Frps Going Bad?

Discussion in 'SN95 4.6L Mustang Tech' started by Redfire93, Jun 15, 2014.

  1. Hey guys, just have a quick question, I'm pretty sure I've narrowed it down to the FRPS going bad. But, here lately, my car (2003 Mustang GT) has been giving me trouble starting, it'll turn over for a solid 5-8 seconds before catching, but once it starts it's perfectly fine. At first I thought the spark plugs were going bad because take off was a little rough, so I replaced them (.054) and got rid of the shaky launch. However, starting was still an issue, then I started smelling fuel in my a/c only when idling, it's definitely not a build up of fungus or bacteria as condensation still collects on the ground from the a/c. I tried giving the fuel pump 3 seconds before starting and when I do it fires right up. So I'm almost positive the fuel pressure is leaking down because of the FRPS. Just want you all's thoughts.
  2. Can you please explain how a car with a bad FRPS runs OK all the time EXCEPT when starting?

    Has the FRPS intake vacuum line been inspected for raw gas?

    What has been done to rule out a leaking Fuel injector(s)?
  3. Well, my understanding is that when the fuel pump pressurizes the lines, the frps doesn't send correct info to keep the pressure stable so it leaks down.

    Haven't seen any raw gas in the vacuum line, and nothing has ruled out an injector, but considering the symptoms, such as smelling gas in the a/c when idling, I didn't think it would be an injector.
  4. Ughhhh, bump...
  5. Not a good assumption regarding the fuel injector. My Son and I recently troubled shot a problem with an F150 misfiring. Strong gas smell. Monitoring the fuel pressure, we noted that the pressure quickly dropped to zero as soon as the motor was turn off.

    Long story short it turn out to be a stuck partially open fuel injector. When we removed the fuel rail, there as still fuel "pissing" out the bad injector.

    If you are certain the FRPS is bad, then by all means replace it. The part is not all that $$ to replace just to rule it out.
  6. My only dilemma in thinking it's an injector is the fact that it can be smelled in the a/c.
  7. After you have replaced the FRPS and should the problem continue, consider an injector cleaning flow test service such as Once cleaned and tested they are as good as new. Cheaper then new.

    If smelling fuel is the issue and you don't believe it's from a a leaking injector, then that means there's a joint somewhere that's leaking. Marshmallow roast anyone?

    Bottom line. Continued operation with excessive fuel inside the motor could leak to gas washing of the oil from the cylinder walls. The excess gas could also dilute the oil. This could lead to a shorter service life of the motor.
  8. You can run a simple test on the FRPS. While the car is running, remove the vacuum line. If fuel spurts out, the diaphragm inside the regulator is bad.