Massimo T-Boss 410 Died on the run and won't restart

[k-bo]

My T-Boss 410 died hard on a run up the driveway and wouldn't restart. Cranks over fine, 12v at coil, fuel in cylinder (from plug check), and wire from computer to coil buzzes out OK. Computer threw a P0351 ignition coil malfunction message. I pulled the coil, measured resistance across the primary, and it was about 0.8 or 0.9 ohms, nominal for most ignition coils. I measured the secondary resistance as well and got about 6.5K ohms, also nominal for most coils. I checked the plug wire resistance and it was about 5000 ohms, which seems OK. And really perplexing, my spark tester shows spark. I got to feel it too, when I held my fingers too close to the conductor. 💩! Have any of you folks run across this?

[k-bo]

Update: New coil and plug had no effect. Think this is heading toward the pickup coil, which I have not been able to locate. It could be inside the engine cover. Not good. Hope someone else has run into this nightmare before and I am overlooking something simple...

[T-boss 410]

Have you actually seen a spark at the plug? It may be fouled or not functioning properly.

[k-bo]

Hi T-boss 410, yes I have seen a spark at the plug. It is a bright yellowish-white spark. Got an orange-like color on my spark tester. So, I am wondering if this spark is insufficient, which I kind of doubt because if it triggers, it should work. If you have both fuel and a spark, you have to have air too, but I'm reasonably sure that didn't change. The computer thinks the problem is ignition. Whatever failed, it was catastrophic because the T-Boss shut down on the run and hasn't ran since. No unusual noises when it did die, it just shut off. Any words of wisdom or similar shared experiences are greatly appreciated.

Best,

k-bo

[T-boss 410]

When you turn the key to the first stop, do you hear the fuel pump running? It should run for a few seconds to prime the system.

The spark sounds weak as you described it. Have you checked the battery, or maybe something in the charging system? Did you see what the output of the charging system was prior to the UTV stalling?

 

[TapBoss]

Did you replace the fuel injector?  Since you've verified spark.

[k-bo]

To answer T-boss 410, yes the system is priming. I have a fully charged, new battery and it is cranking just fine. I did not see the battery voltage when the failure occurred. The charging system is suspect because of the previous ignition switch and starter motor issues I had. Those issues could have damaged the charging mechanisms inside the engine cover. Most suspect of those would be the pickup coil. I measured the resistance of it through pins 4 and 13 of connector J2 (black). The reading was about 500 ohms which is in the nominal range. I don't for sure know, but I think the pickup coil sends a trigger signal to the computer to fire up the primary in the ignition coil. Something is there because some spark is there, which may or may not be what is needed. I do have a new plug wire inbound.

To respond to TapBoss: I have not replaced the fuel injector. I could do that. I have a new one to put in. When I pull the plug it has gas on it; it's pretty much soaked.

One other little info tidbit, when the vehicle shut down, the voltage regulator was pretty hot. I have no idea whether that was abnormal or not. It has quite a heat sink on it and that makes me think it was fully engaged. My cooling fan was on and the motor was at operating temp.

To review, computer says ignition coil failure, spark observed, fuel pump runs, fuel observed when spark plug pulled, and new starter motor and battery are spinning the motor to no avail.

Thanks for the responses guys! I sure appreciate the assistance!

k-bo

[TapBoss]

Keep us updated!

[T-boss 410]

I don't mean to seem ignorant, but would a improperly functioning voltage regulator cause the issue? Or maybe the stator is malfunctioning, which would cause the voltage regulator to heat up.

Edited February 22, 2023 by T-boss 410

[k-bo]

Well, I don't think any question at this point is a bad one. I brought up the regulator with the idea that it being hot is symptomatic maybe of issues around the stator and/or pickup coil. This voltage regulator is new and I have the old one which is probably working. So, swapping them out would take 5 minutes. Then we can eliminate the suspicion about it or be pleasantly surprised.

I'll keep y'all posted. Have a good evening!

k-bo

[T-boss 410]

Just curious, and off topic, but how well does your engine turn over? Mine will usually only spin once. I hit the key again, and it will spin quicker and start. I have a larger than stock battery (340cca's), but it really didn't change it much.

Thanks 👍

[k-bo]

My starter cranks the motor over pretty easily as long as there is good contact inside the starter switch.

k-bo

[T-boss 410]

So I may have a starter switch problem? This UTV was purchased in an auction from the manufacturer in Texas. I don't use it much (I need a trailer), and it only has 15 miles on it. But it was a demo model, so maybe the switch is a bit worn.

[k-bo]

So was mine! The OEM starter switch was crap and it seems to have caused a lot of issues, beginning with the starter motor. I put in a generic switch and a push button for the starter function.

k-bo 

[T-boss 410]

Can you please explain what you did and how you did it? That's very interesting!

[TapBoss]

"So was mine! The OEM starter switch was crap and it seems to have caused a lot of issues, beginning with the starter motor. I put in a generic switch and a push button for the starter function."

 

k-bo, did this fix your problem?

[k-bo]

It fixed my problem, but the damage was done (imho)...

Not very long after I received my T-Boss 410 from Massimo in Garland, TX through an eBay auction, the starter switch on the dash got to where it wouldn't work properly. I had to hold it in a certain position to make the starter run. This got worse and worse, then finally the starter motor quit working. At first, I could not tell what had failed, but I was sure that the starter switch was bad. I pulled it out and could see it wasn't serviceable, so I went to Autozone and bought a generic car starter switch and a momentary contact push button switch. I used the wiring diagram in my T-Boss manual to sort out the wiring, added crimp on connectors to the wires, drilled a hole in the dash for the push button switch, connected all wires appropriately, and mounted the switches on the dash panel. Later, after throwing various parts at it (like the voltage reg.) and discovering how to read codes, I determined that the starter motor was burned out. I replaced it and got going again as documented in the thread about fault code troubleshooting by Joe Toup.

