Problem Of The Week! Boo

Discussion in 'Fox 5.0 Mustang Tech' started by Jarvis, Sep 19, 2013.

  1. Was driving home from work yesterday and noticed a very obvious loss of power. Was idling rough, different exhaust noise. My fuel pressure gauge doesnt move from about 19# regardless of throttle. It normally idles at 24# and increases with throttle. You can smell fuel when its running. Under the hood i noticed a plug wire came loose and fell off. I assumed that was causing the problems, but after i put it on and tightened the rest of them nothing changed. Any ideas? Im finally going to get a code reader tonight. Just wanted ideas. I recently changed plugs and wires, but that was a couple weeks ago and its been fine.
  2. your FP should be at 39 with the hose off, which would be around 34 or so with the hose on. I would check for vacuum leaks.
  3. fp WAY low!!!!! :eek:
  4. detonation probably blew the boot off :rlaugh:
  5. I honestly had no idea that's low. I'm no mechanic, I'm learning it as i go. What could that mean? I'm going to go run codes in a bit. Check vacuum? How?
  6. Now, I have NO idea if your car is setup with a tune or a chip and the FP is supposed to be other than stock, but my best guess given your mods in the sig is that the FP should be at 39. Given that................

    OK. locate your fuel pressure regulator- behind the throttle body on the fuel rail. It should have a vacuum line attached to it and if you say you have a FP gauge another line off of it.To test the FPR to see if it is faulty, with the car off when you pull the vacuum hose off smell the hose- it should not smell like gas. If it does, them the diaphragm is leaking gas into the hose and your FP will be low. Another way to check is with the car idling. remove the vacuum hose and momentarily stick your finger on the port on the FPR. You should feel it get sucked from the vacuum. If not, again the diaphragm is broken and time for a new one.

    If that all checks out remove the vacuum line and with the car idling your FP gauge should read 39. I assume you have an aftermarket FPR as the stock one does not have a port for a gauge. If you reading is as low as you say, then most likely it needs to be adjusted back to 39., normally with an allen wrench on top.

    To check for vacuum leaks, easiest way is to hook up a vacuum gauge to any vacuum port on the intake or throttle body and plug the hose you removed. Start the car. It should read around 14.7 or so... If lower.. see all of those vacuum hoses? Check every one for cracks and that they are connected. There can also be leaks at the intake, throttle body, or other points. You can remove the intake tube from the throttle body, start the car and then put your hand over the throttle body opening, If the car dies,. probably no leak. If the car smooths out, probably a vacuum leak.
    Jarvis likes this.
  7. ^^^^^^words of wisdon all true :nice:
  8. Definitely fuel smell in the line coming off of the fuel regulator. Which as you said means a ruptured diaphragm? What exactly does that entail? What's the fix? All of the hoses appear to be intact. Their is however a little rubber nub on the back of the intake that has a crack in it. Right beside where the tube from the fuel regulator goes.
  9. The cracked nub

    There was also this
    , maybe A/C related?
  10. bad fp regulator, got to replace it, gotta fix all vaccum leaks also or it will disrupt idle etc, wierd start up problems and on down the line at red lights.
  11. Ok, is the cracked nub a leak? or is it anything at all? Also does the fpr matter? Any suggestions?
  12. yes all matters all important, cracks are BAD, they're called Vaccum leaks= BAD
    inspect all your vaccum lines and conectors and replace as needed also, you're there doing it so check them all:stick:
  13. Yes I understand, wasn't sure if it was related. I'm was working on looking over them. Just lost my light. I'm assuming O'reilly's will be able to get me the replacement hoses? Sorry for dumb questions.
    How is this one?
  14. i say get a kirban but if you like colors etc get what you like, kirbans are highly recommended by people who know durability. Vaccum hoses, conectors etc are very common at all auto parts stores. whatever is closest to you.
  15. That looks like the line from under the intake manifold to the carbon canister purge solenoid. That's a big vacuum leak if it isn't properly connected or plugged.

    Here's how it works...

    Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.


    It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?

    The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

    The purge valve solenoid should be available at your local auto parts store.

    Purge valve solenoid:

    The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
    Carbon Canister:

    Fuel pump pressure test
    Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC
    test connector and jump the connector in the Upper RH corner to ground.


    Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
    If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.
    Jarvis likes this.
  16. If you have a FP gauge hooked up to your existing FPR and want to keep it, then you need to either replace it with another one with a port for the gauge, or get a Kirban FPR and relocate the FP gauge line to the schrader test valve on the rail with a brass T fitting.

    I agree with Jricjhker, that hose goes to the purge canister mounted on the inner passenger frame rail. you can replace it with a piece of regular vacuum hose.
    Jarvis likes this.
  17. I'll look into that.
    Great description, I'll see what i can see after work :( It's still pretty confusing to me though. I need to find someone near Fort Benning that can help me. It's nerve racking doing this stuff when i've never done it before, and I don't want to pay a shop to fix something I can.
    Yeah id like to keep the gauge, it's there. Might as well.
  18. easiest way to test for vac leaks on lines is to spray starting fluid/carb cleaner etc on them. If you have a vac leak the car will idle up significantly (car obviously has to be running).

    Also, at the age that foxes are, its a good idea to invest in all new lines (they are cheap by the foot at your local parts store). 20 yr plus cars have lots of issues that are just age related and cheaply fixed.
  19. One problem is I'm still working on figuring out which ones are vacuum lines. Only had about 10 minutes before it got too dark. Doesn't help that whoever had the car before me had an IQ of about 19.
  20. Great, now I'm insulted....My IQ just came back at 19.

    All ball breaking aside, because i'm just kidding of coarse. It really sounds like once all of these vacuum issues are resolved you will have far fewer headaches.

    Good luck!!