924Board.org

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

I have a 77 924 thats cis injected that starts up for a good 4 seconds then it will die. Then i go to crank and thats all it does. It just cranks. If i wait about 5 minutes ill go to start it and itll start up and then die..... Im at a loss. Ive replaced fuel pump, fuel distributor, fuel filter, fuel accumulator, spark plugs, wires. Im really at a loss. Ive thought of everything. Itll stay running if i give it gas on the pedal
The car was running perfect and one day it was idiling in the garage and just shut off and hasnt been able to run since then.

Eric P · Joined: 21 Jun 2017 Posts: 175 Location: NY, USA

Have you tried jumping the fuel pump relay? Can you hear the fuel pump kick on?
_________________
1980 924 NA, US model
1987 924S, US model

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

Eric P · Joined: 21 Jun 2017 Posts: 175 Location: NY, USA

I would try putting a jumper across the relay socket. The pump shouldn't kick on when the plate is lifted unless the engine is turning over. It's a safety feature. Otherwise porsche could have eliminated the relay and just ran power to the fuel pump from the ignition switch.

It definitely sounds like a fuel delivery issue to me. The best way to check is to get a fuel pressure gauge and test system and control pressure to make sure all of your pressures are correct.

I would start by jumpering the 30 and 87 pins on the relay though. If it still has the same problem, you can at least rule that out. Note that jumpering these two pins will make the fuel pump run whether the ignition switch is on or off.

With the relay jumpered and the pump running, you can also pull the injectors and test for fuel flow when the intake plate is lifted. I usually pull the injectors and put them inside a clear glass bottle then test for even well atomized flow on all injectors.
_________________
1980 924 NA, US model
1987 924S, US model

Ian89C4 · Joined: 01 Apr 2011 Posts: 561 Location: North Carolina

Maybe check the Auxiliary Air Valve...may be a wiring issues with it. I have had internal failures of the connectors before.

A good way to check if it is mechanically OK is to pull it off, stick in the freezer, then check after an hour or so to see if it is as open as it can get. Then hook up 12 volt power to it directly from a battery and you should be able to physically watch it close.

I only suggest to look at the AAV as it sounds like you are having air delivery problems, and when you give her gas she runs OK.

Sounds like you have replaced everything else besides the AAV and the warm up regulator, so it should be one of these two.

Look forward to hearing on the developments.

Cheers
_________________
Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

Paul · Posted: Thu Jun 22, 2017 1:27 pm Post subject:

Early cars have a switch in the airflow meter to activate the pump.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Ian89C4 · Joined: 01 Apr 2011 Posts: 561 Location: North Carolina

The aav is located on the top side of the intake runners towards the firewall. It looks like a cone sticking out of a disk.

This is what is looks like...the smaller of the two:

http://www.924board.org/viewtopic.php?p=383403&sid=b429c29c8ab5fe1598d8539779823876

Hope that helps narrow you in.

Cheers
_________________
Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

brian19600 · Joined: 28 Oct 2013 Posts: 375 Location: NJ/CT

As Paul said, that is normal for fuel pump to run when sensor plate is lifted at least thru '78 models.

Have you done the fuel pressure checks with the gauge and the valve? Not that this would fix your problem, but it's always good to have a solid starting point when working on the CIS system.
_________________
78 924

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

Still having the issue, checked timing. Timing is good, i have a huge hole in my intake boot, would that be an issues its by the throttle body. It starts up and is dying still.

gerben1986 · Joined: 13 Mar 2008 Posts: 232 Location: The Netherlands

phillipbpruitt · Joined: 13 Jun 2017 Posts: 15 Location: texas

nope wasnt the issue new intake boot, still dying. Getting ready to push it off a cliiff. What else can make this not start. Ive replaced just about everything fuel and spark related. the timing is right no vacuum leaks. im about ready to blow my brains out.

Paul · Posted: Fri Jul 07, 2017 4:22 am Post subject:

Have you checked the system and control pressures yet?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Paul · Posted: Fri Jul 07, 2017 4:28 am Post subject:

Have you checked the camshaft timing? How did you check the ignition timing?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.