1997 5.7LX no start

chapp252

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May 13, 2020
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18
Ok guys, I’ll try and be as accurate and succinct as possible.
two years ago, the boat had a new long block installed. Then she sank. Bellows tore i believe. Repairs were made and she was ran for half a season. The last trip she shut down. I noticed that there was a ground left unconnected and the ground bus had melted. So, this season I’m trying to get everything running again.
what I have done so far to my 1997 5.7LX Thunderbolt V
1) replaced the ground bus bar
2) replaces the coil
3) replaced the plugs, cap, rotor, and wires
4) filled tank with gas
5) replaces fuel filter
6) changed Oil/filter
7) replaced both batteries and double checked the block is grounded to one battery and the bus bar. Both batteries are connected at together at the negative terminals.

now, fuel is getting to the carb. I can see it squirt in when I pull the throttle cable.
I don’t seem to be getting a spark. I pulled the coil wire running to the dizzy and I didn’t see a spark jump While cranking. I did the same thing to a plug wire and saw no arch.
The coil appears to have a resistance of 2.2ohms between the positive and negative, but I did not remove any connected wires. Google says that’s a little high, but idk what specs are without a manual. When checking voltage At the coil + KOEO, 9.9v. It is suppose to have 12. Not sure what is going on here. Due to increased resistance inside the coil?

I checked the voltage, KOEO, of the red and white wire coming out of the dizzy and it was 0. Ignition module?

the diag tree I found here says to check the tachometer wire at the gauge, but I have not opened the panel on the head yet to check.

so, what are yalls thoughts? Anything I need to add to aid diag?

thanks!
 

chapp252

Cadet
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May 13, 2020
Messages
18
What would cause the coil to have less than 12 volts?
also, are the ICM’s really $600?!?
 

Bondo

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What would cause the coil to have less than 12 volts?

Ayuh,..... Welcome Aboard,..... A distinct possibility is corroded wiring connections, both power, or grounds,.....
 

chapp252

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May 13, 2020
Messages
18
Thanks for the warm welcome! I hope to get everything solved before the 4th. 🤞
 

Scott06

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Apr 20, 2014
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Look on Ebay for used modules. They are about $200 normally just be careful to get the same one you have, especially concerning alpha/bravo as the bravo doesn't have shift interrupt (I'm assuming you have an alpha...)
 

chapp252

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May 13, 2020
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So, how would y’all test the tach wire? I checked the resistance on the back of the tach between the grey tach wire and the ground on the back of the tach itself. The resistance was 3.5ohm. That should be in spec?
 

alldodge

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Just disconnect the tach from the coil until you get it running again, not needed to start
 

chapp252

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May 13, 2020
Messages
18
Ok, I’ll give that a shot.

i can get 12 volts from the coil positive. The wire hooked up to it has 12.3 volts, but when I connect the wire to the coil positive and bolt it down, the voltage at the coil drops to 8.5v.
bad coil?
 

alldodge

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The wire hooked up to it has 12.3 volts, but when I connect the wire to the coil positive and bolt it down, the voltage at the coil drops to 8.5v.

That shouldn't happen with a TB distributor unless coil is bad (which doesn't happen very often) or the negative side of the coil is grounding
 

achris

More fish than mountain goat
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May 19, 2004
Messages
27,468
It does sound like a bad module. Or a bad connection somewhere. Try running a wire directly from the battery (positive) to the coil positive.... Then check for 12v on the white/red wire...

Chris...
 

chapp252

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May 13, 2020
Messages
18
Ok, I’ll try that ASAP and let y’all know. Don’t have much free time between classes and 1 year old!
 

chapp252

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Joined
May 13, 2020
Messages
18
Sorry, Alldodge. A wiring diagram for what wires need to be connected to the coil.
So, I have a purple wire from the key to the coil positive. There are two grey wires that are on the coil negative and a black wire, also with a ring terminal, that appears to go to the 50 amp circuit breaker. The breaker is attached just in front of the carburetor flame arrester. Does that black wire (assuming a ground) attach to the coil also? If not, where?
 

alldodge

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have a purple wire from the key to the coil positive. There are two grey wires that are on the coil negative and a black wire, also with a ring terminal, that appears to go to the 50 amp circuit breaker.

That just doesn't sound right. On the negative side of the coil there should only be a gray tach and another gray that goes back to the TB ignition module

Here is a 4.3 but wiring is the same

4_3L elect diag.jpg
 
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