Been a while since I've been on.We had this storm last week that left me with no power or internet for 8 days! . I also couldn't get my bike out to ride because the roads were all blocked by down trees and electrical wires.So,Monday night I finally got out , had a great ride and when I got home the bike stalled in my driveway as I was opening the fence gate. It was the fuel pump fuse.It blew 2 years ago too and I thought it was kinda odd because the pump was new in November  2017 and only has 11,000 miles on it.I replaced the fuse and took it out last night and got 5 miles into my ride when the new fuse blew ! I replaced it on the side of the road went 1000 feet and it blew.Had to get this thing home so I put in a 10A fuse to see and it got me home so it's not a short. Any ideas why this would happen ? The pump was a Euro Moto Electrics replacement for the original pump and not cheap.When she is running she runs GREAT ! Can using a 10 or higher amp fuse hurt things?

NEVER a good idea to fit higher rated fuse,Mabe the fuseholder box is the problem.OR is return fuel valve partially blocked.

It seems to always happen when it is very hot out.It was above 90 degrees F all times it blew

Build up of residual heat can show up,poor/loose connections especially in older wiring causing fuse to fail.Fitting a higher rate fuse can overcome this problem BUT
this increases the risk of fire in the wiring.A fuse is a SAFETY item.Run a few tests
with your multimeter.An old trick is to use a lower rated fuse expose the wiring loom
turn on ignition pull/wiggle wiring/start bike,watching for a flash/arc.This is done in the dark.Sounds crazy but it works.Stay safe,enjoy life

You could PM Arlina she is a wizzard with wires

A fuel pump armature can tighten up and blow fuses. For test purposes you can get a circuit breaker fuse that is resettable, they are a little bit taller and might not fit under the cover.
Regards Martin

That fuse also protects the circuit for the temperature sensing unit. Since it only happens on hot days, hopefully just a loose connection there.

Go down to Harbor Freight and get one of these guys:

https://www.harborfreight.com/30-amp-automotive-fuse-circuit-tester-67724.html

It will allow you to see how much current the fuse is seeing.  By disconnecting the stuff in the fuse's circuit, you can see what is causing the problem.  I have one and it's very useful.

Thank you all for your input .Now I have a direction and I can begin to sort this mess out. Luckily I have other bikes to ride while I figure this out.

Another quick option, replace the fuse with your multimeter set to Amps and the tank unplugged, the reading should be very low while cranking, if high it looks like the temperature sensing unit circuit. I spose you would want the 20 Amp setting, and put it straight back to Volts as soon as you're finished.

If you get a reading with the ignition on before pressing the start button, there might be a slight short in the wiring.

G'day All,
On a recent 4 to 5 day ride a fellow forumer experienced the same problem.  We found the the fuse pump circuit was drawing about 7 to 8 amps. On my K100 the same circuit was drawing about 2.2 to 2.3 amps.
After some checking, we found the problem was caused by 3 possible issues:-
1. A blocked or partially blocked fuel pump 
2. A blocked or partially blocked fuel filter
3. A possible dodgy fuel tank connector.

After replacing the fuel filter, fuel pump and connector, the current draw for the pump went down to about 4 amps, low enough for our mate to get home. The 4 amp draw still suggests that there is a blockage in the fuels system.
Hope that helps.
Cheers
Tom

Tom KSR wrote:G'day All,
On a recent 4 to 5 day ride a fellow forumer experienced the same problem.  We found the the fuse pump circuit was drawing about 7 to 8 amps. On my K100 the same circuit was drawing about 2.2 to 2.3 amps.
After some checking, we found the problem was caused by 3 possible issues:-
1. A blocked or partially blocked fuel pump 
2. A blocked or partially blocked fuel filter
3. A possible dodgy fuel tank connector.

After replacing the fuel filter, fuel pump and connector, the current draw for the pump went down to about 4 amps, low enough for our mate to get home. The 4 amp draw still suggests that there is a blockage in the fuels system.
Hope that helps.
Cheers
Tom

I'll go with this, good start to find the bug.

So now I know what to look for and I am going to buy that fuse testing tool from the Chinese crap store. With any luck I'll get it back in service to be able to take it up to my Camp in the Adirondacks in early September on a 2500 mile ride.Thanks again for all your help everyone ,this forum is a lifesaver !

I bought that fuse circuit tester and tested the circuit yesterday . It is drawing 8.3 amps while running. I'm going to take the fairing off and get at the temp sender over the weekend and see where the numbers go when I disconnect it while she;s running . I'm hoping this is the cause . I'm thinking it is because the pump & filter were replaced 10,000 miles ago and I have run the bike all the time so it never had old or bad fuel in it .This problem has happened 3 times and always during very hot weather .

Just curious, what is the current draw with the tank disconnected? 

I have never checked the draw on any of my fuel pumps, but 8.3 amps sounds a bit higher than I would expect.

Point-Seven-five wrote:Just curious, what is the current draw with the tank disconnected? 

I have never checked the draw on any of my fuel pumps, but 8.3 amps sounds a bit higher than I would expect.

I'll run it getting it warmed up then disconnect the tank wire and check with the ign on  and see

So, I just ran it and had 8.8 - 9.1 with the tank wires hooked up  . I unplugged it and put the key on and got 0.1 as the reading for a moment then 0 . cleaned the contacts at the plug and put it back together,started the bike and got the same 8 - 9 amp reading so now I'm thinking it's in the tank . Fuel filter clog ? or bad pump ? With only 10,000 miles on them it seems odd to me.

