Fuel pump problems, races full speed /hot
 

95 f3 , burning up fuel pumps, runs fine when cold but when it gets hot, fuel pump races at full speed. Even when the engine is not running, but key is on. Pinched off fuel line to carbs to see if it could be carbs, but the pump keeps racing at full speed. Pump is 1 year old, and the pump before it only lasted 1 year. The orignal lasted 90,000 miles! Cant keep buying pumps but I think it is a bad pump! Where can I get the contacts for the inside of the pump? Thats what keeps burning up....I put in bypass and can drive almost 100 miles before I have to turn on pump.

The fuel pump on the F3 is supposed to only run when the engine is actually running. It sounds like the fuel cut relay, which is located by the R/R is either stuck, or it's been bypassed. See if you can get a copy of a wiring diagram and take a look.

$ Bill, I have a manual that I can bring into work and scan to adobe (the wire diagram) if you would like a copy? Let me know..

Thanks stix, I have a shop manual. I did by pass the fuel cut off relay, because it went bad and I thought the relay was there only to shut off the pump when the bike is tipped over. I could try to put a new relay back on, and only hope it fixes the problem. Does the bike need the relay?

Yes, it needs the relay. This fuel pump is not a high pressure pump like those used on Fuel Injected bikes. Because of the fuel pressure, they need a Tip Relay in case the bike is in an accident to cut the fuel flow. Our bikes are low pressure, low volume pumps. I would get a relay off of ebay. It's really rare that one goes bad.

Anytime!!!

I have a question for everyone, isn't there some type of pressure switch for the fuel pump? Reason why I ask is because when I turn on the ignition switch (red switch) the fuel pump pulses a couple times and then stops. It will only does it if it's been sitting for a day or so or if I ran out of gas, etc.... Reason why I ask is because it sounds exactly what's going on with $ Bill's bike. Maybe lost the pressure switch which would cause the pump to pulse constantly. Guess I need to check out the schematics and see!!!

No, there is no pressure switch (unless it's a mechanical one inside the fuel pump itself). The fuel pump gets a pulse signal that is coming from the Ignition Control Module (ICM). It's the Bu/Y wire that controls the firing of one of the Ignition Coils. Each time one of the coils is fired, the fuel pump turns on momentarily. This is a low pressure system. It only has to help get the fuel to the bowls of the carburetors, not pressurize an injector nozzle.

Good info!!! So what does this fuel cut relay do if you don't mind me asking?

My understanding of the fuel cut off relay is to shut down the fuel pump when the bike is tipped over. Not of my concern at this time. I dont have the bike or manaul with me at this time. But in the trouble shooting section, when checking the relay with the jumper wire there is voltage to the pump with the key on. And if the relay is good, there is voltage to the pump with the key on. I will try a new relay, if not just to eliminate it from this equation. I have opened up the pump and watched it work and there is a mechanical pressure switch in it. But this is why I am confused about the relay fixing the problem with the pump racing when hot?
Thanks to everyone with comments!

I understand what your saying Bill. I could see if you had a problem with getting fuel to the carb but not the other way around. Interesting to say the least though..