'95 4.0L Cranks but wont start - JeepForum.com
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post #1 of 30 Old 07-15-2019, 01:25 PM Thread Starter
yoyoyo109
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'95 4.0L Cranks but wont start

Hello everyone, it's been a while but prepare for a long post.

Back in 2015 I took ownership of my JKU and my dad took the YJ. It had been having issues running when he got it that needed to be ironed out but he never had the time to work on it. The issues back then were characterized by the engine cutting out when it was above 2.5-3k rpms, almost as though it had a limiter preventing the engine from functioning.

At the time I believed it was something ignition related and replaced the distributor but was never able to get the engine to start after that point (around fall 2015)

Fast forward to the summer of 2019, I finally thought to check fuel pressure only to see that we did not have any fuel in the rail. After removing the pump, sure enough that pump was beyond shot and after replacing it/purging the lines we had good, clean fuel at the rail. Now however the engine still refuses to start. I have performed nearly every troubleshooting and diagnostic test in the book, and before I tore the PCM out to replace the capacitors known to fail I was hoping consult the forum to see if there's anything else I could try.

I have verified the fuel pump activates/pressurizes the rail however power to the pump is cut off after about 1-2 seconds (The same thing happens to the coils' power), I have also verified that every single relay is properly functional.

To differentiate between fuel delivery/ignition problems I have tried spraying starting fluid into the intake to see if anything happened, and the FIRST time it sounded like one cylinder tried to ignite but I have not yet been able to reproduce that. When I unplug the high tension coil wire from the distributor and crank the engine, I do not see any spark jump to the ground. Additionally when I plug a spark plug into the wire, I do not see any spark

I have verified the functionality of the camshaft/crankshaft sensors as well

Is there anything left for me to check besides the PCM capacitors?


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post #2 of 30 Old 07-15-2019, 05:44 PM
Boojo35
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Where did you put the spark plug for testing? Did you ground it? It will not work in open air. It needs a ground.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #3 of 30 Old 07-16-2019, 04:46 AM
Que89YJ
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The pump should cut off. Its only running when you go to start it. When you checked power to the coil, you need to check to the battery negative. It is ground switched from the ECU and will have asd power to the green/orange wire with the key on. Read the green/orange to battery negative. Dont replace the caps, its not your problem. You have the wrong symptoms. POst back voltage reading.

Fault codes:
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post #4 of 30 Old 07-17-2019, 08:30 PM Thread Starter
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Quote:
Originally Posted by Que89YJ View Post
The pump should cut off. Its only running when you go to start it. When you checked power to the coil, you need to check to the battery negative. It is ground switched from the ECU and will have asd power to the green/orange wire with the key on. Read the green/orange to battery negative. Dont replace the caps, its not your problem. You have the wrong symptoms. POst back voltage reading.
My voltage is ~12V for 2 seconds when starting to crank then it drops to 0. Per the FSM, this indicates a bad cmashaft>PCM circuit but checking the pins for continuity shows the wires are good, and the css is brand new (new distributor). For kicks I also put the old css into the distributor (the engine would still run before it was parked 2 years ago) and I still have the same voltage for 2 seconds before it drops

These were done by grounding to the negative battery terminal

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post #5 of 30 Old 07-18-2019, 05:00 AM
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You know how to use a meter. That's good news. The Fuel pump relay only charges for 2 seconds then it will cut off. That is by design to charge the fuel fail before start. The ECU switches ground to control just about everything so if you are doing a power check you need to use the battery negative as a reference when you are checking voltages.

You have to start from the beginning. I know you have done the test but I need to know what you have going. Did you check codes using the Check engine light? What codes do you have?

Fault codes:
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post #6 of 30 Old 07-18-2019, 11:04 AM Thread Starter
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Quote:
Originally Posted by Que89YJ View Post
You know how to use a meter. That's good news. The Fuel pump relay only charges for 2 seconds then it will cut off. That is by design to charge the fuel fail before start. The ECU switches ground to control just about everything so if you are doing a power check you need to use the battery negative as a reference when you are checking voltages.

You have to start from the beginning. I know you have done the test but I need to know what you have going. Did you check codes using the Check engine light? What codes do you have?
I'll start in summer of 2016. By this point, I had taken ownership of my JKU and didn't daily my poor YJ any more. Before parking it, I had an issue where the engine would cut out occasionally when the RPMS were above ~3000-3500 (or highway speeds above 65-70mph in fifth gear). Sometimes if pushing it, the engine would outright die and then not start back up for a few minutes, still with the high-RPM stalls. I didn't know as much back then so I assumed this was the distributor and as such replaced it and the camshaft sensor. Initially, I do not think I installed it properly but since then I have properly installed it many, many times.

