When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Check fuel pressure at the rail using a mechanical gauge. You can get a gauge kit for like $25 or just rent one from O'reilly's. It should hold 40 PSI
Check spark as well. Pull one of the plugs, touch it to the engine cylinder head and have a friend crank the motor over. Spark should be nice and blue.
Hate to say it, but if your mechanic can't even verify timing, fuel pressure, or consistent spark - than he isn't a mechanic and you need to find someone that actually is. Doesn't matter how many sensors he has changed for your family - if he cant troubleshoot than all a parts changer is all he is.
He actually said he checked all that, he's done some good work for me before on other cars but I guess this shows his level if he can't deal with the Jeep. I'm still not sure how much time he really but into it maybe because he thinks he is going to lose out. That Golden Gate Jeep is one of the places I was looking at but its across the Bay. I sent them an e-mail over the weekend but I've yet to hear from them.
Finding a mechanic around here is easy, finding a Jeep mechanic or some one who actually knows and works on Jeep is not easy at all. I went to a Jeep dealer for some other work before and they referred me to some one else because they said the Jeep is old or something like that. So yea, not easy finding a Jeep guy here close to me.
If you can't find a good 4.0L mechanic, perhaps from a 4x4 shop. A shop that works primarily on 4x4's. Try finding a mechanic with a DRB-III scan tool. We use to have a mechanic with a DRB-III scanner, he was able to troubleshoot with and without the scanner, all kinds of non-apparent problems.
You also might want to double check that the security system is actually disabled and not at all tied into the Jeep's electrical. I assume you don't have Jeep's Sentry Key Immobilizer System? Those can become a real pain, often disabling a Jeep with a no start condition.
One thing to first check are all your grounds The NSS operates in conjunction with other electronics and logic control, by completing a ground before startup. An open ground causes a no start condition.
Jeep's service manual does have some troubleshooting procedures.
symptom: ENGINE CRANKS DOES NOT START
FUEL PUMP RELAY
NO START PRE-TEST
POWERTRAIN FUSES OPEN
FUEL PRESSURE OUT OF SPECS
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
FUEL PUMP CAPACITY (VOLUME) OUT OF SPECS
FUEL PUMP RELAY FUSED B+ CIRCUIT
FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
FUEL PUMP GROUND CIRCUIT OPEN/HIGH RESISTANCE
FUEL PUMP MODULEThe fuel must be free from contamination.
The exhaust may be free from restrictions.
The engine compression must be within specifications.
The engine valve timing must be within specifications.
The engine must be free from vacuum leaks.
Check for any open fuses in the PDC or Fuse Block that may be related to the No Start condition. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors, repair as necessary. Replace the Fuse.
DRB-III Scanner has quite a few diagnostic tests. Many which can be done manually.
Very common for a no start condition are tests for the fuel system. Includes test ASD and fuel pump relay, fuel pump assembly and plug connectors (97+ changes were made to the fuel pump assembly and fuel gauge.) Testing fuel line from the fuel injector rail and from the fuel injector rail back to the fuel pump. IIRC the fuel line should be able to maintain fuel pressure of at least 30 psi, after the engine has been shut off, for at least 5 mins.
Fuel pump assembly, is a common problem with XJ. If your XJ was a 97+, a potential problem for starting and running is the fuel gauge sending unit connected to the PCM. The PCM uses this information to control the fuel gauge as well as other reasons such for run-ability, EVAP, etc. 96 fuel gauge sending unit is separate from the PCM. IIRC 96 the fuel filter and pressure regulator is part of the fuel pump assembly as with 97+.
The fuel pump assembly wiring and connectors need to be checked for bad wiring, bent pins, corrosion, etc.
Bad coil is a common problem for no start conditions. Sometimes a coil will test ok using a meter, but not put out a good enough spark for starting.
_____________
More information related to starting
When the ignition is turned on, the PCM uses ambient temperature, coolant temperature, and barometric pressure sensor inputs to determine the correct air/fuel mixture ratio for starting the engine. In some applications, critical data like barometric pressure or altitude might be stored in an adaptive memory built into the PCM so the engine will immediately start.
