2007 Mercruiser 350 Mag EFI

[savetexomabeaches]

I turn the key, it spins and cranks.. but only after I let the key go (from the start position) will it finally spark and fire --- New to me, ideas on what it might be?

 

[alldodge]

I turn the key, it spins and cranks.. but only after I let the key go (from the start position) will it finally spark and fire --- New to me, ideas on what it might be?

My first guess would be your key switch or its wiring, but to help how about a serial number just to help us out

 

[savetexomabeaches]

0W667831

 

[alldodge]

That helps, now were down to a few possibilities. I'm going to say this is a 350 Mag, MPI with a Bravo and not a Horizon (closed cooling) and mechanical throttle body (non-digital) and 555 ECM.

In any case you have the HVS distributor (carp cap)

When the key is turned to ON do you hear the fuel pump run for a few seconds and do you hear the two beeps?

 

[savetexomabeaches]

yes and yes

 

[Fun Times]

yes and yes

Your first test will want to be jump the 3 wires at the rear of the key switch bypassing the key switch altogether.

Try connecting the Red and Purple wires together then temporarily touch the Yellow/Red to the Red wire and see if the engine will start....If not start doing a visual check of all the wires at the helm and engine side for possible corrosion damage. Check the main engine wiring harness pin connectors on both sides.

Also if you have the Mercruiser 14 pin wiring harness connector adaptor, there is a chance the adaptor has developed some internal corrosion on the wiring causing issues. If needed, Search online ( Mercruiser 350 Mag Starter Continually Cranks... ) and have a look near the bottom of the topic for photos of the wires with corrosion on them.

 

[savetexomabeaches]

Gotcha -- will check tomorrow during the day. This is my buddy's boat, he brought it to me and told me he's checked everything (my first thought was loose or corroded wire) He insists its the coil - I haven't got to inspect it other than try cranking it before it got dark. My initial thought is there isn't enough voltage while the starter is turning, and when the starter stops getting power, there is enough power to finally send a spark to cause it to fire. -- Will check in the AM.

 

[QBhoy]

Check and clean/replace distributor. Believe it or not !
Exact symptoms I had last year on my MPI. When letting key go, it would backfire and sometimes start and sometimes not.

 

[savetexomabeaches]

I went out and checked the wiring, unplugged everything I could find, cleaned each connector, plugged it all back in, fired right up. I dont think he checked the wiring like he said. Or if he did, only half way checked it. So, thus far, its working as intended, if the problem pops back up, will inspect further for the distributor, etc. Thanks guys

 

[savetexomabeaches]

Problem came back up. Not by choice of mine, but he bought cap, wires, hall effect, rotor ($482.00 in parts) -- had it all installed.. Problem is STILL there. Will bypass ignition switch to see if she starts.

 

[alldodge]

Does the tach move while the motor is cranking?
Is there a cable attached to the hall effect?
Check the connection on the crank position sensor item 9

http://www.mercruiserparts.com/bam/subassembly/31751/12840/110

 

[savetexomabeaches]

Tach jumps all over when it doesn't start

 

[alldodge]

Tach jumps all over when it doesn't start

Your not getting a clean signal, check on the cable and crank position sensor