TRX420FM 2007 no spark

[Wolf 1]

I am at my wits end trying to get spark on this Rancher that I bought used. The spark plug is new. All the fuses are good. Diodes tested are good. The safety swich has been replaced. The coil test good but I replaced it as well just to be sure. The CDI unit is OEM new. The stator tests good. The pick up coil tests good. I do not have a "peak voltage " tester but may need to get one. If the gap on the pick up is too wide I can see that as a problem. I have not messed with the votage regulator as that should not be involved. I hope that is correect. All the grounds test good. So what am I missing? HELP! wolf

[Fishfiles 20,145]

Hi Wolf , welcome to the forum , I am not a 420 guy by trade and not 100% sure , that it was a 420 that I was reading about ,  but recently read a thread that the voltage regulator was the problem for no spark ---- seems you changed everything else ---- someone more knowledgeable than me will come along @retro , it has be theorized , by me , that a  bad voltage regulator could possibly cause a no spark on a 420 , does that statement hold water ? 

[Wolf 1]

I have read that in the FOREMAN that it may play a role but not in the RANCHER. I just tested the voltage regulator and it tests OK. So that is not the issue. Thanks for the reply. wolf

[jeepwm69 7,619]

Do you have 12V on the black/red wire at the coil?  @Melatv walked me through all of this when I had a 420. 

 

 

[Wolf 1]

The wires going to the coil are green/yellow and black/brown stripe. The g/y is hot with 12 volts plus with ignition on. The blk wire is a ground that tested good to ground. Wolf 

[jeepwm69 7,619]

Sounds like you've covered everything that I would know to try.  Maybe @Melatv has an idea.  He's been around the last couple of days, so hopefully he'll chime in.

 

@retro might be able to tell you how to cobble up a cheap peak voltage meter.

[Wolf 1]

I saw a you tube video that shows the DVA  circuit.  A diode, resistor and capacitor.  They sell for $30 on ebay. I may inquiry if a Honda  tech locally would do the testing for a fee. The prior owner opened the stator  case it is possible that the pickup coil  gap is wrong,  too wide so the signal to fire never gets to the cdi. The peak meter test should detect  that. Stay posted.  Wolf 

[Wolf 1]

So I got a DVA adapter to test "peak" voltage The stator Pikup coil reading was supposed to be > 0,7 V . I got 2.3v. So I gues the pick up coil is OK. The volatge on the  "hot" primary coil lead reads the battery voltage 12V+ BUT when I crank the engine instaed of get >100Volts it drops to 9.2 volts. . So something is not right there. I will look on Utube to see what I should do next. PS the entire rear end is toast and I am rplacing that as well. wolf

[Wolf 1]

There is one more safety "switch" on this ATV . The bank angle sensor. If the ATV tips >70 degrees the ignition turns off. I removed the sensor and get > 3volts when the sensor is upright. It is supposed to be  0volts  or <0.1 volts. When I tip the sensor I get the expected 12v ( battery voltage). I have ordered a used senor. More later. wolf

[toodeep 1,758]

3 hours ago, Wolf said:

There is one more safety "switch" on this ATV . The bank angle sensor. If the ATV tips >70 degrees the ignition turns off. I removed the sensor and get > 3volts when the sensor is upright. It is supposed to be  0volts  or <0.1 volts. When I tip the sensor I get the expected 12v ( battery voltage). I have ordered a used senor. More later. wolf

 

 

You can bypass the bank angle sensor with a jumper wire on the outer terminals of the connector (harness side of course). A couple of my 420s are running with that deleted because it caused issues.

[Wolf 1]

Thank you. I will try to jumper it tomorrow. Wolf 

[jeepwm69 7,619]

@1080PowersportsPartsLLC

[Wolf 1]

15 hours ago, toodeep said:

 

 

You can bypass the bank angle sensor with a jumper wire on the outer terminals of the connector (harness side of course). A couple of my 420s are running with that deleted because it caused issues.

