Motor Shut Down Filter/Pump/Other
 

I have a rebuilt 454 with approximately 200 hours since the rebuild. I change the oil, distributor cap, fuel/water separator, impellor, carb rebuilds, etc religiously. A recent issue which has been escaping me is that the boat will be running beautiful for around 45 minutes and then suddenly shut down like the key was turned off. What I will do is take the fuel/water separator off and drain it and reinstall to get home and the boat will run beautifully for another 45 minutes or so. Could this issue be the fuel/water separator needing to be changed more often with bad gas in tank or is it a weak mechanical fuel pump which isn’t feeding the bowls fast enough? On a side note the fuel pump is 200 hours old, all fuel lines are leak free and tight, and the key ignition is new.

Thanks again for all the help.

Silly question but have you checked your fuel tank vent?

Usually if it's fuel related,it will gradually lose power,not a clean shutdown.

I would be more suspect of a pickup in the distributor or a failing coil. You are probably giving it just enough time to cool down while fiddling with it.

Not a silly question at all, but the vent has been replaced and is clear.

Boat shuts down litterally like the key was turned. Dump the fuel filter and off again like nothing happened. Oddest thing in the world to me.

I thought the same with the distributor as well. As a test one time when it shut down I started it right back up and idled fine but never get on plane after that. Coil is new, however, because I suspected this and again still doing it. Pickup on MSD ignition is not replaceble only, however, it is only 200 hours as well.

I was assuming thunderbolt ignition. Grab an inline spark tester from a parts store and throw it in the glove compartment until it starts acting up and then install it on the engine. Easiest way to verify if it is a spark issue. I assume you are running an MSD ignition box also?

When you started it right back up ,was it running rich (black smoke) or just no power?

No MSD box being run. When starting back up there was no smoke of any color. It started like nothing happened. This last time it lost power down to an idle. When trying to get on plane the RPMs would go up and then it would stumble. I would bring it back to idle, however, the idle was about 200 RPM higher than it should have been. I shut the motor down (dumped the filter) and off we went with no issues running like a champ.

wonder if a fuel line is being sucked down/collapsing.I'd also check for loose wires under the dash.
your gonna need to start to trouble shoot,,check coil for 12v,,then spark out coil,could be coil is cooling off just as your finishing the fuel filter dump.just a thought.really sounds electrical.

I checked for the collapsed fuel line and nothing to the touch, however, their might be something internal. I was also thinking electrical, but I see nothing at the key on the dash or on the motor. I was also thinking possible vapor lock. The fuel line is pulling heat off of something during running?

If it was electrical what would I look for. The key switch is new and all wiring (plugs, distributor, coil) new. I agree it sounds electrical to me because of how the motor just cuts down like the throttle was moved to neutral, however, the motor more times than not will stay running which makes me feel it is fuel related. If the fuel water filter was full of water would this stop the flow of fuel to the carb?

If the carb ran out of fuel, it would not refire instantly. It takes a few for the fuel water sperator to fill and then fill the vcarburetor.

If it starts instantly, your carb bowls are full of fuel.

x 4.

Module or coil or a 45 minute timer wired in. LOL.

Somewhere around 45 minutes each time is a mega rare chance of fuel issue. Unless idle for 44 minutes folowed by 1 minute of WOT. LOL.

If it doesnt show any signs of stumbling or poor performance until it quits or slows down,it's most likely the module.Usually,once the module gets hot, the problem will occur at much shorter intervals than the initial shutdown of the day. Are you trying to restart or get back on plane without opening the hatch? I've had a small exhaust leak build enough CO to choke out one of my 502's.My captain would lift the hatch to check things out (giving it fresh air) ,see nothing wrong, and drive for 20 min before it would do it again. We would test it with the hatch up and never have a problem. Finally found leak at back side of Y-Pipe. Never had any smoke in eng compartment but enough CO to affect it.

I guess I can try another new coil. Is there anything inside the disributor which would cause this. I change the cap and rotor every year. Everything else has looked good besides some minor surface rust. Advance moves freely otherwise there is a magnetic pickup which should be fine. I am stumped.

I have tried to get back on plane without opening the hatch and it will stumble and not get up to RPM. I then shut the boat down and dumped the fuel water filter and off we go again like nothing happened. I will check for an exhaust leak. I have double awab straps on each connection and have never seen water leaking so I assume no leak but I could be wrong. Thanks for the help.

First, get a new fuel water sep filter. When it happens again, dump it into a mason jar and see if it separates. Fuel will float on top.

