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.
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 5.2L Jeep Grand Cherokee:
Disclosure: As an Amazon Associate, I earn from qualifying purchases. If my tutorials help you, using these links is an easy way to support the site at no extra cost to you. Thank you!
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.
TEST 2: Using Starting Fluid To Confirm Lack Of Fuel
Another way to find out if a lack of fuel is causing the engine to not start, is to do a starting fluid test.
This test simply involves spraying starting fluid into the throttle body and then cranking the engine to see if it starts.
If the engine is not starting due to lack of fuel, spraying starting fluid will make the engine start. Although it will only start momentarily and then stall.
IMPORTANT: The only way to get a correct test result from the starting fluid test, is to make sure that all eight spark plug wires are sparking. So if you haven't checked for spark, you must do it before doing the starting fluid test.
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 back to the throttle body 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.
These are the test steps:
- 1
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. - 2
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). - 3
Crank the engine once the air duct is back on and you're clear of the engine compartment.
- 4
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 analyze your test result:
CASE 1: The engine started and ran for a few seconds. This test result confirms that a lack of fuel is keeping the engine from starting.
Your next step is to check to see what the fuel pressure is with a fuel pressure test gauge. Go to: TEST 1: 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 1: Checking Fuel Pressure With A Fuel Pressure Gauge.
More 5.2L Jeep Grand Cherokee Tutorials
You can find a complete list of 5.2L Jeep Grand Cherokee tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Do An Engine Compression Test (1993-1998 5.2L Jeep Grand Cherokee).
- How To Test The Camshaft Position Sensor (1993-1997 5.2L Grand Cherokee).
- How To Test A Blown Head Gasket (1993-1998 5.2L Grand Cherokee).
- How To Test The MAP Sensor (1993-1996 5.2L Grand Cherokee).
If this info saved the day, buy me a beer!
