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gumby
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Jul 15, 2009, 10:37 AM
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very tricky problem
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I have a 1986 351 Windsor in a boat. it was recently rebuilt about two years ago. it has a MSD distributor and a holly carburetor. the boat starts fine cold but if the temperature gets above 150 the boat will not start warm. I have changed the coil that runs on seven volts. put a new module in the distributor. and have put on a new Holley carburetor. the fuel pressure maintains strongly at 4 PSI. I have removed the intake and cleaned it for any rust that may have accumulated over winter. it was clean. so the main question is I have strong spark I have fuel why won't it start. and sometimes it will crank and crank and start when I let go of the key. I am a pretty decent mechanic but this one has me puzzled I can't think of anything that I'm missing so any suggestions would be greatly appreciated thank you all
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Hammer Time
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Jul 15, 2009, 11:15 AM
Post #2 of 24
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Re: very tricky problem
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The reason it fires when you let go of the key is because the starter stopped robbing current from the battery. Your dealing with a weak spark because the starter is drawing the current away from the ignition. You might want to try using a hotter heat range on the plugs and make sure the wires don't have too much resistance. If you have points, they may have too much resistance.
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gumby
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Jul 15, 2009, 11:36 AM
Post #3 of 24
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Re: very tricky problem
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thank you for the post hammer time. no the MSD distributor is electronic. the boat did originally have points. but the wires are what came with the distributor. I don't really have a weak spark and under a warm condition 150 when cranking the voltage drops to 11.25 on my DVOM. it's a fluke so I know it's good. I did change to a hotter plug. it didn't seem to make a difference. they are gapped at 54 thousands. I really appreciate your time thank you
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Hammer Time
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Jul 15, 2009, 11:42 AM
Post #4 of 24
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Re: very tricky problem
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Yes, you do have a weak spark but it only shows up under compression combined with starter draw. If you have electronic ignition, then I don't believe your supposed to have a 7 volt feed going to the coil with ignition "on". There is likely a resister inline (possibly a wire) from when it had points that needs to be bypassed or removed. You should be running on 12v now that you have electronic ignition.
If you want to try an experiment, get a 12v booster and run the starter off that and see if it fires faster.
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(This post was edited by Hammer Time on Jul 15, 2009, 11:43 AM)
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gumby
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Jul 15, 2009, 11:55 AM
Post #5 of 24
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Re: very tricky problem
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yes I do have her resistor and I tried to a wire around it to give me 12 voles at the coil. but that created another problem it started welding my starter solenoid together so I had to get a Honda coil that was set up to run on the resistance so the coil runs on 7 V but distributor runs on 12v but I think that's a good idea to try to start it off another battery. I have heard that I can use a diode in place of the resistor it has something to do with the back flow of electricity that welds the solenoid together.
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Hammer Time
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Jul 15, 2009, 12:01 PM
Post #6 of 24
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Re: very tricky problem
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There something about the way it's wired that caused the feedback to the starter. Yes, a diode is like a one way valve for electricity and will prevent that.
There is really no such thing as a 7 volt coil. Some coils have the resister built right into them but you don't want one of them. All external resister coils work the same way. You just need to get a constant 12v to the coil without it feeding back into the starter and make sure your coil doesn't have an internal resister. You could always just run a whole new wire from the ignition switch or neutral switch.
You might want to try closing the gap on the plugs a little too.
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(This post was edited by Hammer Time on Jul 15, 2009, 12:05 PM)
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gumby
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Jul 15, 2009, 12:12 PM
Post #7 of 24
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Re: very tricky problem
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sorry I didn't explain myself well enough yes has an external resistor. and I had a 76 Honda cvic that had the exact same resistor. so that is the coil I bought. I tried a regular coil first and it burned up. soul I tried a high performance coil from my local speed shop and it burned up. so that's why I went with the Honda coil. so do you think because I'm only running 7 V to that coil. that he could be my problem?
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Hammer Time
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Jul 15, 2009, 12:17 PM
Post #8 of 24
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Re: very tricky problem
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Yes, I do think that is your problem. I don't understand what your talking about with burning up coils. All coils are 12 volt coils and made to operate on 12 volts. Systems with points are reduced to 7v to protect the points. the coils are still the same. All point systems have a resister in line somewhere. some put it before the coil and some put it inside the coil but you can't burn a coil out by running 12v to it unless it's from a 6 volt car.
