TEST 2: Using Starting Fluid
If you don't have a fuel pressure gauge handy, you can use starting fluid to see if the no-start condition of your 4.0L equipped Ford vehicle is due to a lack of fuel.
This method is not the most accurate way of testing the fuel pump, but it doesn't mean it's not effective.
The most important suggestion I can give you, before starting this test, is to make sure that all six cylinders are getting spark.
NOTE: If you haven't already checked the fuel pump inertia switch, do so before you start this test. For more info on the fuel pump inertia switch, take a look at this section: Checking The Fuel Pump Inertia Switch.
OK, to get this show on the road, this is what you'll need to do:
Remove the intake air duct from the throttle body. You don't have to completely remove it, since you'll have to reconnect it in one of the next steps.
Open the throttle, manually, and spray starting fluid down the bore.
When you have sprayed a good squirt of starting fluid, quickly reconnect the air duct to the throttle body (you don't have to tighten the hose clamp).
IMPORTANT: Reconnecting the intake air duct is a very important safety precaution in case you get a back-fire thru' the intake manifold.
Have your assistant crank the engine once the intake air duct is back on the throttle body.
You'll get one of two results with this test:
1.) The engine will start momentarily and after a few seconds will die.
2.) The engine will only crank but not start at all.
OK, let's find out what your results mean:
CASE 1: The engine started and ran for a few seconds. This means that the root cause of your Ford vehicle's no-start is a lack of fuel.
Usually, this also means that the fuel pump is bad. But since we don't live in a perfect world, this could also mean a few other things like: the fuel pump fuse is blown, or the fuel pump relay is bad.
Your next step is buy or rent a fuel pressure gauge and actually check fuel pressure (your local auto parts store, like AutoZone or O'Reilly Auto Parts, will rent the fuel pressure gauge to you for free for a cash deposit which they'll return to you when you return the tool).
CASE 2: The engine did not start, not even momentarily. This usually means that a lack of fuel IS NOT the reason your car is not starting.
Now, remember what I said about this test not being very accurate? Well, I suggest you do one more test.
The next test is to actually verify the fuel pressure with a fuel pressure gauge. You can buy one or rent one (your local auto parts store, like AutoZone or O'Reilly Auto Parts will rent the fuel pressure gauge to you for free for a cash deposit which they'll return to you when you return the tool).
Location Of The Fuel Pressure Schrader Valve Test Port
The Schrader Valve, on the 4.0L Ford V6 engine is located on the injector fuel rail. To be a bit mores specific, it's on the passenger side of the engine between the ignition coil pack and the upper radiator hose.
In the photo above, it's shown without its plastic cap.
Checking The Fuel Pump Inertia Switch
Your 4.0L Ford Explorer (Aerostar, or Mercury Mountaineer) comes equipped with a fuel pump inertia switch, whose job is to cut power (or Ground) to the fuel pump in case of an impact.
When an impact causes the fuel pump inertial switch to activate, the engine will stall (if it was running) or crank but not start due to a lack of fuel.
Although it's designed to activate during a severe impact caused by an automobile accident, sometimes it gets activated by less than severe impacts (and this happens a lot).
You should always check and reset the inertia switch and try starting the engine before testing the fuel pump.
On the majority of the vehicles covered by this tutorial, the inertia switch is located below the right side of the instrument panel, behind the trim panel.
Resetting the fuel pump inertia switch simply involves pushing down on the button located on top of the inertia switch till it bottoms out. If the inertia switch has been jolted into shutting off the fuel pump, you'll feel a definite ‘click’ as you depress the button.
Where To Buy The Fuel Pump And Save
The following links will help you comparison shop for the fuel pump:
Not sure if the above fuel pumps fit your particular 4.0L Ford? Don't worry, once you get to the web-site they'll make sure it fits (by asking you for the specifics of your vehicle). If it doesn't fit, they'll find you the right one.
More Ford 4.0L Ford Explorer And Aerostar Tutorials
If you enjoyed and/or found this ‘How to’ article helpful, I have written several more 4.0L specific test articles. You can find here: Ford 4.0L Index Of Articles.
The following tutorials are a sample of the articles you'll find in the index:
- How To Do An Engine Compression Test (Ford 4.0L).
- Fuel Injector Resistance Test (Ford 4.0L).
- How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L) (at: easyautodiagnostics.com).
- How To Test The Ford Mass Air Flow (MAF) Sensor (at: easyautodiagnostics.com).
- How To Troubleshoot A No Start (Ford 4.0L).
If this info saved the day, buy me a beer!