Fuel pump not priming but works on it's own

[dreygata]

Need some electrical advice. 2000 X1 Lightning. Accidentally let the battery die by leaving the parking light on in the garage for a few days. Battery wasn't able to be recovered, so I bought a new battery. Installed it, and now the fuel pump won't prime (ecm throws a 33, fuel pump short to ground). Fuses are fine, ignition relay is fine (tested with a multimeter), and the pump works when I give it 12V power directly, both at the pump contacts and it's connector (gray and brown w/yellow stripe wires if I'm remembering correctly). Bypassed the bank angle sensor to rule that out. Bike still cranks when I thumb the starter button. It seems like a circuit isn't closing somewhere but I have no idea at this point. Rode fine before I killed the original battery. I have access to the service manual, and I plan on bypassing the clutch and sidestand safety switch to rule those out.
Any thoughts?

 

[Cooter]

If the bike cranks over, it isn't any safety system issue like a clutch or kickstand switch so don't bother with those.

You are right the BAS interrupts the fuel pump circuit, but IIRC there is a specific fuel pump relay on those, not just the ignition relay (and it would throw that code). If I'm right try swapping them around with the key on and see if it primes.

 

[dreygata]

Hm, true about the other safety conditions. I'm just trying to isolate the issue really well.
I think i tried swapping the starter and fuel pump relay, but I can try again. I know I pulled the fuel pump relay out and tested resistances with a multimeter and it's operation with a separate battery, and it seems fine.
Is there a way to see if the ECM is supply power/grounding out the connector properly?

 

[Cooter]

Yep, the relay uses a small current to control a large current, so it's 2 separate +&- circuits.
The large current (big terminals) will have one that goes right to the battery (+), and one that goes to the accessory. In this case the fuel pump. Check continuity on both or just put power to the big terminal that isn't (+), and the accessory should operate.
Jumping the 2 big terminals is an easy way to test the whole big circuit.

Testing the small circuit is easy too (DON'T jump these small terminals). It needs a (+) and a (-) to operate and connect the big circuit together to turn on the accessory. Either it has (+) on one terminal and the computer sends a (-) signal to turn the relay on (like the fan does), OR it has a (-) and the computer sends a (+) to turn the relay on.

You'll need to have your meter hooked up to test the small circuit first because when you turn on the key (and run switch) the signal to prime the pump is only on for a second or so.

 

[dreygata]

I've already tested the relay, and even swapped the starter and fuel pump relays to see if there was any change. No difference. Bike will crank, but pump won't prime.

With the bike in the On position, and the engine kill set to "Off', I can switch the kill switch to "Run" and hear the fuel pump relay click. I'm guessing that means the computer is sending the signal correctly, meaning the low current circuit is fine?
If that's the case, then the problem exists on the large current circuit. Given that I just changed the battery prior to this happening, the problem may exist in the harness between the battery (+) and the fuel pump relay. Does this seem correct?
You mentioned jumping the terminals for the big circuit. Do you mean removing the fuel pump relay, and using a jumper wire in the socket (corresponding to relay pins 30 and 87) to jump the large circuit?
Sorry for the wordiness, just trying to be very explicit.

 

[Cooter]

Yes, jump 30 and 87. If the pump turns on, that circuit is fine, it's something else.

If the pump does not turn on with the pins jumped then check for (+) at the 30. If you don't have power there trace it to the battery, if you do have (+) at the 30, check for continuity from 87 and the power wire at the pump.

 

[dreygata]

Okay, here's what I've done:
30 has continuity to the yellow w/ red strip that goes to the sensor, as well as the black wire that grounds to the pump housing.
30 has continuity to the red (+) wire at the battery. It also will read 13.1V when tested for voltage.
87 has continuity to the gray wire that goes to the pump
86 has continuity to the yellow w/red strip wire (sensor), black wire that grounds at the pump housing, and the black (-) wire at the battery.
Brown w/yellow stripe wire at the pump connector has continuity to the same at the black ECM plug

The pump itself is reading a resistance of 0.6 Ohms

 

[dreygata]

Well, based on the service manual specs, the pump should be 14V operating and draw 3 amps. V=I*R leads me to believe that the pump should be reading 4.67 Ohms, so I'm guessing the pump is bad (despite being able to be run when connected directly to the battery).
Any thoughts?

