what are the signs of a bad fuel regulator?

Discussion in 'Fox 5.0 Mustang Tech' started by 85cleangtvert, May 27, 2005.

  1. how can i tell if my fuel regulator is bad? my car wont start. It has spark so it is a fuel problem. There plenty of gas in the car. I just changed the fuel filter. The old one was clogged. The pump is building pressure and I can hear it when i put the key in the on position. I dont know what else to look at. im thinking maybe i have a bad regulator? what do you guys think?
  2. Usually they tend to leak and/or give you nutty fuel pressure. Get a gauge and see if your pressure is correct.
  3. Exactly! You can get them at autozone...I think I paid $20 for mine. It's another tool in the toolbox... :D
  4. Where are you checking your spark at? My friend had the same problem, had spark from the coil, had us stumped for a while, then we checked spark at the plugs, had nada. Turned out the rotor had broken. Just a thought.
  5. i started checking for spark again and now i am not getting any. i checked the cap and rotor and they look good. The coil is getting power.
  6. are you using an old spark plug to check spark? the air gap method (with a nail, etc) causes as many headaches as it solves. grab a spare plug and put it in a plug wire. set the attached wire and plug on the plenum so that the plug threads are grounded (touching) the upper intake solidly. crank it and watch the spark jump the plug gap.

    rather than play 20 questions, I would search for Jrichker's no start checklist. It is a systematic way to test components.

    good luck.
  7. Cranks OK, but No Start Checklist for Fuel Injected Mustangs

    1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park. Remove coil wire from distributor & and hold 3/8” away from engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
    Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
    No spark, possible failed items in order of their probability:
    A.) MSD or Crane ignition box if so equipped
    B.) Coil
    C.) TFI module
    D.) PIP sensor in distributor
    E.) ECC relay next to computer - look for 12 volts at the fuel injector red wires
    F.) Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid.
    G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire.
    H.) Computer

    See the following links for wiring diagrams...

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model cars

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model cars

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars

    2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
    A.) Moisture inside distributor – remove cap, dry off & spray with WD40
    B.) Distributor cap
    C.) Rotor
    D.) Spark Plug wires
    E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

    3.) Spark at spark plug, but no start.
    Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.
    Two reasons:
    1.) If it backfires, the chance for a serious fire is increased.
    2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
    If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

    Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. See http://www.mustangworks.com/article...c-iv_codes.html for a description of the test connector. If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In pinch you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have.

    No fuel pressure, possible failed items in order of their probability:
    A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
    B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
    C.) Clogged fuel filter
    D.) Failed fuel pump
    E.) Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay. The fuse links live in the wiring harness near the starter solenoid.
    F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect for fuel escaping while pump is running.

    Fuel pressure OK, the injectors are not firing.

    A.) A Noid light available from Autozone, is one way to test the injector wiring.
    B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.

    a.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
    b.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
    c.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the ECC relay and the red wire for the 10 pin connectors.

    4.) Spark & fuel pressure OK.

    A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
    B.) Failed computer (not very likely)
    C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently).
    D.) Firing order off: HO & 351 use a different firing order from the non HO engines.
    HO & 351W 1-3-7-2-6-5-4-8
    Non HO 1-5-4-2-6-3-7-8
    E.) No start when hot - Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.
  8. the fuel pressure regulator is on the return side so if it was bad u would build up pressure u might have a colgged fuel filter or the injector windings may be together causing an either suck open or closed so u might need injectors too