kellyf Posted December 21, 2015 Share Posted December 21, 2015 2012 f 450. Came in with P0087.Tested low fuel pressure.Found at 35 psi and replaced pump. Comes back with repeat code.Found that low pressure pump now only noisy after truck is driven but not noisy when cold. Dropped aft tank and found no problems. Read some things about fuel rail and pcv issues, but would this explain my noisy pump only when switch to aft tank.Both tanks by the way are full and truck has 95935 miles. Quote Link to comment Share on other sites More sharing options...
nelsona19 Posted December 21, 2015 Share Posted December 21, 2015 Is there vacuum in the fuel tank when this happens? Check to see if tank is sucking in or for vacuum released when you open the fuel cap. Quote Link to comment Share on other sites More sharing options...
Matt Saunoras Posted December 21, 2015 Share Posted December 21, 2015 Yup any restriction in the lines or air getting in the fuel can cause the pump to be noisy. How did the sending unit look when you had it out? I'm not sure how the steel tank sending units are but the plastic midship has a bowl that can collect various items dropped into the tank accidentally. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted December 21, 2015 Share Posted December 21, 2015 I would definitely be working from the pump back, if you have 70ish PSI off the front tank and less than 70ish PSI off the rear tank. The fact that you have to drive if for a while backs up what's being said here with a possible restriction being built up as fuel is pumped out of the tank. I would put the pressure gage back on it or monitor the fuel pressure pid while driving off the rear tank and see what you can see. Quote Link to comment Share on other sites More sharing options...
kellyf Posted December 21, 2015 Author Share Posted December 21, 2015 there is very little or no visible contaminants in the tank. I know in the past I have replaced the switching valve on sick liters and that fixed it when the noise on one tank only. Would like to recheck fuel pressure, but gauge was borrowed and that person out of town. I am limited to tools. Quote Link to comment Share on other sites More sharing options...
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