Intermittent Engine Turning Off at Low Speed

[Micoproviso]

I'm a fair mechanic, but new to this bike (last October) and this one has me stumped. I saw some articles about similar issues on this forum, but not quite the same. I'll try to summarize the issue first, then give background details later if you're interested.

Occasionally, my headlight and dash lights turn off. When they're off, the bike still runs fine, except at low RPMs when starting from a stop, or coming to a stop. In those cases, the engine stalls. It starts right up after stalling, and the lights come back on after restarting, and runs fine... until the next time the lights go off and it goes back into "limp mode". When the problem is occurring, if I keep RPM's above 2,000 when starting out, the bike doesn't stall and runs fine at higher RPMs.

If I notice the lights are off while driving , pulling in the clutch and jabbing the starter button corrects the problem (temporarily). The lights come back on, and the bikes runs perfectly. It seems like this happens more often when it's humid outside, but not sure of the cause. Sometimes it doesn't happen for a day or two. Other times, it happens constantly.

I've seen some clues about possibly a relay (which one, where is it located?), a diode (I checked one of the left side of the bike and it flows current the way it should. I do have a service manual and an electrical diagram, but not sure what to look for. From experience, this sounds like some kind of grounding or connection issue, but where? I've separated many connectors, cleaned and re-assembled them, but the issue persists.

Any help or thoughts on what to check would be greatly appreciated. This bike is like new cosmetically, and only 30,000 miles. I love riding it, but this problem is really annoying me, not to mention making me look like an idiot when my bike stalls when starting out and people think I'm clutch challenged.

Background: This bike sat for 15 years before I got it last fall. Previous owner developed a health problem, eventually passed away, and widow couldn't bring herself to sell it until I convinced her that I would fully restore it to it's former glory (which I did, so far). It sat in a garage for those 15 years and developed minor surface rust on many surfaces. I did the usual fuel system refurbishment, tires, and fluid changes, etc.. got everything cleaned up and working properly (even the auto-cancelling turn signals, CB, radio, cruise control, etc..). Without this issue, it runs, looks, and rides like a like a brand new bike. He must have taken very good care of it.

Please let me know if anyone has any questions or can offer me any advice on what to look at. BTW, it's a 1995 model.

[Nails]

The go-to for these kinds of gremlins is the connector next to the headset. You'll want to cut this cable tie (replace it with something looser if you must) and check for damaged wire connections to the plug. You might consider nuking it altogether with cable splices. As a guess, I suspect a poor connection in this connector that only works with the extra voltage of some RPMs. At any rate, this is known problem and must-do mod.

The manual includes a "base" manual and an "auxiliary" manual. The base manual is for the first year, before they added a bunch of stuff described in the auxiliary manual.

In the electrical diagram (pg 15-26 of the base manual), you'll notice some weirdness associated with the starting circuit and the headlight relay. I'm just saying that headlights and ignition going out together is believable. If the 13-pin connector doesn't fix it, I'd look at this little circuit. Your comment about the lights being off after starting makes me think of a sticky headlight relay, as you say.

You might also spend some time researching the reserve lighting system (pg 15-27). I don't know anything about this, but I remember disabling it to use an LED headlight bulb. I have a vague sense that it seemed unnecessarily complicated. Much of this bikes electrical system design seems silly-complicated to me.

The bike has two sets of three relays, one above the headlight and the other on the left side under the "tank" cover. The headlight relay is the back one on the left side (pg 15-42) -- also check the starter-circuit one (middle of the three), as mentioned above. Note that all stock relays are identical so you can parts-swap with yourself. These relays are available at any parts store -- see the Dollar-for-Dollar section for that Toyota PN.

There are two diode assemblies (pgs 15-42 & -43) on the left side. The headlight one is two diodes in one unit, and the ignition diodes are three in one.

I added a ton of grounds, especially one right off BATT- to the first convenient frame bolt. I collected a gob of ground wires on the left side to a new ground bar, also connected straight to BATT-. This in addition to all the stock ground wires.

Good luck!

[Micoproviso]

I took a quick look for the headset connector with the faux tank off because so many threads mention it. I see a cable coming out of the fuse box, but didn't see the connector it goes into. Is is accessible under the faux tank, or do I need to take the left upper fairing off, and take the CB box out to get to it back there?

I have a "Supplementary" manual, but I'll take a look for the "auxiliary" manual in the docs section.

I'll look for the relays in dollar for dollar section and just replace them if they're not too expensive. I saw a bunch of used ones on ebay, but if they're available new, I'd rather go that route.

Thanks for the detailed response. You've given me lots of possibilities to explore.

[Nails]

Yeah, Supplement, not auxiliary. And a radio manual.

[cushman eagle]

Micoproviso,That is kind or like the issues I had with my '99 shortly after I bought it ,which turned out to be fractured wires in the ignition harness.
The harness goes from the ignition switch to a connecter on the left side under the false tank
You can find a post on this forum regarding this issue.
I pulled mine out and replaced the wires and left it loose where it does around the steering head, and have had no issues since over 13 years and 82,000 miles

[Micoproviso]

It was the relay(s)!

