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454 XL runs smooth for 60sec then rough

C

Cinemoves

New member
I need advice/help. I have a Tiara with 1994 454XL's and MSTS modules. When I start the engine it runs fine for approx 30 to 90 sec and then runs very rough. If I try and advance the throttle it dies. If I turn it off and start it again right away it run smooth for 30 to 90 sec and runs rough again. I went out the other morning to try it again and on the first start it ran for 5 to 7 min just fine. I turned it off and started it again and it was back to the 30 to 90 good then bad.

What I tried so far.
When it started running rough I shot a little starter fluid in the carb. No difference.
Checked fuel filters. All good.
Right after it starts running rough or quotes all together I checked the fuel in the carb by pumping the accelerator. It shoots plenty of fuel.
Un plugged the MSTS mod. Still same result

A few weeks before this issue I changed the pickup coil, Dist cap, Rotor, Coil and advance module.

Any help would be greatly appreciated. Im stumped.
 
Assuming the fuel is good, I'd suspect an issue on the secondary side of the ignition....is the spark coming out of the coil consistently? is the spark making it to the plugs?
 
Recommend the following. First check voltage at the coil for 12+ volts when the engine is running rough. This will ensure the wiring and ignition switch are OK. Next check voltage at the fuel pump for a steady 12+ volts. This will confirm wiring, CB, and oil pressure switch are OK. Lastly, Tee in a combo pressure/vacuum gauge to check for about 7.00 psi going from the pump to the carb. If low, check vacuum before the pump to ensure it is not more than 5.0 In-Hg. If more, investigate the fuelline for a collapse or clogged fuel pickup tube or vent line. Also change out the small filter on the carb (Duralast FF1103DL or WIX33051 or FramCG3388) if you have not done so. Might also hook up a timing light to each ignition wire to ensure you are seeing a regular flash. If everything checks out might consider swapping the coil and ICM with the other engine (even though they are new). Please share your progress.
FL Panhandle
 
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I'm led to believe ignition on this one. Prolly one of the new parts you put on. The starter fluid test tends to discount any fuel issue.
 
Thank you all very much for the input. This is my first time using a forum. What a great tool. It appears it was either the pick up coil or the stator. They were both replaced a few months back. When I replaced them again yesterday it fired right up and seems to run fine now. I purchased the parts from Autozone. The brand was SELECT. could this be an issue? Thank you all again.
 
Thanks for the detailed response Mulletwagon. This helped a ton. It ended up being the pick up coil or stator. I changed both of them yesterday and it fired right up and runs fine now. Have a great holiday.
 
Cinemoves said:
Thank you all very much for the input. This is my first time using a forum. What a great tool. It appears it was either the pick up coil or the stator. They were both replaced a few months back. When I replaced them again yesterday it fired right up and seems to run fine now. I purchased the parts from Autozone. The brand was SELECT. could this be an issue? Thank you all again.
Click to expand...
There are no parts you can use on your boat from Autozone......and expect it to be reliable......
 
Cinemoves said:
Thank you all very much for the input. This is my first time using a forum. What a great tool. It appears it was either the pick up coil or the stator. They were both replaced a few months back. When I replaced them again yesterday it fired right up and seems to run fine now. I purchased the parts from Autozone. The brand was SELECT. could this be an issue? Thank you all again.
Click to expand...
Correction. Didn’t replace the stator I meant to say ignition module.
 
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