496 Cranking Issues

mutiny

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May 30, 2013
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Well, I've positively gotten over my head on this one and am looking for any suggestions from the Mercruiser experts here. To make a long story short as possible, a friend took on a 2008 8.1 496 project that was submerged in salt water. He sent the motor out to get an entire rebuild from a local engine shop. They gave the engine back with nothing marine related attached to it, stating that they couldn't figure out where the parts go. We installed new injectors, main wiring harness, PCM or ECM whichever it is on this motor, spark plugs and wires, starter, alternator, Map and TPS sensors, CPS, and new oil and filter. Inspected the fuel system which was cleaned and given new seals and filters after testing good. A bunch of other small things were done to the motor to get rid of the old salt water damaged parts.

Problem is: The motor will not crank. I am using a remote starter ignition switch by Mercruiser. When I initially turn the key to the on position, I can hear the fuel pump kicking on. Once turned to the crank position, Nothing happens. I checked the starting circuit and there is power going into the starting relay, but it has no action that switches power in the relay and activates the starter. I tried swapping relays to make sure that wasn't the problem and it is not. Any suggestions?

I do not have computer software to read fault codes on this motor. I understand that having a computer would be the ideal way to diagnose the issues but at this point it ins't an option. I own the service manual for this particular engine #30 Mercruiser, but the darn thing is more of a burden that a service manual. Under the "No Crank" section, it simply gives suggestions for why the engine will not crank. It gives absolutely NO testing procedures. The very first thing it states is that the engine is not in Neutral. Since the engine is on a stand in my garage, how would I make it "think" it is in Neutral?

Thanks for any suggestions. This engine has been in my garage way too long and I need to do something with it.
 

Bondo

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Ayuh,..... On the Starter's solenoid, are 4 posts, the 2 largest posts are the starter lead on the lower, 'n the battery connection at the top,....

Of the 2 tiny posts, supply 12v to the 1 closest to the block, 'n the starter will crank,..... the yellow/ red wire,....
Normally, the yellow/ red wire gets is power from the slave solenoid, which is activated by the keyswitch,....
 

mutiny

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Ayuh,..... On the Starter's solenoid, are 4 posts, the 2 largest posts are the starter lead on the lower, 'n the battery connection at the top,....

Of the 2 tiny posts, supply 12v to the 1 closest to the block, 'n the starter will crank,..... the yellow/ red wire,....
Normally, the yellow/ red wire gets is power from the slave solenoid, which is activated by the keyswitch,....


Thanks for the quick reply Bondo.

Your input is always valued and I appreciate the help. I understand how to make the engine turn over via direct 12v jumping but I was curious if there is a way to make it crank from the remote key switch that I'm using? I just want to remove any idea of there being other cranking issues that I can't identify without the engine cranking from the key switch. If I jump power as you suggest, how am I to determine if there are any other issues in the cranking circuit? I would hate to run into the same problem once I install the engine and try to crank it with the boat ignition and find it doesn't turn over like now. Any suggestions sir? Or should I not worry about that at this time and just run the darn thing lol.
 

Bondo

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Thanks for the quick reply Bondo.

Your input is always valued and I appreciate the help. I understand how to make the engine turn over via direct 12v jumping but I was curious if there is a way to make it crank from the remote key switch that I'm using? I just want to remove any idea of there being other cranking issues that I can't identify without the engine cranking from the key switch. If I jump power as you suggest, how am I to determine if there are any other issues in the cranking circuit? I would hate to run into the same problem once I install the engine and try to crank it with the boat ignition and find it doesn't turn over like now. Any suggestions sir? Or should I not worry about that at this time and just run the darn thing lol.

Ayuh,.... I don't know what yer usin', much less how ya wired it, so I'm gonna be vague,....

Power from yer keyswitch for crankin' the starter should power the slave solenoid, which powers the starter's solenoid, as I explained above,.....
 

Fun Times

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Without us being there to see what you've tried vs haven't thus far, For us using Bondo's suggestion of first jumping to the starter would help confirm that the engine starter is able to work correctly or not then work back up the electrical system from there knowing if the "engine" is able to spin freely without issues....;)

Once you/we know the engine/starter spins then it's on to figuring out the wiring system. You shouldn't have to trick the yellow/red wire cranking system since the neutral gear indicator switch is located at the helm shifting controller... By connecting power at the engine, you've bypassed that switch already.

