87 F150 Fuel Pressure problem
05-08-2010, 09:41 AM
#1
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87 F150 Fuel Pressure problem
have a 87 f150 with 4.9l straight 6, duel fuel tanks, wont start, replaced frame mount fuel pump and it's pumping, have disconnected fuel lines at new pump and filter and has fuel there, not getting a pressure reading at the fuel rail, tested gauge on a 5.0 mustang fuel rail and reads ok, could in line valve ( 4 in 2 out ) mounted before fuel pump be issue, was going to try and bypass and just run on one tank at a time but dont have correct line fittings
yet to try that. ant sugestions.
yet to try that. ant sugestions.
05-08-2010, 09:51 AM
#3
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If I'm not mistaken, you have 3 fuel pumps on that truck. One pump on the frame rail, and a fuel pump in each tank. You might have a pump bad in one of the tanks.
EDIT: Dirtcrew posted faster than me
EDIT: Dirtcrew posted faster than me
05-08-2010, 05:55 PM
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is there a way to determine if the inline tank valve is bad, that was why I wanted to try and just run on one tank at a time to see which if any of my in tank pumps is the problem. could the inertia switch possibly be the problem and how can you check it. Thanks
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05-08-2010, 08:18 PM
#8
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I've had the resevoir go bad on my truck a couple of times. When it goes out you'll still get pressure to the rail, just won't be able to switch tanks. If you hear the high pressure pump (the one on the frame) running I would suspect the pressure regulator. It's at the back of the fuel rail on the drivers side. Three screws hold it on. They are facing the wrong way so as to be a pain to get off. I replaced mine with allen head bolts to make it easier.
05-08-2010, 08:22 PM
#9
The valve is part of the dual function reservoir. If it's bad your tanks will crossfill. The inertia switch is like a circuit breaker, when it trips the pumps won't come on until you reset it. If you really think there's a problem with it you can bypass it temporarily.
05-09-2010, 11:08 AM
#10
Fuel pressure
When I checked the pressure on my F150 300 I6 at the fuel rail, I had to remove the valve from the stem on the rail. Apparently the valve wasn't long enough to reach the button inside the gauge to make it get a pressure reading. You will lose gas you just have to be ready to screw the line on when you take out the stem....As others have already stated, I would check the regulator also.