91 F150 Fuel System Problem
08-06-2010, 07:19 PM
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91 F150 Fuel System Problem
OK here we go. I am new to the forum so thanks in advance for your input. I have a 91 f150 Lariat. Ext cab 4.9 2wd. Dual fuel tanks. We had a heck of a time getting it running. It would run on starting fluid but not from fuel pumps. We had no pressure at the fuel pressure test port. Replaced fuel pump in midship tank, Fuel Filter, Fuel PumpRelay, Pressure Regulator and tested Fusable Links. All of a sudden it fired up. Now it will run rough from the rear tank and really rough from the front tank. It runs smooth with the starting fluid pumping into the throttle body. Is it possible that there is "gunk" in the fuel lines causing the pressure to drop? Would it cause a difference in the pressure from one tank to the next? If I switch the tanks while its running you can hear the engine change from an "ok" idle to an extremly rough idle.
08-13-2010, 03:21 PM
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New info
No selector valve as far as I can tell. Its in the fuel pump "cube". Anyway we are getting intermittent starts. We had it running yesterday from the fuel pump for about 15 mins. Then after about 3 mins of shutdown it wouldnt fire back up. Another symptom is that sometimes the starter will stick "on". Even if you pull the key out. You have to dis connect the battery to kill it. Does the starter solenoid on the fender well have anything to do with charging the fuel rail? Would a bad solonoid make the starter stick?
08-13-2010, 04:59 PM
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bad solenoid could make it stick, and if its spinning the starter it might not allow enough power to other things to keep it running, check out your fuel pressure from each tank i believe 30 was min. for normal
08-13-2010, 06:32 PM
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New issue.....Sort of
Thanks for the tip on the solonoid. Now we have it running but as soon as we switch to the front tank it bogs down and dies. Switch it back and it fires right up. The front tank has a brand new fuel pump.WTF. Truck has new front pump, new fuel filter, new regulator and relay. Also just did plugs, wires, cap and rotor button. ............Pin hole in the front tank fuel lines?
