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Thread: Ignition Issues

  1. #1

    Default Ignition Issues

    My 2002 PCM 350 H.O. stopped running last week, with what I thought was a running out of fuel condition. Instead, I did some troubleshooting. (crank but no start) and determined that the ignition coil wasn't creating spark.

    The Ignition Control Module ground was suspect (rusty screws that ground the ICM to the distributor case) so a new ICM was sourced, new SS screws added and cleaned the distributor case to verify a good ground for the ICM.

    I also ohmmed out the pickup coil on the distributor and according to the PCM manual, I should have between 800-1500 ohms. But mine shows varying resistance in the 2.5-2.7megohm range. And the value is constantly changing, going up for a while, then stopping and coming back down. Almost like measuring a capacitor.

    I did measure the output AC voltage on the pickup coil and verified it's about 1-3vac, which is within spec according to the manual.

    The engine fired right up and appeared to run fine until I tried planing out. At 2500 rpm and above, the engine starts hesitating and eventually drops to idle rpm and almost stalls.

    If I pull back the throttle it will idle, although a bit rough.

    My gut tells me it's the pickup coil. Any thoughts would be appreciated.



    Thanks,

  2. #2
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    Default Re: Ignition Issues

    could very well be the pickup coil.....may want to verify the ohm meter being used has a good battery - the reading should be steady across the coil. and don't forget to flex the leads to the coil to flush out any broken corroded wiring.

    is the coil still producing spark when the RPM drops? if so, you may wanna check the distributor cap, especially it is one of the 'flat' ones...

  3. #3
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    Default Re: Ignition Issues

    The engine fired right up and appeared to run fine until I tried planing out. At 2500 rpm and above, the engine starts hesitating and eventually drops to idle rpm and almost stalls.
    Ayuh,.... This line sounds like it's runnin' outa gas,....
    Any Grease is Better,... Than No grease at All....

  4. #4

    Default Re: Ignition Issues

    Quote Originally Posted by makomark View Post
    could very well be the pickup coil.....may want to verify the ohm meter being used has a good battery - the reading should be steady across the coil. and don't forget to flex the leads to the coil to flush out any broken corroded wiring.

    is the coil still producing spark when the RPM drops? if so, you may wanna check the distributor cap, especially it is one of the 'flat' ones...
    I actually have two Fluke meters so I thought of the same thing and grabbed the other one. Same readings and were consistent with the other meter, when flexing the lads. .

    I believe it's still producing spark because it never stalls, just surges with the RPM, eventually running better if I pull back the throttle.

    Thanks,

  5. #5

    Default Re: Ignition Issues

    Quote Originally Posted by bondo View Post
    Ayuh,.... This line sounds like it's runnin' outa gas,....
    Next time at the lake, I'm going to do further fuel pressure checks off the FCC. I know at ignition on, cranking and idle, there is consistent 30psi (throttle body system), but now I need to verify pressure at 2500rpm and higher.

    thanks,

  6. #6
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    Default Re: Ignition Issues

    if more than one meters shows the coil has consistent behavior, then I'd suggest you resolve that ....try it....and then go on to the next test....

  7. #7

    Default Re: Ignition Issues

    Good morning everyone. I sourced a new pickup coil and installed Friday evening. The resistance was within spec (800 ohms) and after disassembling and re-installing the distributor, the motor fired right up. All good. Timed it using in Service mode and the boat ran perfect all day Saturday. Yesterday morning, our club raised our slalom course. I pulled my buddy 4 passes, and then I skiied. At the end of my 4th pass, the boat just died.

    Symptoms now are cranks, but doesn't start.
    The injectors are spraying.

    When I got back to the dock, I checked spark with my timing light (inductive pickup connected to the high tension lead between the coil and distributor), and no strobe.
    I verified all coil resistance readings were good (primary and secondary windings) and verified 12vdc was present at the coil, with key on.

    Fuel control cell shows a constant 30psi with key on and with engine cranking, so I don't think it's fuel related.
    The injectors are spraying so that tells me that the Ignition Control Module is creating the signal to fire the coil.

