Mercury 240 EFI M2: Only cranks once - wont start. when warm

[Larry VVV]

My 2002 X20 w/ the Mercury 240 efi M2 wont start when warm. It starts fine when cold (crank, crank, crank, start), but if I turn it off after running it 30+ minutes, it wont restart. I turn the key, I hear a beep, it will crank one time. I can do this over and over and over. Turn, beep, crank once. Nothing. I've tested the battery has a full charge and is receiving charge from the alternator.
-What is the single beep indicating?
-Why will it only crank once?
-How can I fix this please?

 

[AirSniper]

beep is good, means your main power relay works...notice the sound of fuel pumps too.
check your lanyard switch, can even disconnect the connector in back...but more likely, classic symptom of a pickup going bad.
search around this site for "trigger" and crank sensor for help. simple check, ohm meter when it is failing, should read ~ 300 ohms. good likelihood it is much higher when hot. easy check, at the flywheel. ~ $75 fix as long as you dont strip the bolts.

 

[Larry VVV]

Thanks Sniper.
For $75 bucks I'd be willing to give it a try. What part are you referring to "pickup going bad"?

 

[Tim75]

Also check that your shift lever is not moving as you try to crank. It is interlocked to the starter circuit.

 

[AirSniper]

Thanks Sniper.
For $75 bucks I'd be willing to give it a try. What part are you referring to "pickup going bad"?

Don't spend $$ you dont need to, read the resistance from the connector, should be around 300 ohms.
easy to get at, easy to test.

 

[Larry VVV]

Hi Sniper, thanks for the help.
Friday I took the Starter, Solenoid, & Battery to get tested. Everything tested good. The starter repair shop dude said there was very little wear in the starter almost like it hadn't been used much. I told him that you mentioned the "crank sensor". He said a bad crank sensor would keep it from firing and starting, but it would not keep it from cranking.
Since mine will only crank 1 time when hot, do you agree with the starter repair dude, or should I look into testing that sensor?

 

[AirSniper]

I have to agree, this sensor only tells the computer when to send spark; clearly i missed that the issue is that it wont crank (after one time) in the description, as opposed to "cranks, but no start".
So, understanding that the issue is that the starter engages, but only once, not enough to start, then will not engage again? ... I think you start with battery voltage check, then putting a meter on the starter to ensure it gets power the second time - when it doesnt work, this will begin to eliminate electrical.
As i recall, the lanyard will only prevent spark, but the throttle switch will prevent cranking. It is an unusual, but not impossible failure mode for such a switch to be intermittent, but I would guess that the neutral safety switch powers a relay, but this is within the computer. there is a main power relay that could play a roll too it seems, this is also cheap & easy....but you need to determine if the starter motor is getting power when it doesnt crank, first & foremost.

 

[Tim75]

We need to get specific here-
When you say it cranks only once; Why does it stop cranking? Do you release the key or does it just stop cranking?

What happens on attempt #2? Do you hear the fuel pump and solenoid?

Neutral safety switch uses a mag reed switch and a tiny magnet and little delicate wires. Bad connections = intermittent problems.

I must agree with AirSniper- Check the voltage at the starter when you turn the key. It seems that you may have a bad ground. Check those for tightness on the block and at the battery.