916 running way too rich

dan13

New member
Hi, I have a 916 which has started running very rich, fouling plugs, running rough, barely rideable..so far I have checked; Injectors, air filters, plugs, timing, timing sensor, TPS, coolant temp sensor. Both cylinders are affected. Any help welcome.
 

lambrettaboy

New member
someone will be along to give you some advice on what might be wrong shortly :)

in the mean time nice bike :thumbs:


forgot welcome to the forum :D
 

RedRichard

New member
Hi, does the 916 have two coolant temp sensors? my ST2 did exactly this and a change of sensor did the trick. On the ST one sensor switches on the radiator fan the other provides the ECU with engine temp info. Rich.
 

dan13

New member
Hi Rich, thanks for the reply, yes there are 2 sensors, I checked the 1 that sends to the ECU, I also tried adjusting the trimmer/potentiometer on the ECU it seemed to make a slight difference, I managed to get the plugs to be less sooty but when I adjusted it further it made them worse. I put some new pipercross filters in as an initial start point, I think I might try running the bike with the tank off to avoid any doubt of air flow, the bike uses way too much fuel, gone from 120miles per tank to 80! Any other ideas? Cheers, Dan.
 

Derek

Elite Member
Subscriber
Did it just become like this suddenly or after some work had been done? How did you check the coolant temperature sensor?. Like RedRichard I'd have put this as the most likely cause. The air temperature sensor would have a less drastic effect if it were faulty. You could try disconnecting the coolant sensor and see if there is any difference, the ECU should substitute a default value. If there is an improvement it's probably the sensor, if there's not it's something else.
An incorrectly set TPS could cause this but only if it had been set wrong. If it hasn't been touched you can rule that out.
I think the fuel trimmer pot goes round and round. i.e. When you reach full lean it goes off the end and comes back on at full rich.
The only other things I can think of are: The fuel pressure too high, I think that's very unlikely but still possible so is the pressure regulator working correctly?
Or the injector timings are too long but these are determined by the fuel map in the ECU EPROM. As a last resort you could try re-seating the EPROM. Sometimes a little oxidation on a pin interferes with the correct operation and re-seating restores the connection. With ignition off for at least 30 seconds, lift it out of it's socket a little and push it back down firmly. Remember to tape over the rubber grommet when you re-fit it to prevent water from getting in.
 

dan13

New member
Hi Derek, thanks for the reply, the problem came on suddenly, the fuel light came on (a bit early) and it started misfiring as if running out of fuel, I filled up but the problem remained, I checked the coolant sensor by dangling it in a pan of water and checked the resistance with an ohm meter as the water temp. increased the values were in line with spec. The one thing I did notice was the fast idle switch was stuck on which I freed off but don't know if this would leave a lasting problem. I can rule out the whole tps injector part as I put a replacement job lot on to see if that solved the problem. The ecu is a 1.6m does the trimmer roll over i.e. go leaner,richer, leaner as it is rotated, I understood it to have 270 deg. from fully rich at full anti clock to fully lean at fully clockwise. I haven't checked the fuel press. reg. yet maybe that's next. Any other suggestions warmly welcome, cheers, Dan.
 

brian91cfr

New member
If the bike starts ok when cold, and starts to play up when at temp i would check the
air temp sensor in the base of the headlight bucket/bracket.

brian.
 

dan13

New member
The bike starts ok but runs very rich when cold and hot, it seems that something is telling the ecu to chuck loads of fuel in or the ecu is telling the injectors to do it, I have an eprom chip for the standard pipes (it's got Termi's on and has had for years) is it worth switching them over to see if there is a diffference?
 

lidlika

New member
fuel filter maybe? ecu trimmer,does it have to be a certain voltage or give off a certain voltage?have you checked your earths?,also have a look at the connectors behind the battery from your rectifier,1 of mine had melted before, i dare say derek or brian will sort it out between them,hope you get it fixed soon.
 

dan13

New member
Haven't bothered with fuel filter yet as problem is too much fuel, checked connectors- all ok voltage is ok to the sensors (5v) The amount of fuel seems to be too much for the trimmer to rectify...
 

RedRichard

New member
Dan, the coolant temp sensor from some Fiat/Alfa engines is apparently the same, there was an article on the Ducatisti site which related to this, think it was some Punto models. Might be worth a trip to your local Partco etc and see if they can match you one up? What ever happened to the Ducatisti site?
 

dan13

New member
Hi RR, I think I saw the same article, the sensor is ok, I tested it for resistance at various temps and the ohm readings were ok, cheers, Dan.
 

dan13

New member
Hi, I'm back again, unfortunately I have not solved my little problem, I have changed the fuel filter, and fitted a new fuel press. reg. and still no joy. However I did discover that both the breather pipe and the drain pipe were blocked completely with old fuel gunk, I cleaned them out hoping this was the cause of my misery but no. Does anyone know if this has caused the problem, and if so what the problem may be, ECU? Thanks in advance, Dan.
 
Last edited:
Top