Do you get any error codes?

 

No error codes.

 

Check for power at the wires to the fuel pump and coming out of the fuel pump relay.

 

:frown2:e
I tested with a multi-meter in the socket the relay plugs into (with the relay out of course) and also unplugged the fuel pump and tested at that socket as well, with the relay back in. Both showed 12v initially when key was turned and then fell to zero.

Is that what you mean? Not sure I totally understand the results. Is it programmed to energize the fuel pump circuit for a set period of time when you first turn the key? Or is something wrong?

 

Nothing in the system will drop the voltage after the initial ignition on. If the side stand switch or kill switch is in the wrong position or malfunctioning, the pump will not get power but you'll also get a CHEC on the instrument panel and the starter motor won't crank. I'm thinking you might have a bad fuel pump relay that will make momentary contact when first energized but is unable to maintain contact.

 

I'm thinking you might have a bad fuel pump relay that will make momentary contact when first energized but is unable to maintain contact.

That's what I was thinking but I got the same voltage drop in the relay socket PRIOR to the relay. That's what was so puzzling, so I was guessing maybe if the module doesn't sense RPMs it closes the relay?

I might just replace the relay anyway, given its a fraction of the price of a fuel pump assembly.

 

Check the Y/B and O/W wires to the fuel pump relay with the ignition on. O/W should show battery voltage compared to ground from the ignition system and Y/B should show continuity to ground from the ECM. Make sure you don't see a CHEC where the clock normally shows up. If you don't get that, the relay is not the problem.

 

O/W (mines actually Y/R) shows 12v during the 2 sec prime. Y/B does not show continuity to ground. No "CHEC" showing. Bad relay?

 

Y/R is the contact side of the relay. It will show power as long as the relay is activated. O/W is the coil side. It needs to show power to throw the relay. The ECM connects Y/B to ground to throw the relay. If you don't show Y/B continuity to ground to combine with O/W showing power, the relay won't throw. If you don't get O/W+ and Y/B-, that's your problem and the relay is not the problem.

Check for power with the meter probe positive on O/W and negative on Y/B. That is needed to throw the relay. It sounds like you are getting that to begin with then losing it. If that is the case, the tricky part is finding out why. If the ECM is not switching Y/B to negative, it should display an FI or a CHEC, depending on the reason. O/W is hard wired. If you are losing that, it will be easier to trace. I'd hate to think you are experiencing an ultra rare and expensive ECM failure. If you are showing power between O/W and ground but not O/W and Y/B though, it may be the case.

 

I did have an intermittant problem with the relay contacts. It was difficult to diagnose, eventually tried a generic relay and that fixed the problem . I replaced the generic with the correct one. The first thing you need to do is lift the tank, disconnect the fuel line at the throttle bodies and see if it is pumping.

 

Good advice, I will definitely do that at some point, just to verify it's not running. I may also pull the fuel pump and try to get power to it directly to see if it runs.

What I don't want to do is spend big $$$ on a fuel pump only to find out the problem was something else (which is what it's starting to look like....)

 

Oops

Ah, I was checking in the wrong place:

O/W to ground shows power continuously when key is turned.
O/W to Y/B shows power for 1-2 sec when key is turned, then falls to zero.
Y/B to ground fails to show continuity. No error messages on display. I'm mystified! :frown2:

P.S. Thanks for your guidance, it is much appreciated.

 

The ECM is cutting ground continuity to Y/B without throwing a CHEC or an FI. That's mysterious. The backwoods hack would be to connect the Y/B wire from the relay to ground instead of the ECM. I have no idea what problems that could cause long term. I gather it would keep the pump running when the ECM would normally find a fault that would make it shut off the pump.

 

ECM timer?


The service manual says the ECM has a timer which causes the fuel pump motor to stop turning "in three seconds after the ignition switch has been turned on." Then when the ECM receives the "engine running" signal, current flows to the fuel pump motor via the side-stand relay and fuel pump relay.

My point: couldn't this voltage drop just be the 3 second ECM timer? If so, I'd be back to a bad fuel pump. Since I can't start the motor the ECM never receives the signal to send current to the fuel pump again.

 

Pulled the fuel pump today. It's definitely shot. I found an exact match on eBay used for $155, so I'm going to give it a shot. I'll post results when I have them. Thanks to everyone for your input.