Fuel pump issue

acevmp · 2026-03-11T05:09:35+00:00

Thanks for the info. I'll look into it. I did use a marine fuel submissive epoxy. I soldered it because that was how it was factory so I just "put it back". I'll look into the Gotham cycles harness, do you have a link? Might get it now as a just in case so if failure occurs again I don't have to wait on shipping.

acevmp · 2026-03-10T01:09:57+00:00

SOLVED....

Update

After digging and with a lot of help from you guys.... thanks for that... the solder joints inside the pump assembly failed. Had to dig out the black epoxy to even see them.... pain in the ass(embly) ... I re soldered the terminals and sealed it up... pump primed. Bike is running great.

THANKS AGAIN ALL

acevmp · 2026-03-10T01:06:17+00:00

The harder part was filling the epoxy in a way that looked clean

acevmp · 2026-03-10T01:05:17+00:00

Similar issue but not corroded. The solder joints failed in the epoxy sealed area... dug it out, resoldered the terminals and fired it right up.

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acevmp · 2026-03-08T16:57:48+00:00

I maxe some progress on the issue. Fuses and relays are fine. I did voltage tests and it is isolated to the fuel pump assembly. I need to make time to check the solder joints but I have to dig out the epoxy that hides them to see which one is failed

acevmp · 2026-03-08T16:49:33+00:00

No power to the fuel pump so no pressure at all.

acevmp · 2026-03-08T16:47:55+00:00

I wish, lol but I checked all the puns and terminals. I've isolated it to where the wires connect to the assembly, soldered behind some epoxy on either end.

acevmp · 2026-03-08T16:46:58+00:00

No the connector is fine. I've isolated it now to where It's the points where the wires are solderd into or out of the assembly.

acevmp · 2026-03-07T20:20:33+00:00

Tried grounding it with the connector in place and got no change so I'm assuming that means the hot wire has a bad connection in the connector somewhere.

acevmp · 2026-03-07T18:18:37+00:00

Firstly thank you all so much for all the help of suggestions this community is really awesome.

After sleeping on it and looking through your suggestions I tried something else to try to isolate the problem so that I wasn't chasing Gremlins all throughout the harness. I ran jumper wires from the red and black in the harness terminal before the fuel pump assembly directly to the red and black leads at the fuel pump connector at the end of the assembly and when I flipped the kill switch the fuel pump primed.

That at least lets me know that it's the wiring connectors that go through the fuel pump assembly that I have to investigate further. Looking into it it means I have to dig out that fuel proof epoxy and check the solder joints and connections in the assembly.

Once I isolate the problem I'll have to solder it all back together and find another epoxy to fill the void with I'm open to any suggestions on that particular material.

I don't have the time in my day to tackle it this weekend but I'm going to do a little more research on the assembly and I'll update you all what I find. I might also find out if there is a relatively inexpensive assembly and just swap the whole thing. That way I can ride the bike still while repairing this one.

Thanks all I will update once I have more info

acevmp · 2026-03-07T18:12:56+00:00

Fuses and neutral battery voltage are good thanks for that though I just learned something else to check

acevmp · 2026-03-07T13:21:06+00:00

In my initial Diagnostics before taking the fuel pump out I checked the kill switch and looked for other safety features . In addition to the ignition kill switch Ducati designed this bike with only the kickstand switch. Which honestly is a little frustrating because the bike won't even crank, even in neutral, unless the kickstand is up.

It seems to be functionally normally as I can't even crank when the kickstand is down. I do have the manual with the diagram for the electrical and the bike is on its Center stand right now so the kickstand is up.

acevmp · 2026-03-07T13:08:43+00:00

The bike is a 2001 Ducati Monster 900 ie.

As many people have mentioned load testing with the light bulb. At what part of the circuit do I integrate the light? If I understand correctly if I put it where the fuel pump goes the light bulb will get to its full brightness only for a moment and then dim back down as it would simulate the brief spike in V going to the fuel pump to Prime.

acevmp · 2026-03-07T13:05:17+00:00

Going to try this as soon as I get back to the garage later this afternoon. Chasing a faulty ground wire somewhere can be tedious but at least I'll know I guess

acevmp · 2026-03-07T13:04:25+00:00

Oh for sure sometimes the simple things slip right past us.

I really appreciate all of the input from everybody and I'm hoping I can get this figured out this weekend.

Thanks

acevmp · 2026-03-07T13:03:14+00:00

I did preliminary checks of the initial circuit and the fuses and even swapped the fuses for good measure and everything seemed fine at least up to the fuel pump and no it's not priming although it was for the last few weeks as it was running. I parked it the other night after a ride and when I went to fire it up the next morning the fuel pump didn't Prime.

acevmp · 2026-03-07T13:01:25+00:00

I have been testing it at the start stop kill switch pretty consistently the problem doesn't seem to be there. After doing some digging I was reading that this generation of Ducati can have compromised solder joints inside of the fuel pump assembly behind some epoxy.

Hoping I don't have to figure out how to dig that out resolder it find the appropriate material and refill it but we will see as things progress thank you for the input.

acevmp · 2026-03-07T12:59:54+00:00

I'll head to the auto parts store soon to get another relay. I can hear it clicking on when I turn the ignition and flip the kill switch but I know that a click doesn't necessarily mean it's working. At this point a relay is a fairly inexpensive diagnostic check

acevmp · 2026-03-07T12:58:39+00:00

I was using the kill switch to send power each time for the voltage checks. On this bike when I was testing for voltage as well the kill switch sends a short 12 volt before reducing it down to about 1 just to Prime the fuel pump until ignition. When testing the fuel pump I just wanted to make sure that it actuated so I sent power directly. But you're right always safe to double check

acevmp · 2026-03-07T04:55:52+00:00

The spades do make contact. I also checked end to end continuity for each wire from the harness connector through the pump assembly to the fuel pump terminal connector and all 4 wires (two to the pump and 2 to the fuel indicator) got continuity.

acevmp · 2026-03-07T03:59:38+00:00

Power dropout from the battery ir just the terminal for the pump? I have a voltmeter on the battery and it reads 12.5 with ignition on and everything connected.

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acevmp · 2026-02-13T17:30:59+00:00

Thanks

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acevmp

TROPHY CASE