1975 S.. with 77 motor, CIS, when it get's hot it won't start. I've jumped the ground on the cold start switch so it adds fuel when the starter is engaged. I figure the check valve in the pump is bad. Rather than replace the pump does anyone know of a aftermarket or Porsche part number for an external check valve. It use to be pretty common to add a check valve to the system to help the vapor lock problem.

Any suggestions would be appreciated.

 

I had the internal check valve in my 78 fuel pump replaced. Depending on the fuel pump you have you may be able to do this. A knowledgeable mechanic needs to look at you pump.

 

I had the same thing and my mech said it was a VW/Audi part that he used for a check valve. Not much, but hope it helps.

 

Thanks everyone... unfortunately I'm the knowledgaeble mechanic.. just don't know the part number any more... you don't run into many of these that haven't been fixed already...

guess I"ll go search all-data for an audi-VW part number

 

Check the fuel pressures, i.e. the control & system pressures.
The warmup regulator may be misadjusted.

 

I had a similar problem with my 77. It turned out to a badly worn distributor. I think the plastic washers were dead. Sent it to Moto-Parts for a rebuild. Wow, I've owned the car for 4 years and it's never started this good or run as strong, quick and fast. It likes a good hot spark!!

scott

 

I checked with Alldata and found the audi/vw part number... thank's for all the suggestions, distributor's tight, it's the check valve. When its hot and sat for 5 min's of so I lift the suction chamber valve, it should make the gas injection sound (hissing) when it squeezes gas into the intake chamber, it doesn't, but when it's right after it's been running I can hear the sound of the gas. So easy fix.. found the part number for the 12mm screw in check valve. thanks again everyone.

Mike

 

Care to share the number with the rest of us poor sods?

Also a leaking injector could do the same thing, no?

 

Dave ... I can get the number next monday when the part comes in... don't have it with me at home....

Yeah, a leaking injector could do the same thing, but on start you'd hear that soft whompf when it fires off with all the fuel in the chamber.. it's not doing that.. so it's got to be the check valve.. good thought though.

 

ok.. don't have the number for the part I ordered from our supplier, but the porsche number is...

The part number is 911 608 211 00. This should be the 12MM screw in check valve for the bosch pumps. If you have trouble with the number E Mail me and I can research your particular model.

Mike