Hey everyone, glad to be here! I recently picked up a Ducati monster 620 in non running condition. The old owners rode it often until the bike didn't start one day, so they took it into the dealer to get a diagnosis. They were told that the fuel pump had gone bad and bought a replacement, but never installed it. I tested the old pump just to be sure that was the issue, and found that it was seized. After installing the new pump (chinese) and replacing the battery, I decided to try to fire up the bike. I turned the key and primed multiple times and the pump sounded like it was doing its job. Unfortunately though I primed and primed and applied the choke, the starter just cranked and cranked and the bike never fired. I put the fuel hoses into the pump assembly correctly and the lines were getting fuel, so I suspected that the injectors were clogged. Luckily they didn't store the bike with fuel in the tank but one of the injectors didn't click when tested. I've already cleaned the injectors with an ultrasonic cleaner while opened up and sprayed carb cleaner directly through them. The spray pattern looked great and they now seem to open as they should. Resistance was 15 ohms for each injector, but only 8.8 volts got to each wire harness going to the injector. When I crank the starter I can hear the pump but no fuel comes through the injectors. Yes I did prime the pump a bunch of times and fuel is in the lines, it dumps out when I remove the injectors. Oh yeah, the bike did fire up for me when I poured a little fuel in the intakes. It runs just fine like that but obviously won't stay running without the fuel injectors doing their job. When I hooked up 12 volts directly to the injector after cleaning and reinstalling, the injector sprayed fuel as it should. Where should I look for the issue that is causing not enough power to get to the injector?
I'd start by replacing the fuel pump relay. It supplies power to both the fuel pump and the injectors.
Hmm, it seems strange to me that the pump works fine but the injectors don't. Maybe it sometimes only affects one or the other?
Replace it anyway. They are a well known failure point and they are cheap enough. Maybe the injectors are more susceptible to a low voltage than the pump is.
Alright will do. Where would be a good source for a replacement? (part number, or from another bike but equivalent)
They are a generally available standard part throughout the motor industry. Just take it to a local motor factor or auto electrician and ask for an equivalent. Cost about a fiver.
I had a similar problem but the other way round. Not enough volts at the fuel pump. The wire from the relay gets spliced somewhere in the loom into 3 to power pump, coils and injectors. I spliced in a new wire from the relay to the pump. That fixed it.
Alright, I'll try to buy a relay and check the wiring. I think these would work for me but I'm not with the bike right now, do all those numbers on the relay need to be the same as the original? https://www.amazon.com/Purpose-Auto...Y0SJELLeqLWRgdK58lqcSod-V5gaAoxsEALw_wcB&th=1
that's the one apparently, (54140031A) another option:- https://www.ebay.co.uk/itm/13418248...gyq9EtCRF2&var=&widget_ver=artemis&media=COPY
I had to do a very similar thing . I traced a lack of continuity inside the harness but I've never fathomed how or why it happened ..... it's not like it's flopping around , is it ? ..... it's well strapped to the chassis . But it just ..... happens with age apparently .
Five pin eh? I'm out of town right now but I wish I could check whats on the bike now, was pretty sure it was a four pin...
i quoted you the part number above for an injected Monster 620, and it co-relates to the EBay item i added. It's not the "square" relay as used on earlier bikes.
Alright thanks, the wiring is really what I suspect it is, the fuel pump was getting 12 volts and pumping fine. I’ll let you all know what my findings are.
How are you measuring this? - are you backprobing the injector with a normal digital multimeter? - if so, then you won't be measuring the full voltage - the digital multimeter will be measuring the pulse-width modulated output, with the injector being switched on and off rapidly, and 8.8v wouldn't surprise me I don't think. To see the full 12v signal from the ECU/ignition amplifier you'd need to measure with an oscilloscope or similar high-speed capture device. Mike
There should be the same 12v at each injector, the coils and the fuel pump. They are all supplied from the same relay. The injectors are fired by the ECU providing a grounding pulse.
Yes - you're entirely correct Derek! - particularly given previous projects, I knew that! apologies just a brainfart there
Issue isolated! Not found or fixed, but somewhat isolated from the dozens of other electrical gremlins and that could be causing this. I did find the splicing which had a corroded wire running into it. I stripped that wire until I found where the discoloration ended and rewired. I’m was still only getting 8.8 volts to the injector wire harness so I decided to do some more testing. I put one of my multimeter prongs to the frame and the other to the positive side of the wire harness, and got 12 volts. Same deal with 2nd wire harness. I’ve found that the ground wire for the wire harness isn’t grounding properly at the ecu or ecu plug. What would be the more common issue? Is it possible to open up the ecu plug for a cleaning?
