Gas tank/pump problem? 89 F250 5.8 liter
#46
04-16-2018, 09:30 PM
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#48
04-16-2018, 09:56 PM
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There is no external switching mechanism on a fuel system with 2 high pressure FDMs. Hence the term Fuel Delivery Module. The unsed tank has flow activated (actually lack of flow) valves to shut off flow into the tank as the energized tank sends fuel to the engine and the unsed fuel is returned to the selected tank.
The tank selector switch on the dash is electrical to supply power to the selected tank's pump and supply power and feedback for the fuel level gauge on the dash. An open circuit in the fuel sender circuit results in a gauge that reads past full all the time. A short will cause the gauge to read empty.
Bricknose trucks may be opposite of the fuel gauge operation above. Ford changes things between generations.
The tank selector switch on the dash is electrical to supply power to the selected tank's pump and supply power and feedback for the fuel level gauge on the dash. An open circuit in the fuel sender circuit results in a gauge that reads past full all the time. A short will cause the gauge to read empty.
Bricknose trucks may be opposite of the fuel gauge operation above. Ford changes things between generations.
#49
04-16-2018, 10:04 PM
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There is no external switching mechanism on a fuel system with 2 high pressure FDMs. Hence the term Fuel Delivery Module. The unsed tank has flow activated (actually lack of flow) valves to shut off flow into the tank as the energized tank sends fuel to the engine and the unsed fuel is returned to the selected tank.
The tank selector switch on the dash is electrical to supply power to the selected tank's pump and supply power and feedback for the fuel level gauge on the dash. An open circuit in the fuel sender circuit results in a gauge that reads past full all the time. A short will cause the gauge to read empty.
Bricknose trucks may be opposite of the fuel gauge operation above. Ford changes things between generations.
The tank selector switch on the dash is electrical to supply power to the selected tank's pump and supply power and feedback for the fuel level gauge on the dash. An open circuit in the fuel sender circuit results in a gauge that reads past full all the time. A short will cause the gauge to read empty.
Bricknose trucks may be opposite of the fuel gauge operation above. Ford changes things between generations.
#50
04-16-2018, 10:07 PM
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#51
04-16-2018, 10:09 PM
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Make sure the fuel level sending unit is good. Measure it with a DVM set to ohms. If good, connect it to the wiring in the truck. Measure the resistance at the switch.Do not turn on the key, you are measuring resistance only.
#53
04-16-2018, 10:18 PM
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Some good info on the Fuel Delivery Module and how the fuel system works on a 1990 and later truck with two high pressure in-tank pumps: https://www.ford-trucks.com/forums/1...-or-other.html
Your truck has been modded to function like the above.
Your truck has been modded to function like the above.
#55
04-17-2018, 05:07 AM
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#56
04-17-2018, 05:08 AM
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#57
04-17-2018, 05:48 AM
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Yes. If there is enough slack in the harness you can plug in the pump. If you have another set of eyes or very long arms you can turn the key to run and move the float up and down to see if the needle on the gauge also moves. Be aware that any fuel in the pump will be pumped out when you apply power. Personally I wouldn’t bother doing this since.
#58
04-17-2018, 06:40 AM
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Some good info on the Fuel Delivery Module and how the fuel system works on a 1990 and later truck with two high pressure in-tank pumps: https://www.ford-trucks.com/forums/1...-or-other.html
Your truck has been modded to function like the above.
Your truck has been modded to function like the above.
#59
04-17-2018, 06:58 AM
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Technically no you cannot hook it up to power and check ohms. Ohms (resistance) is checked without power. Check the resistance of the sending unit and also check the wiring going to the gauge at the pump connector. If the is an open you will not have a reading.
Yes. If there is enough slack in the harness you can plug in the pump. If you have another set of eyes or very long arms you can turn the key to run and move the float up and down to see if the needle on the gauge also moves. Be aware that any fuel in the pump will be pumped out when you apply power. Personally I wouldn’t bother doing this since.
as for the wiring on the assembly/fuel hanger, where would I pit my leads to test the resistance? Also, am I missing a wire? Is something supposed to be attached to the last spot?
#60
04-17-2018, 07:27 AM
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