Results 1 to 7 of 7
  1. #1
    Race, wreck, repeat delagem's Avatar
    Join Date
    Aug 2006
    Location
    Homer, NY
    Posts
    728
    +1
    2

    I thought holding the throttle cut the ignition?

    I did a ton of reading before I bought the 04 MSX140; one of the things I remember reading was that if your TPS fails, the ski won't have any spark. My understanding was that the TPS fails in a way that makes the CDI think the throttle is pinned, and it won't make a spark that way.

    I figured this would make doing compression tests easy; when you pin the throttle there would be no spark. Well, imagine my surprise when, during my test, my ski roared to life on 2 cylinders!

    Did I misunderstand this? Or is something else going on? I checked the TPS thinking maybe throttle pinned was only 90% open, and sure enough, that was the case. But holding the TPS itself at 100% still let the engine start....

    Michael


  2. #2
    rob2337's Avatar
    Join Date
    Jun 2007
    Location
    Montréal, Québec Canada
    Posts
    447
    Not sure on the MSX, but on a car with fuel injection, holding the throttle pinned will cut the injectors, not the spark. Engine may still start but will die soon after as long as the throttle is pinned. Helpful to clear a flooded engine. Cutting the ignition and still injecting the fuel sounds a little dangerous when you reactivate the ignition.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    36,599
    +1
    1,276
    Quote Originally Posted by delagem View Post
    I did a ton of reading before I bought the 04 MSX140; one of the things I remember reading was that if your TPS fails, the ski won't have any spark. My understanding was that the TPS fails in a way that makes the CDI think the throttle is pinned, and it won't make a spark that way.

    I figured this would make doing compression tests easy; when you pin the throttle there would be no spark. Well, imagine my surprise when, during my test, my ski roared to life on 2 cylinders!

    Did I misunderstand this? Or is something else going on? I checked the TPS thinking maybe throttle pinned was only 90% open, and sure enough, that was the case. But holding the TPS itself at 100% still let the engine start...
    My understanding of the Polaris Ficht was similar, but I always disconnect all three plug wires, and remove all three spark plugs, before checking compression.

    See page 30 (2.10) in the 2003 MSX 140 Service Manual, which recommends the same - all three plugs out.

    There was a thread a while ago about whether having the other spark plugs in place, or all spark plugs removed, was better during compression testing. I think the consensus was that the important thing is to be consistent.

    My perspective is that the faster the engine cranks, the closer to operating conditions the pistons+cylinders are, and the closer the compression reading is to operating conditions. Not the same, but closer. Warm engine helps too, but I usually test cold, again because it is easier to be consistent that way.

    I do not recall where I read that full throttle during cranking would not start the engine. Could have been on here, or in a Ficht service document, or even the Polaris Service Manual. Or maybe I am just confusing it with automotive fuel injection.

  4. #4
    casey67's Avatar
    Join Date
    Sep 2006
    Location
    Lemont,IL
    Posts
    2,571
    +1
    35
    Like rob stated,it is true with cars,especially with GM.From I've read ,the cars PCM is alot more advanced than the Ficht.I would guess the ficht injection does'nt want to shut off the fuel for easier starting when hot or weird conditions.I would'nt worry about it starting,I really suggest removing all plugs to test the compression,Like K said ,it will more accurate/consistent.

  5. #5
    Race, wreck, repeat delagem's Avatar
    Join Date
    Aug 2006
    Location
    Homer, NY
    Posts
    728
    +1
    2
    I've been doing it like as stated on GroupK's site; cold engine, plugs in:

    http://www.groupk.com/tec-comp.htm

    On my SLX there's a nifty little grounding connection; all your spark plug wires go on that, so no chance of starting. The MSX doesn't have that, and the other trick I use on the Kawis, stuffing the spark plug boot over a head nut to ground it, won't work either.

    Guess I gotta buy another one of those little grounding bars!

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    Location
    near Toronto, Canada
    Posts
    36,599
    +1
    1,276
    Quote Originally Posted by delagem View Post
    ...Guess I gotta buy another one of those little grounding bars!
    I never got any for myself. Anybody have any three post plug wire grounding bars laying around?

    I guess I should just order some new ones. Hmmm, I though I did order some with one of my Babbitts orders.

  7. #7
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
    Join Date
    Jul 2007
    Location
    Cedar Rapids,Iowa
    Posts
    6,381
    +1
    23
    You could make a grounding strap with just screws and nuts the size of a spark plug head,mounted into a plate mounted to the block.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	987-9998-040.jpg 
Views:	42 
Size:	112.0 KB 
ID:	113711  

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Thoughts on the 2011 Inner coolers?
    By mstennes in forum 4-Tec Performance
    Replies: 10
    Last Post: 02-21-2011, 06:59 PM
  2. Will using a battery booster pack blow the ignition controller?
    By shelby427uk in forum Polaris Open Discussion
    Replies: 10
    Last Post: 07-11-2008, 04:27 PM
  3. Hold The Vision - "cloverfield" Type Movie
    By Canadian Swamp King in forum Mudbug Nationals PWC.Life Rally
    Replies: 5
    Last Post: 05-16-2008, 10:28 PM
  4. Old Thoughts - Remove the hook or Not
    By tchies in forum Sea Doo Open Discussion
    Replies: 6
    Last Post: 09-19-2007, 09:41 AM
  5. Thought for the Day.....Friends
    By RX951 in forum Yamaha Open Discussion
    Replies: 0
    Last Post: 07-27-2006, 06:18 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •