What causes no pressure to the shrader valve in the fuel rail?

CaifanSC

SCCoA Member
I've got a no-start condition that im attributing to no pressure at the shrader valve in the fuel rail. I've checked for the obvious....innertia switch has been jumped, IRCM is working (fuel pump relay), the fuel pump primes when the key is turned, the vid below shows the kind of pressure im getting form the pump and apparently that seems fine, changed the fuel filter too. what else can be going on? Any ideas appraciated, ill be working on teh car today.



<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i48.photobucket.com/player.swf?file=http://vid48.photobucket.com/albums/f226/Caifanito/V_deo011.flv"></embed>
 
did you try replacing the filter? propably:eek:....there may be a pinched line between there and the fuelrail....could have bottomed out on something and smooshed it:D....id say there is a plug or foreign object causing no fuel...try removing the shrader valve core and see if there is a block behind it...there may be fuel there

just my pathetic $.02

-Tony-
 
Are you still running a OE fuel pump? If not, when you installed the new fuel pump did you replace fuel pump baffle with a piece of hose? That can cause your fuel pressure to drop immediately after the fuel pump primes the system.

Your assembly should look like this:
fp-installed.JPG


Not this:


baffle-pump4.JPG


The pictures supplied by www.mn12performance.com
 
no pressure at the schraeder valve does not always mean you have no pressure there, the schraeder valve could be bad, my buddies car had no pressure there, we changed the valve and he did, but this of cousre doesn't explain the no start. Try changing the valve with one from another rail and see if you can rule out no pressure at the rail.
 
If you hear a humming sound that does not mean the pump is pumping at all I had a brand new walbro 255 pump hum like an SOB and didn't pump worth a dime. I'm not sure if your gettin enough pressure because if you disconnect the line at the filter then the pump has nothing to keep it at 40psi, I'd think it would shoot out harder than that.
Dan
 
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90blkbrd is correct about the hose. At the shootout I had some pressure from the pump but shutting off the engine and the pressure went back to 0. I did not install the hose for the pump like th picture. I had to pull the pump while the car was on the dyno and install a hose. Solved my problem. Might not be yours if you have a stock pump

Ken
 
did you plug back in the fuel pump collision shut off? if you didnt unplug it in the 1st place it may have tripped it when you turned the key on after the pump install reset it if that doesnt work try changing the fuel pump relay thats 2 easy places to start
 
Well, back to square one. Still having this issue...i just replaced the fuel pressure regulator and nothing. I hooked up a fuel pressure gauge directly to the fuel rail (which eliminates the possible bad shrader valve option) and when the pump runs it goes to 40 psi, but it immediatelly falls to zero. Last thing on my mind (and I mean last) is soem sort of freak crack in an injector. Any other thoughts?
 
Well, back to square one. Still having this issue...i just replaced the fuel pressure regulator and nothing. I hooked up a fuel pressure gauge directly to the fuel rail (which eliminates the possible bad shrader valve option) and when the pump runs it goes to 40 psi, but it immediatelly falls to zero. Last thing on my mind (and I mean last) is soem sort of freak crack in an injector. Any other thoughts?

You can jump a couple terminals on the eec code reader port to keep the fuel pump cycling or you can unplug the relay from the trunk and jump the wires there to do the same thing. Either way, this would get you a solid reading for fuel pressure at the schrader valve. Like you said, could be an injector leaking also. Seems wierd that it immediately jumps down to zero though even if you do have an injector leaking. Thats a very large leak if so, you will be able to smell it in the oil. I would say your fuel system is not holding pressure up in the line, main line is allowing fuel to back flow into tank. No external leaks at all though? Interesting.

Try cycling the key from off posistion to on positon 3 times without starting the car, then start it. This will cycle the pump for you a couple times and get fuel up their.
 
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even with that little baffle piece in the tank w/ my 190 pump (didn't know it was there) I could turn the key and hold 40 psi at the rail for over 20 minutes.

When I put the 255 pump in I put the hose in and removed the baffle because I didn't know what it was for. It's a straight through piece but the round section can fill with fuel.

I think the pump is bad in your car. The car should hold pressure after the fuel rail is primed.
 
You still didnt say if it is a stock pump or if not, did you use the hose in place of the valve above the pump like in blkbirds pictures. The exact same thing happened to me and installing the hose solved the problem

Ken
 
Sorry, it must have been another thread where I mention it...I ended up replacing the pump with a high pressure 255lph walbro unit I had and I deleted the baffle and put the straight piece of hose. So the pump is new and no more baffle.

As for leaks, no external leaks visible, no fuel smell...the oil does smell like fuel so im thinking its probalby a sign of a leaky injector...but yeah, its weird b/c it must be a very big leak!

Oh, and mywhite89, i jump the fuel pump connector on the EEC tester plug to make the pump run. Thats how I make it work when I check the pressure.
 
If you have time, pull the blower off, remove bolts holding the fuel rail down, and then hang the rail over the fender, hit the key to prime the pump. The injectors should squirt and then stop and the pressure should hold. If one or more injectors keeps pouring fuel out after the key is turned off, you know you have found your problem.
 
Yeah, thats what I plan to do because there is no other explanation on waht it could be! if its not one (or more) leaking injectors, man im gonna shoot soembody :mad:. Well, not really..i'll just be really pissed off :p.
 
Oh, and mywhite89, i jump the fuel pump connector on the EEC tester plug to make the pump run. Thats how I make it work when I check the pressure.

If the car definitely has spark at all cylinders but just doesn't seem to get enough fuel to all when cranking, I would definitely say leaking injector. You could pull the plugs and probably find the culprit cylinder also. Post what you find out and good luck.
 
Plug your return line, then quickly and carefully check your pressure again.

Leaky injector and no pressure, no way. 6 leaky injectors and no pressure, maybe, but I doubt it..
 
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