I will be out this weekend and will do so. I have pumped some fuel out of the tank after the boat has sit still on the trailer and there is some water so I am sure the filter will show the same.

Uh oh.

Sounds like you should remove the fuel sender and and make sure the trailer is slightly tiled back so you can use a remote pump and pull it all out. Remember, the pick up tube is not going to access all the fuel/water that is in there.

I think it sounds electrical too.
The fuel/separator change seems coincidental, it simply allows time for whatever electrical part or ground/connection that's on the way out to temporarily "get happy again" (cool down ECU module, let some ground wire/power wire make a few corrosion blocked electrons pass through again, jiggle some wires nearby that you move to change the filter etc)

An instant "key off" shutdown is electrical, until proven otherwise IMO.

Fuel related would usually sputter, a few cylinders miss, run lean, shut down after some of that behavior.
It also would not tend to "fire right up and run great instantly" because WHATEVER water or bad gas IN the fuel lines so bad to cause "instant shutdown" is STILL in all those fuel lines and would take some time to crank, cycle the bad fuel through to good fuel (sputtering and acting weird awhile) til "good fuel supply" was there. If the fuel situation was SO bad to cause "instant shutdown" hard to see it fixing "instantly"...

(Fuel injected a bad high pressure fuel pump with sudden 0 PSI if pump is going complete shutdown suddenly could act that way...)
You have carbs so won't "instantly" shut down, NOR REFIRE, from fuel, takes some TIME to sputter the bowls empty, THEN some time to refill them if they WERE empty or filled with water!
Find all possible electricals to coil, ECU, grounds, battery, get out sand paper/file and redo the connections.

Changing ECU sounds reasonable if nothing else found. Parasail941's advice sounds on "If it doesnt show any signs of stumbling or poor performance until it quits or slows down,it's most likely the module.Usually,once the module gets hot, the problem will occur at much shorter intervals than the initial shutdown of the day."

I agree with most of you it does seem electrical, however, this weekend to start as a baseline I simply put a new fuel water filter on and ran the boat alot. Ran like a champ with no proplems at all. It should be noted it was about 10 degrees cooler than the other days so electrical with heat might still be the issue. I have no ECU on the boat, but I followed all wires for ignition (key, starter, plug wires, distributor, and coil. Everything appeared normal and nothing was ever hot. My next step will be to dump the filter contents into a jar and see how much water there actually is.

Any thought on anything else to work on?

So here is what I have found. Electrical is out.....because it happened twice today on the river and each time the fuel pressure gauge was hardly off 0 psi. I would dump the filter and then start the boat back up and the pressure would start at zero and then moments later it would jump to 5 psi and hold firm. The motor would idle perfectly at just a hair above 0 psi and when throttle was added it would backfire. Is this water in the fuel causing the separator to fill with water and block the flow of fuel. Another though is the one fuel line to the gauge from the filter is laying on the water circulator hose and could this be causing vapor lock on a 160 degree consistent temperature motor?

Please help motor heads.

Jed

If engine dies, the fuel psi will instantly become 0. Don't get fooled by that.

Water does not block flow. It flows like fuel...edit in: removed improper info. LOL.

Yes ! Get your fuel line off of any heat source ! Farther away even better. Atleast a few inches minimum.

Is your fuel water seperator near full or near empty when you take it off ?

Breaking the seal of the seperator and then putting back on to make it run fine for a bit tells me one of two things:

1) You have vapor lock before the pump
and/or
2) the antisiphon valve is getting stuck and/or restricted. The quick psi change of pulling seperator makes it move.

Sounds like you have had tons of chances to do that....with all the seperator removing you've done. LOL.

Should have done this earlier.....so, yes....do this ! Get this diagnostic out of the way.

Actually, water is heavier than fuel, hence the reason why it sinks to the bottom of the fuel/water separator.

The motor didn't shut totally down these two times it just dropped from cruising RPM to idle and at idle it was zero psi. I will absolutely move the fuel line off the water hose. The separator is always full when dumped and I did dump in a jar and there was some water settled in the bottom, it nothing crazy. I think with these last tests electrical can be ruled out correct.

Ps-the check valve on the tank was removed years ago thinking this was the issue.

Sunday AM ! hahahahahahahahaha

More coffee.

LOL.

Yes, fuel floats to top of water. Thank goodness.Thus why seperators easy to design / make.

I'll say 100 times -" I'm such an idiot. Don't post/say/diagnose things until you are awake."

hahahahahahaha

I'm actually on my second cup right now, the only reason why I am marginally thinking.

