the filter. I connected the injector bleed off pipe to the tank return line with a clear line. But there is no fuel returning to the tank as of yet. It really only ran for maybe a minute.
I just can't figure out how it can get air in the pressurized lines. Where would it be possible to suck that much air in? If it was a stuck injector wouldn't that inject air through the injector bleed off lines?

[skipperpete]

That depends on how the injector failed and what type of injector pump supplies it.
If the tip gets blown off an injector thats fed by an injector pump with delivery valves... no huge problem. The engine will run badly but only one cylinder will be compromised but if that same injector failure is paired with a DPA pump with no delivery valves and only a pair of plungers the combustion/compression pressure will have fluid resistance briefly and after a number of strokes (maybe 20.... or 1,000) the air or gas wins and reaches the plunger pair and its “goodnight Irene” for the other cylinders.
The failure mode that causes air to exit the leakoff port is a little different and is aided by the delivery valve sealing the injector pump. I’m not too good at explaining these things clearly so my apologies for the rambling.
Pete

[fyrfytr33]

Ok, this is my thought process.
Ruled out air on the intake side. Pulled a vacuum that held for two weeks. Put a clear line on the inlet side of the secondary filter and have no bubbles on that side. Put a clear line on the leak off pipe to the filter and when I run the engine I have a large amount of small bubbles coming from the injection pump.
Skipperpete clued me in that it could be an injector. As much as I hate to think a new injector would be the problem, I can see no other reason for this.
This is the pressure side of the system and any leak would show as fuel leaking out, not air getting in. Best guess is an injector is letting engine compression in through the high pressure lines, back through the injector pump, and into the leak off pipe. Allowing it to run until enough air gets in the line to surge and die.
Anyone else ever seen this?

[skipperpete]

fyrfytr33, here’s another possibility to ponder if you’re not too fond of the tipless injector proposition. The inlet fitting on the top plate of your injector pump IS a potential suction leak source. Normally it has lift pump pressure at maybe 2-2 ½ psi and should leak fuel if the joint seal is dodgy but it’s worth considering this and the tiny shuttle valve within as a possible contestant. .....here’s a couple of screenshots.

[fyrfytr33]

Skipperpete, Haven't been back to the boat yet but I have been thinking, If the injector pressure is about 1900 PSI and the cylinder pressure is about 400 PSI, how can the cylinder pressure push into the injector lines? If the injector was set to a lower pressure it would change the timing and the engine would not run smooth, do you agree?

I did pick up my old injectors and will swap them out to see if I can find the problem. But inquiring minds want to know.

[skipperpete]

A very good question. The line pressure is only 1900 psi with an intact nozzle but drops to ....bugger all when the tip’s missing (or the needles stuck, or the spring is broken).
You got me thinking here! to settle this theory, take off all the injector lines at the injectors and spin the engine over... or with just one pipe attached to the injector only and a jar full of fuel, give her a spin over and see if there are bubbles in the jar. IF NOT, its time to look more closely at the supply line at the pump head.
Oh, on another thread theres a guy whose perkins 4/108 only runs with the case bleeds open ( DPA pump too) so try that as well.

[skipperpete]

About the pop pressure, theoretically the timing would change but my thought is that it would be a very tiny change.

[fyrfytr33]

Ok. Thank you. Looks like I have some testing to do. I'll post when I know more.

[LittleWing77]

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