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No Ignition Mercruiser 350 Mpi

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Old 06-19-2011, 07:10 AM
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Default No Ignition Mercruiser 350 Mpi

I recently bought a boat with a 99 350 MAG MPI / BRAVO 1. Engine had head gasket issues and engine was already partially dismantled. I replaced both gaskets and completed the engine.

Engine is not firing up, no ignition (no spark at the plugs)

I can hear the fuel pump working for a couple seconds when turning the switch on.

When switch is in “on” position, I have 12V at the + side of the coil (red wire)
But I also continuously have 12V at the negative side of the coil (white wire), (not only when switch is on, but also when cranking)

At the distributor, only 2 wires; white/green which is connected to purple/white and red/white which is connected to pink wire.

What’s the problem? How to test the distributor?
Anyone an electrical scheme?
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Old 06-19-2011, 07:46 AM
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dude cmon...really. remove the 12v from the neg side and put a good ground on it.......that simple
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Old 06-19-2011, 05:34 PM
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Thx fast reply, wished it was that easy…

I grounded the – side of the coil directly to the battery (better discription would be "court circuiting" seeing the sparks…

With white (negative) wire disconnected, always 12 v on the – side
When properly grounded, no 12V at the – side, but no changes when cranking, so distributor is not intermittent???

Replaced coil by spare one (good working order???) , no luck, same issues

What’s next???
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Old 06-19-2011, 06:57 PM
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bad control module inside distributor if it doesnt have points style
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Old 06-19-2011, 07:05 PM
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This should help. There is a troubleshooting flow chart near the end.
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Old 06-20-2011, 09:58 AM
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Negative teminal of coil should not go to ground. I had the same issue when putting my engine back in after a long layup with no engine. Neg side should have 2 grey wires, one goes into harness and leads to the tach, the other leads to the ignition pickup coil in the distributor. + side of coil will have 2 purple wires, one coming from harness (and ign key), the other goin to distributor. Distributor also had the white/green and white/red wires coming out of it and going to the ignition module on the exh riser.
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Old 06-21-2011, 12:58 AM
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According to the merc fault diagnosis, I disconnected the wht/red wire and there is 12V

Striking the coil lead to a grounded wire, no spark

When disconnecting the wht/green wire (after grounding the coil/distributor lead) and intermittently striking to a ground no spark!

Only when striking with a grounded wire to the negative (-) side of the coil, I can see a very small spark out of the coil lead

I replaced coil again (3° coil) still no spark

I replaced the distributor sensor, leads and cap, still no spark

Finally I replaced the ecm module, still no spark

Meaning I almost replaced the whole ignition system and still no good

What’s next to try?
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Old 06-21-2011, 10:36 AM
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Quote:
Originally Posted by evaluex View Post
According to the merc fault diagnosis, I disconnected the wht/red wire and there is 12V

Striking the coil lead to a grounded wire, no spark

When disconnecting the wht/green wire (after grounding the coil/distributor lead) and intermittently striking to a ground no spark!

Only when striking with a grounded wire to the negative (-) side of the coil, I can see a very small spark out of the coil lead

I replaced coil again (3° coil) still no spark

I replaced the distributor sensor, leads and cap, still no spark

Finally I replaced the ecm module, still no spark

Meaning I almost replaced the whole ignition system and still no good

What’s next to try?
You either have a wire connected where it does not belong, or you are missing a connection. I see in your post that it is MPI, so it is Thunderbolt V ignition, which may be different than the TB IV that I have. Like I said before, I was stuck too just like you, and was trying different parts like ECM's, coils, etc. My problem turned out to be a ground wire attached to the negative teminal on the coil that did not belong there. You need to go through the wires leading to the coil, starting with the purple wire that feeds into the wiring harness. This wire originates from the ignition switch, but it also feeds power to the gauges and other accessories on the helm. Sometimes one of these can be bad and cause your coil to not have the clean voltage that it needs to fire. Also, the large engine harness connector can have poor conductivity. Remove the harness connector, clean all the terminals with a brush, and put some dielectric grease on it. Check to be sure you have 12V or better from the purple wire coming out of the harness. It will be pin #5 on the connector. That is a good place to start. You can also bypass all of this and just run a jumper wire directly from the + side of the battery to the + side of the coil. If you get spark from the coil after this, then your problem is in the circuit that I just described.
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Old 06-21-2011, 12:07 PM
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Bypassing the 12V + wire, I already tried which didn't changed anything

Does someone has a good electrical schema for this particular engine?
350 Mag Mpi 99 TBV ignition Bravo setup
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Old 06-23-2011, 05:51 PM
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sorry dude wasnt thinking when i replied to you earlier.
1- white wire should go to neg side of coil
2- red wire to pos side of coil
3-wht/red wire from distrib. wheel sensor should be connected to the pink wire
4-white/green wire from distib. whhel sensor should be connected to the purp/white wire.
also google code 45 (coil driver fault) this fault code should guide you on how to troubleshoot your coil wiring. good luck
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