The PCM also activates the in-tank fuel pump for a few seconds during cranking to pressurize the fuel system. As the engine is cranked, the PCM receives a signal from the crankshaft position sensor indicating cranking speed. When the cranking speed exceeds approximately 200 rpm, the PCM re-activates the fuel pump to supply fuel to the engine. At this point, the PCM turns on actuators like the ignition coils and fuel injectors to start the engine and begin operating in an open-loop mode.
As soon as the oxygen sensors located in the exhaust system start producing a signal, the PCM switches into the closed-loop mode, which means that it is now adjusting fuel delivery, spark advance, and idle speed to meet various operating conditions. The PCM also begins running a series of tests on emissions system actuator components to see if they are working. If the PCM finds an emissions-related failure in any powertrain system, it turns on the “check engine” light.
________
Hard Start
Fuel pressure
Coolant temp sensor
TPS Calibration
MAP sensor calibration
Min Idle Air flow
IAC operation
Evap
IAT sensor
Start Stall
pcm powr and gnd ckt
There are other inputs such as from the MAP, IAT, TPS and RPMs
– engine coolant temperature
– manifold absolute pressure
– intake air temperature
– engine revolutions
– throttle position
Fuel pressure isn't monitored by the PCM so it doesn't know if their is enough pressure in the fuel line ... if the fuel line can hold pressure but there is not enough during startup, priming is usually required to build up enough fuel pressure for the engine to start.
The PCM doesn't monitor such things as the fuel injectors, fuel pressure, throttle body air flow, timing, PCM grounds, exhaust system, cylinder compression, oil consumption and quality of gas.
____
Open Loop: Startup
Battery voltage
CTS
Manifold air temperature sensor
MAP
Starter motor relay
Speed sensor
Sync signal
TPS
If you can't find a good 4.0L mechanic, perhaps from a 4x4 shop. A shop that works primarily on 4x4's. Try finding a mechanic with a DRB-III scan tool. We use to have a mechanic with a DRB-III scanner, he was able to troubleshoot with and without the scanner, all kinds of non-apparent problems.
You also might want to double check that the security system is actually disabled and not at all tied into the Jeep's electrical. I assume you don't have Jeep's Sentry Key Immobilizer System? Those can become a real pain, often disabling a Jeep with a no start condition.
One thing to first check are all your grounds
The NSS operates in conjunction with other electronics and logic control, by completing a ground before startup. An open ground causes a no start condition.
Jeep's service manual does have some troubleshooting procedures.
symptom: ENGINE CRANKS DOES NOT START
FUEL PUMP RELAY
NO START PRE-TEST
POWERTRAIN FUSES OPEN
FUEL PRESSURE OUT OF SPECS
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
FUEL PUMP CAPACITY (VOLUME) OUT OF SPECS
FUEL PUMP RELAY FUSED B+ CIRCUIT
FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
FUEL PUMP GROUND CIRCUIT OPEN/HIGH RESISTANCE
FUEL PUMP MODULEThe fuel must be free from contamination.
The exhaust may be free from restrictions.
The engine compression must be within specifications.
The engine valve timing must be within specifications.
The engine must be free from vacuum leaks.
Check for any open fuses in the PDC or Fuse Block that may be related to the No Start condition. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors, repair as necessary. Replace the Fuse.
DRB-III Scanner has quite a few diagnostic tests. Many which can be done manually.
Very common for a no start condition are tests for the fuel system. Includes test ASD and fuel pump relay, fuel pump assembly and plug connectors (97+ changes were made to the fuel pump assembly and fuel gauge.) Testing fuel line from the fuel injector rail and from the fuel injector rail back to the fuel pump. IIRC the fuel line should be able to maintain fuel pressure of at least 30 psi, after the engine has been shut off, for at least 5 mins.
Fuel pump assembly, is a common problem with XJ. If your XJ was a 97+, a potential problem for starting and running is the fuel gauge sending unit connected to the PCM. The PCM uses this information to control the fuel gauge as well as other reasons such for run-ability, EVAP, etc. 96 fuel gauge sending unit is separate from the PCM. IIRC 96 the fuel filter and pressure regulator is part of the fuel pump assembly as with 97+.
The fuel pump assembly wiring and connectors need to be checked for bad wiring, bent pins, corrosion, etc.
Bad coil is a common problem for no start conditions. Sometimes a coil will test ok using a meter, but not put out a good enough spark for starting.
