Fuel pump/starting trouble

[spextattoo]

Hello everyone,
My name is Peter,I have a 1985 K100 rs,I live in Austin Texas. Over the last months I have been working on the bike,doing maintenance and some mods to make the bike more to my liking. I took of all the plastic fairing cases etc.
Rebuild water/oil pump,spine lube,changed all the fluids.modified the blinker relay,rebuilt the brakes etc etc Cleaned and scrubbed and cleaned some more.So I got the bike going and drive it for the first time,it runs great,till I see the temp warning light come one after maybe a mile. Pull over and let it cool off for an hour and drive back home another mile or so. Temp light comes on,shut it off,let it cool again .
I got a new thermostat,coolant sensor, a used cooling relay,removed the vacuum sensor and plugged the barb on cyl 1 on the throttle body.
Installed all that,new coolant for Alu engines.
Now the bike turns over but won't start.I pull the fuel line to the fuel rail ,hit start,but no fuel squirting out the fuel line....
open the tank ,took the fuel hose that goes to the top of the pump off the filter,pushed start... at this time I should have fuel squirting out of the hose,correct? but nothing.It's a new pump,it worked before,has maybe 5 miles on it ,checked the fuse which seemed good,replaced it just to make sure.Even put the old cooling relay back in to make sure that is not the issue,but that shouldn't even have anything to do with the fuel pump,right? So I checked all the fuses and turns out I don't get any power to the fuel pump fuse (fuse6),but I have power to the 4 pin plug,how does that make any sense? I checked the back of the fuse panel and it all looks fine.

 

fuse1  12.88V

Fuse2   6.5

Fuse3   11.66

Fuse4  0V

Fuse5  0V

Fuse6  0V

Fuse7  7.5V



4pin plug to tank:

green/white-brown/black 10.98V

green/white-brown/white 10.97V

green/white-brown 10.87

green/white-2nd brown 0.0V

This is with ignition turned on ,battery is holding a charge 12,7 V

I thought I was gonna jump the pump (just for a second to see if it is running)

from right side of fuse 4 to left side fuse 6,but since I didn't have any power on the fuse locations,I didn't even try.

Put everything together after I pulled the fuel pump relay to inspect and clean contacts,pushed start 3-4 times and nothing,any advice is greatly appreciated,anyone savvy with this stuff? THANX A Bunch

[Scott_]

There should be only 1 solid brown wire, that is ground for the fuel pump and the fuel level float switches.
Brown/white and brown/black are for the fuel level dash indicators.
Green/white is the fuel pump power feed from the fuel injection relay--- thru fuse #6.
check your ground wire(solid brown-- no stripe) connection to the frame. Sounds like you have a weak/no ground connection. I believe that it terminates under the fuel tank.

[frankenduck]

The four pin plug to the tank has these four wires:
Green/white - fuel pump 12V+ when the motor is turning
Brown - ground
White - fuel level sender to instrument cluster
Yellow - fuel level sender to optional fuel gauge

[spextattoo]

There should be only 1 solid brown wire, that is ground for the fuel pump and the fuel level float switches.
Brown/white and brown/black are for the fuel level dash indicators.
Green/white is the fuel pump power feed from the fuel injection relay--- thru fuse #6.
check your ground wire(solid brown-- no stripe) connection to the frame. Sounds like you have a weak/no ground connection. I believe that it terminates under the fuel tank.

THX for the response,
I cur back the plastic tube to have a better look at the wires,and the colors are as follows:
green/white  solid brown  brown/white  brown/black
the wire group makes it directly into the main harness under the tank and looks original and unmolested.
So if I check for continuity with the volt meter between the brown wire and the frame there should be no resistance?
I did mention that the bike had no issues until I started redoing the cooling system,right? I didn't touch the plug wires or the main harness.
I also attached a picture of the 4 pin plug and wires,thx again.