 

[dreygata]

Also, I'm getting a reading of 6V between the gray and brown w/ yellow stripe wires that power the pump. That doesn't seem right, it should be 12V correct?

 

[rb70383]

Is that 6V across the terminals that goto the pump? If the pump runs when wired hot, but not through the relays, its not getting enough juice. Bad/loose connection or maybe even a terminal at one of the connectors. Is the 6V read at the other sensors since the gray wire feeds all of them? If there is a solid 12V on the gray(grey?) wire, check voltage using a different ground wire, since your using the fuel pump trigger wire...bn/y.


I'm not sure if you should see 12V across the fuel pump wires with a signal to run the pump. The fuel pump always has 12V. So if the ECM wire is connected to ground at all the pump will run. Circuit complete. IIRC The br/y should not show any voltage. Can you back probe the harness at the pump and see what happens with the key on. The voltage should mirror battery voltage. If so another thing is to measure the voltage drop across the br/y wire when the pump should be running. You should measure no voltage drop in that instance. Any drop means the wire is providing resistance and taking current away from the pump.

You did hot wire the pump right and it worked?

Never worked on a tuber, so I'm going by these:

 

[dreygata]

Yeah, measured at the leads that connect directly to the pump motor (pump unplugged). Pump harness is connected to the bike harness. The 6V comes on with the flip of the engine kill switch, so the current behavior seems correct (just incorrect voltage output). I'll remeasure the voltage at the bike harness connector with the fuel pump disconnected, isolating the pump system from the rest of the bike. I'll also see if I can't measure a resistance through the wires in the fuel pump system itself, but it seems like the issue is on the bike harness side, just no idea where. Is there a way to jump the wires at the ECM connector to create a running condition? i.e. jumping pins 1 (gray) and 3 (brown w/yellow)?

I'll also, for good measure, go through and clean up all of the ground connections on the bike to see if that's causing a problem somehow.
This is all really throwing me for a loop and not expected when just changing out a battery. Does the regulator or anything need to be submerged in fuel for any reason?

 

[Cooter]

No need for testing for resistance of the fuel pump, you have 6V at the plug when its disconnected.
6V at the pump is not enough, and big clue
Nothing needs to be submerged to test
I am assuming you really did swap relays already, I am assuming it does crank ok.

My testing laid out above will find the problem if you follow the steps.

 

[dreygata]

Well it seems like doing continuity checks isn't enough, and I need to move on to doing resistance/voltage tests. 6V isn't enough to run the pump, but it shows that continuity exists between both 30 and (+) at the battery, and 87 and the power at the pump. There's added resistance somewhere, I just have to figure out where.
I'll need to pick up some contact cleaner and thoroughly clean the connectors between the pump and bike harness. I'll also clean the connections at the relay and its socket.
The ECM plug has never been removed prior to this issue, and the plug itself looks clean but it wouldn't hurt.
And as mentioned before, I'll likely clean up all of the ground connections.

Would it be worth my while to pick up a test light?

 

[TapRoot]

If you know that the brown/yellow is the ground for the pump and the gray signal wire provides 12v then check the gray from the pump to a good ground you should get 12v if so you are getting signal. If you only get 6 v to the brown and yellow then most likely the ground wire is the culprit. You should be able to put your digital MM on the diode scale and get a dead short from a good ground to that brown/yellow, if not I would think it’s the culprit. Now if you jump out the brown/ yellow to gray at the connector and you have a dead short reading at the pump this would tell you the wire is at least not broken and your problem is within the connector, ecm, ecm ground or shorted to another wire. This is my logical thinking looking at the schematic and being an electrician, not to say I’m right so I guess take it with a grain of salt, I’ve only owned a Buell for 2 seasons.

