[kevin kane]

My 748 SPS motor quit at a recent track even and the reason has thumped a number of knowledgeble motorcyclists. Any ideas here of where I should look?
I verified:
- that the tank had gas.
- that the fuel pump cycled.
- that the battery was strong.
- that there are no blown fuses.
- that the spark plugs had a spark.
- that the valves moved with the motor.

Then;
- I switched the entire tank/fuel pump assembly with a spare I have.
- I then put in a bigger battery with a spare I have.

The starter motor turns strongly but the motor will not start. What I am I missing here?

TIA;

Kevin

 

[tye1138]

I'd turn the tank around so its off the air box, open the throttle bodies and using a flashlight to see, make sure there is fuel being sprayed in there. If there is spark and fuel, I'd be very shocked it didn't start. These bikes are very basic and having both of those, even if the timing is way off, usually gives a sign of life.

I'm gonna throw a guess out there; ECU issue...



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[nine16]

Fuel filter clogged? If you are still getting fuel out of the injectors and you know that you are getting spark, then either your timing is off enough to screw things up but not interfere with the pistons, or its a computer issue.

 

[amullo]

Either extermly clogged fuelfilter or an ECU issue. As said above.. verify that fuek is indeed being sprayed under the butterfly valves on the throttlebodies.

You might check the connector on the ECU aswell as the grounding wire to the ECU. Old issue with the Mono mounting of the 16m. I had 2 extra ground wires running to the ecu to prevent it on my 748SP.

//amullo

 

[kevin kane]

Thanks for the replies. I replaced the filter right before (I have done this many times) so I don't think that's my problem since I did use a replacement tank and pump to test it and that set up didn't work either. I did open the throttle butterflies and verified that the valves worked but I will try the reverse mounting of the tank idea to see if fuel is being sprayed in there.

It has also been suggested that I could have slipped a belt so I need to pull off the covers but it would seem that if a belt slipped one cylinder still would have at least coughed and the likelihood of both belts slipping seems remote but I will check them both.

If these steps don't work then it would point to the ECU - but if that's the case, why is there spark at the plugs?

I will also check the grounding wire and report back. Thanks to all of you have responded.

Kevin

 

[tye1138]

Yes, a belt which jumped a tooth, could have caused the same issue, but thats rare.



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[amullo]

If there is a grounding or problem with the ECU, you can get all kinds of weird stuff..
You could have a fault in the wiring loom on the throttle body side aswell.. Or the injectors could be clogged up (not likely).. Or even a stoppage in the fuelline! (not likely either).

You´ve verified that the engine has spark.. Now verify that it gets fuel. After that, then your into weird territory.. But fear NOT! Yea thou you walk through the valley of WEIRD, thou shall fear no evil, for ducati.ms is with thee!

//amullo

 

[moto]

When you remove the fuel cap does it look like a jacuzzi in there?

Those bikes often have cracked lines or disconnected internal fuel lines.

-M

 

[kevin kane]

I have done everything recommended here:
- checked the ground wires.
- rechecked that the plugs had a spark.
- reinstalled tank and moved it out of the way to view throttle bodies.
- verified that when toggled on, the fuel pump agitated the fuel.
- hit the starter button and verified that there was NO fuel visible inside the velocity stack.
- removed the tank and verified that the fuel lines were full.
so...is it the ECU?
Kevin

 

[John]

I went on the wierd merry go round with my 916 and eventually Nichols fixed it by finding the ECU for some reason had some disconnects of some sort. Took them only one shop hour to find a problem I was trying to run down for weeks. However, the main problem with the bike other than not starting was the fact the cylinders were filling up with gas when you hit the starter.

 

[amullo]

Mount the tank backwards so you can see down the throttles.

Push starter and crank the throttle open (you might want to hook up a bigger battery with jumpers to get more juice) and look down through the butterfly valves/throttles.

Is fuel being sprayed?
If not, then its either a fuelproblem or your injectors are not geting the signal to spray from your ECU.
Do you have another ecu chip? You could start by replacing the chip you have.
If that doesn´t wotrk, then try getting hold of another ECU and plug that in to see if your ECU might be fried. If you have a nice dealer, they usually have one lying around.
Since you say that your absolutly sure that fuel is being pumped in the fuellines, i gather that that probably isn´t the issue.. And the injectors are probably not clogged since both seem not to be firing.

//amullo

 

[tye1138]

- hit the starter button and verified that there was NO fuel visible inside the velocity stack.

Umm... you want to see fuel being sprayed into the throttle bodies. There won't be any fuel in the velocity stack, it sprays below the throttle plate.

To check the ECU is a piece of cake, but you've gotta have a service manual and a multimeter. The Hayes manual has many diagnostics for checking the system and making sure its OK.

Also checking the timing is super easy, just align the dots! Cam pulley's align to markings on the top (vertical) or sides (horizontal) of the casings. You'll have to turn the motor (use the rear wheel whilst in gear and motor off to turn over the motor) and align it, but if everything lines up, you can nock that off your list.

Also, if your TPS (throttle position sensor) has completely failed or been unplugged, it can have the same side effect.



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[kevin kane]

tye;
I mis-typed. I hit the starter button and rolled the throttle to be able to see thru the stack and down the throat of the throttle body (I could see the valve heads and piston moving but there was no fuel going in at all.

I have been reviewing the Haynes manual and have a multimeter so I can begin looking there when I am back in town (I am on the road Mon-Fri so I only get to work on this on weekends). From what I have seen so far, there is not a ECU test per se but I will keep reading. BTW, where is the TPS located because I was running WFO when this happened?
Thanks;
Kevin

 

[tye1138]

Usually if there isn't any fuel, then no signal is getting to the injectors. That can be measured off the wiring harness where it hits the ECU.

One thing I do is stick my finger down the throttle body and cover the injector hole and see if I can feel any "puff" of air or liquid. If the injectors are not working at all, you won't get any puff. If you get some sorta puff, then its fuel line related.



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[kevin kane]

Amulo;

Do you know if the ECU change from year to year or from model to model (say a 996 v. a 748)? My 748 SPS is a 1999 model and I can't believe there are a lot of these floating around if they are year and model specific.
Thanks;
Kevin

 

[kevin kane]

I keep thinking it is an electical problem because of testing it with two different tanks and fuel pumps; the fuel is in the lines running to the throttle bodies because when I disconnect them they are full of gas.

I will try the "puff" test and I am already using a bigger battery that I charge before I do any of these tests so I continue to suspect the ECU or the TPS (where ever that bugger is located).

Kevin

 

[kevin kane]

Has this ever happened to you update

It was a faulty cam timing sensor...who knew?
Thanks for all of your advice and help.

Kevin