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Discussion Starter #1
I have a starting issue somewhat similar to one reported by Duc Dodgers in his June '08 thread. My 2002 St4s ( 29,900 miles) started fine until recently (I always follow starting procedure in owners manual). Ist blip would fire it immediately. Beginning mid-week, for some reason, it would take a couple of tries to get it started (Cranks just fine). Then, it died once once going uphill after I filled up at a gas station. I assumed I had overfilled the tank, and had vapor lock. I popped open the gas gap, then it restarted immediately and I was on my way, running as strong as ever.

Fast forward to this weekend, during a 100 degree heat wave. Started my bike 1st try, left the garage with friends and filled up at the gas station. At the pump, bike wouldn't start,I assumed I had overfilled the tank again, and had vapor lock. I popped open the gas gap, wouldn't start (engine temp about 165 degrees.)We were waiting to meet another riding buddy at the gas station so I pushed the bike to a parking space. When our friend arrived 10 minutes later, the bike would not start until I set the fast idle control 1/2 way.!!!??? even though the engine was still warm?

Rode great 30 miles, stopped for lunch for 45 minutes, came out and the bike wouldn't start a few tries until I set the fast idle 1/2 way up (even though the temp gauge was still at 115 degrees) - up to this point I almost never used the fast idle? Nothing else on the bike is mis-behaving; all gauges, lights normal and once started, it runs like a champ.

Now, I just bought this bike and tore it down and did all maintenance - cleaned/checked all electrical connections including connectors, fuses, etc., replaced all starter and battery cables and grounds with new thicker gauge cabling and higher quality lugs, cleaned all grounds/contacts; new plugs, all new filters (including fuel filter); brand new battery; etc. etc. The week before this started, I had it in to my a local Ducati mechanic just to be safe and see if he heard any unusual noises etc. since I was new to the Ducati world - I was nervous about the previous owner's neglect, and my mechanic gave it a clean bill of health.

Today I went through it and double checked all wiring, connections, etc. all looked normal, but it still took a couple of tries to start the bike. I tried all the posts I could find on starting issues, but I didn't see where an issue like this was resolved & how? Any help would be appreciated.

P.S. no one should have to deal with well nuts unless they're a prison inmate... hate those things....
 

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I'll throw out the worst-case scenario, since it's an 02 ST4s - ECU is going bad like many have, including mine. Hopefully it's not that.

Sounds like you know your way around a bike, so I'm probably just stating the obvious - check fuel, air, spark. If I had to guess from your description, you've got a fuel delivery problem, but that's just a guess.
 

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Mr Leakered
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Per my recent experience, you need a solid fuel spray, not just a dribble. LOL.

Did you or the mechanic check the fuel inlet screen on the bottom of the pump. I don't think it would cause this intermittent start, but who knows.

I don't believe the crank position is sensitive to intermittent running, but you might want to check it also. Mine is high in the resistance range, but still registers a signal.

Someone on the SBK forum had a fly or a bee stuck in their tank vent. Maybe check that it is free to breath.

Have a good one.
 

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Have you installed an aftermarket device which allows you to start the bike with the kickstand down? My 02-ST4s had one which was installed by the previous owner. The bike developed starting problems which disappeared after the device was removed.
 

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Life is too short to worry !
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One thing to point out here , the Fast Idle Lever does just that it opens the throttles slightly , it does not richen the mixture so should make no difference if the engine is cold or hot.

It would appear you need more throttle than normal since working on her so suggest it is a fueling problem , if it were sparks (weak or eratic) then the extra fuel would probably make things worse not better.

I would re-visit all the work you did on the pump/filter etc (and take a quick look over anything else you may have disturbed whilst doing so) as seem likley this is where the problem will be found.

Do not go looking for major/expensive problems at thsi stage as 99% of the time these problems are minor and easilly fixed.

Good Luck
 

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Mr Leakered
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+1 Slightly OT, but on my first ever valve adjust, I didn't disconnect the vert TB to set the TPS. My ST developed a sneeze stall afterward that I was trying to sort over the past 6k. This last valve adjust, I ensured that I followed the proper steps. Now, this thing is pulling like a freight train and doesn't even think of stalling. I'm kicking myself for not realizing it until then. ;)

BTW, thinking of vent lines, be sure that one of yours isn't pinched from raising the tank.

Also, do you still have the charcoal canister installed? Sometimes those flood with fuel if the tank is overfilled.

