Flormat

I do have a vacuum pump and will check to see if they hold vacuum tonight. I don't know if I have 2 fuel pumps or not- will check.
Bill- from what I understand I have 2 dampers and 1 regulator. The regulator and rear damper look identical. But there are metal lines to the regualtor and dampers except where the rear damper and regulator are conneceted to each other. If I pinch there will that be affecting the regulator or the damper?

Flormat

Actually now that I look at the picture is looks lke there is a stretch of rubber hose off the front of one of those two items. Maybe the inlet. Will check tonight.

brutus

Hose number 10 is the return line. #8 is inlet .
Number 4 is the single pressure regulator. 5 and 3 are dampers.

Bill Ball

Certainly I would only expect one fuel pressure regulator, just like my S4. Somewhere in some discusssion this got confused. Makes more sense now.

So pinch #10 closed and see what happens to the pressure. You only need to see if it goes much above you current reading of 18. Stop if it reaches 50 or so. If it holds for several minutes with the engine off, then the check valve and pump(s) are OK and the regulator is bad. Oh, it is remotely possible the pump is still bad in this case, as well as the regulator. It may reach pressure but not pump enough volume. So, if things are still not good after replacing a bad regulator, a fuel volume/time test would be called for.

You're closing in on the problem.

Bill Ball

Certainly check that the dampner and regulator diaphragms HOLD VACUUM, but that is not what I am asking you to check. I want you to pinch off the return line from the regulator, jump the fuel pump relay (or crank the starter) BRIEFLY and watch the fuel pressure. Previously you reported it only reached 18 or so. I hope we are both talking about fuel pressure in the fuel rail and not some vacuum reading. Anyway, blocking the fuel return should raise the fuel pressure greatly above what you observed IF the problem is a faulty fuel pressure regulator.

Hilton

Just a bump - did you check the in-tank pump is working? PET indicates that US S3's do have 2 fuel pumps.

If they fail, they greatly restrict the flow of fuel out of the tank, which can cause low fuel pressure with the engine running, but show ok pressure with just the relay jumpered.

Its a common "fix" to replace the in-tank pump with the factory strainer once the in-tank pump dies.

Hilton

I would worry about old fuel lines in this test. The factory pumps will push out 100+ psi of fuel pressure with no release from the return side of the FPR. Not to mention putting the diaphragms in the dampeners and FPR under strain.

Bill Ball

Yes, I said to watch the pressure during a BRIEF test and not clamp on the hose any more than necessary to close the lumen. The return lines are easy to replace and can even be clamped as they normally run no pressure. I believe the diaphragms are exposed to high pressure anyway, so I can't see this doing damage. Do you have another way to test the fuel pressure regulator?

Bill Ball

OK, I thought about this and here's another way to test the regulator. I haven't done this but it should work and not risk the return hose.

Detach the return line from the fuel pressure regulator. Find another long hose that fits the over the FPR outlet and clamp it on. Run the other end into a gas can.

If the fuel pressure regulator is good, there will be no gas emitted from the return fitting until the pressure reaches 50 PSI or so.

WallyP

My first test would be a fuel flow check. If the flow is adequate, but pressure never rises to spec, the regulator is faulty, or you are dumping fuel somewhere else - which would be pretty obvious...

dr bob

Use extreme caution pinching fuel hoses on later cars. There's a service bulletin that discusses the later ('89+) fuel hoses with the plastic liner, and specifically says to not pinch them. The only exception is the tank to pump hose, which has original-style hose so the pump can be serviced.

FWIW, you can check the regulators with a bit of air to the fuel rails. The FPR will hold air pressure just like it does fuel pressure. If it only holds the same 15 PSI, it's a regulator problem. If it holds 45-50, a supply problem.

Bill Ball

Just to be clear, the return lines are NOT rigid plastic (polyamid). That's only used on high pressure feed lines (the supply line loop and the loop between the FPR and rear damper). The return lines are rubber, just like the "exception" tank outlet hose you mentioned. If pinching them would be damaging, they should be replaced whether you pinch them or not. Regardless, if there are other simpler ways to identify if the regulator is the problem, I'm all for it. So, I'm glad Wally and you posted alternative methods. I've done the pinch method to rule out/in the FPR without complications with hoses in good condition. I'm still very careful about pinching any of these rubber lines, including the tank outlet hose when replacing the external fuel pump or filter, and I tried to indicate that.

Flormat

Fuel pressure is good- the car was out of gas and after I added 3 gallons it now registers 36psi when running.
I am still stumped. I have spark on all cylinders, tested each plug grounded to the engine. I have fuel to all cylinders- I pulled the wires from coil to distributor and cranked the engine over, then checked the plugs and all 8 were wet. Connected the coil leads and started it up, no change, shut it off and checked all plugs, #7 is still wet. Check for spark on #7 and check gap and both were good. I checked the resistance on the coils. Per the WSM primary should be .4 - .7 ohms and both coils were .9 ohms. I checked a spare I have and it was also .9 ohms. Secondary was in spec on all. I swapped the right side coil with the spare and no change. It is possible all three of my coils are out of spec but it seems the car is running off of the left distributor and ignitor because if you remember when I unplug the ignitor module that controls the right distributor (cylinders 1, 4, 6, 7) nothing changes but if I unplug the ignitor that controls cylinders 2, 3, 5, 8 the car immediately dies. If both coils are out of spec the same amount I would think everything would both sides would act the same?
My fuel pressure is good but I can hear the fuel pressure regulator, should it make a sound like flowing water? And there is no in tank pump on my car, just a strainer which was not clogged.
So I have spark, I have fuel, cam sprockets line up with the crank pully. Porken's cam timing tool indicates both cams are at 0 degrees.
Thank you to everyone who has offered thier assistance so far.

ryalex

Did you ever resolve this?

African Shark

Seems I have the exact same problem! - was it ever resolved?... (mailed Flormat, but it could be useful to post)