1996 VFR750 odd no start - PLEASE HELP!!

Well I just got back from checking stuff and the fuel pump was the component that blew the fuse when it was reconnected and the kill switch was flipped to run. I tested the resistance across the terminals on the pump and it was 2.1 ohms.

Does anyone have a used pump?

Is my testing and troubleshooting method sound?

 

Make sure that it is not the wiring to the pump, before you go shopping.

 

Like the short connection between the fuel cut relay and the pump? The fuse did not pop until the pump was plugged in and the kill switch was set to run.

Should I put power to the pump and see if it runs?

 

Actually, a faulty short may have triggered a run-away meltdown in the lithium battery. (Versus the lithium battery starting this chain of events.)

 

Yes. It shouldn't hurt to try, as long as you're careful.

 

Please use a non-lithium battery for testing possibly shorted components!!!

 

Actually, you are testing Resistance (of a dc circuit) - Impedance is something a bit different.

2.1 ohms may not indicate a fault - at least it's neither dead shorted, or completely open, and cheap meters are not accurate at low ohm values. Fuel pump may be good.

 

Let's not make assumptions about me using a 'cheap meter' in this thread :mad2:. The meter being used is a Fluke 77 DMM - not a piece of Harbor Freight junk. It knows more about electricity sitting unused in my tool box than I ever will know.

@ Superskip - I meant to say my result of 2.1 ohms DC resistance with my fuel pump test (and I have corrected the post above for posterity) - impedance is the relative AC equivalent, right?

@xorbe - why the 24pt bolded orange warning about not using the LiPo4 battery for testing components? The pump does have resistance across the component - not a completely closed 0-resistance circuit... what is the warning about? I don't have another 12v motorcycle battery for a test.

@kennybobby - how would I determine if it was a bad coil? Or (gasp) the control module?

 

OK, here's another theory - and this is a right fielder:

The contacts in the fuel pump have welded themselves together, closing the circuit permanently, and hence, blowing the fuse any time the circuit is powered up.

Bear with me - I just stumbled across this thread with a CBR 600 fueling issue:
http://cbrforum.com/forum/stickies-91/how-repair-your-f3-fuel-pump-102151/

I think that the VFR fuel pump is the same, if not extremely similar, right?

This a repair that I could definitely handle, I will see if I can get the back of the fuel pump off tomorrow or the next day and verify.

If I am totally off the deep end here, let me know too - I don't want to waste a trip to the storage unit or take apart a fuel pump if it's not necessary.

 

Hahaha sorry 'bout that. Lithium batteries are great at delivering lots of current, where other batteries would just sag in voltage limiting current. This can heat up a wire and start a fire, or also damage the lithium battery starting a fire there that takes a few minutes to get going. Some lithium batteries are better behaved than others. I'm used to Li-Po which is stupid touchy.

 

This snag would not blow the fuse, as the pump is constantly running when the engine is anyway. His problem was that the pump was not running.

The only coil on this circuit is #4 and it is connected to the fuel relay.

I would just test the wires from the relay to the pump and use a jumper to test the pump. If it's shorted, you'll know right away and the battery will be fine, as long as your jumper doesn't weld itself to the contact.

 

The pump may be constantly running when the motor is on, but the contacts are not constantly touching when current is applied. Watch the video in my link above.

FWIW, I don't know if it's even possible what I propose in my theory...

 

Not the fuel pump. It runs when jumped. What now?

I checked continuity from the control unit to all four coils. Resistance tested across terminals for coils in the front was 3.1 ohms for both. Tested resistance at control unit across pins for each coil to ground (black/white), measured all four in the 588 to 592 ohm range. Checked continuity of red/yellow wire from fuel cut relay to front coil #4. I checked the wiring between the fuel cut relay and the pump and found nothing out if the ordinary.

I don't know what else to go after or check at this point...

 

How much steady-state current when jumped? Put your DMM inline on the 10A unfused DC amperage setting.

 

Well, the fuse only blows when the pump is plugged in. It is a dead end in the cct, so the short has to be there somewhere between the relay and the pump. You need to find the live wire that is connected to the ground. Everything so far, points to the black and blue wire, or the related connectors, or the pump.

 

unplug your ign control module, then plug pump in

 

then if it still blows fuse. do as xorbe said and measure pump current directly by using a dmm in series to start pump

 

I would try a 10 amp fuse in the jumper wire to the pump and see if it blows by just directly jumping the pump, that will tell you if it is the pump actually blowing the fuse

 

I tried the fuse to jump the fuel pump leads. It did not blow the jumper fuse when turned on. I checked across the fuse terminals with everything plugged in and the current was so strong it blew the fuse in my meter so I can't tell you how much current was flowing through it.

I also tried disconnecting the two front coils and that did not blow the fuse when the Control unit was pulled out.

I pulled all the electrical tape off of the fuel relay to the fuel pump and it all checks out fine.

It sure is looking like my first Shorai battery cooked my control unit when it blew up.

Is there anything else that I can test to confirm that the control unit is shot?

 

Often a problem with measuring electrical motors, the inrush current is 3-4x the steady state but just for a sub-second. I guess your dmm doesn't have an unfused input