camelman

I bought a fuel pressure tester and tested my fuel pressures today to figure out the engine running problems. Pressure between the fuel distributor outlet and inlet (WUR bypassed) reaches 72 psi, but immediately drops to 60-65 with the FP off. It very slowly falls after that.

Between the WUR and the FD, pressure reaches 72psi with the gauge valve closed, and 35 psi with it open. When the pump is turned off, 72 goes to 65 or so immediately, and 35 drops to 25.

I tuned the AF by turning the screw until I heard the injectors fire. Then backed it off 1/8 turn. When I trigger the injectors by pressing the pressure plate, I hear a whooshing sound, but I don’t think all spray. A couple definitely leak after I release the pressure plate with an audible dripping sound. I’m beginning to think I need to clean/replace the injectors. Thoughts?

The engine will barely start, and hunts at idle. It responds very slowly to throttle, and maxes out around 2500-3000 rpm with nasty black smoke. My car doesn’t require cats, so no problems there.

Rebuilt WUR. Rebuilt FD. New cap/rotor. 65k miles. New fuel pump and filters. All vacuum leaks fixed. Sat for 17 years before I bought it.

Thanks,
Camelman

Mrmerlin

buy a new set of injectors MB injectors work fine and are reasonably priced.
Also get a new set of rubber injector seals ,
spray the collars now with PB blaster so they can start soaking

camelman

camelman

One other thing. I noticed some dirt in the injector lines where they attach to the injectors. It’s fine dirt and looks like yellow clay. There was plenty covering the underside of the car and I cleaned some out of the tank when I changed the in tank filter. What can I do to flush the lines? I just pulled the FD apart again today and didn’t notice any, as well as the WUR, so I think anything left is in the injectors and injector lines.

Thanks,
Camelman

camelman

SeanR

Do you know if you have good flow back to the fuel tank on the return line?

camelman

drooman

You've done all the right stuff so far.. you're close.

1. make sure your cam timing and ignition timing is correct. Static time the ignition if you have to.
2. Vacuum leaks... one more to check: I usually block off the brake booster line on first start up to eliminate a possible giant (but invisible ) vacuum leak from a bad booster.
3. do a fuel delivery volume check... at least 1120 CC per 30 seconds. Best to do it at the return line to the tank where it goes into the gauge sender... that way you also are checking for return blockages. You can have great pressure with low volume and your car will run like poop.
3. your system pressure a little low. 72 psi = 4.96 bar... supposed to be 5.2-5.8 bar. get this into spec before continuing
4. Make sure you have the right WUR : 0438140086 for Euro S.
5. your control pressure with fuel pumped jumped seems low (CORRECTION: HIGH) to me. The important pressure to check is cold start control pressure right after it starts while running at idle. Ambient (garage) temp plays a part.. see the graph, as the engine warms up the control pressure should rise.

jpitman2

35psi control , engine cold is too high in my book (chart says 26.5 at 20C) - half hot might be OK . Pump jumpered , not running, 12V disconnected at WUR should see <=20psi at under 20C in my book. Mine starts stone cold and runs smoothly right through warm up to hot control of 45psi (3.06B, system press 75psi - 5.1B), but if hot control gets past 55psi power drops off badly. Do the delivery rate check , and verify your 37psi reading is when cold. Check for WUR blockage by opening the outlet pipe a little - if the pressure drops and fuel flows out, WUR is not blocked (not fully anyway). Its possible that crud from the tank , or deposits left in the fuel lines by the standing, has got to the WUR inlet screen, so check that also. I had good results by loading the tank with Berrymans etc, and letting the pump circulate fuel for a long time - several hours - to flush stuff into the filter. Hunting at idle and black smoke sounds like RICH. Bad return flow can push up control pressure. The movie sounds like it barely turned over at all? Should positively spin.
jp 83 Euro S AT 57k

drooman

Good call on the new regulator possibly getting blocked by debris. Also thank you for pointing out that the control pressure is HIGH not LOW. I corrected my post.

camelman

Thanks for the advice. I’ll plug the brake booster vacuum line, and I just cleaned the WUR out. I have to stop with fuel tests in the garage though since it’s under the house and I keep fuming it out. Unfair to the lady.

If the brake booster doesn’t solve it, then I’m towing it to a local shop that’s specialized in Porsches since 1985. I prefer to do the work myself, but I seem to keep regressing with everything I do to the car. The brake booster makes a lot of sense since it’s super rusty and the brakes get weak with the engine at idle. Fingers crossed!

Camelman

karl ruiter

Don't give up yet! You have done all the right stuff, but probably something has not gone as well as you thought. My fallback at this point would be the mason jar test. Pull injectors, put fuel line on each one, and run those lines to 8 mason jars. Now run your pump and see what's coming out as you vary the control plate position with your finger. Note also that a little bit of difference in the control pressure make a big difference in the fuel delivery, so try to get it very close.

mantinger

I would also check the bypass valve (auxilary air valve) working. Second, check if the cold start valve cuts out after start or does spray at all.

camelman

The Porsche shop doesn’t want to take on my project, so I’ll be finishing it after all.

I verified the booster is bad. It won’t take any vacuum at all! I’ll plug it for now. I’ve checked timing with a light in the past, but it’s worth another check. Might as well check valve timing too while I’m in there. Once I’m done with those I’ll dig back into the fuel pressures. The WUR pressure might have been affected by having the key switched to on, so I’ll rig up another fuel pump switch to get cold readings (fried the last switch). She will run again!

camelman

jpitman2

Get 2-3M of 2 core wiring, fit male blades suitable for the relay socket on one end, and a momentary switch on the other end. Remove pump relay, connect blades into socket (30,87 IIRC), then you can power the pump from anywhere around the car while you hold the switch closed, and turn off quickly if there is a leak.
jp 83 Euro S AT 57k