930 won't start=HELP

[Greg930]

I went to a k-27 turbo, 1.05 bar wastegate spring, new diaphram, my fuel pumps check out ok. When I start it , it fires right up but immediatly dies, cranking it I get nothing, but after sitting for a while, I give it a crank, same thing, fires right up and dies. Checking the auxilary air valve, removed plug, with ignition on, no power. Volt ohm on valve should be .33 resistance, shows open loop. Also showing no power to warm up regulatore, or cold start valve. Should I look at the thermotime switch, the Jetronics. Any suggestions, I would appreciate the input. Thanks Greg

[acapella8]

Did you check power to WUR? That will cause to die after engine warms if it does not close. It is meant to close after engine warms. Happened to mine this weekend and I need to replace.

[acapella8]

also - If you are not getting power to WUR, check your ground, and the Fuel Pump Relay (red in engine compartment)

[Greg930]

There isn't any power going to WUR with ignition on, and the relay in the engine comp., have power on the 30 pin only, I believe I should have power coming in on the 86 pin on same relay. Will check grounds, thanks. Greg

[ruf-porsche]

Sound as though you are only starting the engine on the cold start valve. That is why you are able to start the engine, but the engine dies immediately and doesn't restart.

Just because the engine starts doesn't mean the fuel pump is o.k. I would check the relay for the fuel pump and confirm that power is getting to the fuel pump.

Originally posted by Greg930
There isn't any power going to WUR with ignition on, and the relay in the engine comp., have power on the 30 pin only, I believe I should have power coming in on the 86 pin on same relay. Will check grounds, thanks. Greg

Unless you have the trigger power for the relay (pin 86?), the power at pin 30 will not be distributed to the other circuits controlled by the relay.

[9dreizig]

Try to ground the Fuel Overboost cutoff switch.. that's a pretty common problem. The engine should run with the WUR out of the circuit ( mine does). Eventuallly it will warm up without any connection just from the heat of the engine.
T

[Greg930]

Thanks ruf, going to re-check pumps, and trace origen of line to 86 pin, u have given me alot to think about
dreizig, first a moment of silence for the late Warren Zevon, ok, I am not showing on any of my charts so far the fuel overboost cutoff switch, but if it's there I'll find it and try your suggestion
One thing I always remember hearing b-4, but don't hear now, is when I would turn on the ign. the throttle valve would activate and I would hear some valve opening, sounded like it needed a little silicone sprey, I don't hear that sound anymore. Any thoughts on that one?

[9dreizig]

Easiest thing to do is jumper the relay up front, you'll here the pumps running, then see if it runs that way.. Then go from there..
Where are you located Greg??
T

[Greg930]

I tried the jumper, you can hear both pumps, when I uased a fuel pressure ga., to check pressure, blew the hose right off the fuel line, think I have enough fuel pressure. If I have air filter ass. off, and when I try starting and it dies, if I push down on the airflow sensor plate a little, and go back and try restarting, it does the same thing, the differance is, I don't have to wait 15 min. b-4 trying to start. Something is telling me that I dont think I am getting enough air. What controls the air flow sensor plate? I live in So. Calif.. Had a place up off Kingsbry Grade many years ago, wish I still had it, I love Tahoe.

[9dreizig]

Well I was having problems and had the cold start valve stuck on. Hence was flooding. I disconnected the connector valve and it runs well.
Be careful when you push down the airflow sensor plate you can EASILY flood it and hydralock the cylinders. IF you think you're flooding it, disconnect the cold start valve connector and see if it starts.
Did you try to start it WITH the fuel pumps jumpered?

[ruf-porsche]

Instead of pushing down on the air flow sensor plate, try lifting it up. You can lift it up with a small magnet. When the plate is lifted up, it lift the piston in the FD. When the piston in the FD is lifted, gas flow to the injectors. When the plate is down it stops the flow of gas to the injectors.

Could be a stuck piston in the FD. Whatever you do, do not take apart the FD. Once you take apart the FD you can never reassemble the FD without it leaking.

The movement of the airflow sensor plate is controlled by the suction of the pistons as they draws air and gas into the cylinders, however in your case since your is also a turbo it is also controlled by the turbo boost.

Does the sensor plate move up and down freely?

Do a search for stuck piston in the FD, or the word TIT.

[Greg930]

Thanks I had it backwards I thought down was more flow, I am going to give it a try, yes the plate moves freely. You have been a lot of help narrowing this down, will have to do checks a little later. the young woman doesn't understand the importance of having my Porsche running, honey do's. One of us doesn't have their priorities correct, Ha Ha, she says it's me. Thanks again and will get back at you and let you know results, Have a great day Greg

[newbe911]

This sounds similar to the problem my son had on his 87 930. There is a relay that times out when you turn off the ignition to prevent fuel from being where it isn't supposed to. If this relay is bad the engine will start but will not keep running. If my memory is correct it is the rectangular relay on the panel, drivers side in engine compartment.

[Greg930]

Newbe, would that be the taller yellow relay?

[newbe911]

His was just plain aluminum. THe relay suts off the fuel a while before the ignition is shut off to prevent fuel in the turbo. I believe thats right. If my memory is right its the larger of the 2 rectangular shaped relays on that panel. I will try to get my son to chime in on this.

[rsrfan]

Yes it is the taller yellow relay. They fail often. Jump the 30 and 87 terminals to bypass the circuit and if iy starts you have found the problem.

JP