I don't believe the gear indicator switch located at the shifting bracket would affect the starting circuit but just to be sure....Ensure that item number 20 is in the center of the V and not being pushed in.. With it being pushed in tells the PCM;) if this engine model is in gear or not.
http://www.mercruiserparts.com/Show_...chanical+Shift

Since the engine went under water (<salt?) then you may have some defective "relays" or corroded wiring harness...If you didn't go with a new harness? Sometimes tapping the top/side of the relays may help free them up internally so give that a try too.

Being an 2008, you must have the 14 pin wire connector vs the older 10 pin cannon plug connector. Did you buy a Merc remote switch that would plug into the 14 pin wiring plug connector?
 
Last edited:

mutiny

Petty Officer 3rd Class
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May 30, 2013
Messages
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Without us being there to see what you've tried vs haven't thus far, For us using Bondo's suggestion of first jumping to the starter would help confirm that the engine starter is able to work correctly or not then work back up the electrical system from there knowing if the "engine" is able to spin freely without issues....;)

Once you/we know the engine/starter spins then it's on to figuring out the wiring system. You shouldn't have to trick the yellow/red wire cranking system since the neutral gear indicator switch is located at the helm shifting controller... By connecting power at the engine, you've bypassed that switch already.

I don't believe the gear indicator switch located at the shifting bracket would affect the starting circuit but just to be sure....Ensure that item number 20 is in the center of the V and not being pushed in.. With it being pushed in tells the PCM;) if this engine model is in gear or not.
http://www.mercruiserparts.com/Show_...chanical+Shift

Since the engine went under water (<salt?) then you may have some defective "relays" or corroded wiring harness...If you didn't go with a new harness? Sometimes tapping the top/side of the relays may help free them up internally so give that a try too.

Being an 2008, you must have the 14 pin wire connector vs the older 10 pin cannon plug connector. Did you buy a Merc remote switch that would plug into the 14 pin wiring plug connector?


As stated previously, the wiring harness is brand new and it comes with all new relays. I've swapped out working relays to make sure the relay is not to blame. There is constant power going into the starting relay, but no trigger that activates the relay upon cranking.

Just before I was about to write a sentence stating how I am a Mercruiser technician in training (not yet received certification) and was about to proclaim how dumb would I be for having an older 10 pin ignition switch plugged into a 2008 engine. So for verification, I ran to the garage knocking over 3 dogs, and almost my wife in such a haste. To find out.... I have a 10 Pin ignition switch.. 84-15000A13. wow.. I'm taking my tech ID number to the back yard and burning it.

Thank you so much.

PS. anyone know the part number for the 14 pin switch by chance?
 

mutiny

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After inspecting my key harness PN 84-15000A13 I noticed that there are only 10 pins at the plug. However, this is the new style plug, and not the old cannon plug which had the elongated male prongs. Is there a different harness that actually has 14 pins at the plug end? All the research I'm doing shows almost identical items, and none verify that there are 14 pins at the plug. Any help is appreciated. Thanks.
 

alldodge

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After inspecting my key harness PN 84-15000A13 I noticed that there are only 10 pins at the plug. However, this is the new style plug, and not the old cannon plug which had the elongated male prongs. Is there a different harness that actually has 14 pins at the plug end? All the research I'm doing shows almost identical items, and none verify that there are 14 pins at the plug. Any help is appreciated. Thanks.

It sounds to me you need a 14 to 10 pin harness adapter
http://www.ebay.com/itm/Adapter-Wir...New-Motor-to-Old-Wiring-Repower-/370561702180
 

mutiny

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No, that is actually the totally wrong way to go for what I am trying to accomplish but thanks. I've stated before what ignition switch I have and it fits perfectly into the engine harness.

I have diagnosed the problem to be somewhere in the in gear switch. If I give the Black/Yellow wire ground from the harness, it will crank with the ignition switch that I currently own. The problem is that I do not have the In Gear switch or bracket from the owner of the engine. It was simply an open plug which I now see will not allow the engine to crank without it.
 

Bt Doctur

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Aug 29, 2004
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