Novak Conversions Jeep Wrangler TJ engine mounts

2003 TJ 4.0 cranks and sputters but will not start

Travis2024

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Michigan
I know there are a ton of these "crank, no start" posts but can't seem to find one with my exact symptoms. I bought this jeep off a guy who owned it for years, and he had went to start it one day and it would just crank and not start. He replaced the camshaft and crankshaft sensors about a year ago, so then he tried replacing them again, but still not starting. He had also replaced the PCM a while ago, not sure how long ago. I bought it this way and my first idea was to check fuel.

After spraying a little starting fluid down the throttle body, it sputtered but did not fire up. I did not hear the fuel pump running when key was on so I checked out the relays. I am getting power to both the common side and the coil side of the fuel pump and ASD relays. The fuel pump will run with a jumper in the relay, but not with a relay plugged in (and yes I did try a new relay). Even with the fuel pump and ASD relays jumped, it will only sputter and will not run. It did seem to kind of "pop" when it sputtered. So this made me think timing?

With the relay plugged in, I can feel the relay click when key is turned on, but it turns right back off, like the computer is telling it to turn off and I do not hear fuel pump run at all. The only code I have is P1495, which I tried clearing and it came back. Could the brand new camshaft or crankshaft sensors be bad and not throw a code and this causing fuel pump to not run? I know the aftermarket sensors don't have a great reputation, and I can't seem to find a place that sells the Mopar sensors anymore. I plan to check the power at both crank and cam sensors, and continuity between the sensors and PCM tonight, but it just seems odd that the fuel pump won't run unless maybe the PCM is bad.
 
Yes the brand new sensors can be bad.

So at this point it's cranking?

What's your fuel pressure at?

Do you have spark?

Do you have a grey key? Do you see a flashing key icon on the dash?

How old is the gas?

Battery voltage at rest and when cranking? Clean the terminals and check grounds?

-Mac
 
Yes the brand new sensors can be bad.

So at this point it's cranking?

What's your fuel pressure at?

Do you have spark?

Do you have a grey key? Do you see a flashing key icon on the dash?

How old is the gas?

Battery voltage at rest and when cranking? Clean the terminals and check grounds?

-Mac
Appreciate the response.


Yes it is cranking just fine.

Not sure on exact fuel pressure, just pressed the test port and it sprayed out (after I had jumped the fuel pump relay), my buddy is going to bring his scanner over tonight. Before I jumped the relay, there was no pressure, like the PCM is not commanding it on.

Yes I have spark because it fired on spray, though I did not check every cylinder individually.

What is a grey key? The key i have for it is just bare metal. I did not see any flashing icon.

Not sure how old gas is but there is less than a quarter tank. I will get some fresh gas tonight and put in.

Have not tested voltage but have kept on battery tender and battery is a year old.


Also, not sure if it makes a difference, but the jeep came from California so it has all the emissions stuff on it. Not sure if this P1495 code would effect it starting or not.
 
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Grey key and flashing icon would indicate skim module...you would be able to start the Jeep but it would shut off after 2 seconds.

Sounds like you have a fuel pump issue. You need a pressure gauge on the Schrader valve on the fuel rail...if you have one...my 97 does, newer ones might not.

Or hell... maybe it's just out of gas...

-Mac
 
Grey key and flashing icon would indicate skim module...you would be able to start the Jeep but it would shut off after 2 seconds.

Sounds like you have a fuel pump issue. You need a pressure gauge on the Schrader valve on the fuel rail...if you have one...my 97 does, newer ones might not.

Or hell... maybe it's just out of gas...

-Mac

I was wondering if it didn't have enough gas in it even though the gas shows it has some and the fuel rail did build pressure after the pump ran. I will dump 5 gallons in it tonight and see if anything changes. Do you know if the pump should still run if it is low on gas, or does it have a shutoff that does not allow the pump to run if the gas is too low?
 
I don't think it has a shutoff. The assembly is essentially a miniature tank...the internal pressure regulator returns fuel to the assembly so it's usually the last thing to run out of gas.

We ran out the other day driving from the Rubicon across northern California on our way home to Oregon. Passed a gas station on a 1/4 tank and drove 40 miles to the next town...to find out the station was closed. Got back in the highway and the sign said 70 miles to next services. Ran out with 2.7 miles to go. Engine just died. Cranked it once, tiny splutter but didn't run. Coasted as far as we could and pulled over as a JK rounded the corner. Flagged him down and he pulled us the last two miles into the station. Didn't even have to wait (and got some great videos for my YouTube channel.)

-Mac
 
Still curious why the fuel pump only ran when I jumped the terminals though. I will check the wiring from the PCM to the fuel pump relay coil and make sure that is switching properly and the wiring is good.
 
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The fuel pump relay will kick on with the key, but will kick back off if the ASD commands it to. I would need to look at that circuit, but I believe if you jumper the relay the ASD can't shut it off because I think the ASD lifts the ground, so the power can still flow if you jump it. <=== all that needs to be verified.

If you have fuel pressure in the rail that will be enough to make it fire up even with the pump off. The ASD will also command the spark & injectors to stop if certain conditions are met. Since you have fuel, and presumably air, my money is on no spark as a result of the ASD not liking something. Really it's the computer that doesn't like something and tells the ASD to shut 'er down.

