Does bad cps **** fuel pressure

[thegreatbriguy]

I can't remember, with a failing or failed crank sensor does that **** fuel? Or is it that it just turns off injectors
Car sitting a long time, now won't start, absolutely no fuel pressure but can Hear pump run??

 

[Off Road SHO]

How do you know there is no fuel pressure? How did you test it?

The PCM only runs the pump for 2 seconds or less to pump up pressure in the feed fuel line, fuel rails, all the way to the fuel pressure regulator. After that the PCM shuts the fuel pump off untill it is sent a signal from the crank position sensor that tells the PCM the engine has started (by rpm's I believe), at that time the PCM again start the fuel pump back up.

Tom

 

[thegreatbriguy]

At the schrader on the fuel rail.
But if I understand what ur saying if the cps doesn't send the signal the fuel pump won't run again

 

[Off Road SHO]

That is correct. But from the initial 2 second run, the fuel rail should be pressurized. Take the return fuel line off at the regulator and turn the key on. You should get quite a bit of fuel come out as the regulator keeps the fuel on the front side at about 39 PSI. The pump should put out about 50 or more PSI so you should get 10 psi worth of fuel out of the return line fitting on the regulator.

So did you put a gauge on that Shrader valve? And did it show any pressure at all? Or did you just depress the stem of the valve?

Tom

 

[thegreatbriguy]

Just depress stem....

With a clogged fuel filter there still wouldn't be pressure at return line at regulator, correct?

 

[rubydist]

since your problem appears to have started after the car sat for a long time, the most likely answer is that the fuel pressure leaked out of the system. That often happens with older pumps as the check valve begins to leak.

The short term solution is to cycle the key to "on" for a couple of seconds, then back to "off". Repeat this about 3-5 times. That should run the pump long enough to build up fuel pressure again and the engine should start.