The fuel pump, in your 3.0L Ford, can be easily tested with an inexpensive fuel pressure test gauge. This is due to the fact that your 3.0L V6 equipped Ford Taurus (Mercury Sable) comes equipped with a Schrader valve and it's to this valve that the fuel pressure test gauge is connected to.
In this tutorial I'm also gonna' explain the simple ‘starting fluid’ test, which is a quick way to confirm a lack of fuel problem causing a no start problem.
Contents of this tutorial:
NOTE: This tutorial applies to the 3.0L OHV (Over Head Valve) V6 engine only. You can confirm this by checking the 8th digit of the VIN number. If your 3.0L is OHV, the 8th VIN character will be a letter U.
You can find this tutorial in Spanish here: Cómo Probar La Bomba de Gasolina (1990-2000 3.0L Ford Taurus) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Pump
The 2 most common fuel pump failures are a complete failure in which the fuel pump stops sending fuel to the fuel injectors or a fuel pump that is sending a volume that's lower than normal to the fuel injectors (provoking a lean air/fuel mixture).
Obviously, when the fuel pump completely fails... your 3.0L Ford Taurus isn't gonna' start. In this type of scenario, you'll see that:
- The engine turns over but will not start.
- The ignition coil pack feeding spark to all 6 cylinders.
- The PCM will still pulse (activate) all 6 fuel injectors.
When the fuel pump is starting to fail and under-performing, you'll probably see one or more of the following symptoms:
- Lean air/fuel mixture trouble codes.
- Rough idle.
- Engine starts after extended cranking.
- Lack of power when accelerating the vehicle down the road.
- Back-fires thru' the intake manifold when accelerating your pickup or van down the road.
Both of these conditions can be tested with a fuel pressure gauge. Alright, with this info under our belts, let's get testing.
TEST 1: Using Starting Fluid To Confirm Lack Of Fuel
I've been using starting fluid, to diagnose a lack of fuel causing a no start problem, since the first week on the job (some 25 years ago). It's a fast and easy test but the successful outcome of this test depends on making sure that all 6 cylinders are getting spark.
This means that you have to precede this test with a spark test on 6 spark plug wires (with a dedicated spark tester).
IMPORTANT: This is a very fast and easy test but you do have to take one very important safety precaution and this is to reconnect the air intake duct after spraying starting fluid down the throttle bore (although you don't have to fasten it). This will prevent any backfire, that might occur, from scaring the heck out of you when cranking the engine.
This is what you have 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 plate and spray starting fluid down the bore.
As a safety precaution reconnect the air duct after you have sprayed a good squirt of starting fluid (but you don't have to tighten the air duct's hose clamp).
Crank the engine once the air duct is back on and you're clear of the engine compartment.
You'll get one of two results with this test:
1.) The engine will start momentarily and after a few seconds will die or.
2.) The engine will only crank but not start at all.
OK, let's find out what your results mean:
CASE 1: If the engine started and ran for a few seconds: This test result tells you that the no start problem is due to a lack of fuel.
Your next step is to check to see what the fuel pressure is with a fuel pressure test gauge. Go to: TEST 2: Checking Fuel Pressure With A Fuel Pressure Gauge.
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 and this is to check the fuel pressure with a fuel pressure test gauge. Go to: TEST 2: Checking Fuel Pressure With A Fuel Pressure Gauge.