1996 Thunderbolt V with Bravo 3 drive.... I'm using the factory service manual #17
I have a question about the base timing mode. The purple/white wire is not on the starboard side of the engine, but looks like someone cut it shorter and I found it near the thunderbolt module/knock sensor module with a bullet connector crimped on. When I ground that wire it should lock the timing into base mode, correct? Because, when I try to set the timing it still jumps around some. I set the timing as close to 8* as I can, but it jumps from 7-9. Then when it's returned to normal mode the timing bounces from 2-12* at idle, but is closer to 10* most of the time. Also, when its in base timing mode if I rev the engine up I still get full timing!
Should the timing be locked in with no advance while the purple/white wire is grounded? What would cause it to not go into base mode, bad thunderbolt V or knock sensor module? The timing is different with the purple/white wire grounded, but it still does not "lock" the timing.
Here's the history... Lost compression in Cylinder 7, took the engine in to a reputable machine shop and had the engine rebuilt as well as stroked to a 383. I put the engine in the boat, aligned it and set the base timing as well as idle mixture and speed. Took the boat out a dozen times and it ran great!..... Then the next time out it idled fine, but sounded like it was missing and would not get on plane. Pulled the spark plugs out for a compression test and immediately saw the #7 spark plug had no tip, that cylinder also had zero compression and a few other cylinder were low.
Took the engine back out of the boat and took it back to the machine shop. They said it was run hot or lean and tuliped several intake valves, they rebuilt the heads and installed a new fuel pump. Also checked the anti siphon valve and found a small piece of a twig stuck in there. So the pickup tube was checked and the anti siphon valve replaced.... After re installing the engine I cannot get it to idle. It surges and dies, but if you give it gas it sounds great above idle.
The carb was rebuilt with the engine initially, and was rebuilt again the second time but they said it looked perfectly clean the second time.
I have a question about the base timing mode. The purple/white wire is not on the starboard side of the engine, but looks like someone cut it shorter and I found it near the thunderbolt module/knock sensor module with a bullet connector crimped on. When I ground that wire it should lock the timing into base mode, correct? Because, when I try to set the timing it still jumps around some. I set the timing as close to 8* as I can, but it jumps from 7-9. Then when it's returned to normal mode the timing bounces from 2-12* at idle, but is closer to 10* most of the time. Also, when its in base timing mode if I rev the engine up I still get full timing!
Should the timing be locked in with no advance while the purple/white wire is grounded? What would cause it to not go into base mode, bad thunderbolt V or knock sensor module? The timing is different with the purple/white wire grounded, but it still does not "lock" the timing.
Here's the history... Lost compression in Cylinder 7, took the engine in to a reputable machine shop and had the engine rebuilt as well as stroked to a 383. I put the engine in the boat, aligned it and set the base timing as well as idle mixture and speed. Took the boat out a dozen times and it ran great!..... Then the next time out it idled fine, but sounded like it was missing and would not get on plane. Pulled the spark plugs out for a compression test and immediately saw the #7 spark plug had no tip, that cylinder also had zero compression and a few other cylinder were low.
Took the engine back out of the boat and took it back to the machine shop. They said it was run hot or lean and tuliped several intake valves, they rebuilt the heads and installed a new fuel pump. Also checked the anti siphon valve and found a small piece of a twig stuck in there. So the pickup tube was checked and the anti siphon valve replaced.... After re installing the engine I cannot get it to idle. It surges and dies, but if you give it gas it sounds great above idle.
The carb was rebuilt with the engine initially, and was rebuilt again the second time but they said it looked perfectly clean the second time.
