2011 TRX500FPM no spark when hot.

[rich250rracer 1]

Working on a 2011 Foreman 500FPM that drops spark when hot. In an attempt for a quick fix, we threw a new coil at it, as it was needed for hunting season. This didn’t work. I went at it with a peak voltage meter and while it tested good cold, it looked like it was having a problem when hot. After all the work of replacing the stator I still had the same problem. I posted this on the Foreman Facebook group and jeepwm69 from this site offered up a good ECU to try. Even after switching this over I still have the problem. All I can see left are the power steering module (since one of the wires from the pickup coil runs through that), and possibly the voltage regulator. I had a Honda utility about 20 years ago or so that had no spark at all, and after throwing parts at it that it didn’t need, my local dealer told me to put a regulator on it, which fixed the issue. Now I’m wondering if that is the issue here, or could it be something in the P/S module? I should add that there is an intermittent TPS code popping up, but not on a regular basis. Any input would be greatly appreciated.

[jeepwm69 7,619]

Glad you found the place.

 

I have a good voltage regulator as well if you want to try that, I can drop it in the mail.   The TPS code I've had pop up before, and it was usually a poor connection from the main wiring harness to the ECU.   Simply unplugging the ECU and plugging it back in a couple of times fixed the problem (guess the friction cleaned up the pins/sockets enough to make a good connection again).

 

Anyhow, this one is a puzzle for sure.   @retro and @Melatv are normally the electrical guys, although @toodeep @AKATV and @shadetree are pretty good at finding oddball issues like this too.

 

All OEM parts have been used thus far, so I'll answer that question off the bat, as it's usually the first thing we look at here on electrical problems.

 

 

[retro 4,049]

Poor grounds can cause intermittent loss of Ignition so I'd remove and clean up all of those before trying a regulator/rectifier swap. There is the negative battery cable where it bolts to the motor, a ground cable between the motor and the frame and a wiring harness bundle to frame ground. All of them are bolted down so they're easy to shine up once ya get plastics out of the way.

[shadetree 5,884]

i have not worked on many trx500's, least not newer models. does this have a thermostat?, i could be wrong here, but they used to have thermostat sensors on these that had wires on them ?, going out on a limb here, chances are, if the temp sensor is bad ?, this being a newer model, i'd wager these shut down when they get hot in order to keep from damaging the motor ?. look up the wire schematics , see if the temp sensor is tied to ecu/c.d.i. ?.

[jeepwm69 7,619]

15 hours ago, shadetree said:

i have not worked on many trx500's, least not newer models. does this have a thermostat?, i could be wrong here, but they used to have thermostat sensors on these that had wires on them ?, going out on a limb here, chances are, if the temp sensor is bad ?, this being a newer model, i'd wager these shut down when they get hot in order to keep from damaging the motor ?. look up the wire schematics , see if the temp sensor is tied to ecu/c.d.i. ?.

 

Has the same sensor like the rest do, single wire on the bottom of the engine that kicks the fan on, and eventually will turn on the temp light on the dash.

 

It's an air cooled 500 like that red one you sold to your mailman.

[jeepwm69 7,619]

Hey @rich250rracer, just to clarify, you've replaced now with OEM

Coil

ECU (from me)

Stator

 

Anything else you've done to it?

 

I have a good regulator on the way, so we can eliminate that if it doesn't fix your problem.

[jeepwm69 7,619]

So, good regulator (off my wife's Rubicon, don't tell her!) was sent and he still has same result.  

 

On a model with conventional steering, both wires from the stator pick up go to the ECU. On a power steering model, the blue and yellow wire from the stator goes to the power steering module. I wonder if I take that wire out of the plug and run it directly to the ECU if that will help with diagnosing the problem. Not sure if that’s going to bypass the PS correctly, since a lot it other stuff feeds into that PS module.

 

@retro you have any ideas on this one?  You know electrical isn't my forte

 

[jeepwm69 7,619]

Looking at schematics, on the regular FM, the blue/yellow wire goes from CKP sensor directly to ECU.

 

On the PS models, that blue/yellow goes to the power steering module, then a violet/white wire comes out of the power steering module and goes to the same spot on the ECU that the Blue/yellow wire goes on the non-PS model.

 

The ECU is the same part for both machines.  Engine (and thus CKP) is also the same on both models.

 

So it is safe to say that if he bypasses the power steering module, running the blue/yellow wire straight from CKP to the ECU, that would reveal if the problem is in the power steering module?

 

He tried his ECU with my regulator, my ECU with his regulator, my ECU with my regulator, and his ECU with his regulator.  Same problem.  Loses spark when it warms up.

[retro 4,049]

Yeah you can bypass the power steering and jumper to the ECU to rule out the PS RPM detection. I suspect that component diags will have to be done while it's hot and has lost spark though. Which means that it's gonna take more time than it normally might.

