What are symptoms of a bad fuel pump?

[SpeednV6]

Just as the topic states. My fuel pressure gauge is bouncing around and that usually means it's time to change the fuel filter, so I did just that. As I was checking for fuel leaks, I heard the pump whinning and cutting off. It's whinning pretty loud. How do I check for a bad pump? It's a Walbro 307.

 

[turbobuickman]

Is the pump hotwired? Check the wiring the way its fluctuating and going on/off. Also, how long will the fuel lines hold pressure after turning the key off? I beleive that if the pressure drops quickly it could signify something wrong with the pump itself. Not positive about that one though.

 

[2QUIK6]

If the lines will not hold pressure, that just means either the regulator is bad, you have a leaky injector, or the check valve in the pump is not holding properly. If the check valve is bad, is not a bad idea to replace the pump. Should not matter at low boost and lower fp, if its bouncing at higher boost, say around 60# fp, then it could be the pump/valve.
You can test by using vise grips to pinch off the rubber fuel lines above the tank. Energize the pump to build pressure, and pinch off the return first..that will eliminate the regulator.
If pressure still drops, then pinch off the source line with another set of vicegrips with the return still pinched...if pressure stops dropping, then its the check valve....if it keeps dropping, it a leaky injector.