    Parts replaced were the pickup coil and Ignition Control Module.

    Any further ideas would be appreciated.

    btw, to make matter worse, my other buddy's MasterCraft snapped a steering cable while in the slalom course.

    Rick

  8. #8
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    Default Re: Ignition Issues

    Do you have the MEFI-4 ECU?

  9. #9

    Default Re: Ignition Issues

    I have a Code Mate Scanner tool. It shows now error codes.
    CodeMate
    MEFI Code Reader


    For GM-Delphi MEFI-1 thru MEFI-4
    This pocket size tester serves as both an EFI Problem Indicator and a Spark Timing service tool. It is the perfect tool for low volume marine repair shops that troubleshoot a small number of EFI systems a year. CodeMate allows fault codes to be read and allows base spark advance to be set when used with a timing light.
    For GM-Delphi MEFI-1 thru MEFI-4
    systems only. Not compatible with
    MEFI-5 and above or 2001 and newer
    MerCruiser PCM-555 / ECM-555.


  10. #10

    Default Re: Ignition Issues

    I also took the coil out and tested all resistance readings on the bench. (all good) Primary reads 1.0 ohm, Secondary reads 8.5k ohms.
    Cleaned the female connectors, re-installed and still no spark at the distributor coil wire.

  11. #11
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    Default Re: Ignition Issues

    The code mate isn't a full blown scan tool.....if you have the MEFI-4 ECM, then you need to set the cam retard value with the distributor's position (vs the actual initial timing value)...but you need to get the spark back first.

    if you do a www search on PCM & MEFI-4 & diagnostics, you should be able to find the factory service manual pretty easy.....section 7 is where you want to start.

  12. #12

    Default Re: Ignition Issues

    Thanks Mako,

    Mine is a MEFI-3, I think because it's an older Throttle body based fuel injection system. IOW, the throttle body has two injectors spraying into it. And I don't have oxygen sensors. As I said, it's spraying fuel on engine cranking, but no spark. That seems to indicate that the distributor components are functioning because I believe fuel injector spraying only happens if proper ignition signals are sent to the coil??? Before I replaced the pickup coil in the distributor, fuel spraying wasn't occurring on engine cranking.
    Rick

  13. #13
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    Default Re: Ignition Issues

    Yes, the pulse from the distributor tells the ECU to pulse the injectors....

    Based on what you have done, I'd suspect the tach.....disconnect the grey wire, at either end, and see if the spark returns.

    In the interim, you can search on L510004 and pleasurecraft to see if you can find the MEFI-3 manual....it goes thru all the rest of the steps as well....and with the -3 computer, your timing procedure was ok - that one doesn't have the cam retard concern....

  14. #14

    Default Re: Ignition Issues

    Thanks for the response, Makomark.

    I'll get back on it tomorrow night but can I ask why the gray wire to the tach might be a culprit? I thought that was only a signal from the distributor/ECM to operate the tachometer.

    RickR90s

  15. #15
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    Default Re: Ignition Issues

    not the gray wire per se but the tach itself....many tachs have a failure mode which inhibits the ignition system's operation....

    If I remember correctly, the Delphi manuals make this 'step #1' for any troubleshooting on a distributor ignition....

    Did you find the MEFI-3 manual?

  16. #16

    Default Re: Ignition Issues

    Quote Originally Posted by makomark View Post
    not the gray wire per se but the tach itself....many tachs have a failure mode which inhibits the ignition system's operation....

    If I remember correctly, the Delphi manuals make this 'step #1' for any troubleshooting on a distributor ignition....

    Did you find the MEFI-3 manual?
    ahh,

    Yes, just sourced the MEFI-3 manual. Starting to go through it now.

    Thanks again!

  17. #17

    Default Re: Ignition Issues

    I disconnected the gray wire last evening. There's two gray wires going to the tach, one a bit darker than the other. The engine still isn't producing spark.

