Serious Hard Starting Issues Continue...HELP!

[TylerHagerdorn]

I'm about to just sell this truck. I'm so sick and tired of dumping money into it and it not being fixed. Here's the run down of the issue. It's a 2004 Flex Fuel.

If it sits for more than 2 hours it loses all fuel pressure. In order for it to start you have to push the gas pedal all the way down and hold it for it to start. It dumps raw fuel out of the tank. I've now replaced the fuel pressure regulator, both purge valves, and the fuel pump yesterday with a Delphi one. After we installed the Delphi pump, and cycled the key a couple times, it fired up immediately like it was fixed. And was fine all evening. Came out this morning after sitting all night and it acted like it wanted to start and then died. Then I had to push the pedal all the way down for it to start. The only codes I've been getting are a purge valve circuit(P0443) and a fuel composition sensor circuit(P0178) code. I'm really getting tired of people telling me this is what's wrong and spending money on the parts for it to not be fixed. Why would it fire right up after installing the new pump, but then have issues this morning?

What else could it be? No, I don't have a fancy scanner than can read everything. And no I'm not taking it to a shop. I need solid legit advice.

 

[S33k3r]

The most legit advice is to get your own scan tool, or take it to a legit shop to have it scanned/diagnosed. That said, I'll give you the best advice I can with the information you have provided: it really sounds like an electrical issue at this point. The cheap fix is to trace all your grounds and clean them up.

I hesitate to say it, but one of your purge valves could be bad. This is why it started right up with the changed fuel pump, but then didn't start correctly later. You could do some testing of the purge system with a "fancy scan to" as could a reputable shop. There's at least one YouTube video I found where the guy commanded purge valves to open and close, measured pressure before and after, and then identified a bad purge valve.

I don't know where you are located, but if you're near the DFW Metroplex, I have a mechanic who can fix it for you, is honest, and warranties his work. As an example, he installed an oem part that failed, and our only cost was the time it took to replace it. AND we didn't even know that was what was wrong. This guy has had multiple opportunities to sneak hundreds of dollars of repairs in, or even has investigated an issue I got wrong and saved me money. My only concern is if this guy retires before I quit driving.

 

[TylerHagerdorn]

The most legit advice is to get your own scan tool, or take it to a legit shop to have it scanned/diagnosed. That said, I'll give you the best advice I can with the information you have provided: it really sounds like an electrical issue at this point. The cheap fix is to trace all your grounds and clean them up.

I hesitate to say it, but one of your purge valves could be bad. This is why it started right up with the changed fuel pump, but then didn't start correctly later. You could do some testing of the purge system with a "fancy scan to" as could a reputable shop. There's at least one YouTube video I found where the guy commanded purge valves to open and close, measured pressure before and after, and then identified a bad purge valve.

I don't know where you are located, but if you're near the DFW Metroplex, I have a mechanic who can fix it for you, is honest, and warranties his work. As an example, he installed an oem part that failed, and our only cost was the time it took to replace it. AND we didn't even know that was what was wrong. This guy has had multiple opportunities to sneak hundreds of dollars of repairs in, or even has investigated an issue I got wrong and saved me money. My only concern is if this guy retires before I quit driving.

It's not ground wires. I've already replaced and repaired them all. This isn't my first thread about this. Go check my other ones. I've been fighting this for months. As I said both purge valves have been replaced and are both OEM and new and fine. I have a nice scan tool but it doesn't do tests and all that. And I'm not dropping money at a shop because it doesn't matter where you go, every single shop is scam artists. I've been doing all my own work for many years and I've worked on shops. I know how they are. I'm not paying someone to tell me something that someone can tell me on a forum or something. I guarantee this is not the first time there's been an issue like this. At this point, I'm leaning towards a PCM issue. Someone installed a 105 amp alternator in my truck when the RPO code calls for the 145 amp alternator. Who knows how long it was on the truck but that can cause serious electrical issues. I replaced it with an ac Delco 145 amp after I got it and found that out. I'm about to just dump this truck because I'm done dealing with it. My 01 Yukon XL I had before this never gave me a single problem when I owned it. The guy I got this truck from acted like it had no issues when I got it. This problem has been since the day I got it. It doesn't just happen overnight. It was fine when I picked it up, then the next morning this started. It seems like it's better when it's warmer outside. It was 60 degrees yesterday. It's 32 now and was 29 overnight.

 

[TylerHagerdorn]

The most legit advice is to get your own scan tool, or take it to a legit shop to have it scanned/diagnosed. That said, I'll give you the best advice I can with the information you have provided: it really sounds like an electrical issue at this point. The cheap fix is to trace all your grounds and clean them up.

I hesitate to say it, but one of your purge valves could be bad. This is why it started right up with the changed fuel pump, but then didn't start correctly later. You could do some testing of the purge system with a "fancy scan to" as could a reputable shop. There's at least one YouTube video I found where the guy commanded purge valves to open and close, measured pressure before and after, and then identified a bad purge valve.

