Distributor question 5.0L MPI

[Fedds]

So, I've been trying to track down a miss / hesitation coming out of the hole and while at WOT. I took the distibutor cap off and there was water dropplets in there as well as a ton of white corrosion on the center post, the cylinder posts, and the button. Is this normal? Also, the base of the distibutor as two mesh vents. This seems wrong to me. Shouldn't all this be sealed up to stop water condensation?

Finally, the hall sensor in the base has a three pin connector. I looked around and it's not connected, further more, I can't find a connector on the harness for this connection? Do the advance come from the crank angle sensor?

More is a 2002 merc 5.0L MPI in a Rinkner 2003 Rx1

Thanks,

Brandon

 

[Don S]

Re: Distributor question 5.0L MPI

What is the Merc SN of your engine. Merc doesn't list anything by the year since 98.

 

[Don S]

Re: Distributor question 5.0L MPI

Nothing in that distributor is used except for the rotor and cap to put the fire on the proper spark plug. The ECM controls everything else along with all the different sensors on the engine.
The fact that you have moisture in the cap is what is causing the miss.
Put a new cap and rotor on it and you should be fine.
There was also a service bulletin on the distributors about not having enough vents in them. There should be 2 screened vents to prevent moisture buildup. But that depends on your SN.

 

[Fedds]

Re: Distributor question 5.0L MPI

Engine Serial OM618927.

Is the corrostion also a problem? The local marina wants $85 for the cap and another $25 for the button Do the posts have a plating / coating on them that I will destroy if I just scrap the white crap off? Finally, how do I keep this corrosion from coming back? The bilge will always have some water in it and the engine heat will make for a humity / corrosion friendly environment. Is it a bad idea to go old school and just seal the distributor up (vents and the cap to distributor plate)?

Thanks Don

 

[MikDee]

Re: Distributor question 5.0L MPI

Try getting a new cap, & rotor from NAPA, they carry aftermarket Sierra parts for Mercruisers, then put a little dialectric grease on the exterior spark plug terminals of the cap.

 

[Don S]

Re: Distributor question 5.0L MPI

Thaniks for the SN, with that, I found the service bulletin.
Here is a link to it.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/BULLET/03/smc03_06.pdf

 

[Fedds]

Re: Distributor question 5.0L MPI

Yep, I read that Service bulletin. I checked the distributor and it had some water droplets on the walls of the cap and plenty of corrosion. The note about a vented base got me thinking about sealing the unit though as the engine compartment is always humid and it seeems to me the water condensation in the cap is inevitable with the vents since I don't see it flowing enough air to make a difference.

Hence, I have ordered the new cap and button, but I also cleaned up the old one. If the new one corrodes even after cleaning the vents on the base, I'm going to take the old one and drill a 1/4" hole in the cap down low to help air flow. If that doesn't work and it corrodes, then I'm sealing the whole thing up, vents and cap to plate with rtv, and I may glue a packet of desicate in the base to suck up any other moisture.

I too, checked the schematic and the hall sensor in the base does not seem to be used, not could I find a connector on the harness. The ignition advance must be controlled though the Crank angle sensor.

The other point in the service bulletin that concerns me that that if after replacing this $100 cap and button the motor still misses, it states to mark the base to motor and then rotate the unit 1-2 degrees. That's the most BS solution I have ever heard. Let's not reset the base timing and just change it. I tell ya, as a automotive engineer for GM with a MS in electrical engineering, this would never fly.

 

[Don S]

Re: Distributor question 5.0L MPI

I'm going to take the old one and drill a 1/4" hole in the cap down low to help air flow.

Don't do it. Those vents in the distributor base have a screens in them due to sparks in the distributor that could ignite gas fuse that could be in the bilge.
You should look into some more bilge ventaltion to prevent all the condensation. Even if you seal it completely, any moisture will still be in there.

I tell ya, as a automotive engineer for GM with a MS in electrical engineering,

Oh No!!! Another engineer going to reinvent the wheel.

 

[Bondo]

Re: Distributor question 5.0L MPI

Oh No!!! Another engineer going to reinvent the wheel.

Ayuh,.............

Is that why I always have to Re-engineer everything for a Mechanic's point of View...................

 

[Reel Poor]

Re: Distributor question 5.0L MPI

The other point in the service bulletin that concerns me that that if after replacing this $100 cap and button the motor still misses, it states to mark the base to motor and then rotate the unit 1-2 degrees. That's the most BS solution I have ever heard. Let's not reset the base timing and just change it. I tell ya, as a automotive engineer for GM with a MS in electrical engineering, this would never fly.

