thunderbolt iv no spark

[chartersj]

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.

Yeah I must of missed some crud some where, i'm going to take the pick up out of the gas tank and look at the filters above the needle seats in the carb

 

[chartersj]

So i changed the fuel sending unit tonight because the old one did not work and was very corroded, and then now when i turn the key to the on position i can hear the electric fuel pump running without the motor running which it did not do before i changed it out. the fuel pump would only start after i went to start the engine. The fuel gauge on the dash still does not work, but i put the boat it the water and worked perfect. So why would changing the sending unit make the difference and is that when the fuel pump is suppose to start running when in the key ON position?

 

[Pete104]

You know the shouldn't run w/o oil pressure.
Eliminate the dash for now. Get the engine dialed in with the dash harness unplugged.

 

[chartersj]

You know the shouldn't run w/o oil pressure.
Eliminate the dash for now. Get the engine dialed in with the dash harness unplugged.

How do you start the engine without being plugged into the boat harness? Could the oil pressure switch stick in the closed position? It is rusty looking on the outside.

 

[Pete104]

12 volts to small yellow/red on slave solenoid to crank. 12 volts to + side of coil is ignition.
Absolutely the switch can stick closed or open.

 

[achris]

So i changed the fuel sending unit tonight because the old one did not work and was very corroded, and then now when i turn the key to the on position i can hear the electric fuel pump running without the motor running which it did not do before i changed it out. the fuel pump would only start after i went to start the engine. The fuel gauge on the dash still does not work, but i put the boat it the water and worked perfect. So why would changing the sending unit make the difference and is that when the fuel pump is suppose to start running when in the key ON position?

This sounds like a serious wiring issue. The fuel tank level sender shouldn't have anything to do with the engine electrics, expect that the key ON position provides power to the gauge.

The wiring for the fuel pump is 'double source'. The first source is a post on the starter motor labeled 'I'. It will have a purple/yellow wire. This provides the pump power while cranking the engine (and before the oil pressure comes up). The second source is the oil pressure switch. Once 4 psi of oil pressure is applied the switch closes and powers the pump. Just be aware that once that switch closes, power is then on the wire that goes to the starter motor. And the converse applies, when the switch closes, the rest of the system connected back through the switch is then powered. Unfortunately I saw a tech using a remote starter switch and leave the key OFF to crank the engine, thinking by leaving the key OFF would stop sparks. When the oil pressure switch closed, he got a very big shock!

Chris........

 

[chartersj]

This sounds like a serious wiring issue. The fuel tank level sender shouldn't have anything to do with the engine electrics, expect that the key ON position provides power to the gauge.

The wiring for the fuel pump is 'double source'. The first source is a post on the starter motor labeled 'I'. It will have a purple/yellow wire. This provides the pump power while cranking the engine (and before the oil pressure comes up). The second source is the oil pressure switch. Once 4 psi of oil pressure is applied the switch closes and powers the pump. Just be aware that once that switch closes, power is then on the wire that goes to the starter motor. And the converse applies, when the switch closes, the rest of the system connected back through the switch is then powered. Unfortunately I saw a tech using a remote starter switch and leave the key OFF to crank the engine, thinking by leaving the key OFF would stop sparks. When the oil pressure switch closed, he got a very big shock!

Chris........

After thinking about it some more, im wondering if I have two different problems. Two nights ago when I tried the boat in the water and it was starving for fuel, I took it home, flushed it out on the hose and put it away for the night. Yesterday when I got home from work I installed the new fuel sending unit before i did anything else with the boat. I am wondering if the oil pressure switch stuck in the closed position when i had it on the hose the night before. and then maybe i still have a problem with the fuel gauge.

 

[chartersj]

I installed a new pressure switch and the boat is working great now. Still not sure why my fuel gauge is not working. I was getting a clunking when turning hard left or right so installed new u-joints and it still clunked. Turns out i did not have the new gimbal bearing in all the way. Tapped it in untill i knew it was fully seated and no more clunking.