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No fuel, no spark, Good ecm,cps and ignition switch, and relays. Relays have power.

1995XJ4.0

NAXJA Forum User
Location
Brandon Fl USA
So here is the story. 1995 Cherokee 4.0 inline 6. I have owned it for ballpark 2 years. It has many many man hours into it and many new parts.

The issue at hand is, i will go to crank it and the starter will spin the motor but the jeep does NOT want to "turn over" or run on its own. Excuse me if i used the wrong terms.

I have chased many issues in the past and am well knowledged on these Jeeps

I hooked a fuel pressure gauge to the rail... no fuel pressure. I put a screwdriver in a spark plug boot and held it by the block... no spark. I put a jumper wire in place of the fuel pump relay and the pump DOESNT run. But if i run power from the battery directly to the pump it will give me fuel pressure. Obviously still no start though because pretty sure theres no spark or injector pulse. Initially i thought it was a fuel issue until i did the fore-mentioned tests.

Anywho, i have access to new parts so i tried replacing a few infamous parts that are associated with no spark and no fuel such as a New ignition switch which did nothing, new ecm didnt help. new cps didnt help.

If i remove the fuel pump relay and the asd relay and hit them with a test light the position to the left has power (i THINK position 86 if i remember correctly) so the relays are getting power that would cause a no start.

All fuses under hood and by drivers feet are fine, all relays are fine.

The Jeep was cranking perfect, about 2 weeks ago i parked it to replace my radiator / water pump / thermostat. Well i got side tracked and it took me until 2 weeks after being parked to finish up. I finish up my install and go to crank it... and thats when this issue presented itself. I initially thought it was a fuel issue (xjs and fuel issues so i checked aspects of the fuel system) Its whenever the fuel system checked out and i realized i believe i have no spark, that is when i realized i was in some deeper trouble than usual.


So what else could i check? Can anyone provide some diagnosing ideas? I have a multimeter and a good amount of auto let alone Jeep knowledge.

I checked all grounds that i could think of or see. I checked for power at the side post of under hood fuse box, i checked battery voltage, i checked all my sensors, even have doubles i keep in the shop for diagnosing purposes alone.

Something else to add, when i go to do the check code sequence on my obd1, the ol turn key turn key wait... well the check engine light just stays illuminated. Doesnt blink any codes.. doesnt do the usual turn on than off when i turn the key to acc, no, i turn key to acc and it just stays illuminated. Now this could be because ive swapped an ecm or two in there to see if its an ecm issue and the jeep hasnt been cranked successfully since the ecm has been reconnected. Thats just a side note.

The issue at hand is plain and simple. The jeep cranks but will not start and run on its own. Something is not communicating to something telling the jeep to allow or activate fuel and i believe spark also. I am just not sure WHAT could do that since ive tried replacing ecm, ignition switch, relays, pcm, etc.

Mines a 95, ballist resistors stopped in 93 ish, i keep getting told to check that a lot... on less knowledged forums...

I am driving myself crazy over here, i have an event at the end of May i need this up and running by. I give it a new cooling system and this is how it repays me... Jeeps... so ungrateful

It ran and started on a dime just fine until now.

new/newer parts: alternator, battery, cps, tps, iac, map, vacuum lines various, ignition switch, remaned ecm, radiator, water pump, tstat, 02 few months ago, etc etc

Other information: 1995 cherokee 4.0 inline 6 247.000 miles automatic. oem motor and tranny. oem rebuilt t-case np231. 5.5-6" lift. Coils upfront leafs outback. shackle relocation brackets. shackes. leafs. d44 rear (yes the rear xj one), d30 hp upfront. 488 yukon front and rear I JUST DID A MONTH AGO.
 
update. im 110 percent positive i have NO SPARK either along with NO FUEL. retried an ecm...cps... and ingition switch from a running jeep just to make sure i didnt get faulty parts at the store.

Got a fancy spark tester and i for sure have NO SPARK. Accompanied by no fuel.
 
A basic understanding of how the system works may help you out.
When you first turn the key to run (or through run to start) the fuel pump will run for a few seconds to prime the system. It won't build much pressure, it basically just fills the lines with fuel, maybe a little pressure.

When the engine cranks you get a pulse signal to the PCM from the CPS, the PCM closes the fuel pump relay and ASD relay. You get fuel pressure and power to the coil etc.

Sounds like you aren't getting a pulse signal, CPS will do that, bad CPS, Bad CPS wiring or no voltage going to the CPS. CPS should have 5-8 volts going in when the key is in the run position, Different years have different input voltages for the CPS, not sure what a 95 is, most likely 8 volts.

Other sensors share that input voltage, mainly the cam position sensor. Test the input voltage, orange wire, either at the CPS or the cam position sensor. I've also heard a faulty cam position sensor will cause the ADS and fuel relays not to close, don't know for sure, just something I heard. A partially shorted cam position sensor can suck the input voltage so low the CPS can'r generate a signal strong enough to pulse the PCM so it closes the relays.

I always test before I swap parts, it not only saves money, it saves time in the long term.
 
Does your check engine light come on when you turn the key to run? If not you may have a short in the sensor input circuit.

If it does come on, try the key test and see what trouble codes come up.
 
I have the exact same situation going on myself with a 92 xj I bought recently. I am gonna have to follow this. I don't however know for sure that all my relays and computer are good (just bought comp and probably all new relays). I did swap around relays with no dice, brand new cps, checked all fuses etc. I have a brand new fuel pump installed as well. Anyways good luck to you and will let you know if I figure mine out.
 
Mine is a fuel issue so I've determined. Replacing my new fuel pump.. really sucks

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