[spextattoo]

THX for the response,
I cur back the plastic tube to have a better look at the wires,and the colors are as follows:
green/white  solid brown  brown/white  brown/black
the wire group makes it directly into the main harness under the tank and looks original and unmolested.
So if I check for continuity with the volt meter between the brown wire and the frame there should be no resistance?
I did mention that the bike had no issues until I started redoing the cooling system,right? I didn't touch the plug wires or the main harness.
I also attached a picture of the 4 pin plug and wires,thx again.

[rbm]

- you should use the continuity / resistance function on your multimeter and you should read 0 Ohms (or close to it) when testing between Brown and battery negative.
- you should use the DC Volt function on your multimeter and you should read 12 volts (or close to it) between Green/White and battery negative when you do the following:  (1) turn on the ignition (2) set the kill switch in normal position (3) press the start button.  The voltage should remain for 1.5 seconds AFTER you release the start button.

[spextattoo]

Thx for the explanation,it's obvious I don't know how to use a meter,much appreciated !

[beemuker]

If you still have issues after testing ok. You still might want to get replace the 4 pin tank connector, a known trouble . I replaced mine with a 4 pin flat trailer connector, but there are other connectors.

[rbm]

That is super hard to do on an early model K100 because the harness plugs directly into the fuel sender / pump connector and there is no pigtail on the tank to allow a substitution.

[beemuker]

That is super hard to do on an early model K100 because the harness plugs directly into the fuel sender / pump connector and there is no pigtail on the tank to allow a substitution.

ya learn something new every day!

[frankenduck]

On an 85, the white nylon alarm connector in the relay box is the same as the fuel tank connector so you can swap that in if the connector that goes to the fuel level sender is flaky.

[spextattoo]

- you should use the continuity / resistance function on your multimeter and you should read 0 Ohms (or close to it) when testing between Brown and battery negative.
- you should use the DC Volt function on your multimeter and you should read 12 volts (or close to it) between Green/White and battery negative when you do the following:  (1) turn on the ignition (2) set the kill switch in normal position (3) press the start button.  The voltage should remain for 1.5 seconds AFTER you release the start button.

Hi RBM,
did the test and I do have 0 ohms on the brown ,but nothing on the green/white with ignition turned on,pressed start button,kill switch at normal.
What do you suggest I ought to test next? It dawned on me that I could have run up the green/white wire to see if I can find the break before the plug.(if that what it is) It.s dark now,will do that tomorrow,just hope I 'll find it before that line disappears in the main harness. Thx so much for talking me through this,really appreciate you doing this.

[spextattoo]

On an 85, the white nylon alarm connector in the relay box is the same as the fuel tank connector so you can swap that in if the connector that goes to the fuel level sender is flaky.

I found one from the alarm system in the relay box,thx a bunch for responding

[spextattoo]

If you still have issues after testing ok. You still might want to get replace the 4 pin tank connector, a known trouble . I replaced mine with a 4 pin flat trailer connector, but there are other connectors.

Gonna do that next,found a connector from the alarm system that doesn't exist,thx

[spextattoo]

On an 85, the white nylon alarm connector in the relay box is the same as the fuel tank connector so you can swap that in if the connector that goes to the fuel level sender is flaky.

I found it  and had it waiting ,thx a bunch for responding

[Scott_]

If you aren't getting +12vdc on the Green/white wire at the tank connector, next location to check is fuse#6.
The FI relay that supplies power has 2 switched contacts in it.
1 contact is the fuel pump circuit.  Battery to relay to fuse #6 to fuel pump....
2nd contact is the +12vdc at the fuel injectors(green/red wire).

You can check the 2nd contact of the relay, use your volt meter on DC voltage and measure for +12vdc on the Green/red wire at the injectors. Measure the same as when checking the tank connector, and fuse #6... key on, kill switch on, starter button depressed.



One step at a time.

[spextattoo]

If you aren't getting +12vdc on the Green/white wire at the tank connector, next location to check is fuse#6.
The FI relay that supplies power has 2 switched contacts in it.
1 contact is the fuel pump circuit.  Battery to relay to fuse #6 to fuel pump....
2nd contact is the +12vdc at the fuel injectors(green/red wire).

