Stingray cranks but wont start

[gski]

I have a 2001 Stingray with a 5.0L Mercruiser 305. I have been boating for many years and have some mechanic skills, can use multimeter, replace fuses, attach wires, change oil, construct docks etc.

This year I got it from storage and did the following.

• Attached water hose and started boat to warm up engine. Started and worked perfect.
• Cut off boat, drained oil, replaced Oil filter.
• Started boat and ran for a few seconds. Worked fine.
• Took it to ramp and it would crank but not start
• Back in driveway it still wouldn’t start, lowered trailer to tilt boat forward and it started. Thought it was a fuel tank issue. Filled with 12 gallons of no ethanol fuel and also added sea foam.
• Back in water it would crank but not start.
• Back in driveway and regardless of boat angle it would crank but not start.

I removed the fuel line going into the carburetor and fuel will come out when key is turned on so I ruled out fuel pump and filter. Took it to an auto mechanic friend and we figured out that the injectors were not pulsing and the distributor was not sparking. We thought it was an electrical or computer issue so we checked every connection and fuse we could find. Just as we were about to give up, I started it again and it beautifully sprayed fuel and turned over perfectly. The last thing we touched was the wires for the kill switch. We cut and spliced the original connections to make more durable thinking it was a loose connection that we wiggled. After that, it crank but not start no matter what we wiggled. We don’t think it’s the kill switch as it seems to function normally. When I turn the key the fuel pump primes and there are 2 loud beeps. If I shut off the kill switch while it’s priming it immediately stops. If the key is on and I flip the kill switch off then on, it primes fuel.

It seems to me that there is some sensor, fuse, relay, component that is malfunctioning and essentially telling the computer to not pulse the injectors. Acts just like the kill switch is doing its job to kill it.

I have read the electrical testing and how to troubleshoot engine starting threads and my friend used the light and said everything seems normal, except for the no pulse or spark.

Any ideas for me to try? Any other information I forgot to add?

 

[Scott06]

So still there is no spark but fuel is present when it won't start? Did you try disconnecting the shift interrupt switch and disconnecting the tach at the negative side of the coil? Both can kill the spark.

Do do you have 12 v to positive side of coil when this happens ? 12 v is supplied of the starter during cranking, then when key is in run from the key. If you have 12 v at coil but no spark need to diagnos the ignition

Kill switch in theory interrupts 12 v to coil , but you sliced/jumpered out the kill switch right? No firing occurred after this jumper? If so were the wires correctly jumped (I assume kill switch is normally closed ? )

 

[Luv2fish36]

That's an old MEFI. The ecms are known to fail.

 

[gski]

Sorry for confusion. We disconnected the fuel line going to the carburetor to see if fuel pump was working. It was. Then after reconnecting no fuel will come out of injectors. No fuel,no spark.

I tried leaving kill switch disconnected, splicing it out and leaving it in. All same result.