4.3 Dies at WOT - otherwise fine

[JagGuy]

Hi

Had the boat out for the first time today since buying it and doing repairs. Didn't go well, but a little background first:

Replaced the ignition system (new distributor, cap, rotor, coil, wires and plugs)

Rebuilt the carb and took the fuel system apart and cleaned/checked everything.
Put a new fuel filter on (I even removed the fuel filter mount & metal lines and blew
them with compressed air) and it had a new fuel pump (electric type) 3 years ago,
but has sat unused for the past two summers.

Set the timing, adjusted the idle and mixture in a test tank,

So . . . . to today

Started the boat at the marina - turned over, started first time.

Idles fine (couldn't be better) and pulled out of the marina.

Went down the river a bit to a local lake (Onondaga) and opened it up.

Everything was perfect. Accelerated without any hesitation, and planed pretty easily.
(Smile on my face at this point).

Then . . . . I felt the engine slow ever-so-slightly and I knew it wasn't me since my had
was on the throttle. Then . . . . . revs went down and it died.

Tried restarting without getting my hands dirty and it wouldn't.

Took the air cleaner off and there was gas, choke was open, nothing looked obviously wrong.

Got my better-half to turn it over while I closed the choke plate and opened the throttle a bit.
Started up after a few tries. Thought (more like hoped) that it maybe was a fluke. Whenever I
think something is a fluke, it never is, so you'd think I would know better right? Well, I must
have a learning disorder . . . . . . .

After a minute or two, back to idling fine and works at low rpm fine too. It did take a little while
to run at idle again though, without me helping it by holding the throttle open.

Opened it up again with the same results. No hesitation, planed perfectly, then died again. Actually,
I heard it starting to die and pulled the throttle back and put it in neutral, so it is actually dying,
not under load.

I am unsure what's the problem. Closing the choke and that making it restart is a big clue, but I'm
not sure what to make of it.

Any chance the fuel pump can't keep up at wot? But then, why doesn't it just start right up again
without using the choke (which should not have to be used on a fully warm engine).

I'm sure I missed some piece of vital information, but I will add anything I can.

Thanks for reading this and I appreciate your help.

Brian

 

[0352Marine]

Re: 4.3 Dies at WOT - otherwise fine

Try using a jumper wire in place of your fuel pump relay. I am having the same problem with mine but it only happens with the relay plugged in. I think the pump is some how sucking air and when it loses rpms the pump shuts off because it is connected to the alternator. If you use the jumper wire the pump will not shut off so don't forget about it. I am actually considering installing a toggle switch on my dash for the fuel pump and just wire it to the switch. I can't remember the numbers on the relay but I think you jump 36 and 80 but not 100% sure that it correct. I'm sure someone will correct me if it's wrong.

 

[Bondo]

Re: 4.3 Dies at WOT - otherwise fine

Ayuh,... See my post, Here...

 

[0352Marine]

Re: 4.3 Dies at WOT - otherwise fine

Hi

Opened it up again with the same results. No hesitation, planed perfectly, then died again. Actually,
I heard it starting to die and pulled the throttle back and put it in neutral, so it is actually dying,
not under load.

Brian

I did not have any ignition problems as I too thought maybe that's what it was but I had spark. Just took a long time to get the fuel back into the carb because the pump was sucking air. I think I have narrowed it down to the pick up tube inside the tank. As the pick up tube inside the tank ages it becomes brittle. The tube just pushes on the end of the tank fitting inside the tank. When I removed mine it was loosely fitted on the fitting. ( now think about this for a minute if the tube is sucking air it will be twice as hard for the pump to suck fuel, kinda like a straw with a hole in it and you want a drink. Now that being said you also have to remember that the pump only gets it's power when the alternator is spinning so if your not cranking your pump is not sucking which in my opinion sucks) So I am planning on using a small crimping tool and a small crimpper and a new tube to ensure I would never have this problem again.

 

[JagGuy]

Re: 4.3 Dies at WOT - otherwise fine

Thanks for the replies.

I'm going to try to do this in a methodical manner.

First, I'm going to take Bond-o's advice about the tach
being a potential problem and simply disconnect it until
I get a new one.

Then I'm going to take it out and try it. If it dies again,
I have a 2010 carb that has a hole in the float chamber
to set the float height, but I can also use the hole to see
if there is any fuel in the float bowl. If not, then it's a fuel
starvation issue.

In that case I will move onto 0352Marine's suggestion and
check the fuel pickup and also try to jumper the pump.

Does anyone know for sure what to jump on the relay to
turn the pump on?

Also, a thought I had was to hook a timing light up and have
my better half watch it when the engine dies. If there is no
spark, then I will know it's an ignition issue. Anyone see
any problems with this idea?

I will try these things at the weekend (weather permitting)
and then post the results here, so perhaps, it can help
someone else.

Thanks everyone . . . Brian

 

[Bondo]

Re: 4.3 Dies at WOT - otherwise fine

lso, a thought I had was to hook a timing light up and have
my better half watch it when the engine dies. If there is no
spark, then I will know it's an ignition issue. Anyone see
any problems with this idea?

Ayuh,... Do it at dusk/ dark,... It oughta be a Hoot,...

 

[0352Marine]

Re: 4.3 Dies at WOT - otherwise fine

Sounds good keep us udated. I would like to know just incase mine does it again as well. Then I know to check the tach. There is alot of good info on here as I have needed help with mine. I would also like to thank everybody.

 

[0352Marine]

Re: 4.3 Dies at WOT - otherwise fine

Ayuh,... See my post, Here...

Ok so just out of curiosity I looked under the dash of my boat to check the tach and to my suprise my tach was unplugged, well the backlight was so I plugged it in and now the backlight works. I don't know if this would affect my fuel pump. At least my light works I will take mine out this weekend as well to see if it dies with the relay. Thanks Bond-o

 

[JagGuy]

Re: 4.3 Dies at WOT - otherwise fine

Hi

A little later than I expected, but here is the update. I had a power steering leak that I wanted to make
sure was fixed so rather than taking the boat on the water I ran it in a test tank. Engine started first time
as usual, but this time, died after 30 seconds or so and wouldn't restart.

If you remember earlier in the post, the problem was with wide-open-throttle, not idling. Apparently, now
there's a problem all the time, which usually makes it easier to fix.

First thing I did was to remove the float bowl plug that's used to set the float height. What I found was
an empty float bowl. So, the problem was fuel. The fuel pump electrical connector just happens to be the
same as a spare one I have for a car, so I made a pigtail for the pump and connected it directly to the
battery, bypassing everything (but I never started the engine like this, or had the boat hooked to the
battery).

I could feel a slight bump movement in the pump when I connected it, but that's it. Tried it about 5 times
and the same thing. Then on the 6th try, the pump started spinning, but very erratic and for want of a better
saying, kinda sick. As soon as it started spinning though, the float bowl filled right up.

But, sometimes when I connected it, it did nothing. It seems that it's working intermittently and when it is
working, it's not working very well. This would explain everything.

I bought a new fuel pump (ouch $258).

Tried the pump with the pigtail first (without starting the engine) and the pump sounds strong and consistent.
Not at all like the old pump. Hooked the boat wiring back up to the pump and sure enough, the engine started
right away (first try) and I ran it for 15 minutes or so.

This problem I hope is fixed, but I have another one that I will create a separate thread for.

The new problem - when I went to turn the engine off, it didn't turn off. The key was in the off position but other
than the voltmeter needle swinging around, nothing else happened. First I couldn't get the engine to start,
now I can't get it to stop.

Thanks everyone for your help . . . . Brian