    As luck would have it, I bent the tab on the rotor to have better contact with the center post of the distributor and of course, it broke. So a new rotor needs to be sourced. Verified that the distributor rotates with engine cranking. (I did remove the gear to replace the pickup coil so, you never know).

    And to verify, the pickup coil resistance measures 800 ohms, and on engine cranking, produces about .7vac.

    I also checked the pink wire going to the ICM, and it has 12vdc present with key on. I ran out of time, but I'll next check the coil's switching signal on engine cranking.

    I believe it's the ICM, but that was replaced a few weeks ago and the boat finally ran last weekend with the new pickup coil installed. Are ICM's that fragile?

    Thanks,
    RickR90s

  18. #18
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    Default Re: Ignition Issues

    The original GM/Delco ones were pretty tough....aftermarkets seem hit or miss....as long as they are installed correctly and not abused, they should last a long time....

  19. #19

    Default Re: Ignition Issues

    Something in the system is degrading the ignition to the point it ultimately fails. So I decided to replace the cap, rotor and ICM Friday night. The motor fired right up, ran smooth. I set the base timing to 10 degrees BTDC, after putting the engine in service mode with the Scan tool.

    The engine ran fine for about 1/2 hour, pulling my club through the slalom course. Then it started missing, sputtering, and finally died. Now it's back to a crank, but no spark condition. 30psi is present on the fuel control cell with engine cranking.

    I didn't check engine ground (from battery terminal as I couldn't locate it on the engine block). If anyone knows where it is connected, I'd appreciate that info.

    Thanks,

    RickR90s

  20. #20
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    Default Re: Ignition Issues

    I trust you put the new module in with a heat transfer grease?

    The ground is usually at the flywheel end of the block....at the 3 or 9 o'clock position.

    If you have an IR thermometer, it may be worth checking the coil to see if it is getting hot and breaking down....especially if it will fire up after sitting over night....

  21. #21

    Default Re: Ignition Issues

    @makomark,

    Yes, a new Ignition Control Module was installed with heat sink paste (the white stuff) and new mounting screws to ensure a good ground.

    As far as the coil, I don't think it's breaking down as I've checked primary and secondary resistance when it runs and after it fails, and they're almost identical readings. I've also sourced a new coil and before I got it running again, last time (with the new rotor, cap and ICM)......it wouldn't start with just the new coil.

    Last night I located the negative cable ground on the block. It was clean, but I removed it, cleaned it further, added dielectric grease and re-torqued everything.

    I'll go back to basics this evening. I'll check 12vdc to the coil with key on and the signal line to the coil (from the ICM) with engine cranking.

    Sure is frustrating. Boat has been bulletproof until this year.

    Thanks for the help.

    RickR90s

  22. #22
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    Default Re: Ignition Issues

    Good on the paste - based on your previous posts, I'd suspected you followed the book but figured better to ask than assume...

    FWIW, dielectric grease isn't good for improving electrical connections - but does help in excluding environmental detracters....

    Intermittents are the most challenging issues to resolve and the 'basics' are usually fruitful.....just be thorough.....connectors (pins, sockets, and the crimped ends) can be contributors, too.

    Monitoring the coil leads can help isolate potential causes, too - volt meter on the + side and dwell meter (duty factor on the newer DVMs) on the - side .... remember - something is changing when the engine acts up and the "change" is what you need to find.

  23. #23

    Default Re: Ignition Issues

    @makomark

    Agreed, It's the change I need to isolate, that's causing the engine to fail.

    One observation.....I ohmed out all the connectors and the 2 pin connection between the ICM and coil has one of the wires showing 6.6 ohms. I thought it was funny, as it should be around zero or .1 ohms, like the other wire (direct short). But looking closer at the harness, it appears there's a resistor (ballast resistor?) in line.

  24. #24
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    Default Re: Ignition Issues

    not supposed to be any ballast resistor on the EST systems.....I do recall somebody posting on here a while back about a small item integrated into one of the harnesses....maybe search for it if you have time....

