weak spark and positive earth??

[speedtkt]

Hi ya

so for a while ive been having a warm start issue ive been though most every thing in the fuel system and still this issue is there.

in my search ive redone the carbs set the pop off cleaned the jets etc checked the breathers filters etc

now ive moved to spark which seems weak and when I had the ski at the boat ramp this after noon and it happened I quickly poped the plugs out and checked the spark which was well almost non existent.

how do I check to see where the problem is? its had a new coil already

also I checked the voltage when it was running and the battery is only at 12.08 V so it looks like ive got no charging

And after all that my ski is positive earth. ive got the book and it says it should be negative earth
any idea's on that any issues buy just swapping it back

 

[LouDoo]

I'm not sure what you mean by positive earth, do you mean the battery is hooked up backwards? Positive side is hooked to ground?

Actually the weak spark is normal, all 2-stroke Seadoo's have a weak spark. It sounds to me that you either have a bad voltage regulator/rectifier or a bad stator. Try temporarily disconnecting the red wire from the rectifier and see if the problem clears, if it does replace the rectifier.

Let's see if our resident vintage expert can take a look at this thread. [MENTION=49703]RodInEscondido[/MENTION]

Lou

 

[Sportster-2001-951C-Stock]

If the system voltage is dropping too low, it will be difficult for the CDI ignition to create enough voltage for ignition spark. Low voltage while cranking is definitely a show stopper, 11V on battery during cranking through compression stroke with good battery, cables and connections is about the low limit voltage for ignition.

Never attach a jumpstart box or cables from another vehicle, any excess or dirty voltage can damage your MPEM and/CDI ignition. The proper way is to charge the battery correctly and allow it to sit a couple hours before installing it, the battery must be in good condition and your charging system must be working correctly. Mine seems to settle at 13.8 volts, engine running.

 

[speedtkt]

Lou doo: yes positive earth mean basically the battery is backwards a few cars have this system aswell
sportster: I take my battery out to charge. have you ever come across positive earth?


Ive got to paint the laundry today then ill be out in the shed ill try the rectifier thin first

 

[RodInEscondido]

Lou gives me much more credit than I deserve; I am pretty new at SeaDoos but do have a number of the older ones that I have been working on for a while.

What sportster said is pretty much on the money.

I cannot wrap my mind around the positive ground thing, seems there would need to be a number of things changed around in the electronics to have this work and, of course, if wrong polarity at the battery source the starter would spin the wrong way (if at all) and never engage. Yes, I have seen positive ground systems in other vehicles, but not SeaDoos that I have.

 

[Sportster-2001-951C-Stock]

have you ever come across positive earth?

I still have an old field truck using positive ground, and long ago a VW bug. It's not in my memory any boats or a jetski using positive ground, always the engine is connected to negative side of battery.

This is "shocking"!!! If positive ground, it's a special version I've never encountered or heard of.

 

[speedtkt]

ive charged the battery and disconnected the the red wire from the rec and still the same 12.30v also on cranking it drops to 9v with the half flat battery was 5v LOL so whats next? stator replacement? shall I just swap the it back to neg earth?

/

 

[LouDoo]

I've had a couple of British sports cars that had positive ground, I've never seen a Seadoo with a positive ground, but just because I haven't seen one doesn't mean it doesn't exist.

Lou

 

[Sportster-2001-951C-Stock]

Try a larger battery, unless you're sure your battery is up to the task. Could be your electric starter is tired, check carefully for corroded copper battery cables, they can be deceiving and saltwater eats them fast.

It's generally best to rebuild the original equipment starters using the rebuild kit as opposed to installing an aftermarket starter, many of them aren't up to the demands.

The charging issue is usually a defective rectifier/regulator unit but sometimes the 3-phase stator wires can corrode if water gets into the housing. You can perform a quick stator electrical check: disconnect from rectifier and measure resistance in ohms of the stator winding between any three of the yellow stator wires should be less than 1 Ohm and there should be no continuity to ground.

You may have a defective CDI unit, the old ones seem to be nearing the end of their lives and more failures are beginning to occur. Kinda doubt it though since system voltage is low but cannot rule it out. Grab a spare and pop it in there if you have one, won't hurt.

 

[speedtkt]

ive got 2 yellow and 1 blk between the 2 yellow I get .9 and with the black there's no reading so im guessing that black wire isn't connected any more.

shall I pull the motor back out? ill be easier that trying to do it in the ski

if I order a new stator for the usa itll take a week or so to get here

 

[Sportster-2001-951C-Stock]

I'm not sure but that might be a single phase stator, that wouldn't surprise me, but I don't have the schematic. Does the black wire have continuity to ground? Normally all the stator conductors are yellow, so the black wire might be for some other purpose if it's not connected to the rectifier, or it could be ground for the rectifier.

I would inspect everything as closely as possible before ordering any parts, I hate ordering parts to discover I don't need them. There are some parts that are difficult to check but the stator is just a winding so that is more straightforward once you know how it's supposed to be wired. I just don't know if those old skis were single phase or 3-phase. Sounds like it's single phase.

