2004 Wrangler 4.0 Auto - Failed Instant Start

Try cycling the ignition switch ON OFF ON 3 to 5 times without cranking the engine.
Then crank the engine over and see if the engine starts first time.
IF this works; then the problem could be the fuel pump check valve not holding fuel rail pressure after sitting for a while. This is actually a somewhat common problem with older fuel pumps.
Resolving this problem will require the replacement of the check valve inside the fuel tank.

typically a fouled plug won't cause it to not start. It might run rough, but it should start. Does it just crank when it doesn't start or does it not even turn over?

I would start by measuring fuel pressure, but that usually happens when cold as well. Might be a sensor that is giving you fits when Its warm...without a scan tool to read some of those sensors though, you'll be firing the parts cannon at it. With the quality of aftermarket sensors these days, that is risky business. I'd suggest a really good mechanic that is willing to spend the time on diagnosis to figure out what is giving you fits.

Mike_H said:

I would start by measuring fuel pressure, but that usually happens when cold as well. Might be a sensor that is giving you fits when Its warm...without a scan tool to read some of those sensors though, you'll be firing the parts cannon at it. With the quality of aftermarket sensors these days, that is risky business. I'd suggest a really good mechanic that is willing to spend the time on diagnosis to figure out what is giving you fits.

Click to expand...

In my experience the fuel pressure thing only happens when it's cold. After it's been driven even a leaky valve will hold some residual pressure & allow it to re-start quickly. You're saying it NEVER has a problem doing a cold start? (If it's truly intermittent I'm thinking electrical).

I assume the starter and Jeep cable kit were attempts at solving the issue and had zero results?

Fill out your profile, please...it would help to know the year and engine in your TJ.

If it's an earlier model with cap, rotor and spark plugs I'd say throw those parts at it...seems like it's due for a tune up.

-Mac

hear said:

In my experience the fuel pressure thing only happens when it's cold. After it's been driven even a leaky valve will hold some residual pressure & allow it to re-start quickly. You're saying it NEVER has a problem doing a cold start? (If it's truly intermittent I'm thinking electrical).

Click to expand...

I've had those regulators get bad enough it was trouble on ALL startups where the engine sat longer than 5 minutes...This was mine before I finally fixed it.


Agree though, I don't think OP's issue is a fuel pump.

You win.

That’s the most markup ever used in a WTJF post.

Have you tried the key trick to read codes?

https://wranglertjforum.com/threads...here-is-a-check-engine-light-illuminated.223/


Once you have codes, we can help more.

Another question, do you have a heatshield on the #3 injector? Since the issue happens when it is hot, that is a classic sign of heat soak.

WWII-Willys said:

Thanx Again Guys ....

After your comments, I'll place a bet on a bad senor (somewhere)? I can get a Code Reader - we'll see how that goes? Profile? I don't know if you guys remember: I'm 75 disabled and don't change/alter anything as long as it runs. Its a 2004, 4.0 Automatic, Throttle Body with 156K. NO Caps NO Rotors. I definitely could use NEW plugs. My buddy and I can do that. The issue again and again (down here in southern Florida), is the LOSS of a RELIABLE HONEST Mechanic. When I lived in Philly (50 years), I personally knew the managers at Quadratec and later hooked up with a laid off mechanic from Roxborogh Chrylser Jeep. I gave him whatever parts he needed.

In southern Florida:
You need basic brakes? = $1200
You need a tune up? = $1200
You need a coolant engine flush = $1200
You need a new starter and cable upgrade? = $1200

Exaggerated but they assume you have the dough to live here, so they stick it to you. From now on, my buddy and I try to do some of that stuff ourselves. Mr. Maclean asked about the recent starter motor replacement and cable upgrade? We did BOTH for less than $250 because they were both needed at the time, (nothing to do with this current issue). We 'BUSTED KNUCKLES' trying to unfreeze those damn bolts. We'll use a Code Reader: (The Check Engine Light Is On), and get back to you guys! BTW: I mentioned previously; sure hope this sensor is not somehow attached to the fuel filter inside the tank?

Thanks Again Guys!

Click to expand...

Not sure where you live in FL, but with prices like that you must live in one of the larger retirement cities such as Miami, Palm Coast, Tampa or Fort Lauderdale.
In Jacksonville there are numerous shops; you need to search for one that specializes in Jeeps or knows what they are doing. For the problems that I can’t resolve; I either contact a Jeep Tech buddy who can provide technical knowledge or make an appointment with Happy Trails 4x4 who specializes in Jeep repairs and restorations.

P0455 could be a loose gas cap. That isn't going to cause the hot start issues.

P0122 is a tps issue, which could cause the starting issue you are having. However, it may not be the sensor itself, it could be a wiring issue, or even a problem with the clock spring. This will take some time with a multimeter to sort out before you shotgun parts.

hear said:

In my experience the fuel pressure thing only happens when it's cold. After it's been driven even a leaky valve will hold some residual pressure & allow it to re-start quickly. You're saying it NEVER has a problem doing a cold start? (If it's truly intermittent I'm thinking electrical).

Click to expand...

I had the check valve issue ONLY when it was warm. It would always start when it was cold. My assumption is when its cold, the fuel pump primes. When its warm, it doesn't always prime.

WWII-Willys said:

Codes I just picked up using Key Trick - but not sure how accurate they are?

P 0122
A P0122 code is the generic OBD-II code defined as “Throttle Pedal Position Sensor/Switch (TPS) A Circuit Low Input.” This code relates to the vehicle's Engine Control Module (ECM) and TPS Sensor Circuit A output voltage and is triggered when the voltage falls below the sensor's anticipated range.

P 0455
The P0455 diagnostic trouble code appears when there's a leak in the Evaporative Emission Control (EVAP) system, and the system can't maintain pressure. The EVAP system usually consists of five main components: the fuel tank, fuel cap, vent valve, purge valve, and the evaporative canister (or charcoal canister).

Looks like Charles & Mike were onto something? Anything leading to the fuel tank is a BIG Deal .....

Here's ONE TUTORIAL

Here's another for Canister Purge Valve

Thanks Again!

Click to expand...

The TPS is most likely causing the issue, without a doubt. I just did a little bit of a write-up a few days ago on how to test it. Grab a voltmeter (or a multimeter set to 20 DCV), and back probe the signal (not the 5V supply) wire running INTO the TPS (not the PCM, that way if you accidentally fuck up the connector it's easier to replace the TPS pigtail, rather the big PCM bus connector). Ground your meter to the ground wire on the sensor or any bare metal (like the valve cover, it doesn't matter). Then, slowly move the throttle lock to lock with the ignition on. Look for any dead spots where the voltage goes to zero. I know you said you're disabled, but if you have a neighbor or someone else who can get up there and get the probes in there, it's not too hard. The sensor itself is also easy to change.

While you're driving, if it drives of course, does it stutter? Do the RPM's fluctuate at idle? A TPS is nothing but a potentiometer, just like your fuel sending unit. There are a multitude of plates that a little arm moves against that have different resistance values. As you push the pedal down, the sensor tells the PCM a different resistance value for input. So if you're trying to start it, and it hits, the TPS failure will confuse the PCM, because it thinks you are applying throttle. So when you start it, the PCM is going to immediately start dumping fuel in the cylinders despite the butterfly valve being closed. It riches out and dies. When you're driving, it's going to tell the PCM all sorts of wrong inputs that are going to cause the PCM to lean out, rich out, all over the place causing stuttering, or in many cases, just dying. Also look for chewed wires, charred insulation, etc. My 2003 TJ 2.4 had the TPS go out right after a car wash. It would stutter all over the place, idling at 2000 RPM, and sometimes would die out. I couldn't find the keys to the Gladiator so I had to drive it to AutoZone to get the sensor lol. I found that the connector was zip-tied in place after a PO broke the connector clip. Water got in there after the connector backed off slightly (the 2.4 TPS is VERY close to the cowl where water pours in, and I had the hood up after the wash to check my oil), and killed the TPS. Somehow 5V and a few mA can kill a TPS I guess. I had to replace it and electrical tape the connector back on.

As for your fuel pump, get it changed soon. It's likely original. Mine had the check valve issue as well, and if you DO have that as well, it'll probably go out on you soon. The check-valve won't likely cause you to be stuck on the side of the road, but if the pumps original, it is time for a new one. The EVAP code is very possibly a gas cap, but a large leak is usually a rotted vacuum line running to the purge valve/canister. TBH, I don't know nor care how an EVAP system works completely. Once my Jeep hits 25 years old and is exempt for emissions testing in Lorain County, if I get an EVAP code, I'm not giving no shits.

If you still can't figure it out, I'll hop on a plane and take it off your hands (kidding, unless...)