98 GTI, Dealer said MPEM is dead

[platinumtron]

I've usually read through the forum and never had to post. This time I feel it necessary.

98 GTI, ~75hrs. Always garage kept, very good condition. Sat for 2 years, then upon restart everything seemed to be fine, and once in the water it died and wouldn't start back up. Diagnosed as no spark. I decided to bring it to the dealership just to have them diagnose the issue, and it came back the computer(MPEM).

My questions are:
1. Should i believe them? What tests can be done to verify their diagnosis?
2. If so, who sells the best aftermarket MPEM modules.

 

[Dr Honda]

I never trust dealers. That's the simple answer to them... replace a part they can't get anymore. There's a member here who can test it properly. His shop is Westside Powersports.

 

[platinumtron]

update.

I depinned the supposed wire for the MPEM to kill spark, and still, no spark.

 

[platinumtron]

I never trust dealers. That's the simple answer to them... replace a part they can't get anymore. There's a member here who can test it properly. His shop is Westside Powersports.

I have seen both his website and other posts regarding him. I just don't think the dealership actually tested anything and really just guessed.

 

[platinumtron]

update:
Checked voltage at white and black wires of coil while cranking. I got different voltages then i expected. 35VAC and 6.2VDC were the highest numbers i saw. The shop manual says 20VDC, however ive seen some take AC voltage readings. My multimeter(fluke 117) may not react quick enough to pickup dc voltage fluctuating like that.

 

[RCL]

Is it turning over? If so, they make a spark plug that will clamp to the block so you can see if you are getting spark. If no spark, check and see if you have a coil pack some where. I know my dads 97 has a coil pack in it that may do what you describe also. If its not even turning over, check the voltage coming from the mpem to the startstop button. Should be 12 volts. If its any thing but, your mpem is probably done.

 

[platinumtron]

It turns over plenty.

I’ve tested the coil via resistance checks and it passes them. However that doesn’t mean it’s a good coil. I have ordered a new coil. I’ll see what that does.

 

[RCL]

See what the voltage is coming from the mpem to the coil. If the mpem is not sending the proper voltage, that could do it also. Unfortunately or fortunately Im very quickly becoming a mpem expert.

 

[platinumtron]

Mpem voltage to coil is as states above. However it pulses at a high frequency, without a peak voltage meter I won’t know what the peak voltage is. However my meter will read 35vac and 6vdc. Which is probably ok.

 

[RCL]

My mistake. I thought you were reading between the coil and the plugs.

 

[Dr Honda]

OK... 98 GTi has the 720 engine... so you are on the right path. The ignition is simple. Mag coil, and the ignition coil The MPEM controls the rev limiter, and the kill function. If you don't have spark after pulling the kill wire... then it's only one of those 2 parts.


It's most likely the stator coil... but sounds like it's OK. The ignition coil has a CDI built into it. They rarely fail... but it could be the culprit too.

 

[platinumtron]

So new oddity. Everything seems to test fine. I checked for power to the primary wires of the coil (black and white today while cranking and i got 20vdc and still no spark. I compared GTI coil to the coil on my 72 cb750 with an electronic ignition conversion, the coils look exactly the same, probably are not but close enough. I hooked the seadoo coil to the motorcycle electrical connections and the coil produces spark for the motorcycle.

 

[platinumtron]

Multimeter used Fluke 117, last cal date(yes sent to a cal lab, Feb 2015)
Magneto test results,
60.3ohm static check
~20VAC dynamic check(depending on speed, sometimes i get a long and fast crank and itll go all the way to 32VAC)
~12VDC dynamic check

Coil static check,
Primary side 1ohm
Secondary side 12.79k ohm

continuity of all wires is 1ohm or better.

 

[mwat65]

The rectifier rarely goes out on the 720 but it could be the culprit with your fluctuating numbers but most likely the stator as Dr H says.

 

[Dr Honda]

The rectifier rarely goes out on the 720 but it could be the culprit with your fluctuating numbers but most likely the stator as Dr H says.

The regulator isn't part of the system at the moment. The 720 has a pure "Mag/CDI" ignition. You could literally remove the MPEM, Regulator, and battery... and pull start it. If this was n 800 engine... then yes... he needs clean 12v DC from the electrical system to get the CDI to come to life. (The 800 is a DC-CDI, and the 720 is an AC-DCI)

Anyway... since you got a spark hooked to another MAG coil (on the bike)... and since you get a good static resistance check... then the coil needs to come out. I'm guessing you have a bunch of metal fillings stuck to the magnets... OR... a cracked magnet... OR a shorted wire behind the flywheel. (The short may not show up unless it's rotating)

 

[platinumtron]

The rectifier rarely goes out on the 720 but it could be the culprit with your fluctuating numbers but most likely the stator as Dr H says.

Im not too scared of having to replace the magneto, i know it'll likely suck, but taking these engines out isnt that big of an ordeal. I work on electronics for a living however my line of work doesnt deal with magnetos so my understanding of them is limited.

So apparently on the 98+ GTI the MPEM is not the same as the GTX or earlier models. 98 GTI has a single connector MPEM. I am sure the basic parts are the same, but the MPEM cannot be troubleshot the same way. Minnetonka4me(westside powersports) suggested i put a test light to the black/red wire coming from the magneto, it lit bright. This indicated the magneto is putting out power. I then proceeded to check the primary wires to the coil, although i read the same voltages as i do from the magneto, With the light connected it completely shorts the circuit. The light will not light. If i use the light inline with the multimeter i read voltage until the light is hooked up. This might mean with the coil hooked up, it will also short the circuit, and not produce spark. It might actually be the MPEM.

 

[mikidymac]

I would trust what Dr. Honda told you, the MPEM isn’t the issue.

 

[platinumtron]

Can the stator cover be borescoped? I’d rather eliminate everything else before condemning a part that tests fine.

 

[Dr Honda]

In this case... you need to remove it and get a good look.

 

[platinumtron]

can i check the magneto by connecting the wires from the magneto straight to the coil, i should get spark then correct? if no spark then magneto is bad?

 

[platinumtron]

When I pull the flywheel, what am I looking for to condemn the part?

 

[platinumtron]

Dr Honda,
So as you suspected, I did find particles. I have attached pictures of what I found. My questions are now,

1. Clean these up and reinstall or are they bad?

2. Also the flywheel itself has particles stuck, is this condemned as well?

Also it's obvious this issue is created by the starter and its contact with the flywheel. Do i replace it?

 

[mikidymac]

Just clean it all up and try it.

 

[platinumtron]

is the stator easier to remove the second time? dont really want to be using my propane torch inches from a full gas tank more then i have to.

 

[platinumtron]

well, i cleaned everything, reinstalled everything. No spark. I get the same voltages, and no spark.

how sure are we that the 98 GTI MPEM is not more integral to spark then other engines. it has a different MPEM then most other 717s.