Circuit 3 is the one that runs to the fuel pump (via the inertia switch) and delivers the voltage/current it needs to activate.This activates the fuel pump relay to pass current from circuit 4 to circuit 3.The fuel injection computer then Grounds circuit 1.This voltage comes from the ignition switch.Power (in the form of 10 to 12 Volts) is applied to circuit 4.This voltage comes from the EEC Power relay.Power (in the form of 10 to 12 Volts) is applied to circuit 2.To get into more specifics, this is what happens when you turn the key and crank the engine:
By ‘closing’ the high current circuit, I specifically mean allowing voltage to pass thru' the relay (internally) and on its way to the fuel pump. The low current circuit is the control circuit that ‘closes’ or ‘opens’ the high current circuit. In it's ‘open’ state current does not get sent to the fuel pump. When the fuel pump relay is off (not activating the fuel pump), the high current circuit is ‘open’. The high current circuit is the one that delivers the voltage (and thus current) to the fuel pump in the gas tank (or on the frame rail).
Well, every Ford fuel pump relay has two basic circuits and for the purpose of our discussion, we'll call them:īoth of these are completely independent from one another, in other words, voltage/current flowing thru' these circuits don't mix. The core purpose of a relay is to control a high amount of current with a smaller (lower) current. Relay Basics: How The Fuel Pump Relay Works * Your specific Ford vehicle may have different colors. You will be able to use the info in this article to diagnose the fuel pump relay on your Ford vehicle even if the colors of the fuel pump relay connector's wires are different! Ford Fuel Pump Circuits This is no big deal, since the circuit descriptions are the same. IMPORTANT: Your specific Ford vehicle may not have the exact same colors listed below. The Ford fuel pump relay has 4 wires that connect to it.Įach wire has a specific job to do and these are their circuit descriptions: You'll need two of them with alligator clips on both ends (you can make these yourself).To see what this tool looks like, click here: Wire Piercing Probe. This tool is a time saver of the first order.If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.A digital or analog multimeter will work.
You need a few basic things and they are: You can find this tutorial in Spanish here: Cómo Probar El Relé De La Bomba De Gasolina (Relé Verde) (at: ). ORIGINAL ENGINE MANAGEMENT Part # DR1039.
#Ford taurus fuel pump problems how to#
The following tutorial may be of help: How To Test The Fuel Pump (Ford 4.9L, 5.0L, 5.8L) (at: ). If it has already been replaced with an after-market one, this relay won't be green, but will have a gray body. If your fuel injected Ford pickup, van, or car still has the Ford relay, this bad boy will be a green color (like the one in the image above). You'll be able to find out if the fuel pump relay, or the fuel pump inertia switch, or the fuel pump is the cause of the no-start condition on your Ford car or pickup. With the help of this ‘How To’ tutorial, I'll show you how to do it using only a multimeter. Testing the Ford fuel pump relay on the car is not that hard to do.
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