Bosch Fuel Pump Upgrade

[BoxsterGT]

I have been making up quite a few Fuel Pump adapter hoses lately as early 911 (66-73) owners want to upgrade their fuel system to modern specs or are upgrading to later model motors.

Here is an example of the 10mm Supply from the Tank.......



adapted to the 12mm "IN pipe" of the Bosch Flow-through Fuel Pump....



This new Bosch pump is very reasonable in price from our host, and can be used with all the early 911 models.

If with carbs, a PMO Fuel Pressure Regulator is used.

If with Fuel Injection, this pumps works well with the existing Fuel Injection pressure regulator (FPR).

For more information, please email me: len.cummings @ verizon.net without the spaces.

Len

[PeteKz]

The FLAPS sell a fuel filter that has different size in and out. I put one on my car (1973, rear pump), and I put it between the line from the tunnel and the line to the pump. It serves both to adapt the fuel lines and provide a pre filter to the pump. I'll take a pic of it and the numbers on it later. It may be a bit tight on cars with front mounted pumps.

[BoxsterGT]

Thanks for the reminder Pete.

A Pre-Filter for the Dansk Fuel Tank was the reason we began this upgrade work originally.

Multiple Pump failures after installing a new Dansk Fuel Tank made it obvious something was needed.

A Flaps or NAPA basic Fuel filter will certainly help.

We have found using a Lifetime washable filter has worked out even better.

Once we added a fuel shut-off it allowed for more frequent inspections & cleaning.

Here is what we have for the SC and Carrera....



No photos yet for the Early 911 66-73 models, the subject of this discussion. We are close to having a solution.

Protecting the expensive Fuel Pump is the goal, for all models.

Len

[BoxsterGT]

Here are a couple photos that just came in from a customer of his 73.5 CIS 911 with Front Pump and my "Upgrade" Fuel lines.....







Takes a while to have everything Yellow Zinc plated, but the results are "as Factory original" as I can make them.

The Hoses are Metric Compression ring attached to the original steel tunnel lines.

This is necessary with the high fuel pressures of a Front CIS pump.

And with my E85 Rated Hose shown above, this should last for the lifetime of the vehicle.

For info, please email me.... len.cummings @ verizon.net without the spaces.

Thanks for looking.

Len

[BoxsterGT]

Valuable information.....

Bringing to the top.

Len

[PeteKz]

I said I would post the filter I used on my 1973.5 car. It adapts the two different size fuel lines. Belatedly, here it is.

[BoxsterGT]

PeteKz-

That Cotton Braided Fuel hose is for low-pressure carburetor use, not the high pressures of CIS Fuel Injection.

Hope you are not using it with original CIS.

Len

[PeteKz]

Those are on the suction side of the pump (rear mounted pump in 1973). I would never put that filter on the high pressure side either.

Yes, it's CIS, and on the high pressure side it's fairly recent Gates fuel line, rated 250psi, IIRC.

[BoxsterGT]

Glad to hear this.

I got worried when I saw this filter, as this style is common for the early model carbureted motors in the engine bay just before the carbs.

Looks like the original cloth braided Hose from the late 60's/early 70's. You might want to replace this with the latest E85 Rated Hose like this.....



.....just for safety sake. The clamps are "Constant Tension" and perfectly adequate for low pressure (suction) on the supply side.

These early models are becoming so valuable. I lost my beautiful Yellow 72 911 while in storage at Dawe's getting work a couple years ago. Burned to the ground along with a couple other Porsches & a motorhome.

I am a little "gun-shy" when it comes to fuel leaks & fires.

Len

[PeteKz]

Sorry to hear you lost your 1972. That must have hurt. "Once burned, twice shy" as the adage goes.

Yes, I'm still using the braided low pressure lines, but I replaced them some years ago with fresh stuff bought from our sponsor, so they are not 50 years old!

[PeteKz]

And let me pull this thread a little more towards the fuel pump. As stated above, I am using the new style generic Bosch pump, which I installed 5 years ago. I put it in the same rear location as the OE pump. I vaguely considered moving it to the front to be closer to the tank, as in the newer cars, but it was easier to just leave it in the original location.

