05 Mercruiser mx6.2mpi no spark

[Justin Kennedy]

Ive just completed a long block replacement, motor is back in boat, turns over but no spark. Triple checked connections etc... replaced coil.. still no spark. fuel pump was coming on prior to replacing coil, it sat for 5 days while i waited for coil, new coil installed no fuel pump or spark. No guages either. Suggestions greatly appreciated.

 

[Fun Times]

Hi there, with the ignition key in the on/run position, first ensure that the lanyard safety kill switch is in the up/on position by physically moving it a few times to see if it helps bring back your 12v power as the purple wire going to the switch is basically the power heading to the ECM to fire up the ignition system.

Also if your engine model has the 10 pin style black cannon plug wiring harness going to the engine, ensure there is a good connection by inspecting the plug pins then try wiggling the plug with the key on to see if you get power.
You've ohms checked the fuses found on the engine itself? You could try swapping the two relays to see if you have any changes as maybe one relay is stuck closed.

Do you have 12v power at both sides of the 50 amp circuit breaker wires? http://www.bing.com/images/search?q=...sp=1&qs=AS&sk=

Also see if you have 12v power at the orange wire off the back of the alternator

Being that you just had all the engine wiring harnesses and power cables apart, the problem may just be a backed out wiring pin connector someplace and a thorough visual inspection of all the wiring pins (ECM too) and power/ground wires/cables may just lead you to a solution.

At the boat ignition key switch you should have 3 main wires. Red for battery, purple for ignition/gauges, yellow/red which is engine crank/start... See if you have 12v at both red and purple (< with key on). Then see if 12v power is getting to the yellow/red wire while holding the key over to start.

If you have the 10 pin black cannon plug connector design then once you've checked for power mentioned above, you could try jumping the engine connector like seen in the following links as that will help bypass the boats wiring. This procedure will tell you if you have a boat wiring problem or an engine problem, https://www.youtube.com/watch?v=NUoXFIo2Ab8
http://forums.iboats.com/forum/engin...e-stand-update

If you have the 14 pin connector like seen in the red area below, then jump starting is harder to do as the power pins may be a little different.

Let us know what you find by testing the info above so we can try helping you out further.

 

[Justin Kennedy]

Thanks for the reply Fun Times. No luck yet. The lanyard switch was off and that restored 12v power as you stated. However, still no spark. 12v is present on 50amp. I switched relays(and i can hear both clicking) 12v is present at orange wire on alternator. I performed the jump procedure as I do have the 10 pin cannon. The procedure worked fine but did not start engine because still no spark. I have 12v+ at the coil and distributor as well. Oddly, my batteries go dead overnight. I wondering if I have made an improper connection somewhere. Is it correct that the engine will not fire without and ECU signal? If so, what wires carry that signal? Also, my fuel pump now just clicks when the key is switched on instead of running for a few seconds, is this because it is pressured up? is this normal?

 

[Fun Times]

Looks like your engine model uses the Cam Shaft Sensor found under the distributor cap since you were able to plug in a wiring connector to it? Right around 2005/6 is when Merc started using the Cam sensor too and not just a Crankshaft sensor.

Is your engine serial number handy?

I don't recall hearing the mercruiser gen 3 cool fuel module start to click when it's fully pressurized but I believe it becomes really hard to hear due to less movement being inside that module. The relays usually click the most/loudest.

If your battery keeps going dead in a short time frame then you may have an internal bad/dead battery cell which in-turn could be causing the battery to be very weak on the required minimum 750 cold cranking amps this engine model needs to start the engine. It's best to use a marine starting battery with 800+ CCA's.
Bear in mind that even if the battery shows 12.? volts right after a charge that it doesn't necessarily mean the cold cranking amps are high enough to start the engine properly. At the very least you may want to have your battery tested to see it's internal condition either at an auto parts store or, http://www.amazon.com/BA5-100-1200-Cranking-Electronic-Battery/dp/B0017R5EQK

Since you now have 12 volts throughout the engine once again which includes the wake up power to the ECM, Now you'll need to find out if the ECM is sending an output to the sensors such as the three main sources for a ignition firing signal which is the Crankshaft, Camshaft sensors, Ignition Coil Module..... And find out if the sensors are sending back a signal to the ECM without any impeded wiring in-between.

http://forums.iboats.com/forum/engi...ta-5-7-gi-f-won-t-run?p=10170826#post10170826

Also check your private messages.

 

[Justin Kennedy]

Thanks again Fun Times. That's very heplful info. I will look into that camshaft sensor tomorrow. I did replace the crankshaft sensor today, no luck. Also determined that tach jumps when switch is turned on but does not register any rpm while cranking. I unplugged the tach at the dashboard but it did not correct the problem. I'm thinking the camshaft sensor or maybe ecm. Do the ecm's fail often? I am going to follow the troubleshooting/ manuals you sent and hope i find the culprit. Thanks again.

 

[Justin Kennedy]

In the last few minutes of daylight, I replaced the camshaft sensor. No luck. Earlier you mentioned the battery. My batteries are less than 1 year old interstate 1000 cca, but they haven't been used much, if at all and they did go dead really fast, I've been charging all day at 30amps and havent hit 100Percent yet. I had my son turn the key as I held a spark tester on the lead from the coil to the distributor. It did fire but only on the first revolution or so then stopped. I believe it may very well be the batteries. After this procedure, my charger reads only 11.5 volts coming from batt #1, the one I've been using. Ill find out tomorrow if I can sneak out on Mothers Day to get a new battery. Again...thanks for the help.

 

[Fun Times]

Also determined that tach jumps when switch is turned on but does not register any rpm while cranking.