It still wouldn't start so later that year I replaced the coil, wires and plugs (I swapped the coil out for a lifetime warranty exchange 2 days ago)

Fast forward to this summer, I'll go through everything I've done in order.

First I checked my fuel rail pressures and had 0 PSI. In hindsight, my initial symptoms seem to indicate the fuel pump was the issue all along, and after replacing the entire sending unit, if it was not the initial cause it most certainly was now after sitting 3 years.

After replacement, I bled the fuel lines at the rail by removing the valve and attaching a hose to the port until the gas flowing out was actual gas.

Next I tried starting her up again with no luck. It was at this point I checked for spark and did not have one. First I checked continuity between all wires from the coil, CSS(camshaft) & CPS(crank position) with their respective cavity in the PCM (and everything was good). After checking the wires, I ran the diagnostic tests for the CPS from the FSM, and I felt as though the resistance values weren't great so I replaced that last night. I have not technically done the test for the CSS just because it's a brand new sensor, and installation of the old sensor also turned out nothing.

I wanted to test the coil for a spark so I built the special jumper from the FSM and was, in fact, able to get a spark. I ran the coil positive to the battery and then connected the coil negative(/ground pin) to the battery with the 330uF capacitor, and did the momentary grounding

To test for ignition I've tried spraying starting fluid into the intake to see if the engine will turn over, although I haven't been able to do this test since replacing the CPS this morning. The fuel that was in the lines from the old fuel pump was incredibly disgusting and bad, and while I have purged the fuel rail, I haven't taken the rail off to inspect the injectors or anything

When I turn the key, I get the CEL that is supposed to mean the PCM is turning on. After checking DTC codes I get 11 (crank reference signal not detected by PCM) and 12 (battery disconnected recently). That being said I haven't tried much since installing the new CPS. I do believe I might have isolated the old CPS as being bad back in 2016 and then forgotten because the bolts on it were loose, which only I would have done since it has been parked

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Last edited by yoyoyo109; 07-18-2019 at 11:07 AM. Reason: typo
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post #7 of 30 Old 07-18-2019, 12:04 PM Thread Starter
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Update: After installing the new CPS, a timing light on cylinder 1 shows I'm getting ignition to the cylinder. I am now going to remove the fuel rail to see if there's still some bad gas inside or see if anything is obviously wrong with the injectors

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post #8 of 30 Old 07-18-2019, 12:20 PM
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injector wiring?
12v at injectors?
Have you tried a NOID light to see if injectors are being pulsed?

I saw the comment ASD only powered @3 seconds - standard if the PCM is not seeing a CKP signal, might want to power the circuit with a fused 12v for testing.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #9 of 30 Old 07-18-2019, 04:51 PM
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Maybe your problem is two fold. You may have parked it with a bad CKP sensor and now resolved that. The looks of your fuel sender..... Wow.... cannot put that into words. Have never seen anything like that. It would lead me to believe that the possibility of crud and corrosion throughout the system is quite high. I would think that your fuel filter has to be trashed.

Now that you seem to have spark by testing with a timing light, maybe hit the throttle body with some carb spray, gas or starting fluid and see if it lights up.

I like that you do test things and research what is going on.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #10 of 30 Old 07-18-2019, 06:20 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
injector wiring?
12v at injectors?
Have you tried a NOID light to see if injectors are being pulsed?

I saw the comment ASD only powered @3 seconds - standard if the PCM is not seeing a CKP signal, might want to power the circuit with a fused 12v for testing.
Since then I have replaced the CKP sensor and now the ignition system is WORKING. It sounds as though it's trying to start now, but still nothing just yet

I have not tried a NOID light, but testing the wires to the injectors shows the PCM is sending the switching signal.

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post #11 of 30 Old 07-18-2019, 06:24 PM Thread Starter
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Quote:
Originally Posted by Boojo35 View Post
Maybe your problem is two fold. You may have parked it with a bad CKP sensor and now resolved that. The looks of your fuel sender..... Wow.... cannot put that into words. Have never seen anything like that. It would lead me to believe that the possibility of crud and corrosion throughout the system is quite high. I would think that your fuel filter has to be trashed.

Now that you seem to have spark by testing with a timing light, maybe hit the throttle body with some carb spray, gas or starting fluid and see if it lights up.