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gumby
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Jul 15, 2009, 12:25 PM
Post #9 of 24
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Re: very tricky problem
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no I assume they didn't have enough voltage which cause them to fail. so I will try to go around this resister without welding my starter solenoid together. and try the extra battery trick. he have any suggestions on where to get this diode I need. and what micro farad it should be?
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Loren Champlain Sr
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Jul 15, 2009, 12:25 PM
Post #10 of 24
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Re: very tricky problem
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Just my 2 cents worth; If this is an I/O, you should go back to stock type distributor and carburetor. An explosion is just waiting to happen. Fuel vapors can build up in the bilge and BOOM! Too much carb? Not enough voltage? If it starts and runs okay cold, then I'd say too much fuel warm. A 351W should have about a 550-600cfm carb. A MARINE type. I've owned several I/Os, all with V8s. All with point type distributors. Trust me....this is not something that you want to be modifying. I've also seen several boat fires. Really sucks. JMO.
Loren
SW Washington
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gumby
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Jul 15, 2009, 12:30 PM
Post #11 of 24
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Re: very tricky problem
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no it's not an I/O it is a direct drive and the 351 is not much different than the one you're Ford truck and MSD distributor's marine grade. for the 351. but I do understand your concern. but I wouldn't do it wrong
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Hammer Time
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Jul 15, 2009, 12:37 PM
Post #12 of 24
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Re: very tricky problem
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Loren, all inboard boats have vent fans for preventing explosions. A set of points is no safer than electronic ignition. He has an ignition problem because the engine fires after letting go of the key which is a typical low primary voltage issue. I had the same PCM engine he has in a Ski Nautique for years.
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gumby
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Jul 15, 2009, 12:46 PM
Post #13 of 24
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Re: very tricky problem
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yes it's exact same PCM engine except mine is in a supra. and proving to be a pretty big pain in the butt.
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Hammer Time
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Jul 15, 2009, 12:49 PM
Post #14 of 24
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Re: very tricky problem
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You may ultimately find that you have a starter drawing too much current here. It would probably be a good idea to measure the starter draw. If it's over 225 or 250, that's a bit high and could be contributing to this problem.
Anything you can do to increase the cranking voltage to the coil or reduce the required KV to fire the plug will help your problem.
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gumby
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Jul 15, 2009, 12:56 PM
Post #15 of 24
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Re: very tricky problem
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thank you for all your help. I will spend another weekend working on my boat instead of enjoying my boat. and tried to talk to you Sunday or Monday although not be pessimistic I really don't think I'm going to have good news. welcome to my troubleshooting hell. but you have been a great help thank you
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gumby
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Jul 26, 2009, 7:12 AM
Post #16 of 24
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Re: very tricky problem
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Well problem fixed it was simply moving one wire from one side of the resistor to the other which gave me 12 V to my coil and it works just fine now thank you for all your help
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Hammer Time
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Jul 26, 2009, 9:15 AM
Post #17 of 24
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Re: very tricky problem
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Your welcome............. Glad I could help.
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Loren Champlain Sr
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Jul 26, 2009, 11:55 AM
Post #18 of 24
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Re: very tricky problem
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 Geez, at least he could have offered to take you skiing. LOL. It's always funny watching an old guy ski.
Loren
SW Washington
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Hammer Time
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Jul 26, 2009, 11:58 AM
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Re: very tricky problem
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I think I could still handle it even though I haven't skied in years. I barefooted on my 40th birthday. It's just too painful now. My joints are paying for all the falls I took earlier.
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Loren Champlain Sr
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Jul 26, 2009, 12:09 PM
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Re: very tricky problem
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Barefooting? My son did it, but I could never bring myself to try it. Real weanie, here. I did take some nasty falls, but none that had any lasting effects. LOL. Had a rope break on me once. Tore up my shoulder, but just for a couple of weeks. We sold our boat in '95, so it's been a while for me, too.
Loren
SW Washington
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Hammer Time
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Jul 26, 2009, 12:12 PM
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Re: very tricky problem
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My joints have been bent in ways Stretch Armstrong couldn't handle.
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Loren Champlain Sr
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Jul 26, 2009, 12:13 PM
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Re: very tricky problem
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Hmmm. Gonna have to start calling you Gumby!
Loren
SW Washington
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Loren Champlain Sr
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Jul 26, 2009, 12:21 PM
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Re: very tricky problem
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Try 'right' clicking for the image?
Loren
SW Washington
(This post was edited by Loren Champlain Sr on Jul 26, 2009, 12:22 PM)
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Hammer Time
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Jul 26, 2009, 12:23 PM
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Re: very tricky problem
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That worked.............
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