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Cranks but dies, oil pressure maxed out

D

doubleOHxj

NAXJA Forum User
Location
Greenville,SC
I'm kind of at a loss here. 2000 4.0/aw4 173k and was running perfectly. I have fuel and spark. It will run but not for long. And now it just cranks and won't run. No CEL. Everything seems fine it just won't stay running.
 
Do the fuel injectors fire ? Test with a noid light. Are any of the gauges on the dashboard reading goofy ? Is the Check Engine Light ON ?
 
neutral safety switch? had the same prob on my 2000, and it ended up being the coil pack rail
 
Oil pressure gauge is maxed out. No check engine light. God I hope its not the coil rail. I can hear the fuel pump cycle when the key is in. I guess I gotta go get a noid light. And whats the resistance on a good coil? Guess I get on testin that.....of course this would happen a week before its for sale.
 
Does it run at all, even for a few seconds ?

There are a number of common issues that would cause a no-start. A faulty or mis-adjusted NSS would no allow the starter to engage. Coil rail failure is the least likely and should only be considered after some routine diagnostics and trouble shooting of other components.

Test the CPS/CKP, inspect the camshaft pickup in the distributor.
 
Well because its a 2000, I have no distributor. It would run for a second or 2 last night but today it would not run at all. I'm gonna have to look up some resistance numbers and start testing stuff i guess.
 
IGNITION COIL RESISTANCE—4.0L ENGINE​
PRIMARY RESISTANCE
21-27°C (70-80°F)​
0.71 - 0.88 Ohms




as per the FSM
 
As Tim said, check your Cam and Crank position sensors. Also rent a fuel pressure gauge to make sure you're getting the right PSI of fuel at the rail.
 
The 00-01 cam pickup is mounted on the cam sensor assembly, and the cam sensor is in the same hole the distributor would be in. It can be tested, and it can become damaged.

I am going to bet $2 on the CPS.
 
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Remember that on these Jeeps a maxed oil pressure reading = no connection or open connection. Have you done a physical check of wiring? How about fuses? The coincidence of no running with no oil pressure signal seems suspicious.
 
I did the visual inspection, no lose/dirty connections, no disconntected wires. I'm going to check my CPS and fuel pressure and injectors tomorrow after class. I'll update accordingly. Thanks for all the info and positive responses!
 
I tried starter fluid today and no luck so i'm thinking my spark is not there. I have to coil rail out to test the packs but I'm not exactly sure how to test it, Where should i put my leads?
 
Check the wire to the oil pressure sensor. If the oil pressure sensor is connected and the sensor is working properly, I had this once on a Renix jeep, when the exhaust was blocked by an internally busted Cat converter. The blocked exhaust would choke off the engine, blocked exhaust, and it pegged the oil pressure sensor.

This would also tend to flood the engine, and make it very difficult to dry out!!!!!
 
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Ecomike said:
Check the wire to the oil pressure sensor. If the oil pressure sensor is connected and the sensor is working properly, I had this once on a Renix jeep, when the exhaust was blocked by an internally busted Cat converter. The blocked exhaust would choke off the engine, blocked exhaust, and it pegged the oil pressure sensor.

This would also tend to flood the engine, and make it very difficult to dry out!!!!!
Click to expand...
The gauges on post-Renix XJ's work backwards. A pegged oil pressure gauge means an open circuit. If the gauge behavior coincides with the failure to start, the first thing I'd do here is short the sender wire to ground and see if it drops the gauge to zero as it should. If not, it's time to get into the wiring a big further.
 
well i tried a new camshaft position sensor today as well with no luck. I need to test my crank position sensor but it looks like the wire routing is different than in my manual. I can see the sensor and put my hand on it but the wiring goes back over the transmission instead of out to the top of the motor. Frustrated!:confused:
 
So just to be sure I'm thoroughly explaining this and putting everything on the table(I've been using search with little results): 2000 4.0/AW4 173k, has ran perfect since I bought it(150k-ish). I started it Sunday, after driving across town and filling up on the way, I went to a baby shower at the bar I work weekends at(I know, baby shower at a bar, awesome) and about 5 hours later, I cranked it. It started right up per usual and ran for about 10 seconds and cut off. Puzzled, I cranked it again and it, again, started right up. I gave a little gas and waited for a second and scanned the dash. Situation normal. Reverse, back up 10 feet and we start loading up for a quick trash run. It idled fine for about a minute this time. But when it died this time it was hard to get it started again and my oil pressure gauge was pegged. Fast forward to today and I can't get it to run on starter fluid with a new coil rail. And now nothing with the new camshaft position sensor. My next step is checking my crank sensor and seeing what I get but I have to locate figures first, which I haven't been able to do.
 
Matthew Currie said:
The gauges on post-Renix XJ's work backwards. A pegged oil pressure gauge means an open circuit. If the gauge behavior coincides with the failure to start, the first thing I'd do here is short the sender wire to ground and see if it drops the gauge to zero as it should. If not, it's time to get into the wiring a big further.
Click to expand...

In my case, the sensor was working, and was connected. The day the Cat busted (from running super rich), the oil pressure gauge read over 80 psi. Replaced the Cat, and the oil pressure gauge returned to 40 psi.

So if his sensor is good, and connected, he needs to look at this rare possibility.

OP!
Have you check the wires going to the oil pressure sensor, near the oil filter and distributor?
 
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