The fuel pump can be tested, to see if it's bad or not, with a fuel pressure test gauge.
In this tutorial I'll show you how to do it. With your test results you'll be able to find out if the fuel pump is bad or not.
Contents of this tutorial:
- Symptoms Of A Bad Fuel Pump.
- Fuel Pressure Specifications.
- Where To Buy A Fuel Pressure Test Gauge.
- Fuel Pressure Test Gauge For Non-Schrader Valve Fuel Injector Rail.
- TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.
- TEST 2: Using Starting Fluid To Confirm Lack Of Fuel.
- Fuel Pressure Release Procedure.
- More 5.2L, 5.9L Dodge Ram Diagnostic Tutorials.
You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1992-2003 5.2L, 5.9L Dodge Ram Pickup) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following Dodge Ram pickups:
- 5.2L V8 Dodge Ram D150 Pickup: 1992, 1993.
- 5.2L V8 Dodge Ram D250 Pickup: 1992, 1993.
- 5.2L V8 Dodge Ram W150 Pickup: 1992, 1993.
- 5.2L V8 Dodge Ram W250 Pickup: 1992, 1993.
- 5.2L V8 Dodge Ram 1500 Pickup: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001.
- 5.2L V8 Dodge Ram 2500 Pickup: 1994, 1995, 1996, 1997.
- 5.9L V8 Dodge Ram 1500 Pickup: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 5.9L V8 Dodge Ram 2500 Pickup: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002.
- 5.9L V8 Dodge Ram 3500 Pickup: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002.
Symptoms Of A Bad Fuel Pump
For the most part, fuel pumps usually fail in one of two ways: The fuel pump will fail completely and the engine won't to start. Or the fuel pump still functions but it doesn't send enough fuel to the fuel injectors.
When the fuel pump fails but sends just enough fuel to start the engine, you'll see one or more of the following symptoms:
- 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 vehicle down the road.
- Lean air/fuel mixture trouble codes: P0171 or P0174 or both.
Whether the fuel pump is the cause behind your Dodge Ram pickup's no-start problem or engine performance problem, you can find out with a simple fuel pump pressure test.
Fuel Pressure Specifications
| 1992 | |
|---|---|
| 5.2L | 39 PSI (Key On Engine Off -KOEO) |
| 5.9L | 14.5 PSI (Throttle Body Injection -TBI- System) |
| 1993 | |
|---|---|
| 5.2L | 39-41 PSI (Key On Engine Off or Key On Engine Running with vacuum hose connected to fuel pressure regulator) |
| 5.9L | 35-45 PSI (Key On Engine Running At Idle -No Load) |
| 1994-1995 | |
|---|---|
| 5.2L | 35-45 PSI (Key On Engine Running At Idle -No Load) |
| 5.9L | 35-45 PSI (Key On Engine Running At Idle -No Load) |
| 1996-1997 | |
|---|---|
| 5.2L | 44-54 PSI (Key On Engine Off) |
| 5.9L | 44-54 PSI (Key On Engine Off) |
| 1998-2000 | |
|---|---|
| 5.2L | 44-54 PSI (Key On Engine Running At Idle -No Load) |
| 5.9L | 44-54 PSI (Key On Engine Running At Idle -No Load) |
| 2001 | |
|---|---|
| 5.2L | 44-54 PSI (Key On Engine Off) |
| 5.9L | 44-54 PSI (Key On Engine Off) |
| 2002 | |
|---|---|
| 5.9L | 44-54 PSI (Key On Engine Off) |
| 2003 | |
|---|---|
| 5.9L | 47-51 PSI (Key On Engine Off) |
NOTE: If your Dodge Ram pickup does not start and there's only a key on engine running (KOER) fuel pressure specification, then that KOER specification will apply to your key on engine off (KOEO) fuel pressure test.
Where To Buy A Fuel Pressure Test Gauge
You can buy a fuel pressure test gauge just about anywhere and is one of the most important tools any serious DIY'er should have in his/her tool box.
The following fuel pressure test gauge kits are pretty good deals and will work with your Dodge Ram Pickup:
Fuel Pressure Test Gauge For Non-Schrader Valve Fuel Injector Rail
If your Dodge Ram Pickup's fuel rail does not have a Schrader valve, then the following fuel pressure test gauge will have the adapter you need:
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
Some Dodge Ram pickups (1996-1999 models) don't come equipped with a Schrader valve on the fuel injector rail.
On these models you can still connect a fuel pressure test gauge, but you'll need to use a special adapter. You can see what this adapter looks like in image 3 of 3 in the image viewer above.
FUEL RAIL WITH SCHRADER VALVE: If you don't have a fuel pressure gauge and would like to buy one, take a look at the section: Where To Buy A Fuel Pressure Test Gauge.
FUEL RAIL WITHOUT SCHRADER VALVE: The fuel pressure test gauge kit with the adapter you need isn't expensive. You can see it here: Fuel Pressure Test Gauge For Non-Schrader Valve Fuel Injector Rail.
OK, let's get started with this test:
- 1
Place a shop towel around the Schrader valve. The shop towel's job is to absorb any fuel that may leak when doing step 2.
- 2
Connect the fuel pressure gauge to the Schrader valve (see image 1 of 3 and image 2 of 3).
Dodge Ram pickup without a Schrader valve:
A) Release the fuel pressure in the fuel line (see: Fuel Pressure Release Procedure).
B) Disconnect the fuel line from the fuel injector rail.
C) Install the fuel pressure gauge adapter between the fuel injector rail and the fuel line (see image 3 of 3 in the image viewer above). - 3
When ready, ask your helper to cycle the key on and off but don't crank the engine while you observe the fuel pressure tester's gauge.
Check the connection at the Schrader valve for fuel leaks and if any tighten the fuel pressure a bit more (by hand only) to eliminate them. - 4
Crank and start the engine and check the fuel pressure gauge.
Your fuel pressure gauge should register the indicated fuel pressure for you particular year model. See: Fuel Pressure Specifications - 5
If the engine doesn't start, crank the engine enough to get the fuel pressure up.
Your fuel pressure gauge should register the indicated fuel pressure for you particular year model. See: Fuel Pressure Specifications.
NOTE: If your Dodge Ram pickup does not start and there's only a key on engine running (KOER) fuel pressure specification, then that KOER specification will apply to your key on engine off (KOEO) fuel pressure test.
Let's take a look at what your results mean:
CASE 1: The fuel pressure gauge registered 0 PSI. This test result lets you know that the no-start problem is caused by a lack of fuel from the fuel pump.
I recommend that you take one more precaution, before condemning the fuel pump as bad, and this is to make sure that the fuel pump is getting 12 Volts as the engine is cranking. This is just to make sure that the fuel pump relay and fuse are OK and doing their job.
What you'll have to do to accomplish this is to attach a multimeter in Volts DC mode to the wire that supplies this voltage to the fuel pump and while a helper cranks the engine, verify that the fuel pump is getting this power. If the 12 Volts are being supplied to the fuel pump, you have now 100% verified that the fuel pump is fried and needs to be replaced.
CASE 2: The fuel pressure gauge registered less than the specified PSI. This test result lets you know that the fuel pump is failing.
CASE 3: The fuel pressure gauge registered the indicated PSI. This is the correct test result.
With this test result you can conclude that the fuel pump is working and delivering enough fuel to the fuel injectors. You can also conclude that your Dodge Ram Pickup is not starting due to another reason. The fuel pump is OK.