Intermittent Shutdowns - I think its fuel related but looking for advice
 

Hey all,

Welp after putting about 400 hours on my A4 this summer going fishing offshore with my A4 running great the whole season I am now having shutdown issues.

I checked my ignition and wiring connections, re ground my E- fuel pump hoping that was the issues. Test run it in my slip for 2 hours, it runs fine. Go out daysailing with people and it shuts down while we are headed back to the harbor. I replaced my filters and re did my fuel line, tested the engine on short runs and in the slip for a few hours. It ran great, then go out day sailing again with friends and it randomly shuts down and it takes some starting and restarting finagling before it runs long enough to get us back into the slip. Now I am running it in my slip and trying to get it to shutdown so I can go through my shutdown spark and fuel tests. But its running great in the slip for about an hour and I can't get it to repeat the issue. My hypothesis is that my fuel tank has crud in it and every once in a while (seems like whenever I am out sailing with friends) the fuel pickup is grabbing a piece of crud and clogging the line so the engine starves and shuts off suddenly. Our last outing the way I was able to finagle the boat back into the slip was to unplug the E-fuel pump + wire then plug it back in. This seemed to keep the engine running for a few minutes. My thought to fix this issue is either to do a diy fuel tank polishing or hire a company to come do it. Wondering is there any other issues you guys recommend me checking out before spending the money on a fuel tank polishing service?

I leave on a 6 month cruise to Mexico in a few months so I am very keen on getting this problem sorted and return to an engine that I trust. (Ive cruised about 1,500 hours and 3,000 NM on my A4 in the past two years)

A few things to note: This spring before my summer fishing outings, I re did my E-ignition with the indigo kit, new distributer cap, new spark plugs and wires, new OPSS etc. With this in mind I am leaning towards this being a fuel related issue rather than spark problem.

A common issue. If you have decent access and a port to snake a tube in you can wiggle it to the bottom corner and suck the krud out from under the "good fuel". Most often it is the access at the "pick up" port itself that is the easiest to suck out from. You just need to get deeper than the pick up is.

A drill motor pump will work fine into a large container. When it runs clear your good to go.

Do change the filters after your done and say farewell.

Dave Neptune :cool:

Here's possible scenario:
If there is a filter on the end of the pick up inside the fuel tank:
The boat motion when under way stirs up crud that is in a low area of the tank close to the pick up tube. The crud is pulled to the filter blocking it and the engine dies. When the engine dies there is no longer any suction at the end of the pick up tube so the crud falls off.

ex TRUE GRIT

If there is a filter on the pick up tube it could be partially blocked all the time which would lead to poor engine performance.
I took the filter off the pick up tube inside my tank so this didn't have a chance of happening - let the down stream filter handle any garbage that came from the tank.

Install a pressure gauge in the line to the carb. If you lose pressure (for whatever reason) the gauge will tell you, then you can track it down.
Install a test light (LED?) to coil +. If the light goes out, you've lost electrical power, then you can track it down.
Right now you're groping in the dark.

Thanks you for the suggestions. I’ll be installing a pressure gauge and doing a fuel tank cleaning soon

You'll be glad you did, the gage will help in the future and the tank will be clean.

Dave Neptune :cool:

Can someone suggest a source for a small marine grade fuel gauge? The one I installed few years ago is getting rusty.

Lots of good brands out there like Faria-Beede or Seastar. I have had a Faria gauge for 5 yrs and no issues... but then I sail on fresh water only...

I have a Marshall brand 0=15psi from ebay about $20. Stainless steel body, glass lens and liquid filled - works well and no problem.

Fuel pressure or fuel tank gauge?
I used a JEGS fuel pressure gauge - stainless steel case, glass lens, liquid filled. It worked well for many years.

ex TRUE GRIT

I like my electric fuel pressure gauge, it glows red when the pressure drops below 1 PSI.

Update…tracked down the sympton
 

Just installed a fuel pressure gauge. I turned my engine on in low rpm’s turned my iPhone camera on and went about my business. After about the twenty minute mark my engine shut down. I looked back on my video and found the pressure slowly dropping about 1 minute before the shutdown occurred. 30 seconds before the shutdown fuel pressure was at 0. Now I’m for sure certain it’s a fuel issue and since my pump, lines and filters are all brand new pretty sure I fuel tank cleaning and pickup line crud check is where I’ll find my problem. Thanks for the help! May also install that led test light that Al suggested to diagnose future spark problems. Any pics of that led install that I can refer too?

Thanks for the help. Now my Sunday afternoon will be spent digging around this fuel tank.

TANK VENT?
 

Did you try running with the fill cap slightly open to be sure the tank vent line is clear?

ex TRUE GRIT

If you want to verify the "crud in tank/pickup tube" theory try an using a gallon tank in the cockpit. Depending on your layout you can[1] connect directly to carb and siphon gas if the height is high enough - provides about 1+psi or {2] connect to directly pump. If it runs more than your 20 min. you know.

Same problem?
 

This is the same issue (maybe) I had bringing the boat in last season (2021).

The marina tuned up the Atomic 4, replaced the ignition coil, cleaned/adjusted the carburetor and replaced the fuel filters. He said he found silicon sealer inside of the fuel pump...

This season I set off from the marina to head to the dock. The engine started and ran just fine. I ran at no-wake speed out of the channel and at full power about half a mile. Then it lost power and shut off.

I took it out of gear and restarted. It ran at full power for 5-10 minutes then lost power and shut off again.

I took it out of gear and restarted. I ran it at 3/4 speed for 5-10 minutes then lost power again.

This happened a few more times before getting back to the marina.

It seems to only happen when the gears are engaged.

The fuel intake tube in the tank is short because I was fiddling around with it a few years ago and the original intake tube fell off into the tank. I had to replace it with a shorter tube to make it fit.

There is no screen on the end of the intake tube. It's just a tube.

The crud issue hypothesis sounds interesting. But I would think it would be less consistent of an issue than every X minutes.

Does this sound like crud? Is cleaning the tank worth the cost?

as usual, reading the fuel pressure is a must: it will confirm you if it is a fuel issue (crap in the fuel, lack of tank venting, etc..), or something else (over-heating coil (that was my issue), or seen a couple days ago with somebody else on that forum the shaft stuffing boat too tight that blocks itself when starts running).

Until you see the pressure gage go down, you are just guessing it is fuel...

At one time I had endless random shutdowns. I ended up with a pressure gauge and two vacuum gauges, one on the intake side of the filter and one on the output side but still before the fuel pump.
If just the second one goes up, the filter is clogged. If they BOTH go up, the clog is back at the tank. This was the case with me and it turned out the fuel fill hose was slowly dissolving and dropping rubber bits into the tank, which would randomly suck onto the fuel pickup and randomly fall back off again.

If the fuel pressure starts looking erratic, dropping, coming back up, and then finally dropping for good, that is likely vapor lock or an air leak slowly getting air into the system.

If it just drops to 0 and stays there, that is likely a clog someplace, the FPSS is erratic, or you have a defective pump. You are on your way to solving this.