When everything is in normal working order, You should be seeing right around 350 RPM during a good, healthy engine cranking speed.

I unplugged the tach at the dashboard but it did not correct the problem.

When you bypassed the wire harness plug connector, essentially you've removed the helm gauges altogether in-turn proving/testing your engine has the issue and it's not a typical shorted out tachometer problem or 12 volt power connection problem somewhere upstream. That mentioned, you now know for sure that the problem lies within either the battery itself or somewhere on the engine.

Do the ecm's fail often?

Not necessarily "often" but there are cases that a few of the many circuit drivers inside these ECM's are known/do tend to fail and it could be a possibility in your case. If everything else that still needs testing turns out to be okay, Then there is a place in CA that you can send the ECM into for inspection and possible repair depending on damage. Heard it's $100.00 for diagnostics and $500.00 if it's repairable. New ECM's are over $1,500.00....
https://whipplesuperchargers.com/index.php?dispatch=products.view&product_id=73

In the last few minutes of daylight, I replaced the camshaft sensor. No luck.

Hope you are finding reasonably priced sensor components as throwing parts at it gets to be expensive too.

Earlier you mentioned the battery. My batteries are less than 1 year old interstate 1000 cca, but they haven't been used much, if at all and they did go dead really fast, I've been charging all day at 30amps and havent hit 100Percent yet.

That's the problem with battery life, they can last one day or 6+ years... You just never really know. Interstate's are typically good batteries though so being only a year old, one would surely think it's good. Do you own a multimeter? 12.6 volts wise is considered a good battery.... As long as the CCA's are good.

I had my son turn the key as I held a spark tester on the lead from the coil to the distributor. It did fire but only on the first revolution or so then stopped.

This testing procedure would be much easier on you if you can buy, rent or borrow a ignition timing light. Connect the timing lights inductive pickup clamp around the coil to distributor cap high tension coil wire, connect the power and ground of the timing light to the battery, hold the trigger and watch the light flash. Being on the coil wire, the light should have a very consistent flash. If you have good flash at the coil wire then test each spark plug wire and time the flashes as it will be at a slower rate as the rotor turns.

I believe it may very well be the batteries. After this procedure, my charger reads only 11.5 volts coming from batt #1, the one I've been using. Ill find out tomorrow if I can sneak out on Mothers Day to get a new battery. Again...thanks for the help.

Hopefully it is the battery. Do you only have 1 battery or two?

If you have two batteries, have you tried using "ALL" (both) on the battery switch? And have you tried number 2 only as well? If not, give it a try. And if you have a multimeter, see what the voltages are at.

 

[Justin Kennedy]

I have 2 batteries, one is very low, I've had the charger on #1 all day and haven't gotten to charge #2. I bought a new battery this morning and no luck. However I have a tester similar to a timing light, it goes around the wire and flashes when it gets a charge. When using this test on the wire from the coil to distributor, I only get a flash on the first revolution each time the key is turned to the starting position. So, it fires only withing the first second or two when cranking. What connections could I have mixed up or missed when reassembling?

 

[Fun Times]

While the ECM and ECM pin-outs that was discussed below are just a bit different in design than yours, there is a possibility that you have an issue sort of similar to the quote & link below due to maneuvering the wiring harness around during the recent rebuild.
Of course I'm guessing at this point but it's something you're going to have to keep in mind during the testing procedures you're going to have to do with a multimeter to find where the problem may lie.

http://forums.iboats.com/forum/engin...o-audible-beep

Post# 41,

Story time....So after checking all of the fuzes, batteries, relays, grounds, connections, deadman switch, neutral safety switch, keyed ignition terminals, back of the dash, etc. I pulled out my best tool, my wallet.

Ryan, the mechanic met me at the boat yesterday morning. He and I went over almost everything that I went over and almost in the same order, so I felt pretty good that I had done the right things and didn't miss anything simple. We started to think maybe the ECM was bad, but I had just had it tested.

Next we called Bob over at OBD Diagnostics and he was adamant that the ECM was fine. What I learned from Bob is that part of their diagnostic process is to hook up the ECM to a full engine harness so they can make sure that the it is doing its job correctly for every component that it interacts with. So we started down the road of why the ECM wasn't working.

We pinned out all of the ground wires in the J connectors (J1/J2 are the 32 pin connectors that plug into the ECM), these were fine. The J connectors were also showing that it was getting both constant power and switched power, but there was a drop in the constant power of about a half a volt. 11.96 I think vs 12.56 for the switched power. Now Ryan, the mechanic, took my test lamp and touched the constant power wire at the J connector and it did not light up, he checked the switched power and the lamp work perfectly. At this point we checked the constant power coming out of the fuze box and it was 12.56. Somewhere between the fuze box and the J connector, we were dropping the .6 volt in the constant power wire and with any type of load, the constant power failed at the J connector. We pulled apart the J connector on the off chance that the wire was not seated properly in the connector, but it looked fine. So we jumped the constant power wire from the fuze box to the J connector and turned the key. I got the audible alarm and the fuel pump primed.

I thanked Ryan and told him that I could handle it from here. I soldered a new wired in place, wrapped it in plastic sheathing to protect it and ran it parallel to the harness. Turned the key and nothing....for a brief second I thought about drilling a hole in the hull and watching the boat sink, but I remembered that Ryan had pulled the fuze for the constant power so that I would not have to undo the batteries again when I put the new wire in place.

Put the fuze in, turned the key, got the beeps and the fuel pump primed. Turned the engine over and it fired first try.

I am a very happy person today.

Thank you for all of the suggestions from everyone here and the time you guys spent thinking about how to solve my problem. I really do appreciate it.

Justin Kennedy Are there any updates on how you made out with this issue? Thanks.