stinger390

Hi,

Having a minor issue with my 454 mag bravo, 1992 vintage, carb engine.

I have been having a hard starting problem on my stbd engine when cold for a little while, but it always starts and runs fine...just takes a little more cranking than the port engine.

Today I was out warming them up for winterizing, and the problematic engine would not start as long as I held the starter engaged. As soon as I released the starter it would either fire up or cough with a little smoke out the flame arrestor. (little backfire I guess) As I would re-engage the key, again it would not start until the key is released.

Once running, it runs fine....no noises, prefect o.press, temps, etc. I thought it would be timing, but I checked it and it was right on the mark at 8 degrees btdc at idle. Advance was normal as well. Ign is Thunderbolt IV with v8-HP module and msd coil new 2 years ago.

I put my timing light lead on all spark wires and had good fireing on all cylinders. All plug wires attached, new cap and rotor early in the year and ran the boat very little this season.

My thoughs are on a voltage interruption to the ignition with the key engaged somehow. Not sure where to go next with this one. Port engine is rigged the same and starts just fine.

Thanks in advance for any insights anyone might offer.

Todd

ljsmith1

You need to hook up a DMM to the purple (ignition) wire on the coil to see if you have 12VDC when you crank and after you release the key. I would not be surprised if it is the ignition switch going bad.

Good Luck!

stinger390

On some local advise, I replaced the key switch....not the problem, same scenario exists. I also tried for sh#ts and giggles another ignition module, and coil, but never really entertained either as being the problem since the engine runs great.

Is there a way to jumper power from the starter solonoid to the coil, so that when the key is engaged another shot of 12v goes from a jumper wire on the starter solonoid to the coil....and then when the key is released the jumper wire would be de-energised????

Someone locally had suggested such a way to wire the system...something about the key on being 8V and the start position energizing another wire to 12V.....no such wire in my wireing diagram of the 454 mag.

I'm thinking it might be the ignition amplifier, but the engine runs fine once it starts after the key is released......

Have a potential buyer for the boat coming next week, and would like to have this glitch resolved.

Wierd how stuff breaks while the boat is sitting on the trailer huh...?

jayhawk261

Are you sure it isn't just too rich or possibly flooded? Is there a smell of fuel? Try opening the throttle all the way while cranking it. It seems to me that when I had hot rod engines with carbs and they were running very rich for one reason or another and were flooded that they would act similar to that. Easy check out anyway.

stinger390

Nope, not flooded....as soon as I let go of the key, it starts right up. Definitely no spark while cranking over.

As far as jumping a wire from the starter circuit.....the yellow wire from the solonoid to the starter is only hot when the key is engaged to start right??? So if I ran a wire from the yellow start circuit wire to the positive side of the coil, would that not give me ignition for the start? Or too much amperage would be going to the coil....?

stinger390

Turned out to be a bad wire. Ran a new higher gaugw wire and she started right up.

I love it when it's simple. I always seem to have this natural tendency to go to the morre complicated items first.

Thanks