I would be looking at cam & crank sensors for sure, and the wiring around them. But pretty much any sensor under the hood could be at fault (or the wiring).
 
The fuel pump relay will kick on with the key, but will kick back off if the ASD commands it to. I would need to look at that circuit, but I believe if you jumper the relay the ASD can't shut it off because I think the ASD lifts the ground, so the power can still flow if you jump it. <=== all that needs to be verified.

If you have fuel pressure in the rail that will be enough to make it fire up even with the pump off. The ASD will also command the spark & injectors to stop if certain conditions are met. Since you have fuel, and presumably air, my money is on no spark as a result of the ASD not liking something. Really it's the computer that doesn't like something and tells the ASD to shut 'er down.

I would be looking at cam & crank sensors for sure, and the wiring around them. But pretty much any sensor under the hood could be at fault (or the wiring).

Do you know if it is possible to still get the OEM Mopar sensors, or are they all obsolete? If not, any good recommendations on aftermarket? I found a wiring schematic so I will definitely check out the wiring tonight and make sure I have power at the sensors and continuity back to the PCM for the signals.

Also, since the jeep has the California emissions stuff on it, could the code P1495 be causing the PCM to not allow the engine to run? This code says it is the Leak Detection Pump, which I don't think would usually cause the engine to not run, but I wasn't sure if the California emissions thing was different.
 
Do you know if it is possible to still get the OEM Mopar sensors, or are they all obsolete? If not, any good recommendations on aftermarket? I found a wiring schematic so I will definitely check out the wiring tonight and make sure I have power at the sensors and continuity back to the PCM for the signals.

Also, since the jeep has the California emissions stuff on it, could the code P1495 be causing the PCM to not allow the engine to run? This code says it is the Leak Detection Pump, which I don't think would usually cause the engine to not run, but I wasn't sure if the California emissions thing was different.

The FSM will show circuit variations for CA emissions (I'm thinking of the O2 sensors, I know I've seen that variation called out). The PCM programming is a bigger mystery, but Wranglerfix.com are the experts there.

I think you can find OEM sensors, but NGK/NTK are well regarded here. That said, I've had tons of success with Standard Motor Products, and honestly I've never had a bad sensor from a parts store. So I'm either legendary level lucky or the variance in sensor quality maybe isn't quite as bad as the internet would have you believe.
 
The FSM will show circuit variations for CA emissions (I'm thinking of the O2 sensors, I know I've seen that variation called out). The PCM programming is a bigger mystery, but Wranglerfix.com are the experts there.

I think you can find OEM sensors, but NGK/NTK are well regarded here. That said, I've had tons of success with Standard Motor Products, and honestly I've never had a bad sensor from a parts store. So I'm either legendary level lucky or the variance in sensor quality maybe isn't quite as bad as the internet would have you believe.

I just ran home on my lunch break and messed with it a little. By the way, the PCM that is on it is from Wranglerfix.com. But it looks like I am not getting the signal from the PCM to the ground side of the coil of the ASD relay or the fuel pump relay. I have the key switch + signal to the positive side of the coil but not the ground. I will trace the wires back later and check for any breaks, but do you have any other ideas why the PCM wouldn't send both of these signals?
 
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I added fresh gas and checked all the wiring between the cam and crank sensors and the ASD and fuel pump relays and that all checks out good. However, I am only getting 12v on the ASD relay coil with no relay in it. As soon as I plug relay in, voltage goes to zero. Like the PCM is telling to turn off only when the relay is plugged in. What could be causing this?
 
Failed relay? Switch it with the horn maybe and see if it works?

-Mac

Tried swapping relays with no luck. I jumped the ASD relay with a paper clip and it still only sputters. I’m leaning towards the brand new cam or crank sensor is faulty, or the PCM is bad. Wish there was a way to test the sensors
 
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Wish there was a way to test the sensors

Would need an occiliscope. You can verify that you're getting 5v to the sensor. Sometimes the sensor doesn't work because the PCM supply is broken or a wire is shorted to ground. One person had a bad clockspring shorting the 5v supply to ground.

-Mac
 
I had 5V at both sensors and both signals wires had continuity back to the PCM connectors. Might try ordering new sensors again and if that doesn’t work try a new PCM. Do you know if I need to get the PCM programmed, or will any junkyard PCM work?
 
I'd send your PCM to @Wranglerfix for testing before I rolled the dice on a junkyard PCM.

Otherwise it's going to need to be the same year, same transmission, and not have been touched by a SKIM module. And not have all the same issues a 20 plus old PCM has like leaky capacitors.

@hear found a way to test the CPS using a $30 Amazon Bluetooth occiliscope.

-Mac
 
I'd send your PCM to @Wranglerfix for testing before I rolled the dice on a junkyard PCM.

Otherwise it's going to need to be the same year, same transmission, and not have been touched by a SKIM module. And not have all the same issues a 20 plus old PCM has like leaky capacitors.

@hear found a way to test the CPS using a $30 Amazon Bluetooth occiliscope.

-Mac

Crank sensor too, they work the exact same way. But sometimes it’s not the individual function but the phase angle between them.
 
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Novak Conversions Jeep Wrangler TJ engine mounts