 

[dreygata]

Okay, I'm getting 12.8V between the gray wire at the pump and a good ground. Checked a couple grounds just to be certain and they are consistent.
So that isolates the brown with yellow wire, however, I'm not fully understanding your explanation about setting my multimeter to the diode scale and getting a dead short between ground and brown w/ yellow. Isn't the diode setting directional? Or should I be getting a short (0L) regardless of probe direction?
I'm a mechanical engineer, and I've dealt with a fair amount of light electrical work, but I'm not nearly as familiar with diodes

 

[dreygata]

Out of curiosity, I disconnected the ecm and jumped the black and brown w/ yellow wires on the black plug. This caused the fuel pump to run.
Not sure if this provides more info or not

 

[dreygata]

Honestly, it's as if the ECM doesn't want to connected the brownw /yellow wire to ground.

 

[Cooter]

"Well it seems like doing continuity checks isn't enough, and I need to move on to doing resistance/voltage tests."

Same thing man. "Continuity" in this case means there is acceptable resistance in that circuit, allowing full voltage through it.


The ECM does not power the fuel pump, it activates the relay ONLY and relays are only ON or OFF. No "6V" BS. It connects the 30/87 circuit to power the pump.

So, do you have 6v at the pump plug when activated? And 12.8V when testing with a good ground (ground path is compromised)

OR

does it run when you manually trigger the relay from the ECM plug? (ECM is toast), did you hook up the battery backwards when replacing it?

Bad clues, so confuse.

 

[TapRoot]

Yes the diode scale is directional but if the connector at the ecm is off and the pump connector is disconnected then this should isolate the wires and if you had b/y and gray jumped at the connector or pump then you should read a dead short with polarity either way and OL between the two when the jumper is pulled. If you are picking up significant resistance with the wires open then I would say either of the two may be shorted, also it gives a nice audible when checking for ground faults as you probably know but if you prefer the Ohms scale that’ll work also. If all worked before and all you did was change a battery there is a chance something may have gotten shorted or taken a spike. Maybe Cooter or someone else may know but does the b/y rely on the pumps ground within the tank for completing the circuit? If so, this could bring your pump back into play but I’m not sure. I guess if you were able to manually jump it out at the connector to get it to work then the ground should be good. Not sure if this is even a good idea but if you jumped the b/y to a good ground then all should work I would think? Would this narrow it down to the ecm and would it need to be jumped before the relay to Eliminate one of those possibilities? Just trying to spit ball here

 

[dreygata]

Cooter,
Yes, technically continuity check and voltage/resistance checks are the same thing. On my meter, I have a separate continuity check setting that simply beeps when there is a good connection. This is separate from the settings from where I measure voltage or current. So for me, a continuity check just provides a little less detailed information as opposed to voltage/resistance, but there wasn't a way for you to know about my specific meter. My fault there.

I understand that the ECM does not provide power and it's basically a solid state relay (from what I can tell). The 6V thing is strange (I think it was reading a steady 4.5V yesterday when measuring between the gray and bn/y wires), and I'm tempted to discount that as user error.
Yes, when I remove the black plug at the ecm and jump the bn/y wire to ground (black wire) the pump runs. Honestly, that more or less seems to isolate the ECM, unless I'm missing something else.

As for cause, battery was not installed backwards. The original battery was attempted to be jump started via push starting the bike, which worked, albeit for only 200ft or so. There was a voltage error with the fuel pump error originally, but I chalked that up to the original battery being dead. It's possible that it could have been a high voltage spike that damaged the ECM.
At this point, I think I'm going to grab a used ECM from ebay. $160 isn't the end of the world, just annoying.