 

It is behaving like the ignition coil primary winding is shorted. Or it could be a poor ground somewhere... I'd shine every one of those up before starting hot diags.

[jeepwm69 7,619]

Got a message from Rich last night.  He bypassed the PS module, said it still dropped spark after a half hour of running, 25 degrees out.

 

So OEM ECU, regulator, coil, stator have been installed.  Still dropping spark when hot. 
 

@rich250rracer did you try cleaning up the grounds?  I assume you’ve replaced the spark plug, but just to clarify, new NGK plug?

 

@retro and other ideas?  Ignition off/on/off  switch on the handlebar maybe?

[shadetree 5,884]

1 hour ago, jeepwm69 said:

Got a message from Rich last night.  He bypassed the PS module, said it still dropped spark after a half hour of running, 25 degrees out.

 

So OEM ECU, regulator, coil, stator have been installed.  Still dropping spark when hot. 
 

@rich250rracer did you try cleaning up the grounds?  I assume you’ve replaced the spark plug, but just to clarify, new NGK plug?

 

@retro and other ideas?  Ignition off/on/off  switch on the handlebar maybe?

just guessing here, but would the oil temp sensor cause this on this atv ?.

[retro 4,049]

I don't see how an oil temp sensor could cause loss of ignition. It behaves like the primary winding in the coil is shorted (coil overheating). So clean all grounds first, including the harness-to-frame ground (important!). Then when it gets warm and loses spark walk through diags until the failure is found. Start with the coil. When it loses spark measure for battery voltage on the Red/Black wire (other multimeter lead on frame ground) plugged in to the coil. Then check peak voltage on the Yellow/Green terminal on the coil, then check the CKP peak voltage at the ECU connector.

[jeepwm69 7,619]

6 hours ago, shadetree said:

just guessing here, but would the oil temp sensor cause this on this atv ?.

I don’t think so. I’ve had one of these with a bad fan control module so the sensor was taken out of the loop and it ran fine

[retro 4,049]

In the first post you mentioned that a TPS code pops up sometimes? When does the TPS code come up, is it only after it gets warm and loses spark, or is it occurring randomly while the motor is running? Please explain.

[AKATV 823]

Really late to the party on this one - grandkids were here for a week

Heres a shot in the dark

We had an 07 Foreman 500 (non PS) a few years back we went crazy with the same symptoms- dropping spark when hot

finally after all the same troubleshooting and swapping I decided to pull sparkplug boot off when it was hot and not sparking, it sparked from end of wire, put boot back on and no spark- replaced boot and its still working to this day.

Not sure if it was OEM boot on there but know we replaced it with OEM (yellow)

Might be worth checking out? I sure sure you have swapped sparkplugs at this point

-AKATV

Edited February 26 by AKATV

[jeepwm69 7,619]

1 hour ago, AKATV said:

Really late to the party on this one - grandkids were here for a week

Heres a shot in the dark

We had an 07 Foreman 500 (non PS) a few years back we went crazy with the same symptoms- dropping spark when hot

finally after all the same troubleshooting and swapping I decided to pull sparkplug boot off when it was hot and not sparking, it sparked from end of wire, put boot back on and no spark- replaced boot and its still working to this day.

Not sure if it was OEM boot on there but know we replaced it with OEM (yellow)

Might be worth checking out? I sure sure you have swapped sparkplugs at this point

-AKATV

 

Spark plug and coil were the first things he replaced....this one is a stumper for sure!

[rich250rracer 1]

4 hours ago, retro said:

In the first post you mentioned that a TPS code pops up sometimes? When does the TPS code come up, is it only after it gets warm and loses spark, or is it occurring randomly while the motor is running? Please explain.

It had a TPS code on start up, sometimes. Sorry can’t get more clear than that. But after unplugging, inspecting, and cleaning the connections at the ECU the first time I had it unplugged, I have not gotten a TPS code since. 

[AKATV 823]

Did he pull the boot and check spark directly at the wire?

[jeepwm69 7,619]

11 minutes ago, rich250rracer said:

It had a TPS code on start up, sometimes. Sorry can’t get more clear than that. But after unplugging, inspecting, and cleaning the connections at the ECU the first time I had it unplugged, I have not gotten a TPS code since. 

 

I rode my 06 around for a bit with the TPS code blinking.  Never caused any problems other than the annoying blinking on the dash.

[retro 4,049]

I can't think of anything else to do except clean the grounds and troubleshoot it while its hot and no spark.

[jeepwm69 7,619]

@rich250rracer you having any luck?  
 

I’m still in the same boat with this 2013 Foreman that has no spark.

[rich250rracer 1]

15 hours ago, jeepwm69 said:

@rich250rracer you having any luck?  
 

