Let There Be Light!


Well, the headlight issue was indeed a simple problem.

When I removed the stock ignition coils, I neglected to secure two ground wires that had been held by one of the ignition coil bolts.

One little bolt and the lights are back on! 8)

Now I just need to fix everything else. I’m looking for the ground wire that will fix the throttle body issue… Wish me luck.

One Step Forward, Two Steps Back


Ok, maybe it’s not that bad. One step forward, 1.273 steps back…

As suggested by a XJ-lister with MegaSquirt experience, I set about reinstalling the butterflies for the subthrottles, the intent being to set them to restrict the air intake. My theory, verified by his experience, seems to indicate that my throttle bodies are probably way too big for this engine. The butterflies restricting the overall air flow into the engine may serve to widen the throttle range a bit. I fear the only real option will be to change them out for smaller unit or perhaps build a manifold to let me use only two of them. Much remains to be discovered, but I need to start somewhere.

I removed the air filters and was able to reinstall two of the butterflies without difficulty. Of course, the first one I tried on the “dark” side of the bike (the side away from the lighting in my workspace) crossthreaded and twisted in half in the removal attempt. After warming the area with some rather colorful language, I removed the throttle bodies, drilled out the broken screw, installed the two remaining butterflies, LockTite’d all of them and finally secured the assembly at the recommended 9 degrees from open.

I reinstalled the throttle bodies and started the bike up, only to find that now the throttle doesn’t close against the stop. I can gently force it against the stop, but it springs back open, reving high the whole time. The only thing that comes to mind is that maybe when I put thread lock on the screws, a drop fell in on one of the throttle butterflies, dried there and is now holding them open. I suspect it will be #3 because it seems like it’s always #3. :roll:

Well, with the bike trying to idle at it’s maximum attainable RPM of about 3800, the air restriction does not appear to have been too much. The advance is still crazy up there and it surges like it’s hitting a rev limiter, but at this point, I have done no adjustments to the ECU, just added the subthrottle butterflies back into the intake tract. That, and broken it such that the throttle is cracked open pretty much permanently.

Just this moment, I’m far too frustrated to safely pull the throttle bodies back out to troubleshoot the stuck open issue, so I will call it a night.

Juice and Fuel


As suggested by an XJ lister, I checked over my meter and there is indeed something flaky about it. I turned it on and with nothing connected, it showed 38V. One sound tap and it settled down. I found that I could spin the selector switch a few times and make it screw up a bit, but after running through the ranges, it settled down. This meter has bounced around in tool boxes, floorboards, saddle bags and my driveway for about 10 years now, so I think it’s due a little crotchitiness, especially since it’s almost always sitting on the 20V range :)

In any case, with it settled down and reliably measuring 12v and 5v from a known good PC power supply and 9V from a fresh 9v battery and 15.5 from my laptop power supply, I now feel I can trust it.

So, I started measuring voltages on Buzz.

Before I started, the battery was at 12.6V. I turned on the key and saw it drop immediately to 12.4V then slowly ‘drain’ down to 12.1V after 3 minutes of just sitting there with the key on. At that point, running lights, instrument lights and the ECU would be the only current draw.

While cranking, it dropped to 10.5V. As is the current state of the project, it was hard to get him started and running, but once going and warm enough to idle and run, I had enough hands and eyes to watch the meter. At idle, battery voltage is about 12.8V, at 2000RPM steady, it’s 14.1. As I recall, those seem to be reasonable figures to indicate that the alternator is at least working.

The headlight is still quite dim, but it does fluctuate with reving. It still never gets above what I would subjectively call about 40% brilliance. More on that subject later.

The battery itself is still slightly suspect, because the cranking voltage drops pretty deep, so I will probably replace it anyway. I have not checked the spark while cold cranking the engine lately. The low cranking voltage is probably contributing to the trouble starting.

