slipmahoney

Hi all,

I have a 09 STX regular cab with a 2 valve per cyclinder 4.6L motor. My issue started about 3 weeks ago. When the truck sits for good amount of time, like over night, the problem I have is it starts right up, and then abruptly dies. I have to do this about 15-20 times until it stays on! I had to replace the starter in it a few weeks ago as I think I might have fried it from having to do this. Most of the time there are no codes stored, once in a while I will get a P0130 code. Now I have a code reader and have looked at the freeze frame data. For the FUELSYS1 parameter, a CL-Fault is stored along with a P0130 code. Like I said, it doesn't always throw a engine fault code. And when I look at live data, periodically, the FUELSYS1 parameter changes to CL-Fault, or OL, then it goes back to CL.

The things I have changed so far are a used throttle body and a brand new TPS sensor. Yesterday I changed the air filter, and cleaned the MAF sensor. It seems to have gotten a little better as it started right up this morning and it was colder than it has been. But when I went to lunch today, it took abnout 4 tries until it stayed on. I know a P0130 code is for the O2 sensor, but when I look at the live O2 sensor data, they appear to be working, both are usually around .6 V. I haven't given in to bringing in to the shop yet, I would rather fix it myself. But I am getting close to I had my wife turn it over, and I pushed on the schrader valve of the fuel rail, and gas shot out like a geyser, so I think the pump is ok! I was thinking maybe the Fuel pressure sensor might be bad, but I don't know where the heck it is to test it. Any help WOULD be GREATLY appreciated.

ji603

Have you replaced the evap purge valve? No sign or burning around your fuel pump fuse (27) in engine bay box?

slipmahoney

As a matter of fact, there is some melting by this fuse. But the fuse is good. I check it with an ohm meter. I have disconnected the wire to the purge valve and then took the hose off that comes from the tank, and did not detect it leaking, so I would assume that the valve is ok, no?

It took about 40 cranks this morning until it stayed started. I am about ready to take it to the dealer. This has been going on for about 3 weeks. I'm afraid I am going to burn up my starter.

The truck has about 163k miles on it. The o2 sensors have never been replaced. Both look bad on my Autel AL519 scanner. I can get a graph reading of the voltage. The PCM has thrown a P0130 every now and then. So I'm going to replace them this evening, but I'm not sure that this will cure the stall problem.

ji603

I don't believe your O2 sensors are causing your no start problem. If you are at the dealer, have them look up the fuse 27/fuel pump tsb and buy the terminal relocation kit in the tsb. It's less than 15 bucks. I feel like your fuel pump fuse is the problem

slipmahoney

Really, interesting. I googled it and read a couple of post about it. They say that it happens after it heats up, but my problem is the opposite. It happens when the coolant is cold.

slipmahoney

Well it was not the o2 sensors and I figured it wasn't because it passed the o2 monitor test. But looking at the sensor voltage waveform, I could tell they had very slow response time. The throttle response is so much better.

But I still have this annoying issues. I don't think it's the fuse either. Because it starts right up. It just doesn't stay on. Took about 25 tries this morning. I'm thinking that it might low fuel pressure during starting, because as I understand it, it should be higher when starting the motor.

It only seems to happen when the ambient air temperature is colder than 60 degrees. I'm getting a fuel pressure gauge from harbor freight today.

slipmahoney

I think you might be onto something. I took fuse 27 out, and you can see that one end of the fuse receptical is spread apart. I'm thinking that when it's cooler the metal contracts just enough to open the circuit to the fuel pump. I put a slightly larger body fuse in to make better contact. We'll see tomorrow morning.

slipmahoney

Since putting in the new o2 sensors, I'm getting 18.4 mpg around town. I was getting a P0130 code once in a while, so the sensors were tired. And what was cool is that I could see the sluggishness of the response of the sensors on the graphic display of the Autel AL519 code reader. I highly recommend this tool at $65 dollars on Amazon.

slipmahoney

Being the fact that the fuel pump only fails when it's cooler and after sitting for a while, I am apt to believe that it is this stupid fuse. It definitely melted and there is a gap on the contacts to where it makes a connection to one side of the fuse. If the pump were bad, it would be happening at almost anytime. But I ordered a pump just in case.

I went out at lunch time and got that terminal relocation kit and will install it when I get home. I sure hope this is it!

slipmahoney

I did the fuse 27 relocation. Needless to say, I still have the problem. But here is funny thing I noticed. I went out this morning to start the truck. Of course in died a second or two later. Did this a few times with same results. Then I attached the fuel pressure gauge to the fuel rail and put the gauge where I could see it. Turned the ignition to on and the pressure shot up to 50 psi. Then I started it, and the gauge dropped down to about 30 psi and then back up to 50 psi and it stayed on! Then I turned the motor off, took the gauge off, and it started but died a few seconds later! It seems if I put the gauge on, the motor stays on. The pressure drops a little, but then kicks back up to 50 and stays on. What the heck is going on. Also, when I turn the motor off with the gauge still hooked up, it holds the pressure at 50 psi. Is this normal.