View Full Version : No Voltage to Fuel Pump???

07-13-2006, 09:57 AM
I first thought I had a failed fuel pump in my 2004 X2. But after some testing I have come to another conclusion. I am not getting any voltage to the pump.
Does anyone know of any wiring issues, fuses, relays etc. That I could check. I have checked all of the basics but cant chase this one down. My next step is to remove all of the drivers side paneling inside the boat and trace every inch of the wires. But, if any of you have any experience with this I would appreciate some tips. Or if you know where I can find the relay without removing all of the paneling that would be even better. Thanks for you help on this one.

07-13-2006, 04:47 PM

Maybe MYMC or JimN will see this and know more.............

07-13-2006, 04:50 PM
That's what I am hoping for. I would love to be back on the water this weekend.

07-14-2006, 12:10 PM
on my last boat (350 merc eng) the fuel pump power went through an oil pressure switch on the side of the motor. it was a sensitive enough switch that the oil pressure from the engine turning over was enough to close the contacts and provide power to the pump. It was a carbureted engine.

dog paw
07-14-2006, 12:48 PM
on my last boat (350 merc eng) the fuel pump power went through an oil pressure switch on the side of the motor. it was a sensitive enough switch that the oil pressure from the engine turning over was enough to close the contacts and provide power to the pump. It was a carbureted engine.

I could be wrong but I think the ingnition switch runs 12 volts to the pump while cranking. If it is fused on its own or run through a relay I don't know

07-14-2006, 05:44 PM
It was a purple wire that went from the ignition switch to the engine fuse block. From there it split into 3 wires. 1 to the electric choke. 1 to the coil/distributor and 1 to the fuel pump via a oil pressure switch. not the oil pressure sending unit but a separate oil pressure switch. It was a factory installed safety so fuel would not continue to pump out if the ignition was on, the engine was off, and there was a leak in the line/ fire. I had to replace the in question oil pressure switch because I also had no power to my fuel pump.

08-24-2007, 04:00 AM
With these symptoms of not having power to your pump, did you have an oil pressure reading on your guage with a faulty oil pressure switch? Also in what vacinity of the motor would I find this switch. I have an lQ9 in a 2002 197TT.


08-24-2007, 09:33 AM
The fuse and relay should be on the motor. Did you check for spark? If you don't have spark or voltage to the fuel pump, I would be looking at the safety switch and lanyard. Do the gauges fire up? How did you come to the conclusion that there's no voltage getting to the pump- using a meter, or otherwise?

Which motor do you have?

08-24-2007, 09:34 AM
AFAIK, Indmar and MC don't use the oil pressure switch for the ignition.

08-24-2007, 10:09 AM
I've had fuel pump issues since last summer with '04 X-star. The fuel pump will pressurize the lines with the key in the on position but not running. Problems started with a fuel pump failure and since then, it has been the connector on top of the fuel pump. I cleaned it with WD-40 and applied dielectric compound and it has helped, but the problem persists and occasionally I have to just fidget with it to get it to work. The good thing is that I can leave the key on and then fidget until I feel and hear the pump working again.

P.S. I also learned in my experimenting that the fuel pump from a SAAB 9000 will work in the MC pump basket.

08-24-2007, 10:36 AM
All my guages work, have a 50amp breaker relay on the engine including three standanrd relays (which i have replaced) on the same mounting plate ( I have an LQ9 cadillac motor) currently I have no power to the pump diagnosed through removing the pump and testing leads at both the plug and the acutal pump with a meter. This was a very short term intermitant problem of not starting up immediatly. I would give it a few more cranks and the it woudl fire and run. That happend for three nights in a row and now nothing. Coincidentally my perfect pass crimp broke off and I curretnly do not have throttle control and the lever but can manually of course move the throttle arm on the engine. I have removed spark plugs and verified spark with grounding out plug and visually seeing spark

Very confused?

removed wire from oil pressure switch/sensor? and oil pressure guage read 80psi when touching previously connected wire to ground.

What else can I do here?

Thank You

08-24-2007, 07:03 PM
I used a meter on both the plug and the pump when I removed it, both had no voltage. I verified spark by pulling plug grounding out while cranking. Guages fire up. Today I pulled the plug off of the oil pressure sensor and grounded it with the key on. Oil pressure guage spike at rading 80psi. ( I am guessing that means atleast the wire works. what are my next options here?

08-24-2007, 07:27 PM
MYMC, [email protected] or Will can probably verify this but as I said, MC and Indmar don't use the oil pressure switch to determine whether the motor will run. Mercruiser has for years but I think they're one of the only ones that do. Nice to know the gauge works, though. Mercruiser systems are very different from Indmar and MC, so unless it's short block related, it won't be applicable to these motors.

Now that we know it's an LQ-9, we can be more specific. If nobody has anything else to add soon, I'll dig my manual out but in the meantime, I would recommend not changing parts until you know they're actually bad. Those relays aren't expensive but they're also really easy to check. Look for three fuse holders on the motor. They should be marked as to their function and one will be for the fuel pump. Make sure you have voltage on the terminals marked 85 and 30 when the key is on. You should see a green/white wire and that will only be on the fuel pump relay. Grounding 86 should cause the fuel pump to work. This is low current, so a big wire isn't needed. Grounding this tab should also latch the relay and when this happens, it should click. You will be able to measure 12Vdc on terminal 87 when the relay latches and the wire that is attached to this feeds the pump. If you have no voltage to 85, you won't have voltage on 30 or 87.

If you have no voltage on 85, you'll need to check the other fuses.