No Fire/no Spark Thunderbolt
 

I have a 93 baja with 454's. I just bought the boat and when i got home i started it on a hose and it fired perfect. after about a minute it shut off like the ly was turned off, and it owuld not start again. then a few days later i went and started to work on the boat and it started instantly but i only let it fire then i shut it down. i took it out today and put it in the water and it would noit fire. i searched the threads but eveyone is talked about ignition boxes. I only see a coil and distributer on this motor, i dont see any ignition box. Could this be a coil? Thank you for any help!

The first thing I would look at it the pickup sensor in the distributor. Its probably something simple.

Double check the engines large wiring harness plug. A buddy had his work loose 2 yrs ago. Same symptoms as yours. The plug was in just enough to work most of the time, but then without warning, just shut down. dead.

Another thing to check is the grounds for your ignition module. The bracket must be grounded and the black wire. If the engine is stock then it has a module and it is bolted to the side of the exhaust riser.

I have a troubleshoot paper i'll scan and post for ya when I get home. It's shows the process of troubleshooting the TBIV ignition system. Very simple and will tell you the culprit. I've had a similar problem in the past and it was the distributor ignition sensor in the dist housing.

I doubt it's the ignition advance moudule. They are made very well and don't go bad very often. On a stock application they are sometimes mounted on the riser or the back of the cyl head.

I checked the main wirring plug and it looked good, that also happened to my old boat. I stll cant find an ignition module but will look again when i get home. If you post the wrring diagram it may not let me look at it because i am not a gold member. if you want to email that would be great! [email protected] thanks for the help so far!!

Your ignition module looks like part #25 and may be bolted to the distributor
http://www.mercruiserparts.com/Show_...BUTOR%29+TB+IV

or if its bolted to riser, it will look like part #9

http://www.mercruiserparts.com/Show_...+ELBOW%29TB+IV

The sending/pick up is part # 7 and is the most likely cause of your problem.
http://www.mercruiserparts.com/Show_...N+COMPONENTSup is part # 7 and is the most likely cause of your problem.

I would also check for a bad coil.

Try this.
http://www.marinemechanic.com/site/page251.html

rdoactive beat me to it. That link was the same thing I was gonna send you.

Happened to me at the river last week. Allothesuddn' DEAD! 10 miles from anywhere. Plugged in my spare module and away we went. Thank God I allways carry a spare! Most likely, it's the module. Attaches to drivers side riser with three small bolts and plastic spacers to mount it with 4 or five wires to it . It is a trangular mount.

Wait a minute here, both engines or one?

Just one engine wont work. if i hook up a test light to the coil on the neg and the positive on the coil i get nothing. if i ground my light to the block i can touch either the pos or neg on my coil and the light lights????? that doesnt make sense... this is all with the key on.

Pull your cap and rotor off, the ignition module should be to the back of the distibutor, that sounds like the issue

Just one engine wont work. if i hook up a test light to the coil on the neg and the positive on the coil i get nothing. if i ground my light to the block i can touch either the pos or neg on my coil and the light lights????? that doesnt make sense... this is all with the key on.

I re -up my first thought. Its the module, plug a new one in and play.....

That does make sense. The coil is energized from the purple wire on the + side. The coil is continuous to the - side so you will get 12 v there too. The ignition module grounds the coil to fire it based on the timing and distributor sensor input. After checking grounds/connections, switch coils between motors first. Then switch distributors between motors. Last thing I would look at is the module.

Hmmmm, i will try module first, cause its the easiest, then the coil. after i check all the grounds. I will let you know. I appreciate the help!!

I show 0 volts on the bad side but i only show 3.5 volts on th side that works perfect.

I think my problem has nothing to do with the ignition system. I have 2 volt power in weird places. They have electric fuel pumps on this boat. They pulled power from the purple wire that goes to the main wiring harness for the pump. some times i have no voltage at the coil on the positive side and sometimes i have 12v. If a boat has electric fuel pumps where should the power be taken from?

duh

But the boat runs fine when i removed the wire from the fuel pump to where it was spliced in to the purple wire. It started right up and would have kept running if it had fuel. So i hot wired the fuel pump and it ran perfect. Now i dont know how to wire the electric fuel pumps correctly or put mechanical pumps in. The other engine is wired the same way and seems to work fine. The fuel pumps are grounded and have a red wire going to the main harness hooked to the purple wire, they turn on as soon as i turn my key on.

The module is not under the cap!

You could always just wire the electric fuel pumps from scratch to a switch on the dash with an oil pressure cut off in between.

Heck I agree, you should have a spare on the boat anyway. Do you want me to send you one to try? You can ship it back to me afterward. [email protected]

Any word as to what was wrong yet????

Fuel pump was hooked to the coil purple wire and causeing a voltage drop. Previous owner had it hooke dup wrong, worked sometime and not others. I ran the fuel pump with a relay. Now runs fine.

Darn I thought I had it!!!! Glad you got it cleared up... Cheers!

Good job troubleshooting!

You guys are awesome here!!