Testing the fuel pump, on the 1993-1998 5.2L V8 Jeep Grand Cherokee, is a breeze. This is due to the fact that you can connect a fuel pump pressure test gauge to the fuel system easily.
In this tutorial, I'm going to show you how to test the fuel pump in a step-by-step way.
You'll be able to find out if the fuel pump is causing an engine performance problem or is causing a no-start problem on your 5.2L V8 Jeep Grand Cherokee.
Contents of this tutorial:
WIRING DIAGRAM: You can find the fuel pump circuit wiring diagram here:
- Fuel Pump Circuit Wiring Diagram (1993-1995 5.2L Grand Cherokee).
- Fuel Pump Circuit Wiring Diagram (1996-1998 5.2L Grand Cherokee).
Symptoms Of A Bad Fuel Pump
It's been my experience that fuel pump problems will cause one of two things. Either the engine will not start due to lack of fuel or the engine will start and run but will have no power because the fuel pump is not supplying enough fuel to the engine.
When the fuel pump doesn't supply enough fuel to the engine, you're going to 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 causing a no-start problem or a lack of power, a fuel pump pressure test will help you diagnose the fuel pump as the cause of the problem or not.
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
To test the fuel pump you're going to need a fuel pump pressure test gauge. If you don't have one, you can run down to your local auto parts store and buy or borrow one from them.
If you're interested in buying a fuel pump pressure test gauge and would like to save some on its purchase, check out my recommendations here: Where To Buy A Fuel Pressure Test Gauge.
Here's the fuel pump pressure specification:
- 1993 5.2L V8 Jeep Grand Cherokee:
- 39 PSI with the key on and engine running (KOER).
- 1994-1995 5.2L V8 Jeep Grand Cherokee:
- 37-41 PSI with the key on and engine running (KOER).
- 1996 5.2L V8 Jeep Grand Cherokee:
- 47-51 PSI with the key on and engine running (KOER).
- 1997-1998 5.2L V8 Jeep Grand Cherokee:
- 44-54 PSI with the key on and engine running (KOER).
If your Jeep Grand Cherokee's engine doesn't start, then the fuel pressure specification is still the same as the one listed above.
CAUTION: Gasoline is extremely flammable, be careful and take all necessary safety precautions when connecting the fuel pressure test gauge to the Schrader valve.
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 on your 5.2L Jeep Grand Cherokee's fuel injector rail.
- 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 specification listed in the test introduction above. - 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 specification listed in the test introduction above.
Let's examine what your test 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 one more test, 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 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 5.2L Jeep Grand Cherokee is not starting due to another reason. The fuel pump is OK.
