Mecruiser 5.0L MPI distibutor proper clocking?

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Fedds

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5.0L MPI Engine Serial OM618927.

read a service bulletin on my issue of a miss fire at higher loads. It also stated to rotate the distibutor 1-2degrees if the issue persisted. I did this and the problem got so bad that at about 2500 RPM it misses so bad it sounds like the ECU is reducing power (are there knock sensors on these motors?)

So I put it back where it was, but now I question what the right postion is (who knows who did what before I was in here). Is there a mark on the base of the distributor to line up to the engine block? The reason I ask is if there is only 45 degrees between cylinder posts in the cap (360 / 8), and I line up TDC to cyl 1, and there is more than 22.5 degrees of advance max, then the spark will jump to the wrong cylinder. Soooo, really you need to place the cap pointing some amount past cyl 1? Does that make sense? Note that the base timing is NOT set by the distibutor location in this engine (no halls or trigger in the dizzy base).
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Also, what is the max ign advance on this motor?
 

GA_Boater

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Fedds - You should get a service manual for your engine and read up on setting timing. Your cap has nothing to do with adjusting timing. 45 degrees X 8 = 360 degrees or 1 rotation of the rotor. You seem to be confused. I don't know about your set-up, but the distributor is rotated to time the engine in most cases. You may have a trigger on the flywheel or front pulley, but I think the distributor is still used to set timing. Like I suggested, get a manual.
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

GA_Boater, I don't think I'm confused. The CAS tells the ECU the angular position of the motor, and is no different than the electronics in the base of the distributor, just more accurate and more cost effective (I'm an automotive engine in a past career). All this marine crud is typically 5+ year behind what automotive is, some for good reason, some not. Anyways, that, the MAP, TPS, air and water temp, and if there is a knock sensor all set the timing based on a calibration map in the ECU.

That said, you can twist the dizzy cap all you want and the engine will not change running RPM or the timing, that is until you move it alot. At that point either the spark is too weak to jump the large gap in the dizzy and the spark plug, or the spark jumped to a cylinder post in the dizzy cap that was closer. I just tried it. The issue is that I don't know where to put the cap because when all the ignition timing advance comes I believe the second conditon above becomes true and I here the miss.

Your right, a manual will probably tell me where to set dizzy with respect to the block, but I was hopeful someone else could help me who has done it a few times before.
 

GA_Boater

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Well Fedds, It appears you have been working on this problem since 2007. So I might not be qualified to offer any advice. Good luck!
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Not really. The first time in 2007 it was just the corroded distibutor. I wish I had pictures...suprised it ran at all. This time I thought it was the same thing, but i ALSO rotated the dizzy a bit and it wouldn't get on plane. I put it back, but now I wonder it was ever in the right place. I guess I could rotate it all the way one way till it misses, then the other, then choose the middle minus the base timing...but I would think there would be a better way.
 

dubs283

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

what style igniton do you have, ecm/pcm 555 or hei/est??

ecm/pcm 555 (flat dist cap) you will NEVER be able to set the timing by turning the distributor, idle speed and igniton timing is controlled by the ecm/pcm

hei/est timing is set by using a jumper on the harness connection (service mode) and setting base idle timing with a timing light (conventional method)

here is a link to download the manual for your engine:

http://www.4shared.com/document/UA6kxFEY/Service_Manual_31.html
 

Pete104

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

I'm thinking that the engine has been replaced. And who ever did it should left the automotive experience at the door.
Restab the distributor. A timing light is a thing of the past. And yes there is a knock sensor!
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

She's the triple dime (555) and yes I know you can't set the timing by rotating the distibutor.

The engine has not been replaced from what I can tell (it has a external crack on it from freeze damage, but no internal cracking, oil hasn't had water mixed with it over the last 5 years).

I don't think I need to actually remove the distributor, I just need to know how to clock it...either through finding TDC and pointing the button to the right cylinder post and then rotating it some additional amount, or by some marking on the distibutor base and some marking on the block.
 

04fxdwgi

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

I would start with the "set at TDC and point rotor to #1 tower" method and go from there. Your firing order is 1-8-4-3-6-5-7-2, isn't it? Sounds like problem is "something other" than plug wire placement on the cap. Have you put a scan tool on it to see if she throws any codes? Checked the fuel pressure?
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Let me see if I can put this another way. When I put the dizzy cap back to where it was, the boat seems to run just fine (I need to get it back on the water to confirm). So yes, the wiring and firing order it correct. The problem is, how do you know it's the right position? It doesn't control the timing of the motor, so all you really know if when the coil collaspes the path of least resistance in the cap is to the correct cylinder. Typically, this is because the button is pointed toward this cylinder.

