GM 350 not starting and locking up. I need help

[kolnerspieler]

Hey Guys,

I am a bit stumped right now with my Gm 350 in my 1990 cruisers Holiday. So here is the story. Last year I started having this issue late in the season. I went to start the boat, the engine cranked for 20 seconds and then something happened and the starter was broken. I first thought that it was a hydrolock and I pulled the plugs out and turned the engine oiled the cylinders down, took the elbows and manifolds off but everything looked good, So definatly no water in the engine. When i put the plugs back in the the starter was grinding and was not turning the engine. I pulled the plugs back out and it could turn the engine, but as soon as I put the plugs back in the starter could not turn and it was making a grinding noise. I got a new starter and the engine turned fine with the plugs in the engine, but after about 20 or 30 seconds of cranking the engine locked up again and broke the starter. I thought that I was getting a strong backfire, so I proceeded to check timing etc. but now it looks like the engine is flooding or locking up for some other reason.

Here is what I did so far.

I checked the timing
I replaced the spark plugs.
I checked the distributor, etc. all good here
I made sure that all wires are conencted to the correct plug and the correct location on the distributor
I checked to make sure that I have a spark. I pulled all the spark and looked at them to make sure that they are sparking.
I replaced the fuel pump and fuel filter
I had the carb rebuilt at a shop
I hooked up a seperate fuel tank with a fresh gas to the carb after the carb rebuild
I also checked compression and I have 150 to 160 psi on a cold engine with a somewhat weak battery turning the engine, so I have good compression.

After doing all these things what the engine will do is with a new starter turn over as long as there is no fuel connected to the carb the engine will turn without locking up, as soon as I hook the electric fuel pump to a gas supply after about 20 or 30 seconds of cranking the engine will just lock up and break the starter. the starter after this will no longer turn the engine. I just do not know what else to do anymore. If anyone has had this issue or has any suggestions I would be all ears.

My only other though is that I do not have a spark in the cylinder which could be bad cables or something else igniation related, but I did have a spark when the plug was pulled out. I checked the ignition coil and the reading and resitanance was good. The resistor is good and there is a spark but not sure if there is on inside the cylinders. Otherwise I do not know what else to try.

The engine was a repower 3 years ago that I did on my own. It ran great until now. It is a GM block 350 by pleasurecraft with a holley 650 carb and mallory ignition. the only other thing I could try is a new ignition module, but that would be a long shot. Let me know what you guys think what else I could try and if anyone had this type of problem at some point and what resolved it.

 

[NHGuy]

Sounds as if it's combustion chambers are filling with a liquid which then won't compress. If you continue to crank like that you overwhelm the starter.
Try cranking it without the fuel supply enabled, but with spark plugs. If you get the usual compression and release sounds while cranking it could be too much fuel. If that works you might have a sticky float loading the engine with fuel.
Also, since it does not start recharge the battery, you won't get a start with a poor battery.

 

[NHGuy]

If it halts while cranking, stop. Don't force the starter and break it again.
When the engine won't crank after 20 or so seconds remove the spark plugs and crank it to see what comes out. Gas, water, oil, or air.

 

[Bondo]

Ayuh,.... What drive is behind this motor,..??

Pull or disconnect it,.... it could be the problem,....

 

[Rick Stephens]

Ayuh,.... What drive is behind this motor,..??

Pull or disconnect it,.... it could be the problem,....

Smart.

 

[kolnerspieler]

So I already tried all of that. I had the outdrive off, but that has no affect on it. Also as long as there is no fuel the engine does not lock up. If i leave the fuel hose disconnected I can crank as much as I want to with the outdrive on or off. I tried cranking with the blcok drained and the outdrive off as well just to make sure. That has no affect either it still locks up. As soon as I connect fuel and crank for about 30 seconds it locks up. I just dont get it. I charged both batteries also overnight to make sure. The floats I checked 3 times myself and decided to have the carb rebuilt, so all should be good there. Not sure what else to try. The fuel pump runs at 4 to 6 psi, so it should not be overloading the carb.

My only thought is the ignition module as a long shot, but what I do not know is why it locks up. Even if I had no spark the engine should be able to push the mixture out unless I have so much in there that it cannot push it out because of the manifolds? I will pull the manifolds also to give it a shot. if you have any other ideas I would appriciate it.

 

[Bondo]

The fuel pump runs at 4 to 6 psi, so it should not be overloading the carb.

Ayuh,..... Is it a mechanical pump, or electric pump,..??

A Real L o n g shot, but if mechanical, I wonder if it could bind the motor by mechanical advantage over the starter,..??..??

 

[Grub54891]

Possible that it jumped time and when it does fire it fires way to early? I've seen distributer gears strip out before.

 

[kolnerspieler]

Problem solved. I took out the ignition coil. The coil stated not for external resistor and I have an external resistor. I measured the coil and got he correct resistance measurements but because it was not the right coil and probably lost some power also it did not provide enough power to the plugs. I purchased a marine msd coil correct for my ignition and it fired right up. The sad part is that this coil came with the engine when I purchased it 3 years ago as a brand new repower from pleasurecraft and worked until now but must have gotten burned up.

 

[Grub54891]

So it sounds like you had hydrolock, from fuel. I personally never seen that happen, but I guess it's possible. That would take a fair amount of fuel. Hope ya changed the oil right away.