rich250rracer

Gear indicator on the dash indicates every gear, so I don’t think there is one.

I am going to clean and check all the grounds again. The frame ground was cleaned with a roloc Scotchbrite on a die grinder, it is like a mirror now, I got all the wire eyelets too. I will pull that ground off of the engine and clean it also. It is tight. I don’t see any others besides the battery ground. Am I missing any on this thing? One other question, why do you believe my multimeter is nuked? Seems to still be working fine.

My apologies, this thing has taken up far too much of my time and space. I really want to get it off of my lift so I can get back to engine work, but it’s fighting every step of the way.

Just frustration setting in with this thing. Using a test light, there is nothing at any of the seven wires going to that switch.

Unfortunately that is 100% incorrect. There are seven wires to this switch, one for each gear, 1-5 and one for reverse, one for neutral. By your theory, every one of these wires should be hot. None of them are. This switch takes each circuit to ground when a gear is changed. Look at the OEM service manual wiring diagram for a TRX500FPM, this switch provides ground for the circuit. It takes each position to engine ground. There is absolutely NO power to the switch.

I think I misspoke in my video. Continuity wasn’t the terminology I was looking for. That gear position switch isn’t hot, there is never power to it. All it does is provide a ground to the appropriate wire that goes to the ECU, and the display on the dash. In essence, I was trying to determine that it was indeed providing that ground, which I should have realized it was, since it displays properly on the dash. So what I was doing was confirming that the green/red wire was indeed grounding as it should…..until I turned the key on. Why would the ground disappear? And since the coil is grounded to the frame, like the green/red wire in my test, is it losing ground when I turn the key on?

I will recheck and get exact readings, but I remember peak voltage at the coil being above 100v.

I have a true peak voltage meter, I never trusted the adapter that I bought. I bought an ESI 530 DVA multimeter hoping for better results. Running the troubleshooting that Honda has outlined. Originally this problem would arise when the machine reached operating temperature, but it will not start at all now. No spark! I now have no peak voltage to the coil. Nothing. I have wiggled, pushed and probed the ECU connections. I have voltage at the black/white wire of the ECU, from what I can see there is connection of the green ground wires to the ECU (continuity between those green wires and the frame with the key on or off), appears as if the gear position switch is working correctly since it shows all gear positions. I have checked peak voltage from the new CKP, first from the plugs at the ECU and PS module, then at the plug from the CKP as Honda recommends. Both readings are in spec.

Electrical is not my forte, but with a good service manual, my peak voltage meter, and some probes I can usually pick my way through this stuff. While I kind of grasp what you are saying here, forgive me if I seem skeptical. The reason for that is while the green/red wire in the harness for the gear position switch loses ground when I turn the key on, BOTH of the green ground wires at the ECU do NOT. I back probed those, and used the same ground as when I tested the neutral position wire. This is one of the items Honda lists in the trouble shooting for no peak voltage at the coil.

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.

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.

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.

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.