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'94 E350 460 RV Cutaway Motorhome. With no warning, after always starting and running good, I shut it off, 2 hours latter, I hit the starter, the engine seemed to try to fire for an split instant, and then cranks good, easy, smooth, but won't start. Spark ok at distributor output, seems to be no gas. When ignition is turned to the on position, for a moment the fuel pump relay activates ok and 12volts through fuel inertia shutoff switch (located behind panel in front of right side door) is ok.

I hear no noise or feel no vibration with my hand on top of the gas tank as my partner turns the ignition on and off with my volt meter connected to the downside of that switch, reading 12 volts momentarily each time the ignition is turned to the on position or the crank position. A diagram I found online shows the 12 volts from the fuel relay directly through the shutoff switch and then directly on to the fuel pump.

There is a threaded fitting welded to the fuel rail (looks like a tire valve stem threaded tip) and when I press the pin inside, as the engine is cranking, there is no gas present.

There is also a fuel pressure regulator devise welded or bolted to the entrance of the fuel rail with the gas tank line feeding it and a vacuum line attached to the top. Removing that line, cranking the engine, I feel some suction with my finger.

I can't figure out how to open the fuel line anywhere, even at the fuel filter attached to the frame thinking I may jump the contacts of the fuel relay and see if gas flows from the open line. Can't figure those hose clamps out.

Does anybody have any suggestions as to what my next steps should be. Very appreciative. Wilson


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contributions: 2050
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Location: Oregon
it sounds like your fuel pump has stopped working. the schrader valve in the fuel rail that feeds the injectors is where you would put a fuel pressure gauge to check fuel pressure. Fuel pressure key on engine off, (after cycling the key) should be 35 - 45 psi.

have some one cycle the key a few times while you bang on the bottom of the fuel tank. Banging on the tank could jar the fuel pump and let it start up. Don't hit the tank hard enough to dent it but a pretty good hit. If you hear the pump start to run (whirrrr) Start the engine and drive it to where you can have the pump replaced. If you shut it off it may not restart again. Banging on the tank may jar the pump and allow it to run for a while but the pump is bad. Starting to run after banging on the tank is a sign that the pump is bad. if you have found a diagram of the wiring to the fuel pump, verify that your ground wire to the fuel pump has a good ground. It seems like you have good battery voltage to the power side from your description of what you have done so far but a bad or poor ground connection could also make it so the circuit is incomplete.


   
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Thank you 'carriedi', you were the only respondent, appreciated, but my problem ended up being a little deeper than most normal customary responses can initially explain.

12 volts at fuel tank pump assembly, ground ok. So, after dropping the tank, removing the pump assembly from out of the top of the tank, replacing the pump motor, reinstalling the tank, and no start, then, out of frustration, removing the metal gas filler pipe to gain access without dropping the tank, removed the pump assembly again, found 12 volts on top of the pump assembly plate, but not directly under the assembly plate were the pump motor is connected, because those connections were bad (open), therefore, this time around, I changed the entire fuel pump with assembly. Vehicle starts now.

Hindsight: Mistake, not checking for 12 volts directly under top plate of pump assembly where the pump motor is connected, therefore assuming the pump motor is bad.

P.S. In the crank position of the ignition switch, the computer sends voltage to the control winding of the fuel pump relay, expecting verification from the crankshaft position sensor that the engine has started. If the engine starts or the starter continues to turn the crankshaft, the computer continues to send the control voltage to the fuel pump relay keeping the relay output contacts closed and sending 12 volts to the fuel tank pump assembly. In the on position of the ignition switch, the computer only closes the fuel pump relay for about 3 seconds. That is not enough time when troubleshooting for that 12 volts back at the fuel tank. The solution is, remove the relay, there is usually a diagram on the side of the relay, jump the output contact points at the relay socket, therefore, no ignition activation is required, 12 volts in continuously supplied from the relay to the tank, find it.


   
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Location: Oregon
most relays are numbered at the prongs. #30 and #87 should be the power and the fuel pump prongs. #85 and #86 are for the electromagnet side of the relay.

One of the things you check when doing a fuel pump is the connector. corrosion and/or burned contacts are common. when you know you have power and ground going to the connector from the wire harness and you unplug the wire harness and drop the tank, I normally check the fuel pump out of the vehicle.


   
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