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Discussion Starter #1
Well, that did not last long. I replaced the fuel pump in July and the bike started right up. Next time I went to ride, it would not start again. Cranked, but wouldn't start. Thought maybe something came loose in the tank. So I pulled the fuel pump assembly back out. Did not see anything wrong with it. Put it back together and it started right up. Bad weather and other commitments for numerous weekends, so the bike sat in the garage. Went to start it today and it won't start again. Same issues as before. I can hear the relays clicking, but don't hear or see anything happening in the tank.

A friend suggested I check the fuses for a hairline crack. Instead, I replaced all the fuses. No difference. I lifted the tank and disconnected the wiring pigtail from the harness and connected my multimeter to the fuel pump wires from the wiring harness. When I turn on the ignition I am seeing around 14V for about 2 seconds. That is what I would expect. Connected the mutilmeter to the pigtail from the tank and I am seeing 9 ohms. No clue what it should be, but at least it is not open.

One other thing that I did not think was related, but just maybe. Before all this started, I hit a really bad bump in the middle of a turn. Nearly threw me off the bike. Rode the bike home (about 30 minutes) with no issues. As I was pulling into my subdivision, the bike died and would not start. Since it was mostly downhill, I started pushing the bike home. After a few minutes, I sat on the bike to take a rest. Thought I try starting it again and it fired right up. Could I have broken something on the bike when I hit that bump?

Nick
 

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There might be a connection. I'd start by going through all of your bike's...connectors. You may have jarred one loose when you hit that bump.
 

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A friend suggested I check the fuses for a hairline crack. Instead, I replaced all the fuses. No difference. I lifted the tank and disconnected the wiring pigtail from the harness and connected my multimeter to the fuel pump wires from the wiring harness. When I turn on the ignition I am seeing around 14V for about 2 seconds. That is what I would expect. Connected the mutilmeter to the pigtail from the tank and I am seeing 9 ohms. No clue what it should be, but at least it is not open.

Nick
Are you sure about that reading? I just happen to have a fuel pump assembly on my kitchen counter (I hope to get it back into the bike today). There are two pairs of wires in that pigtail. The white/black pair go to the fuel level sender, the red/black pair to the fuel pump. Are you sure you got across the right pair?

My new Bosch pump reads 0.002 Ohms and my old still-running one reads 0.004 Ohms. It should be low considering what one is measuring is the resistance of a longish copper wire. These measurements were taken with my good quality Fluke digital meter. In my experience, even the el-cheapo Chinese meters of the past few years are pretty good, but I'd suggest making the measurement again with a different meter just to be sure there's not a problem with yours.

If you still get 8 Ohms across the red/black pump lead wires at the pigtail, I think something is wrong with either the pump or the connection to it. Some (in the Monster section) have had problems with the potted part of the pigtail where it feeds through into the tank.
 

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Disassembled as you described, run 12V to the pump and ground it to see if it works. If so, then run from the connectors that normally go on it. You can get voltage through a relay when the rely won't pass enough current to run the pump. There are 2 points of failure that are most common, relay and inline connections to the pump. You have it far apart to identify the problem. You identified that the relay is being properly energized already. So, the connection that the relay plugs into and any inline connectors and the $5 relay, if the pump runs.
 

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Retired Pipe Polisher C2H6O+
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Try this. Turn the key on and with the tank lifted wiggle the wires where they go into the bottom of the pump flange. Listen for the pump to prime. It’s a simple test to see if the wires are broken at that point. I went through this on both my Monster and ST3.


Sent from my iPhone using Tapatalk Pro
 

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Discussion Starter #6
Are you sure about that reading? I just happen to have a fuel pump assembly on my kitchen counter (I hope to get it back into the bike today). There are two pairs of wires in that pigtail. The white/black pair go to the fuel level sender, the red/black pair to the fuel pump. Are you sure you got across the right pair?

My new Bosch pump reads 0.002 Ohms and my old still-running one reads 0.004 Ohms. It should be low considering what one is measuring is the resistance of a longish copper wire. These measurements were taken with my good quality Fluke digital meter. In my experience, even the el-cheapo Chinese meters of the past few years are pretty good, but I'd suggest making the measurement again with a different meter just to be sure there's not a problem with yours.

If you still get 8 Ohms across the red/black pump lead wires at the pigtail, I think something is wrong with either the pump or the connection to it. Some (in the Monster section) have had problems with the potted part of the pigtail where it feeds through into the tank.
Yeah. That is what I read with my Fluke 26 III across the red and black wires. Did not test the fuel level sending wires...
 

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Discussion Starter #7
Try this. Turn the key on and with the tank lifted wiggle the wires where they go into the bottom of the pump flange. Listen for the pump to prime. It’s a simple test to see if the wires are broken at that point. I went through this on both my Monster and ST3.


Sent from my iPhone using Tapatalk Pro
Yep. Tried that. Disconnected the wires and twisted on of the connectors 360 degrees too.
 

