89 4.3L starts, runs fine, stalls

[Liquid_force]

Hi,

First trip out after de-winterizing...

I started it a few days ago on muffs and things seemed normal. Had to crank it for several seconds, pump the throttle etc, but basically normal coming out of storage.

Took it to the lake, fired immediately. Ran fine across the lake for 5 min or so at ~3k rpm.
Sputtered a couple times, ran a few more seconds and died.

Fired up another couple times but died as soon as I gave it any throttle. Eventually wouldn't start.

Started poking around the motor, thinking fuel, pulled the water separator off.
Thought I MIGHT have seen some film looking stuff in the bottom, but didn't have a spare.
Swirled the fuel around a little and put it back on.

Engine fired and ran for a couple minutes then went through the same process as above.

2nd time I unthreaded the filter I heard a suction sound as though I was breaking a vacuum, or releasing positive pressure.
I don't know if there should or shouldn't be pressure there, but it's the only thing I could come up with as a possible problem.

Basically, it seemed as though I could have cruised all day as long as I stopped every 2-5 minutes to release pressure/vaccum from the fuel line.

Could my vent line be clogged (I replaced the fuel inlet and vent lines 3 yrs ago)?

I really have no idea what's going on.

 

[86 century]

Re: 89 4.3L starts, runs fine, stalls

Pull the gas cap blow some low pressure air in the tank vent. Then blow in the fill neck to see if you have air coming out the vent.
If by chance some thing clogged your vent line this will tell you.

Don't do this on the water as fuel may come out of the fill neck.

 

[Howard Sterndrive]

Re: 89 4.3L starts, runs fine, stalls

I really have no idea what's going on.

on the contrary - sounds like you know the system pretty well
I suspect plugged anti-siphon valve at tank pickup fitting got some crud in it, or mudwasps packed your vent screen shut.

 

[indybleck]

Re: 89 4.3L starts, runs fine, stalls

I thought that was my problem and I loosened up the fill cap still didn't help then it was on to the fuel delivery from the pick up all the way to the carb.

 

[Howard Sterndrive]

Re: 89 4.3L starts, runs fine, stalls

float might be stuck in the carb.
dead fuel pump.
probably a screen filter at the inlet of the carb too

could check fuel pressure between pump and carb next.

 

[Liquid_force]

Re: 89 4.3L starts, runs fine, stalls

using the exhaust port on my shop vac I was able to blow air in the vent and get it out the fill neck and vice versa.
So it seems that those are generally clear.
Then I removed the deck plate covering the vent line, fill line, and sending unit on the tank.
What a corroded mess.
I replaced both those hoses a few years ago and replaced the standard plastic circular deck plate/frame with a piece of appx 12" x 12" diamond plate aluminum - which looks great, but seems to have something to do with my problem.
I believe we used stainless screws, and probably some steel tee nuts under the floor - the combination of which seems to have resulted in a pretty significant amateur boat mechanic screw up.
I guess some sort of galvanic corrosion has been taking place because the bottom of that aluminum deck plate is a white powdery mess as are the fuel components close to it.

The wire helix on the fill hose was corroded and splitting the hose - so I cut that back a couple inches and reattached it.
And worse, the aluminum plate on the sending unit is corroded down to almost nothing, and the 90 degree aluminum fitting that is attached to the pickup hose is in about the same shape.

It looks like the build up of corrosive material might have dropped chunks in the tank. One appears to be just about the right size to be sucked up in the pick up hose like a cork.

I've spent the last hr and half hand pumping the gas out of the tank so I can attempt to suck out the debris.
My hand pump is suited more for ounces than gallons, this hasn't been fun.

What's worse is I'm 50/50 at best that this actually IS the problem.

 

[indybleck]

Re: 89 4.3L starts, runs fine, stalls

That's a start.

 

[HCMQA]

Re: 89 4.3L starts, runs fine, stalls

rebuilt the carb lately?
I have a 4.3 that was doing the same thing.
All fuel lines were clear and the filters were all changed still did what you described.
Rebuilt carb. One main jet was clogged. One venturi was clogged and float was not even close to being adjusted correctly.
So far she is running great.

 

[Liquid_force]

Re: 89 4.3L starts, runs fine, stalls

I got the tank dried out, but trying to get the shop vac directly on the bottom surface with only the sender hole as access proved to be pretty difficult. I waved it around as well as I could but I was never SURE I got any/all debris out of the tank. Put in a new sender also.

Got it back together and went to the lake.

Fired up immediately. Ran pretty smooth. Thought I heard a slight stumble or two but with older plugs wires and other ignition parts I didn't think much of it. Pulled my daughter on the wakeboard a few times. No issues. Pulled her on the tube for a few minutes and it died again. That was an hour or more after leaving the dock.

Thought i was out of the woods.
Guess not.
There IS the possibility of just low fuel. I only put 6 gal in it. Probably ran 2 or 3 off in that hr (wild guess), and the tank is only 6" deep so must be fairly long and wide to hold 20+ gal. Maybe it just sloshed around and sucked a little air. Frustrating though because it did EXACTLY what it did the first time with ~10 gal.

I suppose the carb is my next consideration.

It just seems so unlikely to me since it starts fine, idles fine, generally runs fine, then simply dies, but turns around and starts/idles/runs fine again for a few minutes.
Then again, I know nothing about carbs.

 

[jbetzelb]

Re: 89 4.3L starts, runs fine, stalls

I have a 89 4.3 and had the exact symptons you describe. Mine was the water seperator / filter was blocked. Sounded like you already replaced that. Did you check the filter that is in the carb?