2004 Starting Issues After Warm

[KY_SimpleMan]

I have a 2004 with the 4.0. When I first get in the Jeep it fires right up with no problems. After I drive it, I have to cycle the key at least 3 times before it will start. If I try to start without cycling, or cycling just 2 times, it just cranks and cranks. Part of me thinks it's the fuel pump, but I can't figure out why it starts on first crank when it is cold? Anyone else have this problem, and what is the fix? Thanks.

 

[macleanflood]

Get a fuel pressure gauge on the rail and start monitoring your PSI.

This adapter will let you add a Schrader test valve or a dedicated gauge to your fuel rail.

https://www.racetronix.biz/p/adapter-qdf-5-16qdm-5-16-1-8-port/qda-56f56mp

-Mac

 

[KY_SimpleMan]

Get a fuel pressure gauge on the rail and start monitoring your PSI.

This adapter will let you add a Schrader test valve or a dedicated gauge to your fuel rail.

https://www.racetronix.biz/p/adapter-qdf-5-16qdm-5-16-1-8-port/qda-56f56mp

-Mac

What would this do exactly? I’m not familiar with it. Thanks

 

[TJ Jim]

Get a fuel pressure gauge on the rail and start monitoring your PSI.

This adapter will let you add a Schrader test valve or a dedicated gauge to your fuel rail.

https://www.racetronix.biz/p/adapter-qdf-5-16qdm-5-16-1-8-port/qda-56f56mp

-Mac

Nobody ever follows through with this? It works fantastic on mine and obviously on yours too.

 

[TJ Jim]

What would this do exactly? I’m not familiar with it. Thanks

You can monitor your fuel pressure on our jeeps that don’t have a shrader type valve to check

 

[macleanflood]

Your fuel rail doesn't have a Shrader test port...at least I don't think it does.

So you can't test fuel pressure.

That adapter slips on to the quick disconnect fitting and allows you to install a gauge or a test port.

-Mac

 

[TJ Jim]

 

[KY_SimpleMan]

Ok. But what am I looking for? How much psi? On the initial turn of switch or when it doesn’t start. Does this confirm it’s the fuel pump? I know just enough mechanical work to be dangerous.

 

[macleanflood]

48 psi is specified. Mine ran on 30 but the fuel trims were not good. You also want to see how it changes over time.

-Mac

 

[TJ Jim]

Close to 50psi. Supposed to keep the pressure after shutdown but mine does not. Not keeping the pressure after shutdown is a sign the regulator is failing. Mine runs and starts fine so I haven’t worried about doing anything.

While running you should maintain close to 50psi. Mine runs closer to 48

 

[KY_SimpleMan]

Thanks everyone. Does that make sense though with it starting fine from cold start?

 

[macleanflood]

Thanks everyone. Does that make sense though with it starting fine from cold start?

Data will help answer that question.

Anything else is speculation.

You want my guess...you probably have a bad pressure regulator in the fuel pump assembly.

-Mac

 

[TJ Jim]

Thanks everyone. Does that make sense though with it starting fine from cold start?

Makes no sense at all. We’re just giving you best guess and where we would start.

 

[squirrelmaster]

A failure to start warm is often indicative of a fuel pressure regulator failing. As long as the fuel pressure regulator hasn't failed completely open, it will allow enough fuel pressure to build at the rails for a cold start. Warm starts become a challenge because engine heat will heat-soak the fuel rail. When the fuel pressure regulator is working properly, it effectively maintains pressure (it very, very slowly bleeds off pressure) in the fuel rail and the heat-soak heats the fuel but is unable to cause it to vaporize due to the aforementioned pressure. When the fuel pressure regulator begins to fail, it will bleed off pressure too quickly, allowing the heat to vaporizer the fuel. When you then go to start the engine, the fuel vapor won't atomize correctly inside the cylinder, and the engine cranks and cranks until the vapor is out of the fuel lines and liquid fuel is flowing into the injectors.

 

[TJ Jim]

A failure to start warm is often indicative of a fuel pressure regulator failing. As long as the fuel pressure regulator hasn't failed completely open, it will allow enough fuel pressure to build at the rails for a cold start. Warm starts become a challenge because engine heat will heat-soak the fuel rail. When the fuel pressure regulator is working properly, it effectively maintains pressure (it very, very slowly bleeds off pressure) in the fuel rail and the heat-soak heats the fuel but is unable to cause it to vaporize due to the aforementioned pressure. When the fuel pressure regulator begins to fail, it will bleed off pressure too quickly, allowing the heat to vaporizer the fuel. When you then go to start the engine, the fuel vapor won't atomize correctly inside the cylinder, and the engine cranks and cranks until the vapor is out of the fuel lines and liquid fuel is flowing into the injectors.

Sounds good. Now if we only knew what the pressure is actually doing?

 

[macleanflood]

One additional alternative to adding that Racetronix adapter to the rail is outright replacing your entire fuel rail. Either a used older one like I have on my 97 with a Schrader valve...or you'll find plenty on eBay and Amazon. It's pretty simple to pop off the rail and replace it. You'll want to replace the o-rings on your injectors...super cheap and a pick makes it simple and easy...a capfull of motor oil for a little lubrication before reinstallation. You'd get half the o-rings too if you order a DEI fuel rail heat shield kit... highly recommended if you're already pulling the rail. Keep your fuel cooler.

-Mac

 

[gasiorv]

If you have good fuel pressure and the fuel pump is good. Change the crank position sensor.