I’m still in the same boat with this 2013 Foreman that has no spark.

I removed the spark plug cap as someone suggested and when hot there is still no spark when grounding the plug wire. Now that the weather is warming up, run time is down significantly when it starts to drop spark. It was about 70 degrees yesterday and within 5-10 minutes of idling it started to pop and backfire, then shut off. No spark.

[jeepwm69 7,619]

Misery loves company......

[rich250rracer 1]

 

A recap and an update. My boss asked me to look at this thing because it was quitting when it got hot. Being in a hurry and needing it for hunting last fall, he asked me to just swap the coil out. I put a brand new OEM coil on it and got the same result.

 

 I tested the stator using a peak voltage adapter in my ohm meter. The voltage adapter may have been bad, but it appeared that I had a bad reading on the stator. I replaced it with a new OEM unit. I got the same result with the new stator. 

 

A post about the issue on the Foreman Facebook group got me in contact with jeepwm69. He had some electrical issue going on with a machine he was working on and was offering some suggestions. He sent me a known good ECU and voltage regulator. 

 

I was optimistic that we would track the problem down with these parts to use for testing. 

 

Keep in mind that this is ALWAYS heat related and the amount of time required for the quad to drop spark seemed directly dependent on ambient temperature. If it was a cold day, if might run for a half hour, or even much longer, before it would shut off. On a warm day, it could be as quickly as five or ten minutes. But once it cools back down, it will restart and run until it gets to a certain temp. And all of this can be accomplished with it just sitting there idling, riding it brings on the issue even quicker.

 

I brought the quad to the failure point, and once it shut off, I immediately switched to the ECU and regulator that jeepwm69 had sent me. Still no spark. I let it cool over night and restarted it the next day, bringing it to failure temp, then switched back to my original parts. Once again, no spark. 

 

This machine is equipped with power steering, so that got me studying the wiring diagram. On a standard model, both stator wires from the pickup run directly to the ECU, but on a P/S model, one of the pickup wires runs to the P/S module first, which tells the module that the engine is running and to activate the power steering. Maybe the problem was hiding in that module.

 

In order to eliminate the power steering from the equation, I removed two wires from the P/S module plug, the incoming (blue/yellow) and the outgoing wire to the ECU (violet/white) and jumped them together. This should have eliminated the P/S module as a possible cause for my issue. In testing, if the two wires are not jumped together, the quad will not run, so I proceeded to run it up to temperature and once again it did drop spark. This should confirm that the issue does not lie in that module. 

 

It was at this point that I purchased a set of back probes and a true peak voltage meter. My hopes were that my PV adapter that I used in conjunction with my ohm meter was providing bad info. I planned to use the back probes in the ECU and module connectors without unplugging them and monitoring it as it ran and failed. 

 

My plans to do this were sidetracked as  after putting the P/S module plug make together, I could not get the machine to drop spark. At this point I questioned whether my issue may have just been a bad connection at that plug and by removing and reinstalling the wires, I had corrected the issue. 

 

After about two weeks of starting and idling the quad, I could not get it to fail. I decided it was time to put everything back together, reinstalling all the plastic and the racks. This was apparently not meant to be, as I was shortly greeted by the same heat related issue. 

 

My next step was running through the Honda troubleshooting for a no spark issue. It was then that I noticed that I had overlooked the gear position switch. But the way my luck was going, it would only be appropriate for this to be bad, since I would have to disassemble the entire rear of the quad again to remove the rear cover that I had already had off once to replace the stator. The switch is internal, so it could be directly impacted by heat, and it made all the sense in the world.

 

Since the switch does nothing more than take the circuit to ground when in the closed position, I decided to bypass the switch and ground the neutral position directly to the frame. The quad started, ran until it reached temperature and AGAIN lost spark. There is nothing left in this ignition system for me to replace or bypass, and have no idea where to look next.

 

For the record, this has a brand new spark plug. I did not replace the plug cap, but I did remove it when I had failure, and checked for spark directly at the coil wire. 

 

Here is one thing that I have seen, but discounted because I can’t contemplate how it would affect the spark output. There is a TPS code flashing. It hasn’t been constant but it is USUALLY there. 

 

While I have read that most TPS codes are usually the result of a connection issue, I decided to test it. My ohm meter shows 5k ohms in the closed position, but it does NOT climb when opening the throttle, so this tells me that there actually is a TPS issue. I also checked input voltage as directed by the Honda manual, and ended up with 5.02 volts, right in specifications. 

 

I plan on replacing the TPS, but I really can’t see how this sensor is causing my spark issue, especially a heat related spark issue. 

 

Any input would be greatly appreciated.

