fuel pump questions for a 1979

Just to close out the topic of if using one external fuel pump will work on a '79, I am happy to report that one pump will definitely work. I have been testing my '79 in ~90 deg temperatures at ~6000+ ft elevation. There's no sign of insufficient fuel or vapor lock (which is the most often cited reason for having two pumps) so far. The one (Bosch) pump was able to just hit the two pump flow rate spec (measured at the return line at the fuel tank connection) and there was plenty of system pressure.

Glad you circled back. CIS is an intricate beast no doubt. I had my 78 running beautifully, , after replacing all lines, tank service, fuel pumps, accumulator, FD, ETC, but it has been on lift bars for 7 years. I got side tracked with another 928 project, and neglected her for about a year. Tried to start her, and it wouldn’t fire. Fuel pumps were seized. Wtf? Bought new pumps (my 78 and 79 both have dual external pumps) Installed, and she still wouldn’t fire, FD piston seems seized...left it alone about 2 months, and went back to it....new pumps are seized! What the heck! Left it alone to continue on my 79 restoration.::’ll get back around to it again eventually.

Wow, sorry to hear the fuel pumps are seizing. Are you using Stabil in the fuel, it helps keep fuel from causing problem with cars in storage.

I own two 1979 928s, a road car and a track car and both have in-tank pumps that are working. My 1979 road car sat for 10 years with fuel in the tank and EVERYTHING in the fuel system had to be rebuilt or replaced. It was expensive and time consuming. The intank pump wouldn't budge so I had to replace the fuel tank. EXTREME care must be taken when removing the in tank pump or screen ... find a way to keep the in-tank metal ring from breaking the bond with the tank plastic.

I've had to have the fuel distributors rebuilt in both. I tried to do it myself but wasn't successful. I had CIS Flowtech in Fair Hope, Alabama, do the rebuilds and the cars have run great for years. It is best to start and run the engine every few months even if in storage.

The CIS fuel systems work well when healthy, but don't like sitting for years with no use!

Rich928 wrote: Wow, sorry to hear the fuel pumps are seizing. Are you using Stabil in the fuel, it helps keep fuel from causing problem with cars in storage.

I own two 1979 928s, a road car and a track car and both have in-tank pumps that are working. My 1979 road car sat for 10 years with fuel in the tank and EVERYTHING in the fuel system had to be rebuilt or replaced. It was expensive and time consuming. The intank pump wouldn't budge so I had to replace the fuel tank. EXTREME care must be taken when removing the in tank pump or screen ... find a way to keep the in-tank metal ring from breaking the bond with the tank plastic.

I've had to have the fuel distributors rebuilt in both. I tried to do it myself but wasn't successful. I had CIS Flowtech in Fair Hope, Alabama, do the rebuilds and the cars have run great for years. It is best to start and run the engine every few months even if in storage.

The CIS fuel systems work well when healthy, but don't like sitting for years with no use!

Rich,
CIS Flowtech did a good job rebuilding my WUR and fuel distributor too. They told me that ethanol in the gas is a problem with these CIS components as well. Any idea of how to minimize ethanol effects? I try to regularly add Techron, but I don’t know if it counters ethanol.