2gm20F Hesitated

[dennismenace111]

Over the weekend I motored out to go for a sail and had to turn back as the ocean was to rough for a comfortable sail. On the way back, I slowed to pass a police boat patrolling our local sandbar hangout... I throttled back to almost idle. When I accelerated again the engine initially hesitated. It didn't respond to the throttle for just a second or two! It ran fine till I came upon the first drawbridge to open. Throttled back and put the engine in neutral... When the bridge opened, I put her in gear and throttled up and again the engine hesitated! But only for a second or two! Each time it stuttered, I reduced the throttle to idle and advanced it slowly and it would then accelerate properly.

When I got back to the dock, I looked around the engine cave and didn't see any obvious problems! One minor oozing of diesel from the top of the engine fuel filter around the bigger of the two bleed screws. I replaced the copper washer and the oozing seems to have stopped! I've also ordered a new secondary filter which I should have this evening's Amazon delivery.

Due to local Corona restrictions, I've not been able to test since then.

Any thoughts? High pressure pump starting to fail? It's a 1987 vintage engine with unknown hours!

[Wotname]

Most likely it is fuel supply problem i.e. air in the supply (IMO).

Diesel oozing (even if minor) from engine filter could be the cause.

[dennismenace111]

That was my initial thought as well! Thought it might be fuel starvation as well so I ordered a replacement filter cartridge! It's due to be changed anyway!

Hopefully the new copper washer in the bleed screw will stop the weeping fuel on top of the filter module.

[Kelkara]

Originally Posted by dennismenace111

Over the weekend I motored out to go for a sail and had to turn back as the ocean was to rough for a comfortable sail.

If I go out for a sail in boisterous conditions with less than about 1/4 fuel in the tank, the diesel sloshes around in the tank and air bubbles get into the fuel pick-up (at least I think that is what is happening). Then when I try to use the engine, it can be a bit grumpy for several minutes even after I get back into calm water ... never happens if the tank is full(ish).

[dennismenace111]

Living in South Florida, where on a really dry day, the humidity is 90 percent, I tend to keep my tank full!

That's not to say that it's not possible that I've gotten some water or air in the line from condensation. Even an almost full tank will get some water in it! I carefully check the Favors and never have any in the bowl though!

It's really nerve racking when you're waiting up current, for a bridge to open and it stutters for a couple of seconds! It puts big nibble marks in the helm seat... If you know what I mean!

[GordMay]

Weed on the prop'?

[dennismenace111]

Originally Posted by GordMay

Weed on the prop'?

Possibly, but there really wasn't any floating weed visibile. I just moved the throttle and the engine didn't respond for 2 or 3 seconds! I reduced the throttle and then advanced it slowly and it operated as expected!

If I compare it to a gas engine, it's like I gave it the gas and the ignition failed for a second or two!

[a64pilot]

Originally Posted by Wotname

Most likely it is fuel supply problem i.e. air in the supply (IMO).

Diesel oozing (even if minor) from engine filter could be the cause.

Almost certainly air in the fuel, the weeping goes both ways, in fact the filter should be in a vacuum, as fuel is sucked though it, so it’s shouldn’t weep, but suck air. Changing the filter can’t hurt though, but I bet you fixed it with the washer.

[dennismenace111]

Originally Posted by a64pilot

Almost certainly air in the fuel, the weeping goes both ways, in fact the filter should be in a vacuum, as fuel is sucked though it, so it’s shouldn’t weep, but suck air. Changing the filter can’t hurt though, but I bet you fixed it with the washer.

Interesting....I had thought that the filter was under pressure due to the oozing of fuel as it comes directly from the lift pump. But now that I think of it, the next thing in line is the high pressure pump which seems logical to be sucking fuel through that filter.

Im got my new filter element last evening from Amazon so I ll try and get over to the boat later today to install it. Testing may be an issue as Im not sure what the local law enforcement is doing about pleasure boating under the virus restrictions. I know that they are restricting folks rafting up at our local sand bar...but I dont think that they could say much about me and my wife out on the boat alone. Unless I sneeze on a bridge tender as I pass through!

[Wotname]

Originally Posted by a64pilot

Almost certainly air in the fuel, the weeping goes both ways, in fact the filter should be in a vacuum, as fuel is sucked though it, so it’s shouldn’t weep, but suck air. Changing the filter can’t hurt though, but I bet you fixed it with the washer.

The OP stated it was the engine mounted filter which situated between the lift pump and the injector pump. This means it will be pressurised by the lift pump (a couple of psi IIRC).

At idle, most of the fuel supplied by the lift pump passes though the engine filter and then back to wherever the return line delivers it to.

AFAIK, the injector pump doesn't suck at all, it simply pressurises the fuel supplied by the lift pump.

[a64pilot]

I was thinking that the engine mounted filter was before the pump, but it can’t be since you bleed the filter by pumping the lever on the pump, so it has to be a pressurized filter, your right.
But after shutdown it’s possible it could pull air in as the fuel will try to return to the tank because of gravity. Leak could go both ways, and air is of course thinner than fuel.
Yes, the HP pump should never, ever pull a vacuum, it should always get pressurized fuel, if it pulls a vacuum it could cavitate and that can over time harm it.
Exact same thing for the average watermaker, the kind with Cat pumps anyway, that’s why they have a boost pump, to prevent cavitation and wear on the HP pump.

Either way I still think an air leak is very much more likely than a failing pump, when they go bad most often it’s sudden or for many it shows up as hard starting as the pump pistons leak so bad that they don’t build pressure well at starting RPM as of course pump pressure has to exceed the injector cracking pressure for fuel to flow.
When I had mine overhauled on my old JD410, the guy at the shop told me he was surprised it would start there were so many scratches on the walls, but it ran fine for another 20 years and was running fine when I sold it to go cruising, but it was only used rarely and usually then not for many hours.

[Wotname]

Originally Posted by dennismenace111

Interesting....I had thought that the filter was under pressure due to the oozing of fuel as it comes directly from the lift pump. But now that I think of it, the next thing in line is the high pressure pump which seems logical to be sucking fuel through that filter.
..............

Pretty sure the injector pump doesn't suck fuel, it needs a supply slightly pressurised fuel to operate - either from the lift pump (or gravity in a gravity feed system).

As a side note with the 2GM20F engine mounted filter housing, the alloy is fairly soft and it is easy to strip the threads on the two top screws by tightening them too much. To that end, I have been using nylon type washers rather than copper as they squash with less torque. I understand (but don't know) that Yanmar now supplies either a alloy or nylon type washer for the bleed screw on the filter housing.

[dennismenace111]

Originally Posted by Wotname

Pretty sure the injector pump doesn't suck fuel, it needs a supply slightly pressurised fuel to operate - either from the lift pump (or gravity in a gravity feed system).

As a side note with the 2GM20F engine mounted filter housing, the alloy is fairly soft and it is easy to strip the threads on the two top screws by tightening them too much. To that end, I have been using nylon type washers rather than copper as they squash with less torque. I understand (but don't know) that Yanmar now supplies either a alloy or nylon type washer for the bleed screw on the filter housing.

Have you had any experience with a failing fuel injection pump? What symptoms might I expect? Probably a bad question!!!