Early 911 Hot Start fix / Digital WUR
05-21-2008, 03:52 PM
#1
Track Day
Thread Starter
Early 911 Hot Start fix / Digital WUR
We've had a lot of interest and feedback regarding our UTCIS digital WUR upgrade. Thank you for your support. We've released a fix for early (1974-77) 911 models which solves a rest pressure problem when using the UTCIS.
In 1977 and later models the return flow from the WUR is shut-off by a push valve that sits on the end of the system pressure regulator in the fuel distributor. In early 911s this return shutoff is part of the WUR, not the fuel distributor. If the UTCIS is used on these early models there's no shutoff to keep the fuel sytem pressurized when the engine is turned off. This makes the car very hard to start when hot.
The UTCIS digital WUR can be used on these early models if a valve is fitted to the return line:
http://unwiredtools.com/utcis-cprp.asp
This upgrade is also very suitable for a stock 911 which might be driven in very hot weather. When the fuel shutoff was changed from the WUR to the fuel distributor in 1977 the rest pressure was increased from 1bar to over 2bar. The early 911 rest pressure is so low that you can easily get vapor lock and hard starting in hot weather. We're located in Arizona so hot start problems are very common here. The rest pressure upgrade kit will increase the rest pressure of the early models to as good or better than the post '77 version.
In 1977 and later models the return flow from the WUR is shut-off by a push valve that sits on the end of the system pressure regulator in the fuel distributor. In early 911s this return shutoff is part of the WUR, not the fuel distributor. If the UTCIS is used on these early models there's no shutoff to keep the fuel sytem pressurized when the engine is turned off. This makes the car very hard to start when hot.
The UTCIS digital WUR can be used on these early models if a valve is fitted to the return line:
http://unwiredtools.com/utcis-cprp.asp
This upgrade is also very suitable for a stock 911 which might be driven in very hot weather. When the fuel shutoff was changed from the WUR to the fuel distributor in 1977 the rest pressure was increased from 1bar to over 2bar. The early 911 rest pressure is so low that you can easily get vapor lock and hard starting in hot weather. We're located in Arizona so hot start problems are very common here. The rest pressure upgrade kit will increase the rest pressure of the early models to as good or better than the post '77 version.
05-23-2008, 03:10 PM
#2
Instructor
Good stuff Steve. Do you know a fix for a 1979 911sc hot start problem. My Porsche guy tell me that when she's hot she'll always have problems starting. That I just need to push on the gas as I start the car, and it'll eventually ignite. This doesn't sound right to me.
I'd appreciate the advise.
Thanks
roscoc28
I'd appreciate the advise.
Thanks
roscoc28