I'm having trouble the finding "dollar for dollar" section. Maybe because I'm new and don't have full access yet? But I did a search for Toyota and came across a thread with that part number, called local parts stores to cross reference the number. Advanced had 3 of them, significantly cheaper than even the used ones on ebay. I replaced the 3 on the left bank under the faux tank and just got back from an hour of stop and go riding with NO incidents.

THANK YOU!

1) you were right
2) you saved me a ton of money on the part

[Micoproviso]

I spoke to soon. I took the bike to work this morning, and problem recurred 4 or 5 times. But when I rode it it home, problem didn't happen once.

I guess next step to find that 13 pin connector. What is the easiest way to get to it? Under the faux cover, or behind the left side fairing?

[Micoproviso]

Is this the notorious 10 pin connector that everyone criminalizes?

[ekap1200]

Is this the notorious 10 pin connector that everyone criminalizes?

If the contacts appear clean and no signs of the plug getting hot, intermittent open in the key switch is a common issue. Wiggle test the harness, while idling and see if circuits start to open. Relay issues usually work or don't work.
Gene Kap.

[Nails]

Is this the notorious 10 pin connector that everyone criminalizes?

"13-pin connector": Sorry, I've got the cruise control "brain" on my brain these days.

It's possible that your bike, which hasn't been used in years, developed more than one corrosion problem. You also mentioned surface rust.

[Scott-(Altoona, PA)]

When my '01 started shutting off like that for me it was in tight left or right turns. I removed the faux tank and cut the wire bundle that was tie-wrapped to the left side of the frame. As Gene said I wiggled each independently while bike was running and found that one had a break internally where the plastic tie-wrap was. I cut, stripped it back and added a short piece as to not shorted the original, hard soldered it in and with shrink wrap sealed it. That was over a decade ago and it's been fine ever since.

[Micoproviso]

I’m in the process of disassembling every connector, cleaning with CRC electrical contact cleaner, assembling and disassembling a few times, then adding some dielectric grease before putting them back together the final time. Not finding any serious corrosion. The 10 pin connector didn’t really look bad at all. A little dirt in there, but no loose wires or corrosion. The male pin of the white wire with black stripe seemed a little more loose than the other pins, but I pulled on the wire and it didn’t budge. After I’m done, I’ll start wiggling things with the engine running based on some of the areas you guys have suggested to try to get the event to trigger. I’ll probably change the other 4 relays behind the headlight also, just because they’re cheap.

[Micoproviso]

I cut all the zip ties holding those wiring bundles to the steering stem and started my bike. I started wiggling the bundle that came from the ignition switch, and my bike shut off. Might be getting somewhere. My inclination is to remove the ignition switch, detach the connectors, remove the sheathing, and take it to the workbench where I can take a closer look and have better access. If I can’t find damaged wires on the bench, I could reconnect the connectors from the side of the bike and wiggle individual wires from there.

Is this the method you used, or is there a better way of doing this? You said there was another thread on this specific subject. Do you recall the subject title so I can find it?

[Micoproviso]

Yellow with red stripe.

[cushman eagle]

I cut all the zip ties holding those wiring bundles to the steering stem and started my bike. I started wiggling the bundle that came from the ignition switch, and my bike shut off. Might be getting somewhere. My inclination is to remove the ignition switch, detach the connectors, remove the sheathing, and take it to the workbench where I can take a closer look and have better access. If I can’t find damaged wires on the bench, I could reconnect the connectors from the side of the bike and wiggle individual wires from there.

Is this the method you used, or is there a better way of doing this? You said there was another thread on this specific subject. Do you recall the subject title so I can find it?

If I recall correctly,it was titled 'ignition harness"
That was the harness I rewired that fixed my" bike stopping" issue

[Micoproviso]

For the next guy..... I did find that the yellow wire with the red stripe (turns out to be the kill switch wire according to the wiring diagram) had a bend in it right where the zip tie held it to the frame. The sheathing of the wire wasn't damaged, but when I bent the wire back and forth, it was obvious that it was fractured inside because it wasn't anywhere near as stiff in that spot as it was if I bent anywhere else on the wire. It felt kind of like a wet noodle in that one spot.

I cut the wire there, stripped, and hard soldered it, covered it up with shrink wrap, and re-encased the bundle of wires in the sheathing, and closed it up with an electrical tape wrap. I did not re-attach the bundles to the frame.

I put the bike back together, and spent a couple of hours riding with no recurrence of the problem. It's true that I've been here before and the problem came back, but considering that I found exactly what several posters said was a problem and fixed it, I'm fairly confident that my problem is solved. Plus, I now have cleaned and waterproofed connectors, and new relays, which IMO is a good idea for a bike this age anyway.

Thanks to all of those that helped me resolve this.

[Scott-(Altoona, PA)]

For the next guy..... I did find that the yellow wire with the red stripe .....................Thanks to all of those that helped me resolve this.

Just glad you found the issue and can now ride with more confidence that your bike will keep running and not leave you stranded! I think I used a piece of Velcro tape to hold mine close to the frame but loosely!