Finally pulled my '93 907 out from the back of the garage to try and get it running again. A few years back it just quit running - no spark. Tried getting it running a few times and then just decided to hang with my kids till they went off to college and/or find someone of the opposite sex to hang out with -both of which just happened so... .

Anyhow... the fuel pump wasn't priming so I troubleshot the problem down to the pump relay which was dropping 11 of the 12V across the relay contacts. I actually found a compatible relay without the 15A fuse up at the auto store for $10 which wasn't a bad price (Part No. R3177P at Advanced Auto if anyone wants to try it - all I can say right now is that it runs the pump to the priming point). So the pump now primes up but I still have the original problem of no spark.

I ohmed out the timing sensor and the rpm sensor and both are around 650m ohms.

I checked the coils and both are reading the same thing: ~1 ohm on the primary (between the contacts where the blue and green wires enter the coil) and ~3.14k ohms on the secondary (between the plug side and either contact on the primary). I checked the tech faqs and it shows a different reading so I think this may be my problem even though I find it hard to believe that I toasted both coils at the same time. Anyone have any readings that match what I see (1 ohm prim, 3.14k secondary)? Anyone know if I read the resistance at the wrong points?

Any input would be really appreciated.

Thanks. That's the tech faq I was referencing. I ordered a set of coils off ebay. They were for a 916 but says they will work on a 907.

Hopefully this is it. Bikes been sitting still way too long.

The 916 coils are the same as the 907ie ones. I used the ones of my 907 to help diagnose a misfire problem on my son's 916.
The fuel pump relay provides power to the pump, the injectors and the coils. So if the relay is faulty none of these will operate. The relay is closed at switch-on allowing the pump to pressurise the line then switches off after 3 or 4 seconds. It will then only switch on when the engine is turning and the ECU receives a signal from the timing sensors. On the P7, P8 and 1.6M ECUs signals from both sensors are required. Note that there is only power to the coils for the initial 3 - 4 seconds while the pump primes and then only when the engine is turning.
The ECU also uses the timing sensors to work out the spark and injector timing. If one or both of the sensors is faulty there will be neither sparks nor injection.
You can test the ignition amplifiers output to the coils by wiring a 12V bulb between the battery +ve and each of the coil trigger wires (green and green/black) in turn. The bulb should pulse on/off as the engine is cranked. If none of the coils are switching it's unlikely that both ignition amplifiers have failed, more likely a timing sensor or the ECU, although the ECUs are pretty robust.

New coils came in and they ohmed out same as the old ones. I put them on anyways. Still no spark.

Going after the 2 BKL3B ignition modules next. I was cranking the engine without the plugs in for a while when I was originally troubleshooting this a couple years ago so maybe without the load I did burn them out. If anyone knows where to get them on the cheap please let me know. I see a couple on ebay but they are a little pricey.

As far as the relays go I think they are ok since the 2nd relay that powers the fuel pump and ignition modules is working (have ~12v at the pump) and based on what I see in the schematic the 2nd relay will only receive power if the 1st relay (the one connected to the kill switch) is working.

I really hope this isn't the ECU.

Hi.

Check the earth that is common to the Ignition modules. From memory, this screws to the mounting plate, then from there, back to the frame under the fuel tank. No earth, no spark. The Ignition module will be a high power transistor. They are usually pretty tough unless you over drive them.

Look for the common points in the circuit. Earths, 12 volt rails etc. Replace the other relay too. If its been there since day 1, it is most likely feeling a little sad.

When it originally stopped, were you riding it, just had it serviced, let the kids play with it etc. The 2 pickups are easily mixed up (there is a post here somewhere about this). The effect of this is spark, but not when it is needed (TDC). Could this be the problem?

Maybe change both spark plugs, if they haven't been changed already. You never know?

Cheers.

Nick.

I managed to get a new ignition module but still no spark. I did get the plugs into another bike and they will spark so they are good. I also confirmed that the ground was ok and I did swap the timing and rev sensors around just for kicks even though no one ever played with them (at least not that I know of).

Just noticed something today that didn't make sense to me nor do I remember this happening before I parked the 907 a few years back... When I put the battery in and connect the power I can hear the fuel pump relays engaging ("click") even though the key and kill switch are not in the on/run position. The pump doesn't prime until the key and kill switch are on but still, the relays are engaging as soon as battery power is connected to the bike. Looking at the schematic I wouldn't think these would engage until the key was on and the kill switch was in the RUN position. Could anyone confirm with their 907's if this is the case (relays engage as soon as power to battery is connected). I'm thinking again that I may have a bad ECU. Heck, I've replaced everything else .

you are dealing with a feedback issue from a bad ground, check all your grounds and clean them up

Checked the grounds and all is ok. Poked around some more and found that the fuel pump relay I substituted for the stock b047 / 12v-2335 was actually a normally closed relay so that's what was causing the 2nd relay to kick in.
Trying to track down the correct relay now (Ducati dealer is looking and I'm trying to cross ref one on the web). If anyone knows of a good source please let me know. Prefer new but if I have to I'll grab a used one off ebay.

I found a fiat recycler that had 10 of the original style relays for 2 buck a piece bought them all
I'm in Pa let me know if you can't find any

Thanks higgy. While I was out running around today I ordered 2 relays from the auto store that may work. They'll be in tomorrow or Monday. If they don't work I will definitely hit you up for the Fiat relays. Actually that's the one we cross referenced the old one to - a 1973 Fiat 124 or something like that. Either way, I pre-paid for them so I'll see if they work first.

When I got home I did take the one old / original relays apart, cleaned up the contacts and slapped the things back into the bike. She fired up after about 15 secs of cranking so that is definitely the problem. The relays are now intermittent with starting so I'll wait for the new ones to come in before taking the 907 out Hey, 1st time she ran in about 3 years. Sounded soooooo good. Can't wait to get out on the road.

any decent relay should do the job fused or not

Well, not an exact match with the relays but all I had to do was switch the wires between blades 30 and 86 - not a big deal.

She fired right up. Aired up the tires and went for a quick ride around the block. Gas was a little old but ran ok.
The relay was a BWD R3245 from AutoZone (Normally Open, 5 blade, dual 87 relay). $12. Switching the wires around only took about 5 min.

Thanks for all the help. Love this website.

Fantastic news.