The yellow wires from the stator denote the alternating current conductors, feeding AC to the rectifier. You should see a fairly high impedance on the AC input looking into the rectifier unless one of the diodes are shorted. Also when there's a shorted diode in this circuit usually there's a fuse leading out to the battery that would blow.

I'm not sure how you can swap it back to negative earth, seems your permanent magnet starter would rotate in the opposite direction in that case.

 

[Sportster-2001-951C-Stock]

I'm looking for the 1991 service manual to find the electrical schematic:

http://seadoomanuals (DOT) net/download/pdf/service/manuals/1991/1991-seadoo-shop-manual.pdf

 

[Sportster-2001-951C-Stock]

Also, the lanyard switch can cause restarting problems too. A lot of guys went round and round to finally end up with a new lanyard switch and big smile on their face. Just FYI.......

 

[LouDoo]

Disconnecting the voltage regulator/rectifier will not improve charging, in fact disconnecting it will cause a no charge condition. Disconnecting the rectifier will only make the ski run better. I don't know of any way to test the rectifier, so if you are going to start replacing parts try replacing the rectifier first, it's a lot easier and cheaper than replacing the stator.

Also since you have a positive ground I'm wondering if the previous owner did some creative wiring, I would download a schematic and try to get this ski back to the original condition.

Lou

 

[speedtkt]

so I have some good progress ( I think) thanks to you guys.

the stator is single phase.
if I change the polarity the starter spins backwards
I tested the rectifier and I think its dead. theres no flow

 

[Sportster-2001-951C-Stock]

This must be a specially made reverse polarity starter, a very rare item. My bet is your rectifier is dead, but there should be a fuse in the circuit to the battery that could be blown. I guess the rectifier has four conductors, two for AC from the stator, one red to the battery positive terminal, and one for ground reference (to enable the regulation).

You have good continuity across the stator, so the only remaining possibilities are a broken or miswired connection, blown fuse, or defective regulator.

I think you've got it licked!

As far as cranking, is it slowly cranking? If the starter motor bushings are worn out this could be dragging down the system voltage. Assuming the battery is in good condition. Keep an eye out for any used spare electric parts at low cost, sometimes buying a spare used ski can be a great way to obtain those parts.

Good luck, let us know how it goes!

 

[Sportster-2001-951C-Stock]

But, since your engine is at positive, the ground wire of the rectifier should not connect to engine block, it should connect to negative battery terminal (somehow, direct or through harness) and the positive terminal of the rectifier should connect to the engine block (or battery positive terminal somehow, direct or through fuse to harness).

So it's a little bit confusing but not impossible to understand, maybe it was connected improperly(due to confusing reverse polarity earthing) thus doesn't operate to keep the battery charged?

 

[speedtkt]

I Got a new rec yesterday cost all of 6.20NZD wired it all up as the old one was red pos black neg etc
I also got a new battery for the sake of 89nzd why not be sure. I got every thing in and fired it up still no charging and now the tether cord isn't working. as soon as I get home from work ill have a look into why the tether cord int working and why the battery still wont charge. Ill admit tho the new battery made a hell of a difference

 

[Sportster-2001-951C-Stock]

Sounds like you've got the rec wired correctly, red is positive of output. Is there battery voltage between the black and red wire (measure to be sure)?

You can measure for AC on the stator with engine running, maybe you see 50~70vac? I'm not sure exactly.

 

[speedtkt]

so a bit of a bugger. the rectifier had a regulator built in and the new one is just a rectifier so if my memory serves me right it still wont charge as it needs the regulator to create a current draw?????

 

[Sportster-2001-951C-Stock]

Good question, I don't have the answer if this needs only rectifier or rectifier+regulator type, both should charge the battery by converting AC from the stator to DC but the rectifier by itself might overcharge.

Regardless, you should experience increased system voltage in either case, hopefully the battery voltage doesn't rise above ~14V. If that happens then it will be obvious a regulator type is necessary.

If there's no AC from the stator into the rectifier, there will be no DC output from the rectifier. It may take some period of time for the system voltage to rise due to your battery absorbing charge, so you could try placing a 10A ammeter in series with the rectifier output to battery and measure if there is some current flow into the battery from the rectifier. Expect some current flowing into battery with engine running, perhaps as much as a few amps, I'm guessing.

Perhaps [MENTION=41828]Minnetonka4me[/MENTION] can fill in the blanks?

FWIW, the 3-phase circuit with regulator(negative earth type) looks something like this:

 

[Minnetonka4me]

Im so confused by this question...I would think the MPEM would be dead reading the description the OP posted.

 

[Sportster-2001-951C-Stock]

Im so confused by this question...I would think the MPEM would be dead reading the description the OP posted.

The question is if the 1991 uses just a rectifier or should have a rect/reg?

This is one of those south of the equator skis.....

 

[speedtkt]

way south:agree:

 

[Minnetonka4me]

It has a rectifier...its the square thing in the top of the grey ebox.