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| any car guys here? 99 mustang v6 |
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| lilshawn:
I'm normally a pretty analytical guy...but I have an issue with a car engine for about a month that's been leaving me stumped. my niece got a car given to her by a friend she met at a car meet. 1999 ford mustang V6. I was told this car was running normally, then one day they went out to start it...and it would not. they had other cars (as car meet people do) so they just used the other car and they just had this one sitting in their driveway. they where going to just call auto scrappers to come get it, but after talking to my niece (who also has a 99 v6 mustang) she said that she could just have it (use it for parts or whatnot) so we get it towed to my house. just for poops and giggles, I throw a battery in it and try and start it. stinks real bad of fuel after a few tries. no spark? nope... it has spark on all 6. means the crank sensor and coil pack are fine... stinks like fuel so it's getting gas. pull out the plugs (soaking wet with fuel) and clean them off with some brake cleaner and the pressurized air hose... hit the key and after a few cranks it starts. it's miserable at the start... but soon straightens out. (probably excess gas in the cylinders) as it warms up it comes about to run pretty good actually. idles okay. stumbles a little bit if you rev it while cold... but gets better as it warms up to operating temp. (typical computer relearning fuel stuff as the battery was not in it.) so I drive it around the block a half dozen times. seems to run pretty good. drives straight. has lots of piss and vinegar. feels like it has an upgraded clutch. park it for the night. next afternoon I jump in it to move it to a different spot in the driveway. wont start, try 3 or 4 times but it smells flooded again. (try the old floor it wide open throttle to get the computer to cut fuel to clear it but no avail) abandon idea come back to it a couple days later. hit the key a few times... still no start. pull the plugs... wet again. clean them out. same thing as the first time... miserable at the start...straightens out once warm. (clearing fuel again) runs good again hook up to the computer. MAF reading properly. O2 sensors are reading, but short term fuel trims reading super rich so it's pulling TONS of fuel out to compensate. like it's getting all sorts of extra fuel from somewhere but can't figure out where. shut car off. leave it for a few minutes, starts back up just fine. about half an hour. starts okay. an hour... it's a tough start but it does start. overnight. nope. so I've been watching fuel pressures...40 to 43 psi and it looks stable even when revving... shut car off. watch pressure... stays about 40 so i don't THINK it's bleeding past injectors... and the regulator seems to work... none of the hoses for the EVAP system look like it has any raw fuel in them getting sucked into the intake. any ideas where this excess fuel is coming from? maybe the injectors ARE partly clogged... but open? enough to slowly bleed excess fuel from the rail into the cylinders overnight? is that a thing? it's the only thing i can think of. wish i had a physical gauge i could put on the fuel rail to monitor it as it's was parked. |
| Falken Hawke:
Does the fuel pressure regulator have a vacuum line connected to it? Typically, the fuel pressure isn't constant from idle to WOT and is reduced with engine vacuum (idle-part throttle). Make sure there is vacuum and the line is tight. If it checks good, the regulator is stuck. If it doesn't have a vacuum connection and keeps constant pressure, then I'd consider looking at the injectors. The computer pulling fuel would hint this shouldn't be the case though as the Fuel Map would be set to reduce fuel flow and the O2 sensor would fine-tune. There are cheap testers out there that pulse the injectors and come with a plastic manifold that attaches to a can of carb/throttle body cleaner and an injector for cleaning and pattern inspection. With a graduated cylinder, one could also flow test. |
| lilshawn:
thanks for the reply! it's good to get a different set of "eyes" on a problem. --- Quote from: Falken Hawke on October 26, 2023, 02:06:38 pm ---Does the fuel pressure regulator have a vacuum line connected to it? Typically, the fuel pressure isn't constant from idle to WOT and is reduced with engine vacuum (idle-part throttle). Make sure there is vacuum and the line is tight. If it checks good, the regulator is stuck. --- End quote --- it does have a pressure transducer/regulator combo on the fuel rail that feeds data back into the computer for fuel rail pressures. and yes, it does have manifold vacuum feedback. I can bleed off the fuel rail pressure, and the computer reports the fuel rail pressure as zero, then upon priming the system before startup, it increases to 40 something PSI. as far as I can tell it's operating as designed. multiple primes does not seem to result in any higher pressures. --- Quote from: Falken Hawke on October 26, 2023, 02:06:38 pm ---If it doesn't have a vacuum connection and keeps constant pressure, then I'd consider looking at the injectors. The computer pulling fuel would hint this shouldn't be the case though as the Fuel Map would be set to reduce fuel flow and the O2 sensor would fine-tune. There are cheap testers out there that pulse the injectors and come with a plastic manifold that attaches to a can of carb/throttle body cleaner and an injector for cleaning and pattern inspection. With a graduated cylinder, one could also flow test. --- End quote --- i was just poking around amazon and saw what you mentioned. i've seen the big huge machines with the pumps and flow tester things that do 4/6/8 at a time and whatnot for like 500 bucks before, but never really noticed the small kits with the tester box and the spray can adapter like you said till now. I'll have to add that to my tool arsenal sometime. the more and more I think about it the more I think there is an issue with the injectors. all of them? and all at the same time? I guess if some bad gas got in there and jammed the valve up maybe they aren't closing properly or something... I'm just keen on exploring all the potential what if's before i shotgun a set of injectors. looks like i can go to the auto wrecker and get a set of 6 injectors for 51 bucks. can't hurt to try i guess. |
| Falken Hawke:
The fuel pressure will be "max" with the engine off as there is no vacuum to the regulator. To test with the engine off, apply vacuum with a pump and pressure should drop. |
| bobbyb13:
Falken Hawke is more intimately familiar with this particular vehicle than I am, but does it have a dedicated cold start circuit/injector or is it utilizing the regular injectors and/or some temporary change to the throttle plate position, air bypass valve or something else to enrich on a cold/cold start? I have seen so many different ways that cold start enrichment was achieved that I wouldn't know where to start without staring at the engine. It could even be duty cycle of the injectors and they are working fine but the computer is screwing it up by sending wrong values. Not sure where Ford was at in '99 with this stuff. |
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