_____________
More information related to starting
When the ignition is turned on, the PCM uses ambient temperature, coolant temperature, and barometric pressure sensor inputs to determine the correct air/fuel mixture ratio for starting the engine. In some applications, critical data like barometric pressure or altitude might be stored in an adaptive memory built into the PCM so the engine will immediately start.
The PCM also activates the in-tank fuel pump for a few seconds during cranking to pressurize the fuel system. As the engine is cranked, the PCM receives a signal from the crankshaft position sensor indicating cranking speed. When the cranking speed exceeds approximately 200 rpm, the PCM re-activates the fuel pump to supply fuel to the engine. At this point, the PCM turns on actuators like the ignition coils and fuel injectors to start the engine and begin operating in an open-loop mode.
As soon as the oxygen sensors located in the exhaust system start producing a signal, the PCM switches into the closed-loop mode, which means that it is now adjusting fuel delivery, spark advance, and idle speed to meet various operating conditions. The PCM also begins running a series of tests on emissions system actuator components to see if they are working. If the PCM finds an emissions-related failure in any powertrain system, it turns on the “check engine” light.
________
Hard Start
Fuel pressure
Coolant temp sensor
TPS Calibration
MAP sensor calibration
Min Idle Air flow
IAC operation
Evap
IAT sensor
Start Stall
pcm powr and gnd ckt
There are other inputs such as from the MAP, IAT, TPS and RPMs
– engine coolant temperature
– manifold absolute pressure
– intake air temperature
– engine revolutions
– throttle position
Fuel pressure isn't monitored by the PCM so it doesn't know if their is enough pressure in the fuel line ... if the fuel line can hold pressure but there is not enough during startup, priming is usually required to build up enough fuel pressure for the engine to start.
The PCM doesn't monitor such things as the fuel injectors, fuel pressure, throttle body air flow, timing, PCM grounds, exhaust system, cylinder compression, oil consumption and quality of gas.
____
Open Loop: Startup
Battery voltage
CTS
Manifold air temperature sensor
MAP
Starter motor relay
Speed sensor
Sync signal
TPS
Thank you very much for this info, I'm making a hard copy and taking to the mech.
The mech said they now found a small leak from the clutch that was dripping on the Fuse box and said it may be causing the injectors not to fire correctly so they are checking my fuse box and wiring in that area. Not sure what the deal is with these guys, I'm worrying about looking at the bill.
Again thank for this info I'm going to have to look into getting the shop manual for my jeep. I've done that for my other cars just didn't find one for the jeep yet that wasn't a digital copy, I prefer the hard copy old fashion manual.
Thank you very much for this info, I'm making a hard copy and taking to the mech.
The mech said they now found a small leak from the clutch that was dripping on the Fuse box and said it may be causing the injectors not to fire correctly so they are checking my fuse box and wiring in that area. Not sure what the deal is with these guys, I'm worrying about looking at the bill.
Again thank for this info I'm going to have to look into getting the shop manual for my jeep. I've done that for my other cars just didn't find one for the jeep yet that wasn't a digital copy, I prefer the hard copy old fashion manual.
I have both hard and the digital copies. Some my hard copy service manuals can't be found in digital form.
____________
For hard and digital copies eBay often has manuals at fairly reasonable prices.
I've also found hard and digital manuals from the links below.
One problem that happened over the last several decades are the logging companies and corporations were exporting more than 60 percent of our forests overseas. Currently they have two man operations with equipment that have replaced what years ago took 12 or more men to operate.
AMEN Anony. Here for the first time in the 35 years I've lived up here they brought in this giant machine that grabs the tree, cuts it with about a 4 foot dia. circular saw, then lays them in decks. I'm not sure what, if any benefit, is going towards this community. Acres of stumps aren't a fire hazard is all I know for sure. Got to wonder where the real money went.
AMEN Anony. Here for the first time in the 35 years I've lived up here they brought in this giant machine that grabs the tree, cuts it with about a 4 foot dia. circular saw, then lays them in decks. I'm not sure what, if any benefit, is going towards this community. Acres of stumps aren't a fire hazard is all I know for sure. Got to wonder where the real money went.
Actually some stumped areas do create a fire hazard as they significantly dry and heat up an area and surrounding forest.
