I figured I better share this in case it happens to someone else. This is the adventure I had this weekend with my 96 2100SR with the 5.7L 2bbl Alpha 1 G 2.
So I arrived at the lake around 6:30 on Friday evening. Unpacked the truck and then proceeded to uncover the boat, get hooked to the trailer and drag it up the street to fill it up with gas. So all goes well here, I get her filled up, brought back to the ramp and dropped it in. She fired right up like always, backed it off the trailer and then proceeded to dock it for the night. No issues at all to this point.
Later that night (like 3:00 AM) it started dumping rain. It must have rained 3 inches or so in about an hour, not sure though as I fell back asleep
Morning comes around and we wake up, have breakfast and then get ready to head out on the boat. Oh, and I forgot to mention that we have company this weekend so it is me and the wife and our 2 little ones plus her cousin, his wife and their 3 little ones
So we get all packed up and lubed up for a day on the water. Walk to the boat, turn on blower, start loading the gear and coolers. Just before the people start loading, I decide to fire it up so it is warm and ready to go when all loaded. I turn key to Start, the motor starts to turn over and then a loud CLUNK. Yep, that is right, a CLUNK. So I pop open the front hatch on the motor box and try again. I see the motor start to turn over and then CLUNK and the motor just stops turning over.
So I am now sitting there thinking, what the in the h3ll just broke that would cause this? I did replace the ujoints in the driveshaft 3 weeks ago, could one have broken under no load at all? This is a rebuilt engine that I did not put it, could a rod have snapped under no load? Could the crank have snapped under no load? Could it be as simple as the starter or flywheel?
So I decide to look at the only thing I could with it in the water, the starter. I proceed to kick everyone out of the boat and sent them swimming at a beach area near the ramp. With help I lift off engine cover and remove the left side of all the back panels so I can easily access the starter. I disconnect negative battery cable, remove starter with cables connected and inspect. Nothing wrong from what I can see. Gear looks good, nose cone is not cracked, flywheel looks good from the small section I can see. So I then re-connect battery and ground the nose cone to the motor mount and cranked it over. Start gear came out and spun just as it should. So now I am still stumped as to what is wrong and now thinking it is more serious like outdrive or motor issues. So I mount the starter back up, re-connect battery once again and then try and crank it one last time before I give up and walk it over to the ramp and push it onto the trailer.
Surprise, surprise! She cranks over fine and starts. What the???
I shut it off and re-started it 15 times and no issues any more.
So now I am really lost as to what could have caused this. Could it have been the starter that looked fine? That is all I touched so it could not have been anything else, right?
So for the rest of the day I was really nervous but all day long she ran fine and started each time I turned the key. So I finish out the weekend, had a blast with the visitors and then come home yesterday evening. I get a call from my brother to see how the weekend went and I explained all the fun I had. He started laughing at my story and asked me, "do you want to know what was wrong?"
Well, you know I do as I am still not convinced the boat is OK and the starter is my issue. So he proceeds to tell me, "your issue was, you had........
wait for it......
moisture in your distributer cap".
Really? I was a mechanic for 7 years and I have never seen moisture in a cap cause the motor to lock up. I have seen them not start, or start and run poorly but to lockup and create a loud CLUNK, you have to be kidding me.
So he then explains that this is a common issue that he has seen on the 4.3 in Astro vans and Pickups too. The moisture causes the spark inside the cap to jump over to another cyclinder. If that cylinder has fuel in it and has started its compression stroke, it will fire off causing the motor to just stop as it forces the wrong piston down. He said he has seen it happen so violently that it caused the starter to actually break off from the block (not sure if nose cone broke or bolts broke). So the time it took me to tear apart everything and put it all back together plus the hot sun beating down on me and the engine dried it all up since it is a vented cap.
So, if anyone ever experiences this right after a rain, take a deep breath and see if you can remove the cap, dry it out and then attempt a re-start. Just might save you a couple of hours or frustration and more than a few grey hairs.
Did my motor just lockup while trying to start it?
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