Merc 5.0L stalled and now won't start

[achris]

Re: Merc 5.0L stalled and now won't start

Did you run the troubleshooting chart that Don posted? What results did you get?

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

Did you run the troubleshooting chart that Don posted? What results did you get?

No, I have been working all weekend...I may be able to head down to the cabin and run the chart on Tuesday...then again, maybe not. Sheesh, works keeps getting in the way of my having fun!!!

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

Well, I am stumped...granted, I didn't do the full flow chart b/c I did not have a spark gap tester. (I will buy one now, and check it when I go down to the cabin on the weekend). I replaced the ignition sensor in the dissy, but it was not the problem (i thought it was for sure b/c of the amount of corrosion on it) The dissy looks good, and the coil looks brand new.

My next step (if nobody has any other suggestions) is that I am going to buy a new dissy cap, as well as ignition control module. I will replace parts as needed (cap first, then module)

QUESTION: I noticed 2 things about the distributor cap:

1. It has 4 screws, but one of them has been snapped off. Could 1 less screw make the motor quit suddenly when it was working fine?

2. I noticed a barb on the cap that looks like there is supposed to be a hose on it. There is no such hose anywher that I can see, but if there were where does it go, and would it restrict the motor from starting?

Thanks in advance for any help you can provide.

 

[JustJason]

Re: Merc 5.0L stalled and now won't start

3 screws is fine.......
I wouldn't recommend it as a fix but i've seen them running being held down by zip ties

the barb is just a vent for the cap..... no hose there.

Have you check for power at the coil yet? Have you disconnected the coil and checked the primary and secondary resitance?
Check your ignition wires to, especially the one from the cap to the coil. OHM them all out.
Your going to need a NEW meter to do this, preferebly a digital one.

there's only 3 things that make the system work, the coil, the pickup, and the module. look around EVERYWHERE for broken, disconnected, corroded wires. Check the reluctor on the rotor as well. make sure the rotor is all the way down and there's an even gap between the reluctor and the pickup. it's not going to be much, maybe .010 of an inch.

just follow don's chart, and don't miss a step. the answer is in the chart, you just have to find it.

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

UPDATE - I have followed the flow chart, and when I tested the pos and neg on the coil, as well as the red/wh wire on the dissy teminal I got 11.2 volts...is this close enough to 12v, or does it need to be 12v for everything to work properly?

As for the next step, I am not sure if I did it right. I bought what I thought was a spark plug gap tester, but I now think it wasn't right. What I used was a spark plug tester thingy (technical term), but it just had a light on it...if there was current, the light lit up? Wrong tool??

I'll tell you what happened anyways...when i tested the wire from the coil to the dissy, I got a strobing light, but it was fairly faint. When i did the same test on one of the plug wires, I got nothing.

Here is my train of thought. I am not sure if this test is sufficient to rule out the coil b/c even though I got light, it was faint, and not exactly what I would expect from 35000 volts. I imagine that I could still get current through the coil, but not enough to cause spark (hence the need for a spark tester???)

The thing that stumps me is that the coil, wires, dissy, and rotor all look brand new. I already replaced the ingition sensor, and I was sure that would be the problem b/c it was pretty corroded. no such luck.

Correct me if I am wrong, but if the coil is getting 12v (well 11.2) then the only things left that it could be are the dissy, Sensor (already replaced) or the ignition module...which I have read that it rarely dies? Am I missing something?

PS. I like a challenge, but this is getting frustrating. My knowledge base is limited, but I am learning tons of useful stuff...perhaps stored for later use Thanks again for all the help so far, I am eternally grateful.

 

[krisnowicki]

Re: Merc 5.0L stalled and now won't start

I had the same problem as you. I had a TB IV and was out all day one day came in and it wouldn't start. I did thyhe same flow chart and I was getting spark sometimes. On my grn.wht wire at the dist i was getting 7-8 v on the red.wht I was getting 12. Turned out it was the ignition moduale. I got one off ebay for 60 dollars and the boat fired right up. I checked the v and i was getting 12v to both red and grn

 

[achris]

Re: Merc 5.0L stalled and now won't start

What they mean by 'spark gap tester' is just a device to create a gap of about 1/2" for the spark to jump... Just put a spark plug in the lead, lay it on the engine block and look for a nice fat blue spark across the gap... You get that, you got spark.... Did you do the step in the chart about disconnecting a wire and tapping it against ground quickly? Did you get sparks?

Chris..........

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

I had the same problem as you. I had a TB IV and was out all day one day came in and it wouldn't start. I did thyhe same flow chart and I was getting spark sometimes. On my grn.wht wire at the dist i was getting 7-8 v on the red.wht I was getting 12. Turned out it was the ignition moduale. I got one off ebay for 60 dollars and the boat fired right up. I checked the v and i was getting 12v to both red and grn

Hmmm..this sounds very similar. I tested a crapload of stuff, but I seem to remember the voltage being different on the red, and green wires. I wasn't sure if this was normal, and meant to post that.

As for the striking the green wire Chris, I tried it, but I am not sure if I did it right. I will be down at the cabin this weekend...hopefully I can get a hold of an ignition module today. Sucks that it has to be an expensive part

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

One more thing, can anybody tell me where to find the serial number? I found a number on a red mercruiser sticker...that's not it is it?

 

[Uraijit]

Re: Merc 5.0L stalled and now won't start

Where was the sticker?

You can usually find the serial number on a sticker on the valve covers.

 

[Viddi]

Re: Merc 5.0L stalled and now won't start

I don't know the name of the part, but it is just above where the ignition module is mounted. To the far right as you are looking at the belts.

 

[achris]

Re: Merc 5.0L stalled and now won't start

Have a look at my signature picture... That is the format of the serial numbers... Find something that looks like that....