[BurgerLord83]

Hey all, so I have a problem with my fuel pump. I have put in a new pump and checked that it works by powering it directly from the battery, how ever when I plug it into the harness it doesn't power. The strange thing is I have checked the voltage at the harness and its good at around 11.8V but when you plug the pump in to the harness it goes down to almost nothing like 138mV. I was able to power it by "hot wire" using a test lead with just the power wire from the harness to the power lead on the plug and it worked fine, but plug the whole thing in and it wont work, any idea why it would do this, I have check the all of the usual suspects (kickstand/tip over sensor/kill switch/clutch lever) any clues I'm at a loss?

 

[jkv45]

Hey all, so I have a problem with my fuel pump. I have put in a new pump and checked that it works by powering it directly from the battery, how ever when I plug it into the harness it doesn't power. The strange thing is I have checked the voltage at the harness and its good at around 11.8V but when you plug the pump in to the harness it goes down to almost nothing like 138mV. I was able to power it by "hot wire" using a test lead with just the power wire from the harness to the power lead on the plug and it worked fine, but plug the whole thing in and it wont work, any idea why it would do this, I have check the all of the usual suspects (kickstand/tip over sensor/kill switch/clutch lever) any clues I'm at a loss?

11.8V is way too low. It's only a 35% charge. A fully charged 12V battery should read 12.7V.

Start by charging, then testing, your battery.

It sounds like a terminal in the plug is not making a connection.

 

[BurgerLord83]

The battery is good at 12.8V, the voltage at the fuel pump harness plug is at 11.8V, but it drops to nothing when you plug the fuel pump in, its strange and I'm out of ideas.

 

[SparkyMJ]

You probably have a damaged harness, that is bottlenecking the current. Probably a worn wire, or a ground awry. Check for wear on all the related harnesses, and luckily if you do need to repair the fuel pump harness, the power delivery wires should be relatively simple to splice in a new wire. But only do that after you are certain you found damaged wiring. No need to mess up perfectly good wiring and possibly introduce more complications.

But yeah, based on your accurate voltage measurements and deductive testing of the pump, I would diagnose it as a damaged wire or partially cooked fuse. Check your fuse box, and if your battery is decently charged, it should still run. I've had my fuel pump prime totally normally but the battery didn't have nearly enough juice to crank over the engine. That said though, charge it anyway if you can.

Hope this helps. Worst case, find a used harness online or buy a new OEM one.
-Mike

 

[jkv45]

The battery is good at 12.8V, the voltage at the fuel pump harness plug is at 11.8V, but it drops to nothing when you plug the fuel pump in, its strange and I'm out of ideas.

As Sparky noted - start tracing the wires to isolate some type of damage between the battery and pump connector.

If the fuse looks OK, I'd still swap it with another of the same.

 

[BurgerLord83]

Its lives!!! Turned out the wiring harness was fine, turns out it was the fuel pump housing. Had to buy a used one for $75 and it runs great, best $1000 bucks I've ever spent.