Thunderbolt IV ignition questions

[PowerAddict]

Hi guys,

I'm chasing down a TBIV issue and I don't want to beat a dead horse; I would just like some quick sanity checks.

The problem started at the end of last year, and I dd the diagnostics check, and I thought the problem was the pick up in the dizzy because I would have spark when tapping to ground.

I replaced it...still no spark.

I disconnected the grey wire from the tach...still no spark.

So I checked all the connetions again and again, and then swapped coils. Still no Spark

I went ahead and found a used TBIV module and put it on...still no spark.

I hooked a testlight in-line (purple wire - test light - + on coil) The light did not blink as I was cranking...seems to me that woudl be a faulty pick up in the distributor, even though it's a brand new one.


I guess I was just wondering what you guys though, and if there was anything else I need to check? there's 12 plus, volts at the key on.

Thanks.

 

[achris]

Re: Thunderbolt IV ignition questions

Disconnect the shift interrupt switch... check for spark...

 

[Don S]

Re: Thunderbolt IV ignition questions

Not sure where you are checking the spark from, but Cap or Rotor if checking at the plugs.

 

[PowerAddict]

Re: Thunderbolt IV ignition questions

Disconnect the shift interrupt switch... check for spark...

I'm pretty sure the shift interrupt switch prevents cranking, and the kill switch cuts off power to the coil, but I have power at the coil. But, I can double check that. Thanks.

Not sure where you are checking the spark from, but Cap or Rotor if checking at the plugs.

I'm checking at the coil and the plugs. New cap and rotor already though; I bought the mallory tune-up kit that came with cap, rotor, and module. So I did it all.

 

[Don S]

Re: Thunderbolt IV ignition questions

I'm pretty sure the shift interrupt switch prevents cranking, and the kill switch cuts off power to the coil, but I have power at the coil. But, I can double check that. Thanks

The shift interrupt switch is what kills power to the coil momentarily when shifting out of gear. Than lanyard kill switch is what kills power to the coil from the helm.

What engine are we working on here, year, Serial number if you really want some help.

And what is the tuneup kit PN, never heard of any tuneup kits coming with a module before.

 

[bungholio]

Re: Thunderbolt IV ignition questions

i think there is a rpm test wire you need to make sure is not shorted to ground?

 

[PowerAddict]

Re: Thunderbolt IV ignition questions

i think there is a rpm test wire you need to make sure is not shorted to ground?

I believe that is the grey wire to the tach that you are referring to. I have already disconnected that and tried starting.

The shift interrupt switch is what kills power to the coil momentarily when shifting out of gear. Than lanyard kill switch is what kills power to the coil from the helm.

What engine are we working on here, year, Serial number if you really want some help.

And what is the tuneup kit PN, never heard of any tuneup kits coming with a module before.

I do not have the lanyard deal, just toggle kill switch at the shifter, I know that one cuts power to the coil because when I first got the boat I couldn't get is started and ended up tracing it back to the switch not being on...D'oh!

It is a 1994 mercruiser 330 454

Oh, and I just checked again as to what I bought. It wasn't a "kit" per se, it was the cap and rotor and the module, but they were bundled as a set.

Thanks!

 

[Don S]

Re: Thunderbolt IV ignition questions

I do not have the lanyard deal, just toggle kill switch at the shifter,

That is the kill switch with the proper lanyard.



Since it's a 454, you don't have an Alpha drive, so no shift interrupt switch.
Do you have an actual serial number for this engine?

 

[dingdongs]

Re: Thunderbolt IV ignition questions

assume the rotor arm is on??????

 

[achris]

Re: Thunderbolt IV ignition questions

Lanyard switch (tethered to the driver) cuts power to the coil (engine can still be cranked).

Neutral safety switch (inside the remote control box) open circuits the starter circuit (engine will not crank).

Shift interrupt switch (I think that's the one you guys are calling a 'kill switch') GROUNDS the negative side of the coil. You will still have 12v on the positive with the negative to ground and the engine will crank, but no spark....

Chris......

 

[Don S]

Re: Thunderbolt IV ignition questions

Shift interrupt switch (I think that's the one you guys are calling a 'kill switch') GROUNDS the negative side of the coil. You will still have 12v on the positive with the negative to ground and the engine will crank, but no spark....

Chris......

94 7.4L Bravo...... No shift interrupt switch.

 

[achris]

Re: Thunderbolt IV ignition questions

94 7.4L Bravo...... No shift interrupt switch.

Yeah, I saw that AFTER I posted... :facepalm:

 

[PowerAddict]

Re: Thunderbolt IV ignition questions

I will have to get the SN tomorrow.

 

[PowerAddict]

Re: Thunderbolt IV ignition questions

the serial number is:

159666

 

[Don S]

Re: Thunderbolt IV ignition questions

What is the letter in front of the 159666?

 

[achris]

Re: Thunderbolt IV ignition questions

Serial number 0F159666 = 7.4L 454Mag Bravo Gen V, model #474B110GS. Year was 1994 (as the man stated....)

I hooked a testlight in-line (purple wire - test light - + on coil) The light did not blink as I was cranking...seems to me that woudl be a faulty pick up in the distributor, even though it's a brand new one.

You can't use a test light like that. The voltage drop across the light is enough so the ignition module won't work. Test lights go from a positive to a ground. If you want to see if (and how much) current is being drawn, you need to hook an ammeter in the circuit...

 

[achris]

Re: Thunderbolt IV ignition questions

What is the letter in front of the 159666?

'F' is the only one that works....

 

[PowerAddict]

Re: Thunderbolt IV ignition questions

I see it now, it is an "F"

 

[Don S]

Re: Thunderbolt IV ignition questions

Then in the future I will not expect the OP to tell us what he has. You can do all the leg work to figure it out . Why should we expect the person with the problem to give us the information when you can figure it out.
I'm not into puzzles tonight.

 

[04fxdwgi]

Re: Thunderbolt IV ignition questions



Here is the TB trouubleshooting chart. I have the TB4/5 manual if you need it.