1997 5.7 LX Thunderbolt V Ignition Engine cuts out

[Darren Gillon]

My name is Darren and I like in the Northwest coast of Australia. The water temp here is about 30 deg centigrade.
I have a 1997 5.7 LX with thunderbolt V ignition on it. I run the engine in a 7.2m Fiberglass boat and are experiencing some issues that I think might be ignition based. When I go out the engine runs fone for a while ( 1hr or so ) and then it cuts out. ( I usually run at around 3300 rpm - 28 knots ). It used to run on and diesel but I fixed that by running a cooler thermostat and adjusting the baseline ignition advance slightly. now it just stops. After it stop you can restart immediately and it runs fine. It will then run for another hr or so without fault. I'm at a bit of a loose end trying to determine wether or not it's the ignition module and wether or not the ignition module can be affected by temp. It seems to do it more the hotter the ambient conditions are.
Any thoughts would be appreciated

 

[guyjg]

Re: 5.7LX Thunderbolt V Ignition Engine cuts out

...trying to determine wether or not it's the ignition module and wether or not the ignition module can be affected by temp. It seems to do it more the hotter the ambient conditions...

Darren: Temp. can affect a failing electronic part. The TB V ignition is designed to operate at 30 C. or higher. Do you have sufficient airflow into the bilge? I run my blower the entire time the engine is running to keep the engine compartment as cool as possible. When an engine cuts out and then restarts right away the problem can be a simple momentary loss of 12 VDC to the spark system. Overheated electronics normally won't function right away; they have to cool off for a period of time. That said, I think your problem may be a cracked wire in the ignition. It could be anywhere. The ignition key could be defective or a ground (earth) wire could be loose. Through vibration the circuit is broken long enough to cause the engine to cut out.

You'll need to perform a wire pull/wiggle test while the engine is idling to try and find the problem part. Start at the ignition module and wiggle each wire. Remove and inspect each wire connection to see if there is a buildup of corrosion which will act like a broken wire. Look carefully at the inside of the distributor cap for a crack in the cap and for carbon tracking (black pencil lines) which will cause the spark to short out. Check the coil wire connections. Wiggle every wire you can find. Inspect the ignition key wiring for a loose or broken wire strands on the switch. Let us know what you find.