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Discussion Starter #1
Okay experts I need your help. I got 2 weeks to fix this issue.

Brought my bike out of storage. changed the oil. rode it around a week or so and went through a tank of gas. It snowed one morning and my bike got a little wet. (not necessarily correlated). later the same day after being wiped off biek wouldn't start.

What I know:
Engine turns, and vertical cylinder is firing(good compression, new spark plug which isnt wet when removed after trying to start meaning fuel is combusting)

***Horizontal cylinder is not firing. spark plug is new. spark plug is sparking. plug is wet when removing from cylinder after trying to start. cylinder also has low enough compression it won't blow my finger off the spark plug hole.

Battery is 1 year old, load tested, holding 12.5 volts. fluid levels good. I also bypassed with car battery (car not running) and same result, engine turning 1 cylinder firing.

Checked timing belt. it is in good shape, was a little loose but no missing teeth or rot.

Replaced gas in tank to make sure no water.

Fuel filter engages when key turns. Already tried spraying some starter fluid down the throttle bodies to see if that would give it some life. still not start.

air filter is fine.

bike won't push start.

both primary and secondary coils for spark plugs are functioning properly for the two cylinders and the fuel injectors read the same resistance across the terminals so they should electronically be fine.

Why wouldn't this bike start? I'm thinking at this point the fuel/air mixture isn't right in the horizontal cylinder to fire cause its getting spark and fuel. not sure if the low compression has to do with it. I am not sure where to go from here.

I have a haynes manual for my bike and I'm not a pro but getting better with the mechanical stuff.

Thanks!
 

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My 750 will run on one cylinder (run like crap, but run). Are you hearing the bike pop on the vertical cylinder? How do you know it is firing? With the plug being dry, and the absence of popping or trying to run on that one cylinder, I would say that you are NOT getting gas.

I would start there.
 

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Discussion Starter #3
Does anyone live near salt lake that has a cylinder leak down tester? I am kind of poor right now (just got engaged and am finishing school) and am not eager to spend $100 for a tool I'll not use very often.

I do hear a pop every couple tries from that area. the bike doesn't just turn it sounds like its really about to start but doesn't. I didn't notice any kinked or obstructed fuel line issues and as mentioned the fuel pump is engaging. a cylinder leak down test will answer compression questions as well as if there is a fuel injector problem according to what I am reading.
 

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Does anyone live near salt lake that has a cylinder leak down tester? I am kind of poor right now (just got engaged and am finishing school) and am not eager to spend $100 for a tool I'll not use very often.

I do hear a pop every couple tries from that area. the bike doesn't just turn it sounds like its really about to start but doesn't. I didn't notice any kinked or obstructed fuel line issues and as mentioned the fuel pump is engaging. a cylinder leak down test will answer compression questions as well as if there is a fuel injector problem according to what I am reading.

So let me get this right:

1) Horizontal cylinder (HC from here on out) IS NOT firing.
2) Vertical Cylinder (VC) IS FIRING every few turns.
3) Gas has been replaced to eliminate issues of water in fuel
4) Air filter is not soaked, or coated
5) Issue with battery has been bypassed (by using car battery)
6) Starter fluid wont start engine, nor will push starting it.
7) Compression on HC *feels lower than* VC, but has not been checked with gauge
8) Timing belt looks decent.
9) You *think* both coils are good.
10) It is Carb'ed

How many miles are on it?
What kind of modifications have been done to the bike?
What sort of tests have you done to verify the coils are good?
When was the last time you have adjusted the valves?
Have you verified that both coils are getting power?


Flip your coils first, to verify that they are both in working order (VC should should fire if issue lies with HC/wiring, OR HC should fire indicating the coil is bad)

If nothing changes

Then call an O'riellys if you have one near you, I *believe* they have compression testers you can rent for free (put deposit down, when returned, get money back).



If I have misread anything please quote and correct in the numbers to make it easier for all to follow. Hope I can help you out.


And good luck with school
 

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Discussion Starter #5
just under 50k miles. Had valves serviced about 5000 miles ago so it's getting time but not quite. only modification is tail chopped and termignomi exhaust pipes.