If you keep finding water in the fuel, it is time to pump the tank. You have found something wrong, fix that before looking for the next thing that may be wrong.

Obviously some sort of contaminants are residing in your fuel tank, perhaps there is algae at the bottom blocking the pickup.

x 2. My thoughts earlier in thread.

o ring seal around the gas cap and fuel vent are 2 big sources of water entering you fuel tank. They are often missed as the source. rain and or washing the boat or waves splashing up against the vent and or gas cap. The oring in the gas cap rots out or is missing causes the those water sources to enter.

So it appears this is either I) something clogging the line in the tank or II) vapor lock from the fuel line resting on water pump circulating hose as everyone is saying that the water seporator being full will not cause this issue of a momentary fuel pressure drop.

I have replaced all gaskets last year to fuel cap as well as the sender unit on top of the tank. Vent is clear with a 90 degree down tube with a hood as well as the boat cover to protect them all when off the water.

Years ago I replaced the fuel sender on my scarab and unknowingly did not have the gasket sealed properly to the tank. I power washed the cockpit floor and the draining water flowed right into the tank via the sending unit. Another time I injested water through the vent in heavy seas. I learned that time the importance of having the hose that hooks to the vent loop upward above the through hull vent a good six inches or so before going to the tank so that it is self draining when water is forced into it. I am curious what type of fuel pressure gauge you are using? If one at the carb I believe they have accuracy issues when they get warm.

I have a fuel pressure gauge right before the carb. I have swapped it out with others and they all seem to be accurate. I also checked and the sender has a new rubber gasket and the vent has been looped since day one.

I am wondering if:

I) It is water in the fuel which seems it would be odd that it is a problem happening every so often. I cant find a clear answer on if a water seporator with water in it will cause a drop in fuel pressure to almost 0psi and then when dumped the fuel pressure will jump back to 6 psi.
II) If there is a problem with the pickup where air is being pulled in and causing the drop in pressure.
III) Can the fuel line running from the filter to the carb resting on the water house cause vapor lock because I have heard several times vapor lock resulting in a fuel pressure drop will only happen before the mechanical pump and not after?

Tonight I am going to pull the pickup tube and inspect, pump the tank to see how much water is really in there, and move the fuel line away from the water hose on the engine. I will be out this weekend and curious to see the resutls.

Anybody have any true answers on some of the questions above.

Vapor lock that I have dealt with occurs after you have been sitting a while, and you get a good heat soak.upon restart engine stumbles and dies.

Answer for #1: I already answered it. Water will not block flow and cause psi to go to 0. It can however make the engine stall (water doesn't combust) which then causes 0 psi since motor not running.

Answer for #2: Most definately. You would be far from the first to run into this issue. Although rare per person, it's not totally uncommon in the boat forums. A bunch of pick up tubes have been found with small cracks that of course will let air in.

Answer for #3: Yes, you can still run into vapor lock with heat after the pump. It probably won't cause the pump (mechanical) to air lock and not pull fuel unless the heat travels down the fuel far enough.

I have seen it turn the fuel going into the carb as a 'frothy mess'. 1, it makes the fuel/air micture coming out of the carb lean and hard to run, and 2 I have seen it able to raise the float and cause the N&S to close with more air than fuel in the bowl. Again, it will run like schit first and then shut off.

Never an issue at restart. Everytime we will be crusing at aroin 3,500-4,000 RPM and the boat will fall right off the RPMS like the key was turned off and either stall or drop to a smooth idle, however, the fuel pressure gauge will show little pressure. Try to get back on plane and the motor will stumble. Shut the mototr down, spin off the fuel water filter, dump out contents, replace, and start right back up with strong pressure the rest of the way. This process only take 1-2 minutes. Is this excess water in filter reducing fuel pressure or is there air being sucked in a line somplace causing lower fuel quantity?

Thanks for the answers SB. The odd thing is the engine will idle fine and wouldnt be the wiser if i wasnt watching the fuel pressure gauge. It is when trying to run the RPMs up it stumbles and falls off. The fuel lines, filter, or pump have never felt hot to the touch so vapor lock seems like less of a concern. Also the motor is only off for a moment which is not a significant cool down time for vapor lock. Maybe it is a small amout of air from somplace getting in. It just seems so odd that the pressure will fall to almost nothing and then after the filter is dumped and replaced it will all be ok for the rest of the day. One would think if significant water in tank it would happen more frequently right?