88 F-150 Starving for gas

Tiny
REVKEV316
  • MEMBER
  • 1988 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
My 88 F-150 v8 5.0 has dual tanks. The truck starts good but is starved for gas intermittently when in gear but will idle fine. Frame mounted fuel pump whines most of the time. I have replaced the fuel filter and flushed the tank switching valve. Doesn't matter which tank is being used. HISTORY: The truck sat for several months and the rear tank hasn't been used for at least a year. Drove 5 hours switching to rear tank every 10-15 mins. To burn old gas. Problem occoured when I stopped for gas, shut the truck off, put gas in both tanks and then had real problem starting truck and hasn't drove far without dying since. Has anyone faced this particular problem before? Fuel injectors. Fuel pump. Regulator? Thanks
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Wednesday, January 12th, 2011 AT 5:37 AM

3 Replies

Tiny
MERLIN2021
  • EXPERT
The tanks have low pressure pumps and the high pressure pump on the frame, it may need the old gas siphoned out and discarded, and the pump pressures tested.
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Wednesday, January 12th, 2011 AT 9:18 AM
Tiny
REVKEV316
  • MEMBER
I put new gas in the front tank, Replaced the high pressure pump and cleaned out the tank selector valve reservoir. Truck still cuts out when I get it out on the street and accelerate. When I stop it struggles for about a minute then evens out like it is going to work right until I accelerate again. Just wondering if the injectors would act like that or if there is anything else that might cause these symptoms other than fuel? I haven't checked the fuel pressure yet. What pressure should I be seeing and will and should I check it while it is idling or revved? Thanks.
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Saturday, January 29th, 2011 AT 8:03 PM
Tiny
MERLIN2021
  • EXPERT
HIGH PRESSURE FUEL PUMP
1. Check fuel tank(s) for adequate fuel supply. Check for fuel leaks at fittings and lines. Install
jumper lead to fuel pump test terminal of VIP test connector. See Fig. 1. Use a test lead long
enough to reach under vehicle. Install fuel pressure gauge. Turn ignition switch to the "RUN"
position. ground jumper lead and refer to FUEL PUMP PRESSURE WITH ENGINE
RUNNING table. If fuel pressure is within specification, go to step 5). If fuel pressure is not
within specification, go to step 2).
Fig. 1: VIP Test Connector
Courtesy of FORD MOTOR CO.
FUEL PUMP PRESSURE WITH ENGINE RUNNING
2. If fuel pressure is low but greater than 3 psi (indicates pump is working), go to step 3). If not,
go to step 4).
3. Check fuel system for plugged fuel filter or restricted fuel lines. Check for low voltage at the
fuel pump (voltage should be with .5 volt of battery voltage). Disconnect fuel return line. If
fuel is returning , adjust or replace pressure regulator. If filters are clear, voltage correct and no
fuel return, replace fuel pump.
4. Ensure that battery voltage and ground are present at fuel pump connector. If circuits and
voltages are correct, replace fuel pump.
5. Disconnect grounded test lead and note fuel pressure. Fuel pressure should remain within 2 psi
for 3 minutes after disconnecting test lead. If fuel pressure holds, go to step 7). If not, go to
step 6).
6. Inspect for fuel leaks. If no leaks are found, disconnect and plug fuel return line. ground test
lead and raise pressure to normal level. If fuel pressure now holds, replace pressure regulator.
If not, replace fuel pump.
7. Disconnect vacuum to fuel pressure regulator and start engine. Fuel pressure should within
specification of FUEL PRESSURE WITH ENGINE RUNNING table. If fuel pressure is
correct, go to step 9). If fuel pressure is not, go to step 8).
8. If fuel pressure is low, check fuel filter, fuel pressure regulator adjustment, fuel line restrictions
or voltage to fuel pump. If all systems are normal, replace fuel pump.
9. With engine idling and fuel pressure regulator vacuum hose disconnected, measure fuel
CAUTION: Fuel system is under pressure. Before removing any fuel lines,
depressurize fuel system. Disconnect inertia switch and crank
engine for a minimum of 15 seconds to depressurize system.
Application Pressure
pressure. Accelerate rapidly and note fuel pressure. If fuel pressure drops more than 5 psi,
repeat step 8). If fuel pressure does not drop, fuel system is operating correctly.
LOW PRESSURE IN-TANK FUEL PUMP
1. Check fuel tank(s) for adequate fuel supply. Check for fuel leaks at fittings and lines. Install
jumper lead to fuel pump test terminal of VIP test connector. See Fig. 1. Use a test lead long
enough to reach under vehicle. Raise vehicle and ground test lead. Use a stethoscope and listen
for pump operation. If low pressure pump is running, go to step 2). If not, go to step 3).
2. Disconnect test lead from ground. Remove reservoir inlet hose at reservoir. Place fuel hose in
one quart calibrated container and ground test lead for 5 seconds. Fuel level should be at least 6
ounces. If fuel pump volume is correct, fuel pump is okay. If not, restrict fuel line momentarily
to prime pump. If no flow develops, check for blocked fuel lines. If no blockage is found,
replace pump.
3. If pump does not run, inspect all electrical connections. Check inertia switch and fuel pump
relay for operation. If high pressure pump runs, but low pressure pump does not and voltage is
present, replace low pressure fuel pump.
CAUTION: Fuel system is under pressure. Before removing and fuel lines,
depressurize fuel system. Disconnect inertia switch and crank
engine for a minimum of 15 seconds to depressurize system.
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Monday, February 7th, 2011 AT 10:44 PM

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