StupEd05

I know, I know, I am stupid, but please. I have tried searching and can't find a straight out answer. So here is my question. I jump the DME for about 3 minutes, then pop it out. Go take the the fuel rail cap off and only a little trickles out, no pressure behind it at all. So anyways, my question:

Shouldn't there be PRESSURIZED fuel in the fuel rail right after running the pump?

Just wanting to check before I start to buy fun new things like a new FPR and Dampner and what not...

StupEd05

bump, come on someones got to know. I just want to make sure this is an accurate check on fuel pressure before I start to claim I have a fuel related issue.

PorscheDoc

Aaron, go to clarks-garage and checkout fuel pressure checking procedure in his shop manual. Sounds like you have a bad check valve by your fuel pump. Read through it, do the procedures, and see what values you come up with.

PorscheDoc

Also read the section on FPR checking.

PorscheDoc

I just posted over on Kcws as well, 1300ccs of fuel in 30 seconds is almost double of what your pump should be putting out. Indicative of a bad FPR according to clarks garage.

StupEd05

Yeah, Ive read a lot of the stuff over on clarke's garage, I was just wanting to know if pulling the cap off of the rail right after shutting it off should let lots of pressurized gas out or not. When I pulled it off I was half-expecting to get sprayed in the face.


p.s. Nice Avatar!

PorscheDoc

Leave your fuel pressure gauge hooked up, after 20 minutes there should be 1 bar pressure in the rail if i read clarks garage correctly.

StupEd05

Alright, so that means by taking off the cap you should atleast some sort rushing air sound or pressure release. I have yet to spring for the actual gauge, Adv. Auto wanted $37 for one that I would still have to find a weird adapter for. Couldn't find anyone in Lawrence with the VW gauge.

StupEd05

Will a bad FPR cause the release of fuel pressure as well? Or would even a bad FPR keep the rail pressurized? Sorry, just trying to better understand how this beast works...

*cross posted with KCWS, which forum are you on! aagghh!! lol

StupEd05

If my problem is strictly fuel related, i.e. FPR/check valve. Wouldn't a liberal shot of ether in the intake boot fire it right up? Cause it doesnt... Anything that could cause instant lose of fuel pressure after turning off AND no firing even with ether? Just one more of those "why doesnt it work" questions...

StupEd05

Whoa whoa whoa. Ive been doing some thinking (kinda rare) and I have came up with this conclusion. (please correct where Im wrong) First of all the FPR is on the return side of the fuel rail, right? So when you are running a flow rate test, the FPR does NOT come into play, only the Dampner and pump, correct? So the 1300cc's/30 sec flow rate I got is non-dependant on the FPR, it only shows that my pump is pumping really fast. Now, the fuel comes into the rail and as pressure is increased the fpr OPENS allowing more to go back to the tank, right? Thus, if my FPR is stuck OPEN then I would still have a lot of fuel going into the rail, just no pressure cause it all goes right back to the tank. This would explain why after shutting pump off I immediately lose pressure in rail. This would also explain why my injectors are still firing (cause its not cause there is TOO much pressure, there is non/too little pressure) and in result I am not getting enough fuel (or atomization of fuel) into the cylinders, which in turn is a "Spark, (some) Fuel, yet NO start" situation. Any problems with my theory???

Whew, sorry, I just HAVE to know how things work and what could be wrong before throwing parts at it.

nine-44

It's possibly the FPR, are you sure you have an injector pulse?? bad solder joint on the injector harness? I looked in PET, I see no check valve on the return side. Only the regulator.

StupEd05

Well if the regulator is stuck open then doesnt all pressure flow right into the tank? Doesnt the regulator block fuel to build up pressure? So if its stuck open there is still lots of fuel flow but no pressure, right? I dunno, maybe im not understanding how it works exactly...

nine-44

You're right. some cars do have a restrictor on the return for a gross fuel pressure, yours does not tho, my Corrado did.

StupEd05

hmm... dang it. Then Im confused again I have lots of fuel flow, but doesnt keep pressure!?! Could I be losing pressure throught "in" side. i.e. Fuel Pump check valve. After pump stops running, it depressurizes back through the pump and into the tank?