But, let's just say someone else moved the cap at somepoint in time, so at TDC the button is pointed 1/4 of the way towards the right cylinder, 3/4s of the way to the wrong one. She will still run and idle just fine. As engine load increases and the RPM, the ECU will advance the timing (again, dizzy position on this system means nothing about the timing, just what cylinder will get the spark when the field collapses in the coil). As the timing advances the coil will fire closer and closer to the previous cylinder in the firing order. Once it's advanced to the point where it fires half way between the the right cylinder and the wrong cylinder, we are going to have a misfire.

Thus, what is the maximum advance the ECU can ever supply? I've heard numbers in the 30's for advance. In my first post I thought that if I point her to cyl 1 at TDC for that cyl that 30+ of advance would be impossible (45 degress between cyl post in the dizzy cap, thus anything over 22.5 is going to be a problem.). I think I missed one very important point though, the button rotates at the cam speed, not crank speed. Thus, 30 degrees of advance is really only 15 mechanical degrees in the dizzy. Does that make sense to everyone? I'm a electrical engineer, and these non overhead cam motors with this older technology is not common to me. Is my theory sound?

Anyways, the bottom line is the dizzy cap will corrode on this model no matter how clean the vents are in the bottom plate (known issue), and it will not do it in a nice even fashion on all the cyl posts in the cap. Thus in reality the path of least resistance to cause the misfire will be less as time goes on. If the clocking is off but just marginal, I might get what, a few wet weekends? I'm in here now, I want it clocked right. My guess would be then you take the TDC of cyl #1, point the button to post for Cyl #1, and then rotate the cap half the degrees of the base timing so that at idle she's jumping the smallest gap and at max advance you have enough margin to keep from misfiring...but someone at Mercruiser had to have ran tests and thought of all this, so there procedure is really what I want.

Sorry for writing a book. Oh, and she is not through any soft or hard codes that are setting off any alarms when this misfire happens...never has even when the cap back in 2007 was corroded to the point of not even idling ( I took it to the marine and they hooked up the tool with a NTF result (NTF = No Trouble Found))
 

Don S

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

The Merc manual a a little light on how to install those distributors properly. Here is from a Volvo manual. Same engine same distributor.

Oh, and she is not through any soft or hard codes that are setting off any alarms when this misfire happens...never has even when the cap back in 2007 was corroded to the point of not even idling ( I took it to the marine and they hooked up the tool with a NTF result (NTF = No Trouble Found))

There is a lot more to using the diagnostic computer than just looking for a trouble code.
http://boatinfo.no/lib/bulletins.html#mercruiser-service-2003_06
2003_06_Page_1.png

2003_06_Page_2.png


2003_06_Page_3.png
 

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Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Thanks Don for the pdf. And yes, I know there is a ton of data messages and variable you can look at in real time and log, just the bozo I took it too didn't seem to want more than to check the codes for my money, and my attempts thus far at using my existing automotive tool to decifer the data has been a failure.

I'll review the pdf and see if it makes sense and perform the work
 

Fedds

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Just to close the loop on this one. I checked the distributor clocking per the PDF in the link, and as I suspected, it was off...by about 10+degrees. So that explains why under load it would miss. She is back to running like a raped ape. Thanks to all.
 

Micke9000

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Re: Mecruiser 5.0L MPI distibutor proper clocking?

Just to close the loop on this one. I checked the distributor clocking per the PDF in the link, and as I suspected, it was off...by about 10+degrees. So that explains why under load it would miss. She is back to running like a raped ape. Thanks to all.

Hi Fedds.

Maybe a late question but..

You said you had about 10+ degrees off. Was the gear mesh off one tooth or was just the distributor in wrong position?

10 degrees is much, can you get 10 degrees off by just turning the distibutor?

/ Micke
 

nickzlb77

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Hey having the same issue on a buddies boat (positive the clocking is off as the HVS was loose and getting it pretty close gets the motor started). Set to TDC mark but going to check TDC tomorrow as a sanity check, this boat is a total disaster so who knows! Anyway are any of those pdf's still available? The links are no longer valid and the manual is fairly basic.
 

Bt Doctur

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But you really should start your own post to keep current
this is all you do
click to enlarge
Untitledds.jpg


Also Don's post in post number 12 above should still work and should be of great help of how to set this design distributor. Click the following link and if it don't work on one device, try another device..., https://forums.iboats.com/filedata/fetch?id=7001823
 
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