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Explain double firing

M

Mmtbpz

Member
New to boating and this forum..
Can someone please explain double firing and the symptoms associated with it?..I have a early nineties 200 xri that runs poorly yet I have good compression and spark on all six cylinders..Using a timing light port side of engine fires twice as fast as the starboard..had a regulator and bullet connector burn up on me and it has been suggested I need a switch box or at least start with the cheapest possible part first..what kind of driveability issue should I expect with this scenario ?
Pls and thx in advance
Peter
 
That is the intention here
I bought the boat and was sold an issue ...to put it nicely
Things I've learnt ..tiltpump leaks down and reqs repair..within 1 season strg cables seized up..no charging or tach display..battery nfg...and lastly the running issue..on initial start up it throttles out nicely..throttle response is quick and rpm revs nicely..second or third brap of the hot foot pedal results in a poor running scenario...replaced the regulator..which corrected tach and charging issue...was told to inspect port and starboard firing with a timing light and noticed one side much faster than the other..light was almost like using a flashlight.. suggested this was an double firing issue and to change out corresponding switch box..read stator can do this also..does this scenario sound plausible..not misfiring as I know it to be but runs poorly ..under load won't pull the skin offa rice pudding...
Tia
Peter
 
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Index the flywheel(find TDC on each cylinder) and mark . Then take timing light and check. If you see 2 different numbers in the same flash its double firing. Also if timing light pickup is near the green primary wires it can pickup stray voltage ...
 
So put in a new switch box and issue is still there..redid the compression and still getting 120+ in all cylinders..after running in and pulling individual plug wires 3+5 are the only ones making a very noticeable difference..1-2-6 make a difference only when re connecting ..the difference is slight...2 doesn't seem to make any difference..plug was a bit wet when I took it out..very smokey..stinky everytime I run it I stink for the remainder of the day..starting to think injectors..fuel was a tad stinky when we got it..we flush tanks and changed filters but maybe we.re gummed up..can I get at the injectors to disconnect and test ? can I remove them without removing entire manifold ?
 
Don't know that I have a double firing issue at all..was suggested to me..runs like.a misfire or has been said sounds like it's loading up..but never cleans out a higher revs.. any thoughts..
Thx in advance
Peter
 
Don't know that I have a double firing issue at all..was suggested to me..runs like.a misfire or has been said sounds like it's loading up..but never cleans out a higher revs.. any thoughts..
Thx in advance
 
Head gaskets are cheap.-----Remove the heads for inspection.------What is " good compression " in actual numbers ?
 
Ok..could / would there be a reason that would give me a way too rich scenario ?..pulled back the throttle body to check injector operation and spray pattern..seems ok..but tough to see in the daylight..as I wrote earlier only 2 of the six cylinders seem to make a significant difference when I pulled the ignition wires..rest of them were tough to notice a difference until you reinstalled the wire and only slightly ..1 didn't seem to make any difference.that one cylinders plug had a large fuel drop on it when I removed it after running..swapped coils from know good cylinder...can hear electrical snapping between plug and wire when pulling it away..any suggestions ?
 
I believe I have a rebuilt powerhead here..my compression test results were 125 across the board..multiple tests done..when removing heads for inspection what would I be looking for in regards to my issue ?
Thx for all replies...
Bit of a headbanher
 
Will do..Thanx..
Can I assume with that scenario I would have a hard start issue ?
This motor starts on a quick key turn..after initial start I may get 1-2 good accelerations but then starts the loading up ....if I can call it that...
Boat is new to me..2 strokes as well..had the boat some 5 years seem to remember it not being like this when purchased but have had to fix so many things on it already I'm not sire ..fuel got stinky at one point.. unfortunately no history on it as previous owner vanished..powerhead looks like a rebuild as it's freshly painted and no serial number on frost plug..just fresh paint..had a voltage regulator and bullet connector burn up at one point but repaired..
Would a fuel pressure regulator or set of reeds be suspect in this scenario ?
 
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I believe they are correct..
1-3-5 on left side(looking at heads) 2-4-6 on the other side
Individual wires are labelled
 
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So..to update ..Ive checked fuel pressure ...I have 36 psi at idle ..just over 40 psi when press regulator is disconnected..no leak down when key is turned off..ran for approx. 2-3 minutes and I stink to high ----..never have I smelled so bad so fast working on any snowmobile ive ever owned..none the less..checked for map sensor vacuum and hoses..any additional help steering me in the right direction would be greatly appreciated..
Peter
 
Should there be an improvement in the way it runs after disconnecting the map sensor..can I test the sensor ?
Thx in advance
Peter
 
Nevermind the only inputs i could find are throttle position, temp and it will also see RPM but sounds like something is telling the ecu it needs too much fuel?
 
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I should have stated previously perhaps..my motor is a early 90's two smoke..map sensor is in the ecm..manual says anything related to map is a dealer repair...can I remove and clean..does this motor run an o2 sensor ?
Peter
 
Would disconnecting it while running make a difference in the way it runs...
Ie.if it's signalling for a rich scenario after unplugging would it clean out..
This motor never seems to clean up ..even at high rpm..under load it's just a dog and can't get on plane..will rev out of water on muffs but sounds like a loaded up snowmobile..ran for maybe 3 minutes today testing fuel pressure and I smell so bad I got a headache all day....starts fine .. idles fine..can get 5800 rpm but not a clean acceleration..auto mechanic four stroke exp..clean many MAF sensors but map didn't know you could clean a map..is that not just a vacuum sensor ?
 
If the map is part of the ecm it should have a manifold vacume hose to it. You can check tps senser with a analog ohm meter see if the needle sweeps nice and smooth in relation to throttle position ifit jumps or skips the throttleposition sender its basically a rheostat.
 
According to the service manual ..the map is part of the ecm..also states it is not serviceable..it does have a vacuum line going to it ..should I notice any difference in the way it runs when I disconnect the line ? I don't ....would a faulty TPS or improperly adjusted one cause a loading up scenario ?
 
With only a couple inputs that would condemn the ecu pretty quickly..don't have a known good to test with either..I didn't get oil or fuel into the map but I have no idea what the previous owner may have done..can't see that as it's not exposed really..is it possible I'm getting too much oil and making it way stinkier than normal ? is it possible to inject too much oil ? I'm kinda admitting defeat here..I don't have the required knowledge to fix this
 
What is the exact year of motor? The MAP sensor fitting being clogged will make it run rich as will TPS setting out of wack. I re-read your earlier posts and you stated 1-3-5 was on left bank?????
 
1-3-5 is on the side with the vapor separator..I may have called it left as I'm not sure of proper terminology..I put a vacuum gauge on the map sensor fitting and had vacuum so unless it's plugged further up..I do know that disconnecting the line while running doesn't make any noticeable difference..
Appreciate your help
Peter
 
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