Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


GZ250 - No Spark - At Wit's End - PLEASE HELP!

Reply to topic
Bike Chat Forums Index -> The Workshop
View previous topic : View next topic  
Author Message

rebeltaz
Renault 5 Driver



Joined: 02 Jul 2005
Karma :

PostPosted: 19:27 - 22 Nov 2021    Post subject: GZ250 - No Spark - At Wit's End - PLEASE HELP! Reply with quote

So, I've got a Suzuki GZ250 in here that has no spark. The customer has completely screwed up the wiring, lost the original switch, installed the wrong switch, fried the pickup coil and possibly the ECU.

I replaced the pickup coil and now get 5+v on the blue and green wires at the ECU connector. I have tested that the ignition coil reads as per the manual and that it will generate spark when excited externally (using a pulse generator I built specifically to test coils). The odd thing is that, even though every wire ohms out pin to pin, the o/y wire - which should be grounded - rises to about 20ohms when power is applied to the switch (which I am manually jumping as per the wiring diagram). Also, even though the battery stays at 11-12v when you spin the starter over, the o/w wire - which should be tied directly to positive voltage - drops to about 8v before jumping back up to about 10v when the starter is spinning. To combat this, I cut those wires and tied them directly to ground and positive respectively. Still no spark.

I bought an ECU on eBay and the guy claims to have checked it prior to sending it out. He also said that there is supposed to be a 100ohm resistor between the b/w (ground) and o/y (ECU signal/reference(?) ground) as a kind of anti-theft / can't hot-wire it measure. I tried that and still no spark.

I am at my wits end. Can someone, anyone help here?
____________________
Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)
 Back to top
View user's profile Send private message Send e-mail Visit poster's website You must be logged in to rate posts

jaffa90
World Chat Champion



Joined: 06 Apr 2016
Karma :

PostPosted: 21:20 - 22 Nov 2021    Post subject: Reply with quote

Any good?
https://www.motorcycleforum.com/threads/no-spark-2003-suzuki-gz250.242483/
Also google "gz250 wiring diagram"
 Back to top
View user's profile Send private message You must be logged in to rate posts

rebeltaz
Renault 5 Driver



Joined: 02 Jul 2005
Karma :

PostPosted: 23:32 - 22 Nov 2021    Post subject: Reply with quote

jaffa90 wrote:


Looks like a similar problem, but I didn't see a resolution. As for the wiring diagram, I have the service manual. That's where I'm getting the specs to check voltages and resistance. Sadly, in this one case, it ain't helping. Sad
____________________
Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)
 Back to top
View user's profile Send private message Send e-mail Visit poster's website You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 00:27 - 23 Nov 2021    Post subject: Reply with quote

Don't measure resistance when a circuit is powered. It's a passive measurement with a standard multimeter and any readings you're getting when power is applied will be erroneous.

If you're getting a healthy spark when you manually switch the coil primary then the problem is either in the ignitor or the pickup.

The principle of operations is fairly simple. The pickup generates a pulse of current when the trigger magnet on the rotor goes past it, the ignitor shapes the pulse and amplifies it and the output stage (shown as a transistor) acts as a switch much the same as mechanical points.

You can test the pickup by connecting the output wires directly to your multimeter on a low AC range (somewhere around 2V) and turning the engine on the starter. You should see a voltage generated by the magnet passing the pickup on each rotation of the engine.

You should also be able to measure an AC voltage on a higher range (around 20V) on the primary side of the coil when the engine is turned and everything is connected.
 Back to top
View user's profile Send private message You must be logged in to rate posts

rebeltaz
Renault 5 Driver



Joined: 02 Jul 2005
Karma :

PostPosted: 00:50 - 23 Nov 2021    Post subject: Reply with quote

Islander wrote:
Don't measure resistance when a circuit is powered. It's a passive measurement with a standard multimeter and any readings you're getting when power is applied will be erroneous.

If you're getting a healthy spark when you manually switch the coil primary then the problem is either in the ignitor or the pickup.

The principle of operations is fairly simple. The pickup generates a pulse of current when the trigger magnet on the rotor goes past it, the ignitor shapes the pulse and amplifies it and the output stage (shown as a transistor) acts as a switch much the same as mechanical points.

You can test the pickup by connecting the output wires directly to your multimeter on a low AC range (somewhere around 2V) and turning the engine on the starter. You should see a voltage generated by the magnet passing the pickup on each rotation of the engine.

You should also be able to measure an AC voltage on a higher range (around 20V) on the primary side of the coil when the engine is turned and everything is connected.


When I said that I was measuring resistance with the system powered up, I mean that I was measuring the resistance of the o/y wire at the ECU - with the ECU out of the circuit - to ground. As per the schematic, that should be a dead short - powered up or not. That path shouldn't change when power is applied to the rest of the circuit. That is actually the ONLY way that you can measure the resistance of that line.

I've got a peak voltage adapter I built to test components like the pickup coil. If you measure it directly, you will only get about 1-2 volts ac. You have to have a peak voltage adapter to get the correct reading of at least 5 vdc as specified in the service manual. Which I have tested and do have, after replacing the faulty pickup coil / stator assembly.