 

[Wolf 1]

I see my connector wires are not the same color as your photo. I have (in order) red black and green. I already blew one 10amp fuse with an ill placed jumper and want to be sure to place the jumper correctly. Is your guess the jumper goes between the red and the green?  wolf

[toodeep 1,758]

Yes, the red and green. The center wire is black with a green stripe if I remember correctly.

[Wolf 1]

I got busy but did the jumper today and no luck . Still no spark. My peak voltage tester died. I have ordered anothe one and will run through that diagnostic again when the new one arrives. wolf

[Wolf 1]

So I got a new peak voltage tester and got nothing at the saprk plug ( no surpise there) got battery voltage at the + (GRN/Yellow wire) at the ignition coil that dropped to 9V while cranking the engine. AT the 33P Grey CDI box connector on temianl B23 & B12 got 4.4V consistently and got 4.6 V at the 5P altenator connection (Blue/yellow and Green wires)  The spec is >0.7 V. So that is good. There is a line in the manual to check the resistance of the stator yellow wires "Measure the resistance between yellow wire terminals of the altenator side connector. 0.1 to 1 ohm at 68 degrees F)" I do not under stand that. I see everyone checking the stator for continuity but no info on resistance testin or how you do it. What is a "side connector"? Thanks for any help. wolf

[Wolf 1]

Apologies! I found a motorcycle video that does resistance testing . You test across each yellow terminal ( 1to 2, 1to 3 , 2to3 etc) and I get 0.7ohm . That is in spec 0.1 to 1 ohm..I rechecked the terminal to ground and there was no short. So mesuring wise the stator "tests" good. Someone prior to me has been in the stator and my stator may not be OEM. You always see the warnings "don't get a foreing made part it will screw thisngs up for you." I remain frustrated and confused. wolf

[Wolf 1]

So let me add some more confusion here. I retested the volatge to the coil primary. Previously I always got battery voltage to the 2 wires. NOW I GET NOTHING. The only thing I have done is yank the wireing harness around to get at various connections. I am thinking I may have a short in the harness. wolf

[Fishfiles 20,145]

13 hours ago, Wolf said:

So let me add some more confusion here. I retested the volatge to the coil primary. Previously I always got battery voltage to the 2 wires. NOW I GET NOTHING. The only thing I have done is yank the wireing harness around to get at various connections. I am thinking I may have a short in the harness. wolf

Hi Wolf .

 I have seen wires get corroded inside the plastic outer covering , you would  never know  the wire was broken or severely corroded ,  unless you pull on the wire , the plastic may stretch , also did you open every connector on the harness and clean and apply some dielectric grease to the connector's innards 

[Wolf 1]

Thank you Fishfiles. I am in the process of doing that. wolf

[jeepwm69 7,619]

Factory service manual should have troubleshooting info, including checking continuity of wires.

 

That's how I found the broken wire going to the shift motor on that Rubicon I had a couple of weeks ago; the FSM specified which pin in the ECU connector went to the shift motor, so I checked for continuity between that pin on the ECU connector and the pin on the shift motor plug, and was able to find the broken wire when one of the wires I tested didn't have continuity.

[Wolf 1]

The service manual does have troubleshooting but it is a bit arcane and uses a lot of abreviations that a non-professional has to learn. My issue is no spark and I have examined and ruled out so far the coil, stator, pickup (CKP if you prefer), kill switch, and bank angle sensor, P33 connector (multiple pins). I am looking for the TP/MAP sensorand have not yet found it. I will remove the air box for a better view of the top of the engine. Thanks for your interest. wolf

[Wolf 1]

Some news! I mapped out all the individual 33 pins on the PCM/ECM ( CDI if you prefer) and pin #11 is a G/Y wire that goes to the coil and subsequently to the spark plug. I get an open circut on that wire. I am not very good at electric work. I test that with the ignition off as well as ignition on. There is  12V current on that wire at the coil. Several other pins have current ie.) #1, #19, #21 and #33. I cannot find out if #11 should have 12V or not. I do not see a way to take apart the grey CDI plug. Is there a safe way to run a jumper wire and see if it solves my problem? 

[Wolf 1]

Do any of you know how to open the grey P33 ECU connector apart to be able to inspect and repalce a pion? wolf