I don't know where you are located, but if you're near the DFW Metroplex, I have a mechanic who can fix it for you, is honest, and warranties his work. As an example, he installed an oem part that failed, and our only cost was the time it took to replace it. AND we didn't even know that was what was wrong. This guy has had multiple opportunities to sneak hundreds of dollars of repairs in, or even has investigated an issue I got wrong and saved me money. My only concern is if this guy retires before I quit driving.

And how would it be an electrical issue if I have to mash the gas in order for it to start and it dumps fuel out of the exhaust? That's a fuel issue. It loses all pressure within 2 hours. That's a fuel issue. That's not an electrical issue. A purge valve doesn't control fuel pressure.

 

[S33k3r]

Purge valves control the pressure in the tank. If there's too much vacuum in the tank -- say, after it's gotten really cold -- then the fuel system has to work harder to get fuel where it needs to go. The sensor systems and computers that control how fuel is demanded and used are electrical. Please don't get hostile with me -- I'm not accusing you of being an idiot. I apologize if it sounded that way.

My experience with crap like this is that it's almost always something basic, so I try to be methodical in fixing things.

Also, when asking for help, I do think it's unreasonable to expect people to know there are other threads out there, much less expect us to go find and reference 5hem. I don't even know what year vehicle you have, for example. I did want to help, I've recently been diagnosing a "large leak" in my evap system, and so I offered suggestions from what I know.

Good luck in getting it fixed, and if it is an '03 or newer, let me know how much you want for it and where you are. I might be interested in messing with it.

To be clear, there is no I'll intent in my response and I am not upset. Please understand I know you are upset, and the last thing I want to do is antagonize you further. My post was not intended to be condescending, though I see how it might be interpreted that way; I am sorry.

 

[mattbta]

Tyler,

Sorry for kinda hijacking your other thread. I'll follow this one and start my own. I've got issues, too.

 

[Fless]

I'm about to just sell this truck. I'm so sick and tired of dumping money into it and it not being fixed. Here's the run down of the issue. It's a 2004 Flex Fuel.

If it sits for more than 2 hours it loses all fuel pressure. In order for it to start you have to push the gas pedal all the way down and hold it for it to start. It dumps raw fuel out of the tank. I've now replaced the fuel pressure regulator, both purge valves, and the fuel pump yesterday with a Delphi one. After we installed the Delphi pump, and cycled the key a couple times, it fired up immediately like it was fixed. And was fine all evening. Came out this morning after sitting all night and it acted like it wanted to start and then died. Then I had to push the pedal all the way down for it to start. The only codes I've been getting are a purge valve circuit(P0443) and a fuel composition sensor circuit(P0178) code. I'm really getting tired of people telling me this is what's wrong and spending money on the parts for it to not be fixed. Why would it fire right up after installing the new pump, but then have issues this morning?

What else could it be? No, I don't have a fancy scanner than can read everything. And no I'm not taking it to a shop. I need solid legit advice.

You could check the fuel trims if that hasn't been done, then dump it.

 

[TylerHagerdorn]

Purge valves control the pressure in the tank. If there's too much vacuum in the tank -- say, after it's gotten really cold -- then the fuel system has to work harder to get fuel where it needs to go. The sensor systems and computers that control how fuel is demanded and used are electrical. Please don't get hostile with me -- I'm not accusing you of being an idiot. I apologize if it sounded that way.

My experience with crap like this is that it's almost always something basic, so I try to be methodical in fixing things.

Also, when asking for help, I do think it's unreasonable to expect people to know there are other threads out there, much less expect us to go find and reference 5hem. I don't even know what year vehicle you have, for example. I did want to help, I've recently been diagnosing a "large leak" in my evap system, and so I offered suggestions from what I know.

Good luck in getting it fixed, and if it is an '03 or newer, let me know how much you want for it and where you are. I might be interested in messing with it.

To be clear, there is no I'll intent in my response and I am not upset. Please understand I know you are upset, and the last thing I want to do is antagonize you further. My post was not intended to be condescending, though I see how it might be interpreted that way; I am sorry.

Purge valves on these don't control tank pressure. The "fuel tank pressure sensor" mounted to the fuel pump does.

 

[Doubeleive]

after it has sat overnight or a couple hours (when the issue happens) key on engine off, fuel pressure is what?

 

[TylerHagerdorn]

after it has sat overnight or a couple hours (when the issue happens) key on engine off, fuel pressure is what?

Fuel pressure when running is 50-51 which is now within spec. Old pump was only at 45 max when running. I got to work at 2, I shut the truck off with it connected and after I shut it off it went to 40psi. After an hour of sitting it was down to 20psi. It's now been two hours and the pressure is down to 0psi. I've checked the plugs and they've been dry no gas smell or anything. Not right after running the truck but an hour or two after. Only thing I can think of now is maybe a leaking injector? My buddy said with the heat in the engine the fuel could evaporate fast