Oh man, what a head-scratcher.
So, I thought I was getting close, but the problem is getting worse. Now the bike REALLY doesn't want to start. It will behave almost as badly as when it was at its worst for 20 or so start attempts. Starter kicks just fine. Fuel pump comes on and stays on until after the bike dies. But the bike just sputters to a stop. After repeated attempts to start it does get better. It will get to the point where it can just barely idle. Any gas kills it, The 'choke' switch kills it. After idling a few minutes it will start to have bursts of running better. Just for a second at first, but becoming more frequent and lasting longer until the bike is running okayish. Still definitely not great, but running. It will rev up for a moment, but then sputter and threaten to die unless I drop it back to an idle.
A squirt of starter fluid does help. For a moment after the squirt it will be able to rev up much better. Still not perfect, but noticeably better. After a few seconds it goes back to being wonky. That made me think gas delivery is the problem, so I've been taking another look at that.
The whole gas system is immaculate. I cleaned the tank super thoroughly. All hoses are new. Pump is new. Filter is new. Pre-filters on the injectors are new. I ultrasonically cleaned the injector rail. I wondered if I might be getting low voltage to the pump, so I tried connecting it directly to a 12-volt power source. No difference. I did a more careful pressure test. I don't know why I got 35psi the first time I did the test. Now I'm getting a very consistent exact 36psi, both with the external power source to the pump and hooked up normally. That's with the pump running but not the injectors. When the injectors start firing the pressure fluctuates a bit. Basically, the pressure gauge needle gets fluttery.
I do still wonder if the injectors themselves could be clogged, but with the random, sudden fluctuation between running badly and running okayish, that doesn't seem likely. I'm tempted to make a test rig for the injectors. I can use my old pump (which I'm pretty sure is fine), powered by external power, sitting in a jar of gas. I'll use that to supply the rail and a 12-volt source with a button switch to power the injectors to see how they're squirting. I might try that tomorrow, but honestly, I don't think that's it. Oh, and they're all clicking just fine while the bike is running.
I'm back to thinking that the coils are the problem. I tested them with my
tester thingy again. I tried the tester at spec gap, .040, .060, and .080 inches. I used the same lead for each test. Just connected it to the 4 outputs in turn. At each gap I found that output 1 and 4 sparked okay (though I was not impressed by the spark), 2 was really weak, and 3 was basically not sparking at all. I know, I know, 2 shouldn't be able to be different from 3 but it just is. Really noticeably. I found
this discussion about someone else having that same issue and there were some ideas about how that might be possible. Oh, and I tried switching the coils and got the same problem from the same coil even with primary wires swapped.
So it sure looks like at least that one coil is crapped out, right? It's weird that starter fluid helps, but I'm wondering if starter fluid can perhaps be ignited by a weaker spark than gas. Oh, and I do have the terrible black-capped early coils. I'm looking for replacements, but they seem kind of non-existent. BMW themselves say the part is discontinued. MaxBMW don't have them. I tried searching for the part number directly and found nothing. There are a pair
on Ebay, but man they look terrible. And have no guarantee that they're functional. I'm very disinclined to go that route.
I did find
this discussion that indicates the Dynatek DC1-1 could be a good alternative. 3-ohm primary, modern technology. Could be a good way to get my bike running again.
So, what do you guys think? I feel like I have JUST about exhausted all fuel possibilities. The internals of the injectors could still maybe be an issue, but I doubt it. I think I have a spark issue. In fact, I really think it's the coil (both?). The weak attempts at sparks it's making are just not getting the job done. Do the Dynateks seem like a good idea? I saw in that other thread about them that the mounts need to be grounded. Is there anything else I would need to do to make them work?