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 Help, fuel pump fuse keeps blowing. 
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Test Rider
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Joined: Thu Mar 05, 2009 2:33 pm
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Location: Hillcrest
Post Help, fuel pump fuse keeps blowing.
Hey Guys,

Tried to go for a Sunday ride and got as far as the driveway! Fuel pump fuse 15 amp keeps blowing. This is out of nowhere....been riding the bike everyday for a month w/ no issues. Before I get my volt meter and take things apart....any known issues with my 95 900 SP fuel pump fuse blowing. (I posted this on the Ducati.MS forum too)

***UPDATE***

Before taking out my volt meter I did some investigating for obvious faults. I did find one of the black wires under the tank for the pump flattened and some insulation gone.(there were two and assuming one of them is the ground) It must have been sandwiched between the frame. I isolated the wire and taped it up temporarily. Here is the weird thing.

The pump is running fine with the tank up and unlatched. As I bring it down everything is still good. I hook the latch to the frame and as soon as I latch it down the fuse blows! I looked for 30 minutes to see what wire/relay can be "catching" or crushing when the tank if latched and couldn't find anything. I even pulled the wiring for the pump away from the frame or anything metal. I did this test while my buddy watched 10 times! I'm glad I have a box of 50 15 AMP fuses. Does the latch on our bikes complete some type of circuit to ground? Are there wires attached to it inside the tank for the latch? I'm just really dumbfounded. I also tried leaving the unlatched and just using my body weight to push the tank down and fuse doesn't blow. SO I'm pretty sure it's not a physical issue causing the problem. :cry:

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1995 900 SP ( Black w/ red frame)
88 Dinan M5 - Euro Restoration
09 Aprilia Mana 850


Sun May 31, 2009 9:56 pm
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Joined: Thu Apr 23, 2009 7:44 am
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Location: Point Loma
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shoot. If I had time I'd go over and help you but I'm working til 5 tomorrow and got to meet up with some people in Rancho area right after... :cry:

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-Charles
2010 Aprilia RSV4R


Mon Jun 01, 2009 12:15 am
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SloAss848 wrote:
shoot. If I had time I'd go over and help you but I'm working til 5 tomorrow and got to meet up with some people in Rancho area right after... :cry:


No worries, I'm off Monday so I'll have all day to solve the mystery. Just my luck all Duc bike shops are closed Monday! :roll:

I found an interesting fix for now, I put electrical tape on the tank where the metal catch makes contact when "locked" down. No more blowing fuse but I'm afraid this may be a dangerous band aid to the issue. Something inside the tank may be shorting out and when the catch makes contact with the tank body....it completes the circuit and pop! Wish I paid more attention in electrical 101.

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1995 900 SP ( Black w/ red frame)
88 Dinan M5 - Euro Restoration
09 Aprilia Mana 850


Mon Jun 01, 2009 12:21 am
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Joined: Thu Apr 23, 2009 7:44 am
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Location: Point Loma
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haha being an electrical engineer, I probably could help you with it. I would just hesistate to take your whole bike apart. I couldn't imagine there being any form of electricals on the latch that the bike is looking for as a check to make sure the tank cover is down (car -> hood idea). that's just unneccessary on a bike...you may have to take off your lowers and check under the tank, see if there are any stripped wires underneath touching the tank as well. Trace the frayed wire(s) from the pump to the fuse see if you have any additional breakages.

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-Charles
2010 Aprilia RSV4R


Mon Jun 01, 2009 8:19 am
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Post 
SloAss848 wrote:
haha being an electrical engineer, I probably could help you with it. I would just hesistate to take your whole bike apart. I couldn't imagine there being any form of electricals on the latch that the bike is looking for as a check to make sure the tank cover is down (car -> hood idea). that's just unneccessary on a bike...you may have to take off your lowers and check under the tank, see if there are any stripped wires underneath touching the tank as well. Trace the frayed wire(s) from the pump to the fuse see if you have any additional breakages.


I guess I never asked you what you did on our last ride together huh? I may have to have you over more often since electrical gremlins seem to be common on older Ducs. :egrin: I trust your suggestion and will try tracing the wire today. However, I wanted to know what your thoughts were on my temporary fix? Tape on the front of the tank is not going prevent the tank from coming down lower, possibly pinching a bad wire right?

My buddy in the Army works on Apache helicopters and mentioned the fuel tanks on most vehicles have to be grounded somehow. He believes there are faults in the fuel pump wiring inside the tank and the tank touching metal completes some kind of short circuit issue that may be causing the fuse to blow. Unfortunately he lives in Alabama now. haha.

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1995 900 SP ( Black w/ red frame)
88 Dinan M5 - Euro Restoration
09 Aprilia Mana 850


Mon Jun 01, 2009 10:08 am
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He is correct. The fuel moving around in the tank can create static charge that needs to be dissipated...usually via a ground. He is also correct, unfortunately, that there is a possibility of wiring faults within the exposed area of the pump that is INSIDE the tank. But, because that would be a bit more of a hassle, I would suggest you check all the associated wiring that goes to your fueling system. I would look for wire insulation degradation near the connectors. Give everything a light tug to make sure there's nothing cutting in and out. At that point its a question whether you want to extract the pump to check it or continue to check the rest of the wiring harness. I don't think the electrical tape will be much of an issue, for short term solution.

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2010 Aprilia RSV4R


Mon Jun 01, 2009 11:53 am
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check the ground underneath the bike around the stator. Had a similar problem on my 748. Simple ground wire was exposed and touching frame. Since it was out of plain sight, it took me awhile to figure it out.....good luck.

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JOHN

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Mon Jun 01, 2009 7:23 pm
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Thanks, going to do more troubleshooting in the morning but, look what I discovered! My tank in electrified with ignition on! I think my problem is inside the tank now. Test light is getting voltage at all bare metal surfaces. So far all grounds outside are good

[img][img]http://e28-535i.com/upload/SANY0289.JPG[/img][/IMG]

[img][img]http://e28-535i.com/upload/SANY0292.JPG[/img][/IMG]

[img][img]http://e28-535i.com/upload/SANY0291.JPG[/img][/IMG][/img]

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1995 900 SP ( Black w/ red frame)
88 Dinan M5 - Euro Restoration
09 Aprilia Mana 850


Mon Jun 01, 2009 11:21 pm
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Post ***UPDATE***
Finally got the fuel pump assembly out. tested pump, it was fine. Replaced filter and checked all wiring....found no faults. :angry:

Put everything back together and tank no longer lights up the test light and fuse not blowing! I'm frustrated because I didn't find any obvious faults and even though problem has been resolved.....it's cause is still unknown and will still haunt me when I'm 100+ miles away from home and it happens again. Thanks for all the advice.

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1995 900 SP ( Black w/ red frame)
88 Dinan M5 - Euro Restoration
09 Aprilia Mana 850


Tue Jun 02, 2009 7:26 pm
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