Have a good one.
 

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Same issues on my 02 ST4S. 2 fixes. Upgrade battery cables using Powerlet as per another post and check crank position sensor. Fixed my issues. 23000 miles and going strong. No other problems but have it serviced per manual at Nichols.

Good luck
 

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Upgrade battery cables using Powerlet as per another post and check crank position sensor.
The OP said he already replaced all the starter/battery cables but it didn't help.

I agree it could be the crankshaft position sensor.
 

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It could also be the coolant temperaure sensor, The fact that it needs 1/2 fast idle to start with a hot engine indicates a fueling problem, too rich, which is likely caused by a sensor fault. The coolant temperaure is the one that will have the biggest effect on mixture and they are well known for failing. The engine has 2 identical sensors, one on the verical cylinder head that sends to the ECU and another on the horixontal head that sends to the LCD temperature display. As simple check swap over the wires to each sensor. If the vert. sensor is faulty the display will now read incorrectly and the starting fault will have gone.
 

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Or just unplug the sender. Open circuit = infinate resistance = COLD engine = richer mixture. I did this on my ST2 WHILE THE BIKE WAS RUNNING, and you could hear the idle "change" as the mixture went from COLD to 207 F (by inserting a 220 Ohm resistor into the connector).

And with the 220 Ohm resistor inserted, it was VERY difficult to start the bike if it was stone cold (because the resistor was telling the computer the coolant was at 207F).

Again, with Open Circuit (resistor or sender unplugged), the bike started well when it was stone cold.

WARNING: if you choose to try a 220 Ohm res., be forewarned that the cooling fan WILL NOT TURN ON EVER. (ECU will think the coolant is always at 207F) So if you use the bike, it's got to have good air thru the radiator...
 

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Discussion Starter #11
Upate on starting

Thanks for everyone's input - really appreciate it. I had some time last night so I started with the simpler possible issues - I found a kinked return hose from the gas tank to the charcoal canister & also found the canister seems to be 1/2 filled with gas (I guess I really overfilled the tank somehow?). I took care of that and checked all sensors/connections I could in the brief time I had and all seemed to be good on a quick run through in the garage. I did a number of test start-ups in the garage following this where I fired the bike up, ran it up to operating temps close to 200 degrees and then shut her off, let it cool off 10 or so minutes and came back and re-fired it up. She consistently started first crank without the fast idle lever on so I'm hoping she's cured, but time will tell.
 

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Thanks for everyone's input - really appreciate it. I had some time last night so I started with the simpler possible issues - I found a kinked return hose from the gas tank to the charcoal canister & also found the canister seems to be 1/2 filled with gas (I guess I really overfilled the tank somehow?). I took care of that and checked all sensors/connections I could in the brief time I had and all seemed to be good on a quick run through in the garage. I did a number of test start-ups in the garage following this where I fired the bike up, ran it up to operating temps close to 200 degrees and then shut her off, let it cool off 10 or so minutes and came back and re-fired it up. She consistently started first crank without the fast idle lever on so I'm hoping she's cured, but time will tell.
Glad to hear it was something simple. FWIW those charcoal canisters often fall off after they get some gas in them and cause problems. Just as well, then they don't cause any problems.
 

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Discussion Starter #13
Starting Issue

Further update: I had the fairing off to remove and tweak my forks so I removed the charcoal canister and tried spraying it full of Brake cleaner solvent to help evaporate any residual gas.(FYI in case you try this, be forewarned, I wound up wearing half the solvent due to blowback from the canister's curved hose connectors.) In removing the canister, I found loose hose clamps to the canister I replaced - don't know if worn/loose hose clamps on a charcoal canister would effect the sealed system or not, but I figured, why tempt fate and replaced the clamps.

So, when I finished the forks, the bike wouldn't start. after few minutes, I remembered I had the kickstand down. Put the kickstand up, still wouldn't start. A few minutes of investigation, I found I had the kill switch on the off position. Just goes to show stupidity will overcome engineering every time.

P.S. rode all morning, bike starts fine.
 

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Great news , hope you enjoy plenty of trouble free miles.
 

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Discussion Starter #15
Vapor lock

Further Update: I forgot to add for other members benefit that after I had talked to my mechanic about the possibility of fuel vapor lock, he took my keys, popped my fuel tank door open and yanked out a black rubber bump stopper that's under the fuel door. This leaves an open hole under the fuel door the tank can vent through to prevent vapor lock.
 
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