Yeah, it should be simple. Nothing I ever work on is simple, though. Case in point....
____________________
Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)
 Back to top
View user's profile Send private message Send e-mail Visit poster's website You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 01:05 - 23 Nov 2021    Post subject: Reply with quote

rebeltaz wrote:
When I said that I was measuring resistance with the system powered up, I mean that I was measuring the resistance of the o/y wire at the ECU - with the ECU out of the circuit - to ground. As per the schematic, that should be a dead short - powered up or not. That path shouldn't change when power is applied to the rest of the circuit. That is actually the ONLY way that you can measure the resistance of that line.


That wasn't clear - if you're measuring the continuity of the ignitor connection to ground with the switch closed then that's fine.

rebeltaz wrote:
I've got a peak voltage adapter I built to test components like the pickup coil. If you measure it directly, you will only get about 1-2 volts ac. You have to have a peak voltage adapter to get the correct reading of at least 5 vdc as specified in the service manual. Which I have tested and do have, after replacing the faulty pickup coil / stator assembly.


I have an instantaneous peak meter - it's fairly specialised and I'd never assume anyone would have one in their toolkit. A simple RMS measurement will show that there's output though - if you want an approximation of peak then multiply the RMS result by the root of 2 or 1.414. It's good enough for proof of operation.

rebeltaz wrote:
Yeah, it should be simple. Nothing I ever work on is simple, though. Case in point....


If you break it down and follow it through logically, you'll get there. If the wiring has been messed about with then that's the obvious place to start - continuity checks on all of the connections. Then it's a matter of testing the various outputs and inputs. The key to faultfinding electrical and electronic circuits is to understand what they do, break them down into sections and check the function of each. Smile
 Back to top
View user's profile Send private message You must be logged in to rate posts

rebeltaz
Renault 5 Driver



Joined: 02 Jul 2005
Karma :

PostPosted: 01:54 - 23 Nov 2021    Post subject: Reply with quote

Islander wrote:
The key to faultfinding electrical and electronic circuits is to understand what they do, break them down into sections and check the function of each. Smile


Yeah. My dad taught me electronics back when I was old enough to hold a soldering iron and the one thing he always stressed was to not learn how to fix something - e.g. this repair fixes that problem on this unit - but to instead learn how things work. Knowing that, you can work on anything, whether you've ever come across that particular issue before or not. That's how I transitioned myself from electronics repair to small engine repair when the consumer electronic market fell out. Still learning everyday, though.

I appreciate your time. I told the customer to go buy a new wiring harness since he screwed this one up so royally and I was tired of chasing dragons. I'll report back if - no, scratch that - WHEN I get to the bottom of this!
____________________
Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)
 Back to top
View user's profile Send private message Send e-mail Visit poster's website You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 11:52 - 23 Nov 2021    Post subject: Reply with quote

rebeltaz wrote:
Islander wrote:
The key to faultfinding electrical and electronic circuits is to understand what they do, break them down into sections and check the function of each. Smile


Yeah. My dad taught me electronics back when I was old enough to hold a soldering iron and the one thing he always stressed was to not learn how to fix something - e.g. this repair fixes that problem on this unit - but to instead learn how things work. Knowing that, you can work on anything, whether you've ever come across that particular issue before or not. That's how I transitioned myself from electronics repair to small engine repair when the consumer electronic market fell out. Still learning everyday, though.

I appreciate your time. I told the customer to go buy a new wiring harness since he screwed this one up so royally and I was tired of chasing dragons. I'll report back if - no, scratch that - WHEN I get to the bottom of this!


Good luck!
 Back to top
View user's profile Send private message You must be logged in to rate posts

rebeltaz
Renault 5 Driver



Joined: 02 Jul 2005
Karma :

PostPosted: 23:12 - 11 Jan 2022    Post subject: Reply with quote

Islander wrote:


Good luck!



I just wanted to report back that I FINALLY figured this out. When I replaced the pickup coil / stator assembly, I wasn't getting spark, but I noticed that the wires coming out of the pickup coil were reversed - blue went to green and green went to blue. Since I wasn't getting spark, I tried swapping those around so that blue went to blue and green went to green. Still nothing. But, in the meantime I found that the ignition switch was supposed to have a 100 resistor in one line that wasn't shown on the diagrams or the service manual. After I ordered that, I still had the pickup wire color matched. I didn't really think it would matter since it was an AC signal, but... since I had tested EVERYTHING else, just for the hello of it, I swapped the wires back the way they were - blue to green and green to blue. Sure enough... it now has spark! I guess it DOES matter which is which. Just weird that the colors are swapped on the aftermarket plug.

Anyway... just in case anyone else ever beats their head against a wall on this one... ¯\_(ツ)_/¯
____________________
Derek Tombrello
www.ShelbyCycle.com (for profit)
www.RobotsAndComputers.com (just for fun)
 Back to top
View user's profile Send private message Send e-mail Visit poster's website You must be logged in to rate posts
  Display posts from previous:   

Post new topic   Reply to topic    Bike Chat Forums Index -> The Workshop All times are GMT
Page 1 of 1

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 

Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.09 Sec - Server Load: 0.37 - MySQL Queries: 17 - Page Size: 74.51 Kb