Jeep XJ 4.0L cranks but won't start: step-by-step diagnosis
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If a 4.0L XJ cranks normally but won't start, find out whether it's missing fuel or spark. Turn the key on and listen: the fuel pump should run briefly, then stop [6][7][10][15]. Check for spark while cranking, then fuel pressure: 49.2 ± 5 psi on 1997–2001 trucks [1][7][9][12] and about 31 psi (39 psi with the vacuum hose off) on 1993–95 [6][14][15]. No spark and no injector pulse together point to the crankshaft position sensor: without its signal the computer won't switch on the relay that feeds the injectors and coil [6][7][11].
| Key-on prime | Pump runs briefly, about 1–3 seconds, then stops [6][7][10][15] |
|---|---|
| Fuel pressure, 1997–2001 | 49.2 ± 5 psi (339 ± 34 kPa) at idle [1][7][9][12] |
| Fuel pressure, 1993–95 | About 31 psi, vacuum hose on; about 39 psi off [6][14][15] |
| Relays, 1997–2001 | ASD and fuel pump relays in the power distribution center by the battery [7][11][16] |
| No spark and no injector pulse | Check the crankshaft position sensor [6][7][11] |
Work through the steps in order. Each one narrows the fault to fuel, spark or the signals that control them. The order follows the 2001 service data’s no-start flowchart, with values from the factory manuals.[8]
Step 1: Does it crank at normal speed?
- Slow or clicking: battery, cables or starter. Fix that first; this guide assumes a healthy crank.[8]
- Normal speed: go to step 2.
Step 2: Any trouble codes? (1996–2001)
Read the codes with an OBD-II reader before you start unplugging things.[8]
- P0320 (no crank reference signal) or P1391 (intermittent loss of the crank or cam signal): go straight to the crankshaft position sensor guide.[7]
- 1987–90 Renix: Unverified these trucks store no trouble codes, so a meter is the only way to check. (enthusiast source only)[5]
Step 3: Fuses and relays
On 1997–2001 trucks the auto shutdown (ASD) relay and the fuel pump relay are both in the power distribution center (PDC), next to the battery.[7][11][16] The ASD relay feeds the injectors and the ignition coil(s); on 1994 trucks it feeds the fuel pump too.[6][7][11] Check the fuses in the PDC and in the junction block, which sits on the right-hand cowl side behind the kick panel on left-hand-drive trucks.[7][8] We haven’t checked right-hand-drive layouts.
Step 4: Key ON. Does the fuel pump run briefly?
Step 5: Is there spark while cranking?
Use a spark tester on a plug lead (or at a plug on 2000–01 coil-rail trucks).
- No spark: go to step 7 (crank sensor). The firing order page shows which years have a distributor and which have a coil rail.
- Spark: go to step 6.
Step 6: Is fuel pressure in spec?
Connect a gauge to the test port on the fuel rail.[1][9]
- 1987–92 and 1996: Unverified fuel pressure not yet sourced. Don’t assume the 1993–95 figures apply to Renix trucks. (no factory manual for these years in hand)
- High pressure (1997–2001): the regulator in the tank module is at fault.[1][9]
- Low pressure (1997–2001): look for a kinked or restricted line first, then the pump module.[1][9]
- In spec, still no start: check injector pulse and the crank sensor (step 7).
Step 7: Test the crankshaft position sensor
Without a crank sensor signal the computer won’t switch on the ASD relay, so you get no spark and no injector pulse at the same time.[6][7][11] Unverified The factory manual says it gives up after about 3 seconds of cranking without the signal. (factory manual only)[6][7]
The crankshaft position sensor guide has the voltage checks by year, bolt torque and part numbers.
Still won't start?
FAQ
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What sensor can cause a crank-no-start on a Jeep 4.0?
How long should the fuel pump run when I turn the key on?
What fuel pressure should a 4.0L XJ have?
Why does my XJ crank but not start when hot?
Sources (16)
- 2000 Cherokee (XJ) service manual, Group 14 Fuel System (reproduced by johnmeister.com)
- 1993 Engine Performance, 2.5L & 4.0L Basic Diagnostic Procedures, third-party service data (reproduced by johnmeister.com)
- Chrysler service bulletin 18-51-88, crankshaft position sensor and harness replacement, 1987–90 4.0L (reproduced by johnmeister.com)
- RENIX (non-HO) Engine Sensor Diagnostics, lunghd.com
- XJ 4.0L Renix Wiring Diagnostic Quick Reference (1987–1990), ihatethiscar.com
- 1994 Jeep Cherokee and Wrangler Service Manual (Chrysler publication 81-370-4146), Group 14 Fuel System, archive.org scan
- 2001 Jeep Cherokee (XJ) Service Manual, Groups 8W and 14, archive.org scan
- 2001 Cherokee SE 4WD, No-Start Diagnosis, Engine Cranks But Does Not Start (Cherokee), alloemmanuals.com
- 2001 Cherokee SE 4WD, Fuel Pressure Test (Cherokee & Wrangler), alloemmanuals.com
- 2001 Cherokee SE 4WD, Modes of Operation, Ignition Switch On (Engine Not Running), alloemmanuals.com
- 2001 Cherokee SE 4WD, Fuel Delivery, Auto Shutdown Relay, alloemmanuals.com
- 1997 Jeep Cherokee (XJ) Factory Service Manual, Group 14 (hosted by xjjeeps.com)
- 1999 Jeep Cherokee Electronic Service Manual (Chrysler publication 81-370-9146), Group 14, archive.org scan
- 1995 Jeep Cherokee and Wrangler Service Manual (Chrysler publication 81-370-5146), Group 14, archive.org scan
- 1993 Cherokee service data, engine performance theory (third-party; the archive.org item is titled "Factory Service Manual" but is not a Chrysler publication)
- 2001 Cherokee SE 4WD, Fuel Delivery, Fuel Pump Relay, alloemmanuals.com
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