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How to get fuel pressue in the fuel rail? (S2)

M

Monkeythree

New member
Chaps,
After doing my cylinder head gasket (and fitting refurbed head) I have got a no start which I have figured out is due to having no fuel pressure in the fuel rail. When I crack off the connection where the supply goes into the pressure damper (at the front of the rail) there is fuel there and healthy pressure. But when I crack off the connection where the return comes out of the fuel pressure regulator at the back of the rail, nothing. So basically there is no fuel getting past the damper and into the rail.
My theory is that having had everything apart, there is no vacuum in the reservoir and therefore the fuel damper and FPR aren't operating correctly. But how to get vacuum without the engine running? I've had a look throuh Clarks to see if there is a method for priming the fuel rail but can't find anything. Any suggestions? I've tried sucking!
 
think you got that back to front, pressure line goes through the regulator first I'm sure, then the damper balances the line,

i could be be wrong as the 68 does not have a damper, but the feed goes in the regulator first
 
I'm not familiar with the 968 but on the 944 S2, the pressure goes though the damper first then the fuel rail then the regulator and finally back into the return line. The regulator has to be the last thing in the line in order to regulate the pressure in the rail. I can't get any fuel past the damper and into the rail.
 
You shouldn't need to do anything just run the pump. you can do this using the DME jumper cable described in Clark's. I think it is damper then regulator. Have you established the pump is running? Did you take the fuse or DME relay out? Crack off the nut on the end of the fuel rail to test flow.
 
Pump is pumping fine. I have fuel pressure where the pressure line goes into the damper but no fuel in the fuel rail I.e. The other side of the damper. The damper relies on vacuum to operate but I have no vacuum because the car won't start and there is nothing in the vacuum reservoir. Bit of a chicken and egg situation!
 
You don't need any vacuum to pressurise the rail. You can disconnect it from the FPR and the car will still run but fuel pressure will rise. As vacuum decreases i.e. revs increase the fuel pressure rises to cope with extra demand. You have something else going on. I would remove the rail, check it and start again. Do you have flow from the nut and the end of the rail? Remove it and connect a pipe see what comes out.
 
So I pulled the fuel rail off again this morning and bench tested everything. Damper is passing fuel so not that. Fuel rail itself is not blocked so not that. The FPR is new (while I was in there) so (probably) not that.

The more I thought about it, it seemed the problem was simply an air lock in the fuel rail. So I thought I would use the little port on the side of the fuel rail as a bleed valve but the cap was seized and it seems I am stronger than it is. So the port has snapped off the fuel rail and now I need a new fuel rail!

Aaaaaaarrrrrggghhhh!
 
I may have a fuel rail available off a 944S soon, I believe it may be the same fitment as the S2 ?? but please check though, my 944S booked in for a new replacement this Thursday at Porsche because its fitted with
the "original fuel rail" my vehicle missed the recall on a new fuel rail fitment. So, if its the same fitment for a S2 it could be used to fault find **remember its a pre-recall part its fitted with new fuel lines minus regulator and off a running vehicle and testing only and would like it back ,,,pm me if of help (oh yes has new lines fitted too only days ago)
 
Thanks but I got one for only £36 off ebay. Came within 24 hrs and even has a newish looking FPR on it. Fitted it yesterday (with an actual new FPR) and the car is running fine now.
 
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