You can check the 2nd contact of the relay, use your volt meter on DC voltage and measure for +12vdc on the Green/red wire at the injectors. Measure the same as when checking the tank connector, and fuse #6... key on, kill switch on, starter button depressed.


So to check the fuse: blk lead on battery neg,red lead on fuse 6. Ignition on?  Starter pressed? What side of the fuse socket?
One step at a time.

[spextattoo]

You might have to explain the relay test again...sorry ,THX

[Scott_]

You might have to explain the relay test again...sorry ,THX

As RBM spelled out in post #5 above, use the sequence to test both of the following. Red meter lead to each(one at a time), black meter lead to battery negative.
check for +12vdc at fuse#6 (both sides).
then check for +12vdc at the green/red wire at the injectors(only need to check one as they are all wired together).

[spextattoo]

As RBM spelled out in post #5 above, use the sequence to test both of the following. Red meter lead to each(one at a time), black meter lead to battery negative.
check for +12vdc at fuse#6 (both sides).
then check for +12vdc at the green/red wire at the injectors(only need to check one as they are all wired together).

[spextattoo]

As RBM spelled out in post #5 above, use the sequence to test both of the following. Red meter lead to each(one at a time), black meter lead to battery negative.
check for +12vdc at fuse#6 (both sides).
then check for +12vdc at the green/red wire at the injectors(only need to check one as they are all wired together).

Ignition on I assume,starter button pushed or not? Obvious and total green horn here...thx

[sebas2357]

I thought I was gonna jump the pump (just for a second to see if it is running)

from right side of fuse 4 to left side fuse 6,but since I didn't have any power on the fuse locations,I didn't even try.

Did you end up trying to jump the pump out of the bike? You should try jumping the fuel pump externally directly from the battery to rule out 100% that the pump is not defective. There is a possibility that your pump is bad, which is probably unlikely given that it is new, but not impossible.  (please don't jump the pump inside the tank). I recently had an unrelated issue with my bike regarding blown fuses and erratic fuel pump behavior, and after much troubleshooting, a new pump resolved my issue. I've linked the thread below if you'd like to reference it.

THREAD: http://www.motobrick.com/index.php?topic=14371.0

Best of luck,

Seb

[spextattoo]

Did you end up trying to jump the pump out of the bike? You should try jumping the fuel pump externally directly from the battery to rule out 100% that the pump is not defective. There is a possibility that your pump is bad, which is probably unlikely given that it is new, but not impossible.  (please don't jump the pump inside the tank). I recently had an unrelated issue with my bike regarding blown fuses and erratic fuel pump behavior, and after much troubleshooting, a new pump resolved my issue. I've linked the thread below if you'd like to reference it.

THREAD: http://www.motobrick.com/index.php?topic=14371.0

Best of luck,

Seb
Is there a way to jump the pump without taking it out of the tan? THX

[spextattoo]

Ignition on I assume,starter button pushed or not? Obvious and total green horn here...thx

Test results fuse #6

ignition on                                              ignition on
at fuse: right side 0.03  left side 0.03        starter pushed: right side 0.5 falls to 0.3     left side  0.5 falls to 0.3 

at fuse box
no fuse    right side: 0.03  left side 0.00
I jumped the pump from right side of fuse 4 to left side of fuse 6,I can hear the pump wizzing away.
PUMP WORKS ! good

[sebas2357]

Seb
Is there a way to jump the pump without taking it out of the tan? THX

You most definitely can jump the pump inside the bike, but I wouldn't recommend it given that it is sitting in gasoline and any electrical spark is a risk of a fire. Removing the fuel pump is very easy, it is only held by two clips on each end of the pump. You firstly remove the gas cap. You hold in both clips, pull the pump up and out of the tank. You then remove the hose leading to the fuel filter, and both + and - wires.