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Cranks but doesn't run

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Hi Scotty, 

I have a 2000 Jeep Grand Cherokee 4.0L with 316 000km. I recently went to start my car and it struggled to start and then stalled. After stalling it went into a Crank No start condition. I then changed the battery and alternator and it started once and ran but the next time I went to start it, it went back to cranking with no start. This is a secondary car so I only drive it when I head up north. Nothing was wrong with the car the last time I drove it. 

I have checked fuel pressure, reading 40 psi and spikes up to around 45-50 on cranking, there is pressure in the fuel rail. I replaced stock injectors and there was no improvement. Fuel pump turns on and it was replaced about 2 years ago. Fuel filter was also replaced about a year or 2 ago. 

I checked spark plugs, they were in rough shape so I changed them and the ignition coil. Still cranking with no start. I checked if I have spark by leaving one plug in the coil and cranking but got intermittent spark. Sparked once or twice, then stopped. I then changed both the camshaft and crankshaft sensors. When changing the camshaft sensor and synchronizer. I made sure to align the engine/synchronizer. The engine rotated with a socket as I was able to align it. It is not seized. 

Next I went to air fuel mixture so I cleaned the Idle air control valve (changed about 3-4 years ago), map sensor and throttle position sensor. Took apart of the entire throttle body and cleaned it. Replaced the throttle position sensor. No change. I have no codes reading on my scanner. 

Next I checked my battery connections and replaced the battery terminals. I cleaned the ground locations that I could see by sanding down any rust and inspected all of my wires but don't see any damage. I had one ground that broke off while changing my ignition coil but i replaced it with a new one. Tried checking and swapping fuses and relays for various things ASD, starter ect. No change.  

I'm stuck and can't seem to figure out what's going on. Another thing to add, when I am cranking if I push the gas pedal down while cranking the motor will start to run and black exhaust comes out of the muffler (I assume its because the engine is flooded with gas and its running rich) as soon as I let off the gas pedal it stalls and shuts off. All gauges seem to work fine. The only thing I noticed was oil pressure sensor will move a little back and forth sometimes and the battery voltage stays at 9volts when ignition is on or when cranking. 

I tried checking for vacuum leaks and can't seem to find any. 

I hope all of this information helps. I look forward to hearing from you. 

This topic was modified 2 months ago 2 times by Atwizz23
2 Answers
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I’m glad @scottykilmer answered your question.  Yeah, this sounds like a job for an experienced mechanic with the proverbial “fancy” scan tool.  But kudos to you for working the problem as thoroughly as you have.

Please come back when it is fixed and post the solution.  I’d love to learn what happened.

Hey @Scottykilmer and @Dad2LM2 here's the update:

Replaced the ECM today. Bought an XTOOL D7 scan tool off amazon and rewrote the VIN# on the remanufactured ECM and the car is starting. It's running perfectly. Reading correct voltage and no crazy dash lights. It was the ECM all along.

Cool. Glad it’s fixed.

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Well it's definitely flooding itself out. So you have to figure out why either you're getting too much fuel or the ignition system isn't working right. Now it is a 2000 so it has a reasonable amount of data. You can have it mechanic like me scan and it will give some idea if it's the fuel injectors pulsing too much etc. But if you want to try to figure it yourself when it's flooded out, does that pull all the spark plugs out fast? See if they're all wet or just one or two of them are wet cuz it's just one or two is wet. That generally means those injectors are bad. If they're all wet, they're generally means there's some type of control problem like a computer or sensor failure

Hi Scotty, I appreciate you taking the time to respond. I have been quite busy with work so I haven't had time to post any updates. Here are a few updates:

I put some more focus into two sensors the Mass Air Flow sensor and Idle Air Control Valve. I initially wrote off the Idle Air Control valve because I replaced it a few years ago when it was causing my Jeep to stall at idle, but I know these cheaper aftermarket parts are hit and miss so it's a possibility it could have failed again. I ended up replacing both the Mass Air Flow Sensor and the Idle Air Control valve (Didn't mind spending 180 dollars on the two sensors to see if it would work because I have never had a car payment for this car. I purchased it for 1200$ in 2017).

After replacing both the Idle Air Control Valve and the Mass Air Flow Sensor the car started right up. It was running but running very rough. I know when you replace these sensors it takes the computer some time to regulate it back to normal but now that it was running, I noticed some other issues.
When running the car was very rough, the abs light came on, my check gauges light came on, the odometer started flashing and then disappeared. I then I shut the car off and checked the battery voltage it was normal. Fully charged. Then I started the car and checked the output on the alternator and it was reading anywhere form 17.0 - 18.3 volts, which is high. I once again checked all ground with a voltmeter touching positive to the battery and negative to each main ground wire (all grounds were fine). I then unplugged the alternator and started the car and it started normally with the dash lights reacting normally, but the car was still running rough. This led me to the voltage regulator. In this particular car the voltage regulator part of the ECM. I recently pulled the ECM and one side of it was covered in salt and debris. When I opened up the ECM there was one corner where the water/salt seeped in and corroded the ECM. the copper turned green and was inflated. I have gone ahead and purchased a remanufactured ECM from A1 Cardone. I will be putting it in today.

I was told I need to rewrite the VIN # on the ECM (it already has the program software on it just needs the VIN rewritten. I currently have a simple INNOVA which does not have that capability. I have a guy that would be willing to rewrite the VIN# with his scan tool but I'm considering upgrading mine. I'm just curious if there is any fancy scan tool you would recommend that would be capable of rewriting a VIN as well as all the other capabilities a bidirectional scan tool has?

I wouldn't mind upgrading my scan tool and am willing to pay between 500-1000 dollars for something more advanced considering I do a lot of work myself and have never owned a new car. I buy all my cars used from relatives and friends for almost nothing and then run them to the ground. Just like you mention in a lot of your videos the quality of most new cars is horrible, and the prices are just too high for a car which devalues over time. (Ex: I bought a 2002 Mazda Portege as a daily driver for 700 dollars with only 63 000km on it). 

@Atwizz23 did you check your fuel pump pressure regulator?

Thanks for the input but fuel pump was replaced 2 years ago and fuel pressure regulator was also replaced just over a year ago. I ruled out fuel issues based on the other symptoms I am having.

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