Another 930 COLD START problem... After 5-10 long cranks it finally catches and runs

[solarispete]

Hello all,

I have a 1985 930 Turbo (Euro version), no Computer box under the driver seat.
CIS, adjustable WUR, stock turbo replaced, Fabspeed intercooler, Fabspeed intake/exhaust
done last year.
Had the car since 2010, never had problems with cold starts. One crank will usually get it running.

Few months ago, had issue with fuel pressure when Turbo kicks in and stalling, replaced distributor, CDI/ECU box, and red relays. All was working ok in the summer.

Lately, noticed I have to crank many times (5+) before the engine will even catch. Once
it catches, it dies quickly and takes two more cranks to get it to run ok. Only happens when cold
(left over night). Once it starts, it runs a bit rough for 10 secs and then very smooth with
no problems afterwards.

My mechanic had spent a bit of time troubleshooting, great guy but a bit stumped on this issue.

Fuel pressure seems to drop to 0 overnight. After many cranks fuel pressure builds up and fires.
He found that the AAV wasn't opening so he replaced it with a working one.
Adjusted WUR at 30 psi and running perfect.
checked fuel pressure at and from WUR
checked all ground and power to all sensors on the engine
checked for loose air hoses and wires

He suspects something is leaking internally.

Can someone suggest where else to check?

Thanks in advance!

[krasuskyp]

replace the accumulator next to the fuel filter if it's original - common failure

can use the smaller and FAR less $$$ 911 version vs. the 930 one, I've run mine for years

easy DIY by the way, I'd not pay for that work

[Slantnose Steve]

Try replacing the fuel accumulator, as Paul suggests. It worked for me.

[T77911S]

Don't just replace parts. That's no way to troubleshoot.

Put gauges on it ant see how fast it drops. Mine goes to 0 over night and mine starts fine. Another test would be to remove the connector on the back of the AFM so the ft will run. Then in the morning turn the key to on and let the pumps run for a few seconds.

I hope the 30 psi was cold control pressure.

Check for air leaks.
Check AFR'S With a sensor

[CFD]

The pressure in the system on mine also drops to 0 overnight with new accumulator (smaller type). Starts fine when cold. If the system is holding pressure long enough to prevent hot start issues then I wouldn't go changing the accumulator at this stage. Always best to systematically test each component in the system on your way to a solution.

[mark houghton]

And don't forget to have someone check your thermotime valve. If it isn't working when cold, you won't get the momentary injection of raw gas to set up an initial rich condition to facilitate starting. Once she gets running, your WUR will sustain the proper rich mix until it warms up.

[RarlyL8]

At what temperature is your cold control pressure 30psi? Compare that number to the chart for your specific engine type number.

[gumba]

I've recently started to have the same problem. How do you check the thermotime valve.

[RarlyL8]

The thermotime valve is a solenoid activated by the thermotime switch. If you hit it with 12V it will open/close the vac line that allows air around the throttle. You can also bypass it both open (vac line) and shut (port plug) to verify function.