see my post #18, above, replace the damper before checking the fuel delivery.

A 30 year old car has lots that is ready to break.

That's the reason to replace the known-weak items whether they need it or not.

Its also the reason not to thrash one or add performance parts until fully sorted.

I've violated that once with my 85 and am still paying for the mistake.

Good Catch -
 

Hey Maleficio, If the pressure dampener or either of the pressure regulators leaks internally, raw fuel is being dump back into the intake manifold. This will not only cause low fuel pressure but the unmetered fuel will gradually flood out the engine.

It sounds like you’ve found your problem.

Good Catch, Michael

It looks like I have two problems:

Bad pressure damper causing the no-start, and a dying fuel pump causing the hard stalling after running up to temp.

Cruising I could feel the pessure drop out as if an electrical contact was opening and closing very quickly. I've experienced this before with bad pumps and wiring.

There are three pressure dampers, right? Forward, passenger and driver sides, right? Are they all the same part number?

No, but you probably need to use the Porsche PET to identify what you have.

helpful diagram? and my pic-- when i had same systems, the diverter/damper (has screen,clean) red tape area the hose was ripped open (1), going down the bracket was unwelded (2) , the whole metal line holding from that top hose to the other end at cat. the line running upside the cat to the topside (3) think a check valve there , mine had a red piece of garden hose clamped into it. so the whole L metal lines where holding on by hoses and flopping. huge vac/air leak, stalled out , stays running when warm now , and blew alot of black smoke to clean cause pressure theres now air/fuel ratio good hps and no soot.

http://forums.pelicanparts.com/uploa...1300814929.jpg
http://forums.pelicanparts.com/uploa...1300814945.jpg

Maleficio , you really need to get a copy of PET :-)

No, lfausty, it is not the same damper - in the FI system 10 is the damper, 28 are the regulators :
http://forums.pelicanparts.com/uploa...1300815758.jpg

Thanx, Neil. :)

I think my main pump is dead, and the reason the engine will fire for four to five explosions is merely from accumulated fuel vapors trapped in the charcoal canister.

I've run the tank dry three times now thinking I had enough fuel to make it to the Sunoco station. Running a tank dry, thus starving the pump shortens it's life. I figure I killed my own pump. Those pumps work hard, like the human heart.

duuude???
how are running the tank dry?
why are you running the tank dry?

you gotta be smarter than the car brother!

I didn't mean to. Mileage has lately been dropping causing me to over-judge the range.

I heard the pump running today, but it may be worn out. Will buy a pressure tester soon to verify.

Where are you? There may be someone local who can help you get out of this mess!
Go put at least 5 gals in the tank and a can ( or 2) of your favorite fuel injector cleaner, and report back!

Tank is full, and has a bottle of Heet water remover/injector cleaner. I've run so much cleaner through it I wonder if I scoured the pump to an early death?

I'm actually looking forward to going through the car and slowly massaging it back to life. It's given me eleven months of reliable joy, it's time for me to give it something back.

Good idea.

You still are one of the few guys that has been able to snatch a 928 sub 5K that had sat a bunch --- and immediately put it into service!

Take some time, fix the right stuff and help it last another 20 years.

Hell yeah, Landseer. It's an old fighter jet for the road. Designed to be driven forever.

That's the spirit! Be thankful, too, its the 16V car. Still tightly packed, but a bit simpler.

I opchecked the fuel injection relay, works perfectly, consistently. Checked voltage at relay sockets: 12 volts for the relay switch, 3 volts for the coil. I don't think a 12 volt relay will operate very well with only 3 volts. This explains why I felt the fuel pressure dropping instantly and coming back up, over and over until it finally stalled out while cruising. And also why the car won't start: the injectors are not being commanded to operate, though the cold start valve is operating because it's powered by battery power, thus the little spurt of fuel from the cold start valve makes the engine explode a few times, then stall because the injectors are not opening.

Dang it, I should've read voltage from the hot socket to an external ground instead of the ground socket. Stupid. That way I could've proven if I had a ****ty internal ground or not.

I guess I need to pull the CE panel like Landseer said and figure out what's causing the high resistance before I have a fire in there.

I can't tell from the schematic. Does anyone know if the fuel injector relay gets it's coil voltage from the ignition switch circuit? All I can see is power coming from circuit "31". I don't know what that means.

Thanks.

Always Hot is 30, Switched Hot is 15, I believe 31 is wired to ground not a direct to ground; the control unit gets ground from its pin 35...The relay always has 30 available for 12v and once car is on, 15 provides the juice to energize the relay passing the 12v to the injectors. The control unit gives the other part ot the signal in the proper firing order 1&5, 2&6, 3&7, 4&8.