    The other item that comes to mind is relays - are any on your engine??? if so, have you ever changed them? they are maintenance items and will cause this class of symptoms.....and you can buy the ones at the auto parts store.....

  25. #25

    Default Re: Ignition Issues

    @makomark

    Yes, there are two relays. Fuel and Ignition. I've changed both out earlier in this troubleshooting sequence. I kept the old ones because they ohm out correct. (coils and connections are good)

    I talked to my local auto mechanic and he turned me onto a troubleshooting doc for this type of ignition system off a '98 Chevy pickup and all indications are that I have a shorted GRAY tach wire. So I spent the evening with my trusty Fluke trying to find it. So far, no luck. I'll locate a complete PCM schematic and hopefully be able to divide it up into systems and find it.

    Thanks,

    RickR90s

  26. #26
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    Default Re: Ignition Issues

    new relays - check.....

    I'd think that troubleshooting doc would be consistent with the PCM MEFI-3 documentation....the gray wire concern was what I was getting at in post #13....and if tht is where the problem is, you may not see anything with your meter sitting still on the boat with the engine off.....you can just clip the tach wire at the coil to eliminate that one...

    which wire (color) has the 6 ohm measurement?

    Have you verified +12VDC is at the coil after the issue occurs (while things are still hot)?

    Any idea where the "other" gray wire attached to the tach goes???

  27. #27

    Default Re: Ignition Issues

    @makomark
    Understand about meter reading with respect to checking for shorts to ground, engine off.

    The pink wire (2 conductor between the coil and ICM) is the one with 6 ohms resistance. I'm guessing a ballast resistor? Its stock.
    The other gray wire goes under the dash somewhere. I'll attempt to trace that out this evening. I'll also verify continuity between the larger gray wire from the tach back to the coil. I was talking with my wife when I was measuring that and well, you know how they can talk, and talk and talk, and then next thing you know, you forgot to write things down. If I recall, I didn't have continuity, which surprised me, but I'll check again and record the results.

    Thanks, appreciate your help very much,

    Rick

  28. #28
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    Default Re: Ignition Issues

    shouldn't be any ballast resistor as there's no need for it.....I'd suggest redoing the ohm test on that wire (should be purple) with the 'wiggle test excursion
    . clip the meters leads like normal and wiggle the wire along its length, especially at the connections....poor man's simulator for engine vibration, etc....

    if there's continuity between the tach and the coil's harness, you really need to find out where the other gray wire on the tach goes - if its makes contact with ground, that will kill you ignition....you could just remove it and tape it back to the harness...

    if you don't have continuity in the gray wire (coil up to tach), I don't see how the tach can work....

  29. #29

    Default Re: Ignition Issues

    Have you verified +12VDC is at the coil after the issue occurs (while things are still hot)?
    I have not verified 12vdc after the issue occurs, but there is 12vdc currently (key on), and technically, it's afterwards since I don't have spark.

    I used a test light on the ICM switching signal line as well (gray wire). With ignition on, engine not cranking, it was solid. With engine cranking, it was solid, indicating no fluctuation, and therefore no switching.

  30. #30
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    Default Re: Ignition Issues

    Rick:

    I found the old thread - see link below:

    http://www.marineengine.com/boat-for...-Ignition-HELP!!!!!!

    based on that, I'd say the 6ohm value is "normal"....that said, I thinkthe fix there was replacing that harness - see thread as my memory has been stressed this morning.

    Agree with your test light conclusions, mostly.....would be good to verify the +12VDC feed to the coil is present when the issue occurs....but without the switching (blinking) on the cold side of the coil, it doesn't matter.....the +12VDC, from the switch is there because the light is on....

    so, my current thought is where did you connect the test light to the switching signal (grey wire)?? if at the coil connector, maybe try the ICM side? also, if you have an extra set of hands, you can do the wiggle test on the ICM-coil connections while cranking. the last idea is maybe something was damaged inside the distributor during the pickup swap???

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