Tampa 928s

I an working on an 80 Euro Cis needs a bunch of minor repairs and some air work.
Car has a hot start issue:
New filter, pump and tank cleaned:

The car sat for 10 Years and has been driven a little before I got it. Owner said it started fine but after he drove to my house 40 miles 3rd line on Temp due to non working front fan it sat for about 15 minutes. We tried to start it and it would not fire, I tried a WOT still did not start, after about 6 attempts it fired up uneven at first then stabilized.
What I need to know if the anti siphon valve if bad would it drain the fuel and cause it to vapor lock. Where else should I look for this symptom. When driving it on the lift it stalled but restarted although not as fast as I would expect.
Maybe a lot of driving is the cure, I read that some others have added a couple of cans of Tech and ran the fuel pump for a while, I am not real sure on the approach.

jpitman2

Lots more regular use will help in this sort of case. On mine I had similar problems early on. I found a multi pin plug not connected, which fitted into the side of the fuel distributor, fixed problem for a long time. Then in a major clean up I replaced the accumulator(front of RR wheel), also helped some. Then problem recurred - there is (on mine) a temp sensor on the rh head rear heater water fitting that feeds a solenoid (to drop control pressure on hot cranking) which had gone high resistance. Eventually I found a 924/944 part that needed an adaptor to fit, fixed the problem. Next time it happened, was advised to look at thermotime switch - I removed connected, checked resistances, reconnected, problem went away.
Try some of the above - may help to know next time it fails to start, if its flooding or lean - would need to pull a plug and check.
jp 83 S Euro AT 53k

karl ruiter

Might also look at the idle mixture adjustment. The only way the car gets fuel is if the flapper plate is pushed open. If your cranking airflow is not enough to push it open enough then no fuel. The idle mixture adjustment sets a stop that props it open a little bit.

LT Texan

I spent $1,000's on trying to pay Porsche and independants to remedy my hot start problem over several years.

The combined knowledge of the Porschelist (or was that Porsche Fans?) didn't help (pre Rennlist).

Then I read up on the CIS in Ben Watson's book.

http://books.google.com/books/about/...d=fVm0HYHJr4gC

Bought some CIS fuel pressure gauges from JC Whitney.

And discovered that the fuel system didn't hold "rest" pressure and that a $25 in line fuel check valve in the rear wheelwell needed to be replaced.

oh well. Live and learn.

Tampa 928s

My research so far points to holding the fuel pressure and the two culprits are the check valve and accumulator. I am going to borrow a set of gauges and check the pressure after shut off first.

LT Texan

The check valve in-line past the fuel pump in the rear wheel well is so cheap and easy to replace, I'd just go order that while you wait for gauges.

jpitman2

Yes, definitely get the gauge set - Roger does them now, well priced, you know its going to do the job. And the Ben Watson book if you can find it at an acceptable price - when I bought mine it was $15!!
jp

smiffypr

When you get the gauge, after you check the system pressure to see if it holds, check the hot control pressure. If its too high, and therefore running lean, that will make hot starts difficult.
Also check that the air flow plate is sitting correctly before the engine starts (should sit in the narrowest part of the aperture).
Smiffy

Tampa 928s

Does anyone have pictures of where the gauges hooks up, Shawn just dropped it off!

Fabio421

Mark,

I just texted you some pictures of where the gauges connect. Please note that they can be hooked up backwards. I had the correct fittings on the hoses last night so if you haven't taken them off, it will be hooked up correctly. The long fitting goes to the fuel distributor. Please post the pics here so future generations can benefit.

jpitman2

The hose with the stopcock between the end and the gauge head connects to the WUR inlet, the other side of the gauge goes to the fuel distributor connection that you remove from the WUR inlet. Stopcock closed, you see system pressure- only need to see this briefly to check its in range(65-75psi); stopcock open, you see control pressure. IIRC, to check rest pressure (ie holding pressure after shutdown), you turn engine off as you close the stop ****.
jp 83 Euro S AT 53k

Tampa 928s

I need a little clarification on the hook up of the pressure tester.
My fingers are where I think they need to go is this correct?

SMTCapeCod

Wow, looks very clean in there.
Still, refer back to one of Johns' early posts- that union where the fuel feed enters the fuel distributor is a frequent culprit- takes the first slog of sludge and precipitant from the fuel tank after sitting. Note also that adding fuel system cleaners can 1) dislodge plaque and sediment and put it in suspension in the fuel flow- so instead of happily clinging to the sides of the tank it will wreak havoc on all the screens and etc in the system, and 2) can swell the o-rings in the FD (at least according to the lore).
Check valve is an easy fix- don't recall whether OEM would be internal or external.
Other likely suspects are dripping cold start valve or injector(s).
Lore also has it that accumulator failures are rare and usually evident from fuel on the outside. But I may have missed some of the actual accounts...YMMV...

jpitman2

1. Undo the nut on the line your finger is on where it screws onto the WUR, move pipe to one side. Connect the hose end facing left in your pic to the WUR - you may need to juggle the adapters to do this, or unscrew the adaptor fitted to the WUR.
2. Now connect the OTHER hose end into the pipe fitting just disconnected from the WUR in 1 above - this can be a bit fiddly to do, but its the easiest way overall IMHO.
Now your gauge is in the line from the fuel distributor to the WUR. With the stopcock open (which it is in your pic - lines up with the hose), if you bridge the pump relay, gauge will show control pressure - ie back pressure from WUR. If you turn the stopcock 90degrees to close it, you will see system pressure.
Best way to bridge pump relay IMHO - remove relay and identify correct sockets to jumper (30 & 87, or 15 & 87?); get a few yeards of decent 2 core flex, and a momentary switch(defaults to open unless held down); crimp 2 1/4" male spade tags to one end of the flex; connect the other end to the momentary switch, insulate connections; insert the spade tags into the relevant pump relay sockets, check that the pump runs when you press the switch. Now take the switch end of the flex out to the engine bay, and you can easily turn the pump on and off as needed to take pressure readings.
hth
jp 83 Euro S AT 53k

Tampa 928s

Thanks; I found this cool link:
http://porsche928forums.com/viewtopic.php?f=25&t=694