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Discussion Starter #8
OK. About to lose my mind on this one. Put the key in the ignition this afternoon, turned it on and heard the fuel pump prime. Hit the start button and it fired right up. Have not touched the bike since yesterday. The ONLY difference is the temperature. It was around 60F yesterday and 83F today. When I first had this problem on the 4th of July, it would not start in the morning but started late in the afternoon. Maybe just coincidence, but could this somehow be temperature related?

I'll try it again on Sunday morning before heading to church. It should be around 50-55F.

Nick
 

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Retired Pipe Polisher C2H6O+
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Yep. Tried that. Disconnected the wires and twisted on of the connectors 360 degrees too.


It’s not the connector that’s the problem. It’s where the wires actually go through the molded seal in the baseplate for the pump assembly.

And yes, the problem would come and go but it’s not temp related. Twice I thought I’d fixed the problem because it would start working and after getting 25 miles from home it would quit and I would be stuck.


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I was going to suggest what DuckMan was suggesting -- a bad conection inside the tank flange.

On another note, we helped a gent at the Dragon with an ST3 that wouldn't "prime" with initial key-on. We looked at the relays, connectors under the tank, and THEN, I had the idea to slap his tank when turning the key to ON. The pump ran. So maybe your pump's brushes are old/weak, and you should replace the pump. Try it next time U have no pump sound. Give it a few firm open-palm slaps.

I do the same with my Keurig, and it works with that POS, too!
 

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Discussion Starter #12
OK. About to lose my mind on this one. Put the key in the ignition this afternoon, turned it on and heard the fuel pump prime. Hit the start button and it fired right up. Have not touched the bike since yesterday. The ONLY difference is the temperature. It was around 60F yesterday and 83F today. When I first had this problem on the 4th of July, it would not start in the morning but started late in the afternoon. Maybe just coincidence, but could this somehow be temperature related?

I'll try it again on Sunday morning before heading to church. It should be around 50-55F.

Nick
Well, that experiment failed. When I went out this morning it was 58F and the bike fired right up...
 

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Discussion Starter #13
It’s not the connector that’s the problem. It’s where the wires actually go through the molded seal in the baseplate for the pump assembly.

And yes, the problem would come and go but it’s not temp related. Twice I thought I’d fixed the problem because it would start working and after getting 25 miles from home it would quit and I would be stuck.


Sent from my iPhone using Tapatalk Pro
So if it is the wiring assembly, how do I fix this problem? Could the problem with the wires be inside the tank, and not the pigtail that hangs out the bottom? I'm going to order some female AMP connectors so I can rig up a better connection to the pigtail with my DMM. Then I can wiggle the wires around and look for changes in the reading on the DMM.
 

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Discussion Starter #14
I was going to suggest what DuckMan was suggesting -- a bad conection inside the tank flange.

On another note, we helped a gent at the Dragon with an ST3 that wouldn't "prime" with initial key-on. We looked at the relays, connectors under the tank, and THEN, I had the idea to slap his tank when turning the key to ON. The pump ran. So maybe your pump's brushes are old/weak, and you should replace the pump. Try it next time U have no pump sound. Give it a few firm open-palm slaps.

I do the same with my Keurig, and it works with that POS, too!
I replaced the pump back in July and thought that fixed the problem. But Nooooooooooo.

Interesting adventure you had at the Dragon. I was wondering if my problem could be some form of vapor lock. I'm throwing in the towel for this weekend, but more testing to come next weekend. And I'll try the tank slapping. (I thought that only worked with TVs LOL.)

Nick
 

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So if it is the wiring assembly, how do I fix this problem? Could the problem with the wires be inside the tank, and not the pigtail that hangs out the bottom?
There have been issues with some of the tank flanges -- the wires pass thru from outside to inside the tank, and the wires break or are intermittent "inside of the flange". This is what DucMan was suggesting, and it sounds like he had a bad one on his ST3 (and a Monster).
 
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I had a similar problem with my 907 , long story short........ intermittent relay !!! Used one from a car motor factors ! 1/4 the price of a ducati part .
 

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Discussion Starter #17
So if it is the wiring assembly, how do I fix this problem? Could the problem with the wires be inside the tank, and not the pigtail that hangs out the bottom? I'm going to order some female AMP connectors so I can rig up a better connection to the pigtail with my DMM. Then I can wiggle the wires around and look for changes in the reading on the DMM.
I rigged up this test connection with some AMP female connectors and wrapped some copper strands tightly around to get a good connection. I slipped the leads from my Fluke DMM onto the pigtail from the tank and then wiggled the leads to ensure I had a good connection. I'm reading 2.9 ohms and it did not vary with the wiggling. I then moved the pigtail around and saw some variations in resistance, about 1 ohm. Then I pushed the wires towards and away from the tank and saw about the same 1 ohm change. So I did not see anything that leads me to believe the wires might be broken. However, if there is a problem with the wires where they are potted, I can't think of any way to test that. And I can't test the wires inside the tank without removing the flange...

Nick
 

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