1996 787 no spark

[porky212]

Bought this machine 1996 gtx 787.
With no spark, no AC from pickup coil . Replaced pickup coil still no spark. There is no signal from dc-cdi on white wire , testing at cdi plug in front. New battery , voltage at mpem and cdi above 10.4 when cranking. Latching relay working properly. Receiving AC signal at cdi.
Bought used cdi from ebay-- no spark still. Could be defective as it is used.
Can the Mpem affect spark on this machine?
Frequently when i hit the start button nothing happens. I back probed the switch while operating it and its working but not turning over.

 

[mikidymac]

Sounds like a voltage issue. At 10.4 volts I would be surprised if it could even spark.

It should never drop below 12v even when cranking.

 

[porky212]

Oops typo ,it was 11.4 when cranking. All 12 v systems drop below 12 v when cranking.

 

[Orbitalatx]

Unfortunately sounds like either a bad mpem or a bad magneto not just the pickup. It could also be the wiring from mag to rectifier and mag to rear box. You need to check magneto first. As mag turns and tells cdi to fire white wire back at ignition coil. So your problem is there I have narrowed it down for you now you must do more work. Let us know the results.

 

[Orbitalatx]

Here is my recent discussion about the same issue. I threw all these parts at it and it ended up being the magneto and magneto cover. Ordered a lightly used one off eBay and fixed all my issues with spark.
97 gtx no spark

 

[porky212]

I have a new magneto installed already. The 97 has a mpem only. The 96 has a computer and a seperate dc-cdi to provide spark. From reading about this setup it seems the only reason there are three wires going to the computer from the cdi is for the tach signal and the rev limiter.
Does someone if this is true?

 

[Orbitalatx]

I found out after the fact that I actually had a 96 gtx 787 which does have the cdi separate. I replaced mpem cdi and magneto and finally was able to get spark. I also replaced all the wiring from mpem to rear box and mag to rear box. My mpem and my magneto was bad. I bought an arieltek mpem so I didn't have to get the key redone.

 

[porky212]

I replaced the magneto already. I bought a complete front electrical box on ebay.
Replaced everything except for the computer because i would need to have a key programmed. But what im tring to find out is if the computer has anything to do with the spark?

 

[SIMPLEARKANSAN]

On my 1997 GTX my MPEM was bad. We troubleshot everything. Gauges all lit up, the ski turned over perfectly. My year model had everything combined wit the MPEM. Ordered a tested used one from Westside Powersports and it cranked right up

 

[Orbitalatx]

 

[Orbitalatx]

The mpem supply's power to the cdi. If the mpem is not suppling the power to cdi then you can check the holder relay is functioning correctly.

 

[Orbitalatx]

You could put the key in and check with a 12v test light red wire with purple stripe coming off holder relay to cdi. Check holder relay fuse then check the red/black stripe wire from mpem to holder relay

 

[Poormanracing]

Make sure the ground wire that goes from the battery to the coil ground in the black box is good.it is only held by a stainless bolt into plastic and known to corrode and not ground

 

[porky212]

You could put the key in and check with a 12v test light red wire with purple stripe coming off holder relay to cdi. Check holder relay fuse then check the red/black stripe wire from mpem to holder relay

The holder relay is working.

The mpem supply's power to the cdi. If the mpem is not suppling the power to cdi then you can check the holder relay is functioning correctly.

 

[porky212]

The holder relay is working.

The manual did say a defective rev limiter will cause no spark. The rev limiter is built into the dc-cdi

 

[porky212]

Make sure the ground wire that goes from the battery to the coil ground in the black box is good.it is only held by a stainless bolt into plastic and known to corrode and not ground

I ran another ground wire from battery to the ground in the front electrical box. I cleaned all the eyelets ,coil and terminals first.

 

[artr]

2 things to check
- Poormanracing said to check that the small black wire that connects to the negative battery terminal and goes to a bolt on the coil is not corroded or broken and making good contact on the bolt to the coil along with the other wires on the bolt
- If you only checked that the holder relay is supplying 12V to the CDI when you attach the key you should recheck that it supplies 12V while cranking the engine. I had an issue with mine where it would intermittently drop the 12V as soon as the engine started to crank. It took me a long time to find that but replaced the holder relay and never had the problem since.

 

[porky212]

I monitored the voltage while cranking and it stayed constant. Also tried another good relay.
Because im connected to the white output wire at the cdi looking for a signal it eliminates anything at the back of the machine.

 

[porky212]

So it turns out the Mpem was the issue. Even though it cranked over fine and all gauges worked.