It seems more things got damaged by hard current hits from that bad switch, which leads us here into this current thread. I really feel pretty clueless at this point, but I guess I will have to drain the oil and pull that engine cover off so I can get to the stator and pickup coil. I will try a new plug wire first just in case.

If anyone out there can think of something else to try, I am all ears.

Thanks!

k-bo

[T-boss 410]

My starter has been difficult to engage since I've had it. I thought it was the battery, so I replaced it. The OEM battery did have a weak cell, so the new battery was needed. However, that didn't change things much. I still have to hit the key at least 2X to get it to start.

 

[k-bo]

Yes, those switches are crap!

I just swapped voltage regulators to see if I had gotten a defective one. No difference. One thing I have noticed, however, is when I first crank the motor I get an initial fire, like one little one, then only cranking afterward. Looks like I will have to open the motor up and look inside the beast. I'm not looking forward to that.

k-bo

[T-boss 410]

So replacing the switch with a new one would not be a good idea, huh? Are there any universal switches that would work the same, without the push button start?

[k-bo]

2 hours ago, T-boss 410 said:

So replacing the switch with a new one would not be a good idea, huh? Are there any universal switches that would work the same, without the push button start?

I think the sooner you change it out, the better. Do it before it ruins other electrical parts. If you don't want a push button, all of the starter switches have the starter function built in. I recommend getting something that is not too cheap.

k-bo

 

[T-boss 410]

I'll do that. I tried reading the wiring diagram in the service manual, but it's a bit confusing. Did you get a switch with a harness attached, or with terminals? Is this a 2, 3, or 4 wire switch?

Thanks 👍

[k-bo]

T-boss 410,

My switch needed terminals and I crimped them on. I'm pretty sure there were 4 wires involved. The starter switch function provides the starter relay a ground when the switch closes. That was initially a bit confusing to me too.

k-bo

[T-boss 410]

On 2/23/2023 at 10:06 PM, k-bo said:

I think the sooner you change it out, the better. Do it before it ruins other electrical parts. If you don't want a push button, all of the starter switches have the starter function built in. I recommend getting something that is not too cheap.

k-bo

 

Is there a particular brand you would recommend?

[k-bo]

Update: A new plug wire did not change anything much. I did get a fire off right at first, as I mentioned previously, and this time it was a bit more pronounced. So it seems that the ignition is not completely spark-less.

I have gone further into the issue. I drained the oil and opened up the magneto cover on the motor. The pickup coil and stator (generator assembly) are mounted to this cover. I could not see any identifiable issue with any item and resistance measurements appear to be in spec. I'm going to hold here and not buy any other parts at this point. I believe I need to verify some of the mechanical functions, like check for a sheared woodruff key and see if the rotor and gears will spin properly.

I going to see if Massimo will talk to me. I'm not going to hold my breath on that one...

Don't have any favorite brands for electrical parts, Mr T-boss 410, to answer your question.

k-bo

[k-bo]

Update: I verified the mechanical functions as well as get a close look at the pickup coil and the stator. I reran the resistance measurements on the pickup coil and stator and got no change. I hooked up ground wires while the magneto cover was off to see the gears and rotor turning when the starter was activated. Everything looked like it was functioning normally. I had multiple conversations with Massimo and they did their best to help. Greatly appreciated! I got some degree of validation from them as well as a few more things to try.

So now I'm in the process of reassembling the vehicle. I've just about got it. Need to replace the engine oil and tie harnesses back to the frame. I will attempt another start just in case I have inadvertently fixed it. Aside from that, I will check the engine compression and valve lash. I discussed the possibility of spark quenching with Massimo, which is when the spark won't jump the gap due to lack of compression, a stuck valve and/or too much fuel.

I'll post another update on how it's going over the next few days.

Tenaciously,

k-bo

[T-boss 410]

Sorry you don't have it running yet, but I am happy to hear that Massimo was willing to help.

[T-boss 410]

I don't mean to seem ignorant, but did you replace the key switch as well as add the push button start?

Also, is the brake interlock still functional?

Thanks 👍

 

[k-bo]

Update: I have not had any luck in completing the fix on my T-Boss. I have swapped the fuel injector out for a new one and did a compression test. I decided to do the injector because the computer threw an additional P0201 code along with the P0351. So, I'm at some very expensive crossroads. If the computer is bad, changing it is a several hundred dollar proposition provided that I can even find one. I have yet to see one for sale anywhere. When I did the compression test, I got 75 psi which is quite low according to the service manual. It says 1400 kPa which equates to about 217 psi. I did not hold the throttle wide open during that test. I missed that detail in the book. However, that reading seems way low. I feel like it is time to back off and move on. I have too much other shop work to do. So, I plan to call the closest Massimo service center, 45 miles or so away in San Marcos, and see what their interest level is for working on it.

If anyone has an epiphany (or brain fart or whatever), I'm still all ears. But, I'm tired of banging my head against the wall on this.

Y'all have a great week!

k-bo

[T-boss 410]

Doesn't 217 psi sound awful high? I could understand 135 - 140 psi, but the 217 sounds like 2X what it should be.