With the battery voltage question shelved for the moment, I set about trying to extract a little better running condition. Another one of those little things bothering my subconscious about the fuel system is the tendency of the fuel filter to run “dry” when the fuel pump is running. The fuel pressure seemed to be ok, so I put it out of my mind. Yesterday, I was browsing some of the MS forums for stuff about power loss at certain RPMs. At least one post suggested that fuel starvation could be a factor. I rev Buzz up and, as usual, it sounds like the engine hits a rev limiter at about 3200 RPM, but this time, I watched the fuel pressure gauge during the event. It bounced down from the usual steady 42psi to about 35, jumping roughly in time with the stutter. Hmmmm.

The return from the regulator for my temporary fuel supply is a clear hose. It’s been handy because I can see flow in it and that gives me an operational check at a glance. Well, an extended bonk against the pseudo rev limiter revealed another symptom that simply hadn’t occurred to me and would not have been easily detected without the clear hose. Bubbles. Lots of bubbles in the return line, but only when the engine is stuttering at 3200 RPM. Hmmmm, ok.

I bypassed the fuel filter and tried again. No bubbles in the return line and while it still sounds like it’s hitting a rev limiter, now it does it at about 4300 RPM and there is no fuel pressure gauge bounce. There is still much tuning to do, but I now feel that fuel starvation is probably no longer a factor.

A tweaked around with the fueling settings in MegaTune, but didn’t make any huge progress. By that time, it was getting chilly enough outside that my fingers, especially on my mouse hand, were getting cold, so I wimped out and packed up and went inside.

The brain, however, doesn’t stop and I began trying to figure out why the lights would be dim when the voltage should be high enough for bright lights. Something to check came to mind this morning….

Alert readers following the blog will recall that when I needed to tap an ignition switch controlled voltage, clips on the stock fuse box were pretty much falling apart in my hand. I had a spare DelCity fuse block, so I replaced the stock fuse block. What occurred to me this morning is that I crimped those connections and perhaps I have a bad enough crimp to limit the current available to the headlight.

Current Events


No, no election coverage here… we’re talking amps!

I’m surprised that I didn’t remember to do this until last night, namely measure the current draw of various components of the system.

For each measurement below, I first started and ran Buzz until warmed up, mostly so he’d idle without fiddling. Then I shut him off, pulled the fuse feeding the measured equipment and bridged the fuse connection with my ammeter probes. I started the engine and noted the values at idle, while reving and while holding the speed steady at what is currently the highest at which he’ll run smoothly, about 3200 RPM.

As expected from the start, the fuel pump may be the largest draw, coming in at 3.7 to 3.8A. This is also a fairly steady draw, since so long as the engine is running, the fuel pump is on.

The next big draw is the ignition system, coming in at 700mA at idle and 1.6A at speed. I suspect this value will climb at higher RPMs due to the nature of an ignition system. It’s essentially a PWM signal in which the pulse width stays about the same, but since the frequency increases, the apparent percentage gets larger, thus the current draw will go up.

Everything else is almost trivial, but may not be exactly accurate because the low range fuse on my ammeter is apparently blown.

The fuel injector rails draw 70mA each at all speeds. This will probably go up a little as RPMs get higher for similar reasons that the ignition system will draw more, but proportionally, it will still be a low value. Even at 100% duty cycle, each injector would draw a little less than 1A and with this small an engine, 100% duty cycle would pretty much be a hydrolocking degree of flooding.

The ECU itself appeared to draw about 30mA, but that seems low according to the documentation. I would expect it more like 100-200mA. The final measured value is the FIDLE output. One day, I will have a solenoid there, but for now it’s just an LED. The 10A range on my meter would probably not show it, but since the engine was warm, it wasn’t lit anyway so no reading.

All this measuring of current draw made me take note that the headlight was pretty dim while the engine was running. I checked the battery voltage and it was 11.58V, unchanging when either revving the engine or shutting it off. That is extremely unusual. With no charging system, I would expect the voltage to raise a bit when shut off, the load having been removed. If the charging system were working properly, it should raise when reving. I didn’t even see it change with my external charger connected. Hmmmmm

In any case, Buzz is to the point where I can begin tuning the engine in other RPM ranges, though I now also need to get this electrical issue resolved. No juice, no go.