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Gen1 hard start, cold and hot, not a fuel/battery issue. ignition advance?

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Thomas:
I'm trying to trouble shoot hard start problem to no avail.
The bike when cranking sounds like the battery is flat: every single lamp dims, cranking RPM suddenly droops, it sounds like nyeh-nyeh-nyyyeeeeeeeaaaaah-[everything dims]-nyeh-nyyeeeeaaah-[everything dims]. Bolting another battery and extra ~80A 12V power supply in parallel doesn't really help.
*HOWEVER* if I disconnect the injectors the starter turns crazy fast, hooking injectors back and here we go, the engine suddenly becomes hard to start and sounds like the battery is flat.

It really looks like the ECU is sparking too fucking early? I had carbed bikes with non-CDI ignition and a kickstarter, fuck up ignition advance and you'll get precisely that, albeit the bike will kick you and launch you to the moon.

Background / what I've done so far:

I got the bike few years ago, it's a 2002 busa with 32bit ECU. I got it with full titanium exhaust and DNA air filter and semi-flat battery,  I thought the hard starter issue is due to stock ECU and lean mixture topped with old battery. Replaced the battery with a new one (YT12A-BS) and got an OEM air filter. Doing all that slightly alleviated hard start issue but not that much.

I also got the bike with few thick ground wires bolted here and there from the negative battery terminal,  removed all of them and was unable to start the bike since it was cranking sloooowly as hell. New battery cured that.

Ok what I did since then:

0. new spark plugs, sync'ed TB's and adjusted idle / TPS
1. Replaced started motor/starter clutch/starter motor covers. Got all that from the next gen motor.
2. New in-tank fuel pump, trying first the one from 350z and now I run AEM 320 one with dedicated relay/fuse/wires. External fuel filter. AEM fuel pressure regulator. Fuel pressure is rock steady.
3. Went full retard and replaced starter motor "+" and "-" wires with two 4 Ga in parallel for "+" terminal and one 2 Ga for negative. The wire from the "+" battery terminal to starter relay is now 4 Ga.
4. Adjusted valves, everything is within the spec. Compression test shows 14-16 bar across all cylinders.
5. Tried two different ECU's. Tried OEM flash.

Going to check crank shaft position sensor. If it checks OK what should I do next?

wildphil69:
Check the key for the rotor. Does it roll the same with the coil packs unplugged as it does with the injectors unplugged?

Thomas:

--- Quote from: wildphil69 on May 20, 2018, 08:38:38 PM ---Check the key for the rotor.
--- End quote ---
What key/rotor? I'm kind of lost. You mean ignition key?


--- Quote --- Does it roll the same with the coil packs unplugged as it does with the injectors unplugged?

--- End quote ---
Will check, I bet it will crank just fine with the coils disconnected. I'm leaning towards thinking the ignition timing is wrong.

With regard to CKP/CMP sensors: I've ohm-ed crank and camshaft position sensors, all good. Hooked up the scope, peak values are good. RPM while cranking are good: 300rpm with no choke and 350-38 with choke. Removed stator cover and gave visual inspection to the crank sensor, I thought it could have picked lots of magnetic debris but all is good.

So far I'm perplexed by three facts:

- CKP sensor has blue and green wires, while the schematic for the bike shows green and white? WTF
- Blue wire from the CKP sensor goes to green wire in the loom.
- I have no idea where positives terminals for the sensors are but making an educated guess (ohm-ing both terminals to ground and assigning the wire with the lowest value as a "ground" or "negative" terminal) shows that the sensors do not match, in essence zero crossing slopes do not match).

Thomas:
Pic from the scope is attached.
"+" terminals were connected to green wire in the loom for CKP and black/brown wire for the CMP.

Thomas:

--- Quote from: wildphil69 on May 20, 2018, 08:38:38 PM ---Does it roll the same with the coil packs unplugged as it does with the injectors unplugged?

--- End quote ---
Yep, unplug either injectors or spark plugs and starter spins like a sewing machine. Plug all that back and it starts to hesitate. Tried to swap lead from the crank sensor, nothing changed at least it's hard to notice anything.

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