Still won't start version 2, need exploded view of CIS

rcm · 08-27-2004, 04:00 AM

So, I changed the filter but, not the accumalator (wrong part). Both had gas in them when I disassembled. Fuel pump whines when key is on so, i'm going to assume it's not holding pressure.

It starts runs to 2000 rpm's and quits about 3-4 seconds total.

So, cold start fuel but, no run fuel?

Ideas?

Souk, I checked the plate and it seems to rise on it's own during cracking and settles and motor quits.

Rick

MotoSook · 08-27-2004, 05:29 AM

Rick, after it starts can you coax it into staying running with the throttle? It's hard to go farther in the cyber analysis of your problem with what we know so far. Have you pulled an injector and sprayed it into a clear jar to get a feel of the fuel quality?

Something that might be happening...after the good workout the car had, the WUR may be "loose" by which I mean that the internals have had a thermal workout. So it may be bleeding off more pressure than it did before resulting in a low warm control pressure. That's one possibility. The other may be that it's clogged and holding too much pressure, but I've had a WUR hold over 60 PSIG of pressure and I can still get the car running.

After it stops running, can you lift the sensor plate up for a second or two, then try to fire it?

When you left the sensor plate witht he ignition on, you will hear the injectors scream...high pitch whining.

Don't hold the sensor plate up too long, you don't wnat too much fuel in the cylinders.

Paulporsche · 08-27-2004, 05:47 AM

An exploded view:

http://www.pelicanparts.com/911/911_Parts/1978-83/1-7-2.JPG

Tim Hancock · 08-27-2004, 06:10 AM

I did not see your first post, but if it starts and then dies after releasing the key from start position, it is probably just running on the cold start valve. If your fuel pump is going bad it may produce volume during a timed test, but it may not reach proper system pressure. The fuel injectors need this pressure to open. Then cold start valve injector does not need high pressure to open, it is opened electrically when you engage the starter but only stays on for a short time.

The above scenario happened to me recently on my old 924 that I am fixing up for my sixteen year old daughter. The fuel pump started chewing itself up internally but would still pass the flow test but could only muster about 55psi system pressure

}{arlequin · }{arlequin's Garage

great ideas, all of them. Thanks. Mine is trouble free but if something goes wrong I'll be asking similar questions. It seems reliable, but seeing Noah's removal, it looks very complicated and seems like many things could go wrong.

MotoSook · 08-27-2004, 06:36 AM

CIS is like what we use to think of wrenching on Porsches in general, before we started to wrench on Porsches..after that it was just a wall of ill placed mystique. CIS is an ingenius fuel injection design by the 70's standards and continues to be a great system....

I've said before..learn how the components work and then everything will come together in your head. Pretty soon, you'll be able to feel around the CIS blind folded. I've installed a CIS on a long block fully bolted to a car in less than an hour....not saying anything, just that if a dork like myself can do it..everyone can.

rcm · 08-27-2004, 07:22 AM

Thanks guys, I think Chris Bennet is coming over Monday night to help me sort thru it.

Paul ...thank you.

vash · vash's Garage

rick, when the pump is pumping, and you lift the air sensor bar, do you feel any resistance? or does it feel perfectly balanced like a weight scale? if it feels light, you havent got enough pressure in the system. also, peek into the pop off valve carefully with a flashlight, do you see a mist after cranking? is the bottom of the airbox juicy with fuel?

personally, i think CIS is not a total mystery. if my car doesnt start, i ALWAYS check for spark and fuel. i check fuel by pulling a injector and verifying i am getting a nice atomized spray. whines coming from injectors, and buzzing fuel pumps have fooled me before. if i am getting spray, i move to spark. if no spray, i move upstream until i find the prob. if i were you, i would follow the advice above and yank an injector. that is the only way to be sure.

Paulporsche · 08:51 AM

I'm w/ Vash.

In the 70,000mi I've put on this particular CIS, I've changed the injectors, the fuel pump & check valve and the WUR, all one time. The rest of the time, it always starts and runs, in temps from 20F to 105F.

Knock, knock.