thunderbolt iv no spark

[chartersj]

OK, sounds like the sensor has failed. Yeah, the rotors are loctited on. Get some Loctite 222 for the new one.

Chris.....

Replaced the rotor, cap, and sensor, and still no spark.

 

[achris]

Do you same check, look for 0 to 5v swing on the sensor output.

 

[chartersj]

Do you same check, look for 0 to 5v swing on the sensor output.

Yeah I checked that as well. Still no voltage swing on white/Green, and I'm still getting 12 volt on white/red.
Thanks alot for the help, it's very appreciated. I'm getting very close to just dumping this thing....

 

[Pete104]

Yeah the ground was good on that one too. I have a new rotor, cap and sensor on the way now. The sensor was the newer 3 wire sensor and looks fairly new, I broke the rotor trying to remove it off the shaft...

You said the "3 wire sensor looks fairly new". Did you buy a new one?

 

[chartersj]

You said the "3 wire sensor looks fairly new". Did you buy a new one?

Yeah I bought a new one. I have ohm checked the ignition module harness and any other wires I can get at as well

 

[achris]

Yeah I checked that as well. Still no voltage swing on white/Green, and I'm still getting 12 volt on white/red.
Thanks alot for the help, it's very appreciated. I'm getting very close to just dumping this thing....

That's very odd. What are you using to swing across the sensor element?

 

[achris]

Yeah I bought a new one. I have ohm checked the ignition module harness and any other wires I can get at as well

If you have 12v on the white/red going into the sensor and you are measuring the output of the sensor then the rest of the harness shouldn't matter. Where exactly are you taking the measurements?

 

[Pete104]

Thunder IV w/module mounted on distributor? I can only come up TB V w/mod mounted on dist. with the knock module. Is that what you have? That's serial #'s OL010037 - OM599999. 1998-2001.

 

[chartersj]

That's very odd. What are you using to swing across the sensor element?

I am using a steel ruler just like you said to use. I tried a couple other thin pieces of metal and got the same results.

 

[chartersj]

If you have 12v on the white/red going into the sensor and you are measuring the output of the sensor then the rest of the harness shouldn't matter. Where exactly are you taking the measurements?

I left the white/red coming from the sensor plugged in, I had the white/Green unplugged from the module and interrupter switch and checked voltages on that end from the sensor to ground and got nothing with key in on/run position. At the same time I have the high tension lead from the coil to the distributor unplugged with a spark plug in the end to the coil and resting on a ground, which is the top of my exhaust manifold. I do not have the risers bolted on yet.

 

[chartersj]

Thunder IV w/module mounted on distributor? I can only come up TB V w/mod mounted on dist. with the knock module. Is that what you have? That's serial #'s OL010037 - OM599999. 1998-2001.

Yeah this is the thunderbolt 4. The original module was bolted to the back of the distributor, and I bought a riser mounted module off a running boat (so the guy says). I have been switching back and fourth between them for testing. I don't believe I have a knock module but could be wrong.

 

[Pete104]

TB IV was mounted to exhaust riser. V was several configs. What connection do you have? The 4 wire & 6 wire plug?

 

[chartersj]

TB IV was mounted to exhaust riser. V was several configs. What connection do you have? The 4 wire & 6 wire plug?

Yeah that's the plug I have. Its has a White/red, white/green, purple, and a grey wire.

 

[achris]

I left the white/red coming from the sensor plugged in, I had the white/Green unplugged from the module and interrupter switch and checked voltages on that end from the sensor to ground and got nothing with key in on/run position. At the same time I have the high tension lead from the coil to the distributor unplugged with a spark plug in the end to the coil and resting on a ground, which is the top of my exhaust manifold. I do not have the risers bolted on yet.

Very odd for it to be faulty out of the box. What brand is the new one?

Chris.......

 

[chartersj]

Very odd for it to be faulty out of the box. What brand is the new one?

Chris.......

It is a sierra # 18-5116-1. The one I took out looked to be the exact same as well. The new coil was also a sierra part.

 

[Pete104]

Yeah that's the plug I have. Its has a White/red, white/green, purple, and a grey wire.

There is also a black wire, right?

 

[chartersj]

There is also a black wire, right?

No black wire in the plug. I may have found the problem though. The temporary ground i made for the new riser mounted module was not getting a good connection through the plate. Also i dont think the spark plug was getting a good ground connection when it was laying it on top of the exhaust manifold when testing for spark. I had a buddy hold a ground wire directly from the negative post on the battery to the back of the module and spark plug and got spark that way. The original distributor mounted module was probably not getting a good ground through the distributor housing after the new 3 wire sensor was put in it. I am going to put the risers on and mount the module with an extra ground connection and then test the spark again but its looking good. Also i need to invest in a test light,,,,the voltmeter was not showing a swing on the white/green wire, but then when we tried a test light it was pulsing on and off.

 

[Pete104]

No black wire in the plug. I may have found the problem though. The temporary ground i made for the new riser mounted module was not getting a good connection through the plate. Also i dont think the spark plug was getting a good ground connection when it was laying it on top of the exhaust manifold when testing for spark. I had a buddy hold a ground wire directly from the negative post on the battery to the back of the module and spark plug and got spark that way. The original distributor mounted module was probably not getting a good ground through the distributor housing after the new 3 wire sensor was put in it. I am going to put the risers on and mount the module with an extra ground connection and then test the spark again but its looking good. Also i need to invest in a test light,,,,the voltmeter was not showing a swing on the white/green wire, but then when we tried a test light it was pulsing on and off.

If you really have a ThunderBolt IV, there are 2 configs for wiring, the first being hard wired with eyelet connections that changed to push-on bullet type (male/female) connectors. That was 2nd generation for replacement sensors. The original "ignition amplifier" now referred too as "module" has an independent ground. Either a short black wire right out of the "amplifier" or a short black wire out of the 5 WIRE harness that plugs into the module.
You must use UNPAINTED surfaces for using ground in any scenario. Simply laying a plug on a manifold IS NOT a good ground! Especially in Mercurys case. That paint is an inch thick.

Looks like your going in the right direction.

Good luck!

 

[chartersj]

Thought i would update, I have the engine running now. Good spark to each cylinder. It runs good on the muffs for a couple minutes but then acks like it is starving for fuel. I rebuilt the weber carb with new floats, new fuel pump, new fuel filter, and the gas tank is all fresh fuel. I water tested it for the first time tonight and it ran great for 10 minutes, then i let it come down off a plane to idle and then when i tried to get going after that it would just hesitate and stall everytime i tried to accelerate. I was able to idle back to the trailer.

 

[NHGuy]

You probably have junk in your fuel system, and now you have some in the carb you just redid. Check the contents of the filters. If they did a good job maybe the carb was spared. But it sounds like fuel starvation. There was probably crud in the fuel tank, lines or filter.