That's close to 100 Watts of power draw. That's way too high for a fuel pump. I'd guess its a mechanical problem with the pump although it could be a clogged filter.

Maybe repeat the test with the start button pressed. Fuse 6 gets power from the fuel relay only after the start button is pressed, so the reading should be 0 with only the ignition on.

daveyson wrote:Maybe repeat the test with the start button pressed. Fuse 6 gets power from the fuel relay only after the start button is pressed, so the reading should be 0 with only the ignition on.

So I repeated the test and really cranked it over with the tank wires disconnected.The circuit tester was jumping all over the place . Then I hooked up the tank wires and ran it and it still jumped around a lot but then settled down to the high 8 low 9 range again.I giggled the wire to the sensor and the tester was all over the place again then the fuse blew.So,now I'm thinking a short or perhaps a relay problem ?

G'day All, Would it be worthwhile to measure the current draw with the fuel line disconnected from the pump? If the current draw is still about 8 amps, that would indicate a pump problem. If the current draw is about about 2 amps, that would indicate a good pump meaning that there could be blockage elsewhere, i.e. fuel filter or collapsed fuel line.
As stated before, the current draw on my K100 is 2.2 to 2.3 amps.
Just a thought.
Cheers
Tom

Wow, don't need a coffee to wake up after reading this one.

Yep, could be pump. Another thought, wiggling the wires should not have affected the tester but it did, so a short in the wiring is a possibility.

Remove the fuse. Remove the fuel injection relay and put a jumper wire from 30 to 87b (the one closest to the centre) Remove the temperature unit and unplug the pump. Put your multimeter where fuse six was, set to 20 Volts. It should read 0 Volts, if it reads 12 Volts, there is a short in the wiring. If 0 Volts wiggle the wires to see that it remains at 0. The wires to the pump, or temperature unit, or fuel relay. This way you won't blow fuses or have excessive current heating the wiring (you have 8-9 Amps with a 7.5 Amp fused circuit)

I think you're saying the tester was affected by wiggling the pump wire and the temp wire,  what they have in common is the fuse and the wire to the fuel relay. Check the wiring and the connections are clean, tight and fully pushed home.  From the relay to its connector,  and the connector to the wire, and the fuse box. If it blows again,  one of the wires ends might even feel a bit warm.

Important, remove the fuse first (the circuit should not be closed)  and remove the jumper wire as soon as the test is finished.

daveyson wrote:Wow, don't need a coffee to wake up after reading this one.

Yep, could be pump. Another thought, wiggling the wires should not have affected the tester but it did, so a short in the wiring is a possibility.

Remove the fuse. Remove the fuel injection relay and put a jumper wire from 30 to 87b (the one closest to the centre) Remove the temperature unit and unplug the pump. Put your multimeter where fuse six was, set to 20 Volts. It should read 0 Volts, if it reads 12 Volts, there is a short in the wiring. If 0 Volts wiggle the wires to see that it remains at 0. The wires to the pump, or temperature unit, or fuel relay. This way you won't blow fuses or have excessive current heating the wiring (you have 8-9 Amps with a 7.5 Amp fused circuit)

I think you're saying the tester was affected by wiggling the pump wire and the temp wire,  what they have in common is the fuse and the wire to the fuel relay. Check the wiring and the connections are clean, tight and fully pushed home.  From the relay to its connector,  and the connector to the wire, and the fuse box. If it blows again,  one of the wires ends might even feel a bit warm.

Important, remove the fuse first (the circuit should not be closed)  and remove the jumper wire as soon as the test is finished.

Thanks for this great information.I was planning to take this bike up to my camp on a 2 week ride but have decided to take "old Reliable" my 1975 Moto Guzzi 850-T instead.I need to get out on a motorcycle trip to escape from this damn Covid garbage .So I'm going to shelve this repair until I return from this trip in the beginning of October.At that point I am going to focus on it and get it resolved.I will start with your test and take all the fairings off and have a very close look at all the wiring and connections.I have some spare relays if needed and an old wire harness for stuff I may need.I really appreciate all the help I have gotten here,Thanks , Ed (yamaguzzi)

Tom KSR wrote:G'day All, Would it be worthwhile to measure the current draw with the fuel line disconnected from the pump? If the current draw is still about 8 amps, that would indicate a pump problem. If the current draw is about about 2 amps, that would indicate a good pump meaning that there could be blockage elsewhere, i.e. fuel filter or collapsed fuel line.
As stated before, the current draw on my K100 is 2.2 to 2.3 amps.
Just a thought.
Cheers
Tom

Thanks,I'll also try this test when I return from my trip up to my camp.

Does the fuse circuit tester plug into the fuse socket, and then you put a fuse in the tester?

Yes that is how it works .

Thanks, that's pretty nifty.

Yes, it's a great tool for troubleshooting because it's easy to plug in and read how much current is actually going through the circuit without disrupting the wiring.. 

It is nice to have because to read current you need to disconnect something to insert the ammeter.  This little device makes it really easy to do.  By adding a separate digital voltmeter and a beeping continuity tester you'll have all the tools you need to troubleshoot almost every electrical problem you'll ever run into.  It's nice and small so I can carry mine with me when touring.

I got the one that has the adapters for all three type plug in fuses so I can use it on cars too.I'm going to make an adapter so I can also read old style glass tube fuse circuits and the ceramic VW type on my Moto Guzzi and older BMW R60/5 .