I used a multi meter to check the coils to make sure that the 12 volts of battery were getting to primary and secondary (relative who used to work on planes was there checking electrical stuff with me).

your list summarizes what I know. except my bike is fuel injected

called oreillys they dont have a cylinder leak down tester. as i understand it thats what I need. compression test is pointless cause I already know theres a compression issue??? cylinder leak down tester (CLD tester) helps me identify where leakage is occurring which narrows down the problem. autozone, oreillys etc. dont rent CLD tester to buy one will be more than $50 which sucks for something I'll probably never use again. .

I'll try switching the coils tomorrow morning to see if that helps. I am not an expert mechanic but have learned a lot the last couple years from reading and applying thanks to good forum people and manuals.

Thanks for your interest.
Help Diagnose Starting issue Please. video of how it sounds starting and other information.
 

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Yeah, it is definitely firing on VC.

1) the bike is injected, and the pump is working, ( I can hear it in the video)
2) We know that the injectors are firing at VC, as it is trying to start.
3) We know that the injector at HC is firing, as the plug is getting fouled/wet

Definitely swap the coils, that will eliminate/confirm the possibility of a bad coil(which you have checked that both are getting power with a voltmeter on key on).

If that doesn't fix it, you will need to see if you are getting power to the coils under cranking conditions.

I am trying to eliminate the possibility of all electrical first, while you can hopefully find someone with a leakdown tester.
 

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Discussion Starter #7
Thanks Rex.

It was raining this morning and I have night class. Once I get out I'll try switching the coils. When we measured them with the multi meter we took measurements as I was hitting the starter button/ cranking conditions.
 

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ok, let me know what you find out when you swap coils. I am betting this is where your problem is going to be.

1) It won't start
2) no fire on HC (plug is damp/wet)
3) Getting voltage to both coils under key on, and on crank
4) Injectors are firing (already have visible and auditory evidence for this)
5) Have compression on HC and on VC (though appears lower on HC, but not confirmed with gauge)
6) valves have been adjusted recently
7) newer plugs

What this short list says, is that we can be fairly certain that we are getting a solid 2 of 3 required things to start the engine. We have fuel (confirmed), we have compression(could be low on one cylinder but should still start) , and we know we have spark on one cylinder, but are not on the other. Everything up to coils are "good" electrically, and plugs are good.

1) By swapping the coils, if the VC drops out and doesn't fire like it is now, and the HC fires, you probably have a bad coil.

2) If the VC still fires, and HC is still dead, you can have a bad cylinder, plug, plug wire, or a bad ground issue.


Isn't much else left to check. Good luck and let me know what you find out.
 

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Discussion Starter #9
Ugh I can't really conclude anything at this point. since I switched them the bike won't consistently fire. It only fires once after resting for a while and this has happened twice. I couldn't for certain determine which cylinder was firing. both plugs had fuel on them when removed.

couple questions. do the coils need to be screwed back into their bracket for grounding or any reason? Also do both plugs have to be hooked up while I test or could I just have one cylinder plugged in at a time and that should still fire?

I do want to do this right but i already am feeling like this might not be the solution... bah frustrating. It couldn't be anything with the ECU not allowing the mixture to be right or timing could it? and if it was I probably am not able to fix that...
 

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Ugh I can't really conclude anything at this point. since I switched them the bike won't consistently fire. It only fires once after resting for a while and this has happened twice. I couldn't for certain determine which cylinder was firing. both plugs had fuel on them when removed.

couple questions. do the coils need to be screwed back into their bracket for grounding or any reason? Also do both plugs have to be hooked up while I test or could I just have one cylinder plugged in at a time and that should still fire?

I do want to do this right but i already am feeling like this might not be the solution... bah frustrating. It couldn't be anything with the ECU not allowing the mixture to be right or timing could it? and if it was I probably am not able to fix that...

So the bike was consistently firing before, and now is not?

They should have 2 wires running to the coils (power and ground, so them being on their bracket isn't worth anything), and the plug wire running to the plug, plug wire will supply the power, plug is grounded through cylinder-head.


Plugs should be independent, check the wiring diagram to see if the ground from the coil goes back to the ECU. You can check to see if the coil is firing the spark plug, by removing the plug from the head, and placing it on the block while plugged in. You should see the plug spark from the electrode to the ground strap.

Let me know what you find.
 
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