thunderbolt V ignition

A

Admiral Hill

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Aug 15, 2011

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3

• Aug 15, 2011

• #1

I have 1999 thunderbolt 5.7 liter with thunderbolt V ignition. It starts and runs smooth after 15 or 20 seconds engine runs rough and stalls (tach drops to zero) It is like someone shut the key off. Very hard restarting. It does restart but cuts in and out continuous. Any idea out there on a fix.

 

Don S

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• Aug 15, 2011

• #2

Re: thunderbolt V ignition

It sounds a lot like your oil pressure switch or the wiring to it failed. It controls the electric fuel pump. The pump is activated by the starter when cranking (why it starts when you are cranking, it fills up the carb) then when it starts, the oil pressure switch activates and allows power to the pump. If the switch fails, the pump will only run when cranking. That is why it runs for 15 to 20 seconds and dies.

 

J

John_S

Rear Admiral

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4,269

• Aug 15, 2011

• #3

Re: thunderbolt V ignition

Welcome to iBoats.

Once it stalls, you need to check immediatly if you have spark. If you don't have spark, I'd make sure it is not a faulty ignition switch, loose shift interupt switch (alpha drives). If thats not it, follow the T5 diagnostic flow chart in the service manual.

Now if you have spark, then you might want to look at fuel. Choke not opening, fuel dribling in carb past needle valve, or other fuel related problems could have those symptoms. PS: Would do Don's check first.

 

A

Admiral Hill

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• Aug 15, 2011

• #4

Re: thunderbolt V ignition

The boat has a carb and mechanical fuel pump and I don't believe it has a low pressure shut down.

 

Don S

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• Aug 15, 2011

• #5

Re: thunderbolt V ignition

If you have a 99 engine, it has an electric fuel pump. There was no way to install a mechanical pump on it.

 

J

John_S

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• Aug 15, 2011

• #6

Re: thunderbolt V ignition

Don S said:

If you have a 99 engine, it has an electric fuel pump. There was no way to install a mechanical pump on it.

Click to expand...

And think the elec fuel pump started in '98 model year. A '97 would still have mechanical pump. That would also mean a standard head 5.7L vs Gen+ vortec head. Probably a good idea to post engine serial number.

 

A

Admiral Hill

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• Aug 15, 2011

• #7

Re: thunderbolt V ignition

My mistake...it is a 92-97 thunderbolt v. I am pretty sure it is not a fuel problem, where tack drops to zero and engine shuts down it seems electrical. Key on I get 12 Volt at coil. Trying to determine if it control module or dist pick up.

Could knock sensor cause a problem like this?

 

9

93ultra

Seaman Apprentice

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Jan 31, 2011

Messages

44

• Aug 15, 2011

• #8

Re: thunderbolt V ignition

It sounds like the same thing that was happening with my 7.4 with the Thunderbolt V Ignition. I changed the distributor pickup first because it was the cheapest of the two but it turned out to be the ICM. It would stall for just a split second and the tach would drop to zero like the key had just been turned off, then continue to run, then stall and become impossible to start until it had cooled for a day or two it was very strange.

 

J

John_S

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• Aug 15, 2011

• #9

Re: thunderbolt V ignition

Admiral Hill said:

My mistake...it is a 92-97 thunderbolt v. I am pretty sure it is not a fuel problem, where tack drops to zero and engine shuts down it seems electrical. Key on I get 12 Volt at coil. Trying to determine if it control module or dist pick up.

Could knock sensor cause a problem like this?

Click to expand...

If this is 2brl 5.7L, '97 or earlier, it does not have a knock module or sensor. The knock module retards the timing at high rpms if it detects knocking, not shutting down engine.

Leave an inductive timing light on a spark plug wire. After it dies, crank it over and see if you are getting flashes.

Control module is $400-$500 part. That is one you want to eliminate all possibilities before replacing.

 

N

netting one

Petty Officer 2nd Class

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Mar 23, 2010

Messages

112

• Aug 16, 2011

• #10

Re: thunderbolt V ignition

Going through the same thing right now, starting a new thread.