 

 

 

 

 

 

 

 

Edited April 26 by rich250rracer

[jeepwm69 7,619]

3 minutes ago, rich250rracer said:

 

A recap and an update. My boss asked me to look at this thing because it was quitting when it got hot. Being in a hurry and needing it for hunting last fall, he asked me to just swap the coil out. I put a brand new OEM coil on it and got the same result.

 

 I tested the stator using a peak voltage adapter in my ohm meter. The voltage adapter may have been bad, but it appeared that I had a bad reading on the stator. I replaced it with a new OEM unit. I got the same result with the new stator. 

 

A post about the issue on the Foreman Facebook group got me in contact with jeepwm69. He had some electrical issue going on with a machine he was working on and was offering some suggestions. He sent me a known good ECU and voltage regulator. 

 

I was optimistic that we would track the problem down with these parts to use for testing. 

 

Keep in mind that this is ALWAYS heat related and the amount of time required for the quad to drop spark seemed directly dependent on ambient temperature. If it was a cold day, if might run for a half hour, or even much longer, before it would shut off. On a warm day, it could be as quickly as five or ten minutes. But once it cools back down, it will restart and run until it gets to a certain temp. And all of this can be accomplished with it just sitting there idling, riding it brings on the issue even quicker.

 

I brought the quad to the failure point, and once it shut off, I immediately switched to the ECU and regulator that jeepwm69 had sent me. Still no spark. I let it cool over night and restarted it the next day, bringing it to failure temp, then switched back to my original parts. Once again, no spark. 

 

This machine is equipped with power steering, so that got me studying the wiring diagram. On a standard model, both stator wires from the pickup run directly to the ECU, but on a P/S model, one of the pickup wires runs to the P/S module first, which tells the module that the engine is running and to activate the power steering. Maybe the problem was hiding in that module.

 

In order to eliminate the power steering from the equation, I removed two wires from the P/S module plug, the incoming (blue/yellow) and the outgoing wire to the ECU (violet/white) and jumped them together. This should have eliminated the P/S module as a possible cause for my issue. In testing, if the two wires are not jumped together, the quad will not run, so I proceeded to run it up to temperature and once again it did drop spark. This should confirm that the issue does not lie in that module. 

 

It was at this point that I purchased a set of back probes and a true peak voltage meter. My hopes were that my PV adapter that I used in conjunction with my ohm meter was providing bad info. I planned to use the back probes in the ECU and module connectors without unplugging them and monitoring it as it ran and failed. 

 

My plans to do this were sidetracked as  after putting the P/S module plug make together, I could not get the machine to drop spark. At this point I questioned whether my issue may have just been a bad connection at that plug and by removing and reinstalling the wires, I had corrected the issue. 

 

After about two weeks of starting and idling the quad, I could not get it to fail. I decided it was time to put everything back together, reinstalling all the plastic and the racks. This was apparently not meant to be, as I was shortly greeted by the same heat related issue. 

 

My next step was running through the Honda troubleshooting for a no spark issue. It was then that I noticed that I had overlooked the gear position switch. But the way my luck was going, it would only be appropriate for this to be bad, since I would have to disassemble the entire rear of the quad again to remove the rear cover that I had already had off once to replace the stator. The switch is internal, so it could be directly impacted by heat, and it made all the sense in the world.

 

Since the switch does nothing more than take the circuit to ground when in the closed position, I decided to bypass the switch and ground the neutral position directly to the frame. The quad started, ran until it reached temperature and AGAIN lost spark. There is nothing left in this ignition system for be to replace or bypass, and have no idea where to look next.

 

For the record, this has a brand new spark plug. I did not replace the plug cap, but I did remove it when I had failure, and checked for spark directly at the coil wire. 

 

Here is one thing that I have seen, but discounted because I can’t contemplate how it would affect the spark output. There is a TPS code flashing. It hasn’t been constant but it is USUALLY there. 

 

While I have read that most TPS codes are usually the result of a connection issue, I decided to test it. My ohm meter shows 5k ohms in the closed position, but it does NOT climb when opening the throttle, so this tells me that there actually is a TPS issue. I also checked input voltage as directed by the Honda manual, and ended up with 5.02 volts, right in specifications. 

 

I plan on replacing the TPS, but I really can’t see how this sensor is causing my spark issue, especially a heat related spark issue. 

 

Any input would be greatly appreciated.

 

 

 

 

 

 

 

 

I actually was going to find your post and tag @Melatv and @retro and @AKATV since they seem to love electrical puzzles so much.

 

Sounds like you need a new TPS either way.  I have an extra carb with a good TPS if you want to try it, but if it measures out of spec you probably need one anyway.   I don't THINK that the TPS has anything to do with spark, as my machine ran fine while running with a TPS error, BUT then again, my TPS wasn't actually bad, it was just an error code.

 

We did have someone here who had a Hondamatic with a TPS code and it threw the machine into limp mode, so I guess it's possible that it could be causing spark issues.