2005 Mustang V6 will not start - at my wits end!

[schwaggs]

Long time lurker - needs some help!

2005 Mustang Convert V6
No error codes
Cranks fine - will not start
If you put the throttle to the floor while cranking, it will catch a very little bit but will not run
I've been shot-gunning parts without any luck
Spark plugs
Fuel filter
Crank Position
Cam position
MAF
Fuel pump
Fuel pressure sensor

If the car sits for some time (a week or so) it will start and run very weakly for about 20 seconds then die. Subsequent attempts will not start (like above).

This started when my daughter was driving home from work. As she was driving, it was getting weaker and weaker until if finally stopped.

Cat plugged? Would that stop it from starting (catching) at all?

Any help is appreciated!

 

[Bullitt95]

Weak battery?
If you do get the engine running, check the alternator as it seems it isn't charging the battery.

 

[schwaggs]

It cranks with good speed, normally I would say. It just will not catch and start running.

 

[cbxer55]

For quite some time back in the late 00s, my V-6 Ranger went through a period of difficulty starting. I could near kill the battery before it would finally run, on maybe three of the six cylinders. Then over a bout a five minute span the other three would kick in one-at-a-time. It was irritating to say the least. Like you I threw lots of parts at it to no avail. Last thing and what fixed it was really badly fouled fuel injectors. It seems they had a glaze on the end, and that glaze would harden when cold. When cranking, if cranked long enough, the pressure would eventually poke a hole in the glaze and it would run. Then when shut off it would re-harden and the fun would begin again next time I needed it. And the fix? I started running fuel with ethanol in it. Ethanol is a superb cleaning agent, much more so than almost any of the canned junk. The only canned stuff I buy is Berryman's B12. It has Methanol, Acetone and MEK in it. Really potent stuff.

Sometimes the injectors need to be removed and cleaned professionally if they are really bad. I've read about that on this forum.

Haven't had a problem with the Ranger for years. Sometimes it get's a little persnickety and won't start first turn of the key, nor the second, sometimes even the third. I fill it up with ethanol fuel for a couple tanks and it gets better. I don't run it all the time, just when it needs it.

I bought my Stang in November. It started throwing a random misfire code with in weeks. I replaced the coils, plugs and wires. The issue went away. Then it started leaking at the stupid plastic thermostat housing. Just finished replacing it with a metal one, no more leaks. What's next? Oh yeah, the random intermittent blinking OD OFF light. But the transmission shifts fine and the car is running great, so I think I'll just put a piece of black tape over it. LMAO!!!

 

[cbxer55]

Oh yeah. Fuel pump. That's a biggie. Do you have a fuel pressure gauge? You can buy one at any of the auto stores. Screws onto a schrade valve on the fuel rail, like a bicycle pump to a tire. If the fuel pump went out, it might be gradual as you described. My 98 Ranger, the pump went out on me while out driving. I managed to get it home, barely. Fuel pressure on the Ranger is 56 to 72 psi. It was 20. It ran, just barely. I never tried starting it cold, but likely it wouldn't have.

 

[schwaggs]

Thanks for the suggestions!

I did replace the fuel pump and filter. I can smell raw gas if I try and start it for a while. No schrader valve on the 2005 4.0 V6 unfortunately. The ODBC monitor I have says the pressure is 70ish after turning the key on and hovers around the 50psi when cranking. Can feel the fuel pump running at key on and when cranking.

I'm going to check the smart junction box for water damage and get a spark tester to see if the plugs have spark.

 

[schwaggs]

Update: turned out to be plugged catalytic converter. I removed the upstream O2 sensors to give the exhaust an exit and it started right up.