I like that you do test things and research what is going on.
That's entirely possible. Since replacing the filter I have not yet borrowed a fuel pressure test gauge from the store, but I think I'm about to if nothing happens after cleaning the spark plugs. They didn't look terrible, but did have a good amount of deposits and crud on them. While I do know I'm getting fuel to the rail, I don't honestly know what pressure the rail reaches before the PCM shuts off the pump. My plan was to replace the filter after getting the engine to actually start, but if my pressures are incredibly low even after priming maybe there just isn't enough fuel at the engine?

I'm about to install the plugs and then I'll try blasting some starting fluid into the air hose to see if it will start off of that

Thanks, I appreciate that. I try to do my research through the FSM/searches before asking the community so that I better understand why the issue is happening so I can fix future problems easier haha

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post #12 of 30 Old 07-18-2019, 06:49 PM
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Do not take this wrong. I am not insulting you in any way. But spark plugs in todays world do not fix problems like they did in the past. Why? Ignition systems have way more balls than they used to. A poor choice in replacement plugs can cause driveability issues. It happens all the time. Stick with OEM type plugs and you will be ok. An example is a lot of cars do not run well on Bosch plugs. If it came with Champion, NGK, Denso, AC delco, Stick with the original.

With that being said, spark plugs rarely cause a no start condition. It is really hard for 6 of them to take a poop at the same time.

A lot of forum info will lead you to replacing plugs, cleaning your IAC, replacing a crank sensor, etc, when the symptoms do not match the complaint. Example, I turn the key, no click, no crank. Answers come back to do the previously mentioned repairs when indeed you have a starter, battery, ign switch or cable problem.

Cleaning your plugs though will probably not do anything. Unless they are hopelessly soaked with fuel or oil. And I do mean hopelessly.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #13 of 30 Old 07-18-2019, 06:54 PM Thread Starter
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Quote:
Originally Posted by Boojo35 View Post
Do not take this wrong. I am not insulting you in any way. But spark plugs in todays world do not fix problems like they did in the past. Why? Ignition systems have way more balls than they used to. A poor choice in replacement plugs can cause driveability issues. It happens all the time. Stick with OEM type plugs and you will be ok. An example is a lot of cars do not run well on Bosch plugs. If it came with Champion, NGK, Denso, AC delco, Stick with the original.

With that being said, spark plugs rarely cause a no start condition. It is really hard for 6 of them to take a poop at the same time.

A lot of forum info will lead you to replacing plugs, cleaning your IAC, replacing a crank sensor, etc, when the symptoms do not match the complaint. Example, I turn the key, no click, no crank. Answers come back to do the previously mentioned repairs when indeed you have a starter, battery, ign switch or cable problem.

Cleaning your plugs though will probably not do anything. Unless they are hopelessly soaked with fuel or oil. And I do mean hopelessly.
No offense taken, I honestly didn't think it would be the spark plugs, I was just thinking(hoping) that they might be too weak to ignite. it was easier for me to go ahead and clean them before getting the pressure gauge, but I'm about to run to the store to borrow one so I'll report back in ~30 minutes

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post #14 of 30 Old 07-18-2019, 08:24 PM Thread Starter
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After throwing the pressure gauge on, I read a solid 31-32psi and while cranking I'm starting to get backfires. Not ideal but a step in the right direction because SOMETHING's trying to ignite. Given the circumstances, the only issue I can imagine is that my distributor is still a tooth off from the correct install.

It's difficult to see, but the engine is TDC @ the 0 mark and I've verified the piston is at the top of the cylinder:


This is where the rotor sits at TDC, per the FSM it should be at 5 o'clock but it appears to be closer to 5:30:


And this is how my plugs are wired per the FSM, 1>5>3>6>2>4. As installed the rotor is about at the trailing edge of the #1 post:



At this point given the backfiring, I can only assume the distributor is in fact not installed properly so now I'll move it back one tooth and see what happens!

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post #15 of 30 Old 07-18-2019, 09:01 PM Thread Starter
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Backing it off one tooth did not seem to change much. I put a timing light on cylinder 1 and connected a meter to the injector #1 harness

While cranking the engine, the timing light seems to flash a half second before the injector actuates/gets voltage and then the gap between the injector>next spark is the longest interval in my engines cycling. I'll go ahead and move the distributor forward one tooth (to how it was previously installed) and do the timing light vs injector test again

My thought process based on the generic four-stroke cycle is that the injector should precede the spark or be at the opposite side of the cylinders cycle, because the cylinder must compress the fuel/air mixture before combusting. I would assume the injector actuates when the piston is near the bottom and then the coil is at TDC, meaning (if I'm correct) the interval between my light and meter should be about the same amount of time apart

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