testing fuel pump / relief valve?
testing fuel pump / relief valve?
10-31-2006, 12:18 PM
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Location: Arizona
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I'm not quite sure what you're asking, but I hope this'll help some, especially as you're not getting inundated with replies.
I have a '95 F-150. 5.0L. The EECs are different, but I'd think the fuel injection/pressure systems are similiar. Basically, the system's supposed to be always under pressure, 30-45 lbs, and before you work on any part of it, you should use the inertia switch (I think that's the relief valve you mention) to depressurize it and keep it depressurized. Check your owner's manual for its location.
The switch is supposed to pop open in a serious collision to cut off the fuel flow. There's a red button on its top. It should be down for pump to operate (if in wreck, and truck won't start, check it and push it down if it's up--as long as no puddles of gas!).
To use it to depressurize the system, with engine running, just use a screwdriver to pop the button up. There's a slot on it for that purpose. The engine should stop pretty quick. Disconnect the battery, and that's all there is to it. Remember to reset the button when you're done to avoid undue aggravation when your work appears to have gone for naught!
Actually, my experience was that the system depressurizes itself after an hour or two anyway...I cheated a little, and just pushed in the Schrader valve on the fuel rail while the engine was cold (it was a chilly winter morning, and hadn't run all night).
Nothing happened...so, I did the popup thing without energizing the pumps or starting the engine, and had no problems, not even any residual leakage where I broke into the fuel line. Be sure to use rags under that point anyway, just in case a little gas flows out.
As far as the fuel pump, the OBD-I and OBD-II systems are different. Mine's the earlier. There's a way to use its computer to check the pump and pump relay. Alternatively, you can just turn the ignition to ON, but not start, and listen closely. The pump will come on for a couple of seconds, and you can hear a whirring sound if all is well.
I'm not familiar with OBD-II, but I'm sure it's got some similar feature (asssuming you have a code reader, etc.) As far as the fuel pumps themselves, mine are still going strong, so I can't help you there.
Good luck.
Musselshell
Sooner or Later, Arizona
'95 F-150, SC, SB, 4x4 off road, 5.0L, Kenne Bell T-3000 (1.7L) twin-screw supercharger, 6psi, boost-a-pump, 3.55 LS, Warn M12000 winch, KC off-road and Warn auxiliary lights, and some other stuff (I hate being stuck in the dark!)
"There is a deep, abiding, unshakable satisfaction in a life of complete failure."
I have a '95 F-150. 5.0L. The EECs are different, but I'd think the fuel injection/pressure systems are similiar. Basically, the system's supposed to be always under pressure, 30-45 lbs, and before you work on any part of it, you should use the inertia switch (I think that's the relief valve you mention) to depressurize it and keep it depressurized. Check your owner's manual for its location.
The switch is supposed to pop open in a serious collision to cut off the fuel flow. There's a red button on its top. It should be down for pump to operate (if in wreck, and truck won't start, check it and push it down if it's up--as long as no puddles of gas!).
To use it to depressurize the system, with engine running, just use a screwdriver to pop the button up. There's a slot on it for that purpose. The engine should stop pretty quick. Disconnect the battery, and that's all there is to it. Remember to reset the button when you're done to avoid undue aggravation when your work appears to have gone for naught!
Actually, my experience was that the system depressurizes itself after an hour or two anyway...I cheated a little, and just pushed in the Schrader valve on the fuel rail while the engine was cold (it was a chilly winter morning, and hadn't run all night).
Nothing happened...so, I did the popup thing without energizing the pumps or starting the engine, and had no problems, not even any residual leakage where I broke into the fuel line. Be sure to use rags under that point anyway, just in case a little gas flows out.
As far as the fuel pump, the OBD-I and OBD-II systems are different. Mine's the earlier. There's a way to use its computer to check the pump and pump relay. Alternatively, you can just turn the ignition to ON, but not start, and listen closely. The pump will come on for a couple of seconds, and you can hear a whirring sound if all is well.
I'm not familiar with OBD-II, but I'm sure it's got some similar feature (asssuming you have a code reader, etc.) As far as the fuel pumps themselves, mine are still going strong, so I can't help you there.
Good luck.
Musselshell
Sooner or Later, Arizona
'95 F-150, SC, SB, 4x4 off road, 5.0L, Kenne Bell T-3000 (1.7L) twin-screw supercharger, 6psi, boost-a-pump, 3.55 LS, Warn M12000 winch, KC off-road and Warn auxiliary lights, and some other stuff (I hate being stuck in the dark!)
"There is a deep, abiding, unshakable satisfaction in a life of complete failure."