4.3 No Power and No Ignition Advance

[adamschuh79]

I have a 1989 4.3 with the Thunderbolt IV. Starts and idles great but has no power. I've replaced the water separator, cleaned the carburetor, replaced the plugs and double checked firing order is correct. Checked timing and at idle in gear, about 650 rpm the timing is at 10 degrees BTDC. I know it should be 8 degrees, haven't adjusted that yet. Rev engine up to 2500 rpm and the timing remains at 10, absolutely no advance. At 2500 timing bounces around a bit, but is not advancing.
I have the factory manual and have checked all wires are tight. I have a good ground at the ignition module, getting power on the purple wire at the module. I disconnected the Red/White wire from the distributor and with the ignition on I have 12 volts on the Red/White wire from the module.
I'm thinking bad ignition module? If the sensor in the distributor were bad, the motor would not run at all would it?
Please help!

 

[Scott06]

I have a 1989 4.3 with the Thunderbolt IV. Starts and idles great but has no power. I've replaced the water separator, cleaned the carburetor, replaced the plugs and double checked firing order is correct. Checked timing and at idle in gear, about 650 rpm the timing is at 10 degrees BTDC. I know it should be 8 degrees, haven't adjusted that yet. Rev engine up to 2500 rpm and the timing remains at 10, absolutely no advance. At 2500 timing bounces around a bit, but is not advancing.
I have the factory manual and have checked all wires are tight. I have a good ground at the ignition module, getting power on the purple wire at the module. I disconnected the Red/White wire from the distributor and with the ignition on I have 12 volts on the Red/White wire from the module.
I'm thinking bad ignition module? If the sensor in the distributor were bad, the motor would not run at all would it?
Please help!

Yes ignition module needs replacement. Most of these TBolt ones are no longer available look for used on ebay or take out whole system and put a delco est in

for sure this is the lack of power issue without advance you can’t rev faster

 

[adamschuh79]

Yes ignition module needs replacement. Most of these TBolt ones are no longer available look for used on ebay or take out whole system and put a delco est in

for sure this is the lack of power issue without advance you can’t rev faster

I put in a good used ignition module. I now have spark advance when checked with the timing light. Still lacking power to get on plane quickly because I can't get to WOT without it bogging and popping like in the video. I can accelerate slowly to about 3000 rpm and get on plane, try to give more throttle and I get what you see in the video. Thoughts?

 

[kenny nunez]

Are you sure that the fuel system is clear? Have you checked the filter at the carburetor. What about the spin on filter, when you remove it turn it upside down in a clean container to check for water.

 

[adamschuh79]

Are you sure that the fuel system is clear? Have you checked the filter at the carburetor. What about the spin on filter, when you remove it turn it upside down in a clean container to check for water.

All filters are brand new. No water showing in the separator filter.

 

[Bondo]

cleaned the carburetor

Ayuh,..... Sounds like it needs a full on rebuild,.....

 

[adamschuh79]

Ayuh,..... Sounds like it needs a full on rebuild,.....

I fully rebuilt the carb. Pull it off and go through it again?

 

[rolmops]

I suspect that Bondo implies an engine rebuild

 

[adamschuh79]

I don't think that was what he was implying. He quoted "cleaned the carburetor"

 

[Scott06]

I fully rebuilt the carb. Pull it off and go through it again?

Not only proper cleaning of carb with quality rebuild kit but also make sure fuel system is clean antisiphon valve is working etc.

i have found an inexpensive harbor freight ultrasonic cleaner improved my success rebuilding carbs. Pretty amazing what it gets out of a relatively clean looking carb.
wouldn’t hurt to do a compression test if you haven’t to baseline things and make sure the engine is in good shape mechanically