Universal M-18 engine stall

[bhstech]

I have a Universal M-18 in my 30 year old Catalina 27 TR. This is my 4th season with the boat. The engine ran flawlessly until last Sept. One day we were out sailing and I reached to turn off the engine and it quite all by itself. Not good. I couldn’t restart a few hours later so we were fortunate enough to have just the right winds to sail up the river, turn into the river and stop at our dock. It actually looked like I knew what I was doing.
The rest of the season, until the end of October, I had sporadic starting problems. I could easily restart once I bled the fuel line using the bleed valve on the engine. Over the winter layup I did a lot of internet research on the problem. So in the spring I replaced all of the 30 year old fuel hose, re-routed it to a more direct and shorter length. Changed the Racor 2 micro filter to a 10, changed the engine filter, all fresh fuel in the tank and a new electric fuel pump. When I changed out the fuel lines, I found some of it to be ¼ inch but most 3/8 ID. I even found 3/8 crimped down to a ¼ fitting. Now, everything is ¼ which still give more flow than required for this fuel sipper engine. All new clamps, doubled into the ¼ barb x 1/8 npt fittings.
My reseach indicated that my fuel pump was probably going out because it had to suck the fuel through a 2 micron filter. The old round Facet pump was probably 24” lift at 8 GPH and 6 PSI. My new Facet Pro block is 4-7 PSI with 60” lift and 30GPH. The new hose route in somewhat shorter than before but pulls from the tank up to the Racor filter about 12” above the tank (same as before) forward to the pump about 6” above the Racor about 2 ft. (same at before) and then to the engine’s second filter.
This all worked great and up until a few weeks ago. Engine would start and stall. Bleed the line and its fine, for a while. This past week we were on a trip when the wind died. We motored for about 2 hours without a problem, when the engine started to loose RPMs and finally stop. Bleeding restarted the engine but only for a few minutes and the same thing happened. The wind came up a little so we sailed for about 20 minutes. The temp gauge indicated everything was fine but… We started the iron genny again and it was OK. The next day was windless and we again motored flawlessly for about 2 hours and the same thing happened. Several time of this past week we can run the engine fine for anywhere from 10 minutes to hours and restart with a line bleed. I have re tightened all of the clamps, Racor looks good and no water in the separator in the bottom.
I did notice the bleed valve leeks a bit of fuel on my fingers when I open it, but that is new. I even tried leaving the bleed valve open just a bit and the engine started OK and ran for about 20 minutes.
The PO left me many spare parts including a new bleed valve. I did some more research and maybe my increased lift on the fuel pump is collapsing the tank hose? All of the new hose is brand name A1 fuel hose with a liner and reinforced rubber cover. It would take a lot to crush this hose. The one in the tank is original and thin. But why would it not crush immediately? Why wait so long to narrow? Leaky bleed valve? But why would it run when I leave it open a bit?
Sorry for the long ramble but I put in as much detail to avoid pointing out to advisors “been there, done that”.

[a64pilot]

Check the dip tube in the tank, see if there is a screen on the bottom of it, if there is, remove it.

[bhstech]

Yes there is a screen and it looked clean when I took it out last year but I left it on. I suppose if I have a higher lift rate pump this could cause a collapse of the intake tube. I'll try that. Going up to the boat today. I'll give that a try.
Thanks.

[Cheechako]

Check you tank vent for being clogged. Especially at the hull exit, sometimes little bees build a mud nest in the fitting.

[MarkSF]

You really do have all the symptoms of a blocking screen. How does the actual inside of the tank look? Can you see into it through the filler? The bottom and walls should be relatively clean, with no lumps of bacterial growth in the fuel.

[a64pilot]

Originally Posted by bhstech

Yes there is a screen and it looked clean when I took it out last year but I left it on. I suppose if I have a higher lift rate pump this could cause a collapse of the intake tube. I'll try that. Going up to the boat today. I'll give that a try.
Thanks.

Screens can cause no end of problem as they can clog when there is fuel flow, but the clog fall off when there isn't. I'd remove it, I want any and all contaminates to flow through and the Racor catch them so they are removed, I don't want them building up in the tank.
When I bought my boat I had issues like you describe, mine turned out to be two causes, first I had what I think was dead Bio-mass in the fuel, stuff looked like tofu, would clog the dip tube, but never make it to the filter so the separator bowl stayed clean, once I fixed that, I found out that all three tanks vents had what we call down here dirt dobber nests in them and my water tank, fuel tank and waste tank vents were completely clogged

[tkeithlu]

Could one of you who knows more about this sort of engine (my closest is an M-25) explain to me why this is fuel starvation rather than an air leak into the system? I need to learn something here. Thanks.

[a64pilot]

An air leak,IS fuel starvation


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[a64pilot]

A little further explanation as you know an air leak can and will present itself with the same symptoms.
But, he replaced pretty much everything that should leak, so start with the things he didn't, starting with cheapest / easiest first.


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[MarkSF]

Originally Posted by tkeithlu

Could one of you who knows more about this sort of engine (my closest is an M-25) explain to me why this is fuel starvation rather than an air leak into the system? I need to learn something here. Thanks.

If the strainer starts to block, and the lift pump is sucking on the line, what happens is that the pressure of the fuel drops below its vapour pressure, and then bubbles start forming in the fuel. So then it can seem like you have a constant air leak, as bubbles are constantly forming. However, there is no true leak to fix. Of course, you could also have a real leak causing this, which is what makes it so tricky to troubleshoot.

[Gone Bananas]

Don't know if this problem has been solved- off sailing

Have you had the compression cked on the cyclinders. Vaguely similar characteristics to finding the head was shot on a Universal MBX25. Hard to start- goes just fine, cuts out once in a while- goes on and on the same way and can't find the answer- then finally never can get the engine to start.
Do it now before you have to have the engine overhauled where you need the piston cylinders re bored et al

[bhstech]

OP here. So yesterday I took out the pickup tube out of the tank. Screen was clean but I couldn't pull it out so I just pried it 'open'. It's just a folded over screen so it is now effectively 'open'. Screen and tank look pretty clean.
Still had the same problem.
After the above I did restart the engine OK. It ran for a few minutes and stalled. I bled the system again at the bypass valve on the injector pump. Started OK and ran for 30 min. at the dock. A few hours later going out for a sail I had to bleed again and upon returning restart.
I did check for bubbles in the return hose and I an getting them. I was thinking of bypassing the Racor to see if that was the culprit.
Since I saw the first reply some others have made comments and recommendations. I get the vapor point causing bubbles. I'll look at the vent tube. Much easier than bypassing the Racor. We have Mud dabbers here as well. A few weeks ago one was building a nest on the inside of the cabin behind a curtain. Went for a sail while it was out collecting more mud and just reached behind the curtain and tossed it in the lake. Glad these little guys aren't very aggressive or vengeful.

[a64pilot]

OK, so it seems you most likely have an air leak.
One way to isolate is to connect another fuel source like a 5 gl can straight to the Racor, if problem goes away, it's before the Racor.
I'd be very careful bypassing the Racor, my luck is such that I'd get sand in the high pressure pump, damaging it.

Another way is to temporarily replace sections of the fuel hose with clear tube, look of course for where the bubbles start

[Xthewater]

Seems all possible sources are covered. Only extra I can think to add is if there's a pin hole or small crack in the pickup tube which when not covered with fuel can cause air to be sucked in.

[Stu Jackson]

A frined had this problem. Turned out to be a dented "corner" of his brand new Racor filter. Others have made the mistake of not removing the old filter O ring and putting the new second one on, too.

Good luck, play detective.