Moving the distributor on your engine does not change the base timing. It synchronizes the cam timing with the crank timing. The sensor in the distributor is a cam position sensor. It's all relevant to the computer which controls the spark timing, base and advance.

I tell ya, as a automotive engineer for GM with a MS in electrical engineering, this would never fly.

How long ago was that? GM has been setting cam synchronization like that for years.

 

[Fedds]

Re: Distributor question 5.0L MPI

Yep, thought about the spark in the distibutor igniting fuel vapors, but I don't see how the screens will stop the same vapors from igniting. Maybe the screen is woven tight enough...I'm not sure.

And nope, I definatly don't want to reinvent the wheel, but given the environment for this system and seeing other systems sealed before makes me wonder a bit.

Finally, my engine is not using the hall sensor in the distributor, so I can see how you need to sync up the distibutor timing with the CAS timing, but the non-chilant way they discribe doing it in the service bulletin by just moving it a few degrees seems...well, imperfect. I guess the timing is still controlled by the coil collapsing, so you really just need the button pointed in the right direction though.

I worked for Delphi and quit when the writting was on the wall a few years ago that they where heading to Chapter 11. I designed electronics and controls for ABS and magneto-rheological (MR) dampers...the semi active dampers that try to change the dampening rate every 1mS based on road and vehicle conditions. I never worked on engine controls, but feel I have a much better than average grasp on the concepts and implimentation.

I'll let you guys know what I find and try.

 

[JustJason]

Re: Distributor question 5.0L MPI

Don,
how are you finding those links on alt.merc? unless you have a direct link its all pword protected. are you a dealer with a password or some master hacker???? =)
if you do have carte blanch on the site do you know if OB manuals are available on it? Thanks!!

 

[Fedds]

Re: Distributor question 5.0L MPI

Just another bit of FYI...I was able to save about $35 by taking the distibutor to NAPA and finding a direct replacment. The distibutor and button on my 2002 5.0L mecruiser is the same as those on late model 80 and early 90Vortex GM engines. I'll post up the part numbers when I get back to my boat.

Ironically, I when I was googling this original problem all I came up with was GM trucks of these years that had corrosion issues as well. The solution was to insulate the A/C line above the distributor to stop water from dripping on the unit and causing condensation inside.

 

[Don S]

Re: Distributor question 5.0L MPI

Those service bulletins were not designed for public view. They were sent to dealers only. It never needed to be sugar coated for dealers to understand.

Yes, I use a dealer site for some things, but the service bulletins from 2003 and earlier have been released for public view.
Lots of the links for manuals at http://www-alt.mercurymarine.com/mnetdata/sisdata/mainmenu.pdf which is public are dead, even to the dealers.
Nothing for outboards for the public that I am aware of.

 

[Bondo]

Re: Distributor question 5.0L MPI

Yep, thought about the spark in the distibutor igniting fuel vapors, but I don't see how the screens will stop the same vapors from igniting. Maybe the screen is woven tight enough...I'm not sure.

Ayuh,......

The 2 most common ways of isolating Sparks in the marine environment is with grounded Screens,....
or Elbows.......

Sparks can't pass the Screens,+ Sparks also don't turn corners........

 

[wire2]

Re: Distributor question 5.0L MPI

Ayuh,......

The 2 most common ways of isolating Sparks in the marine environment is with grounded Screens,....
or Elbows.......

Sparks can't pass the Screens,+ Sparks also don't turn corners........

Yes but....

What's to prevent the fuel vapor (assuming there's a leak from a hose or fitting) from permeating the screen, accumulating inside the distributer cap up to a 14:1 ratio and exploding?
The cap would probably blow off and ignite the rest of the vapor in the engine compartment.

True, at speed, the hull vents should keep the vapor from accumulating, and off plane, the blower should be on.

 

[mikey.himself]

Re: Distributor question 5.0L MPI

I was wondering if anyone could point out what Multi Port Injection means exactly (sorry dont mean to throw topic off kilter)

 

[wire2]

Re: Distributor question 5.0L MPI

I was wondering if anyone could point out what Multi Port Injection means exactly (sorry dont mean to throw topic off kilter)

There's an injector for each cylinder at the intake valve.
As opposed to throttle body injection.

 

[Fedds]

Re: Distributor question 5.0L MPI

This turned out to be the distributor cap and button being corroded, as well as the screen vents in the bottom of the distributor being clogged causing condensation. Napa has the parts, have them search under ECH The part numbers for my motor (2002 Mercruiser 5.0L MPI 260 HP serail number OM618927) at Napa are RR207 for the distributor cap and RR256 for the Rotor).

Sorry to get back to the forum so late. It took 3ish years, but the issue just came back and it was time to do it again. Also see Service Bulletin 2003-06