However, a couple days ago, I was low on fuel and sucked air coming up a steep section of private drive to my house. This was due to me trying to run the tank as low as I could before pulling the fuel strainer at the bottom of the tank, to check that it was clear. When I hit that steep section, the combination of forward motion and uphill angle caused the remaining fuel to slosh back and uncover the pickup tube. Anticipating this might happen, I had an extra gallon of gas in a fuel can in the car. I then rolled backwards down to a less uphill spot on the drive, and added the gallon. It sputtered but did not fire up. Okay, maybe one gallon wasn't quite enough fuel to re-prime the fuel lines and pump. I then trudged up the hill to my house and came back with 3 more gallons of fuel and poured that in. Still no start, in fact I finally ran the battery down. A neighbor came out to help me, and he ended up towing my car up to my house with his pickup truck.

There it sat for a couple days on pretty level ground. Then I went to try starting it again, and it fired up. So, it looks like it needed to sit for some time for the fuel to reprime the lines and pump.

Now I'm thinking this is a good reason to move the pump to the front. Does anyone have a similar experience with an old car and moved the pump forward? Did it help with preventing the pump from sucking air on steep hills?

[BoxsterGT]

I think it was just bit harder for a Rear Pump to pull or suck the fuel all that way.

Years ago I recall we had big issues with vapor lock on the 74 models during the hot weather. It likely was the same with the 73.5 CIS models too.

This continued over time for only those early CIS models. Never an issue with the later models as Porsche moved the pump up front from 76 on.

Len

[Old H2S]

Valuable information from both of you..
Can this be pinned so we can always find Len's contact information?
I usually dig through old threads until I see him jump in..

[Geneman]

Thats a beautiful setup Len. congratulations on helping us all. I especially like the fuel filter right there. Thats the way I have the feed going to my regulator the 50mm PMOs (race car only ). hope you are well. Frank

[BoxsterGT]

Bringing this up to date.....

Len

[E Sully]

Originally Posted by PeteKz

And let me pull this thread a little more towards the fuel pump. As stated above, I am using the new style generic Bosch pump, which I installed 5 years ago. I put it in the same rear location as the OE pump. I vaguely considered moving it to the front to be closer to the tank, as in the newer cars, but it was easier to just leave it in the original location.

However, a couple days ago, I was low on fuel and sucked air coming up a steep section of private drive to my house. This was due to me trying to run the tank as low as I could before pulling the fuel strainer at the bottom of the tank, to check that it was clear. When I hit that steep section, the combination of forward motion and uphill angle caused the remaining fuel to slosh back and uncover the pickup tube. Anticipating this might happen, I had an extra gallon of gas in a fuel can in the car. I then rolled backwards down to a less uphill spot on the drive, and added the gallon. It sputtered but did not fire up. Okay, maybe one gallon wasn't quite enough fuel to re-prime the fuel lines and pump. I then trudged up the hill to my house and came back with 3 more gallons of fuel and poured that in. Still no start, in fact I finally ran the battery down. A neighbor came out to help me, and he ended up towing my car up to my house with his pickup truck.

There it sat for a couple days on pretty level ground. Then I went to try starting it again, and it fired up. So, it looks like it needed to sit for some time for the fuel to reprime the lines and pump.

Now I'm thinking this is a good reason to move the pump to the front. Does anyone have a similar experience with an old car and moved the pump forward? Did it help with preventing the pump from sucking air on steep hills?

I've never had an issue with the rear mounting of the pump.
I am a little embarrassed to say the one time I have run out of gas it was with my '73.5 911T. On the flip side I learned how accurate the gas gauge was. In the early 1990's I was driving north on FDR drive in Manhattan on my way home from work, gauge was very close to empty but figured I had enough to get over the GWB and fill up in NJ. Right before 125th st exit it started to sputter. I got off the exit and stalled. Not the best area back then. A homeless looking guy came over and offered to help. He went off for about 1/2 hour and came back with a gallon can of gas. I paid him and put the gas in the car. I put the key on, took off the air box cover and lifted the air plate for a couple of seconds till the injectors were primed, turned the key and it started right up.
Your belief that going up a grade causing the issue may really have been just no gas in the tank, not the slope. The CIS gas tank was a big improvement over earlier ones. If you look at the internals it has well placed baffle and the fuel outlet is the lowest point in the rear of the tank.
My thought is perhaps the fuel filter you added may have contributed to it taking a bit for the fuel to get to the pump in the rear location.

CIS Gas Tank

[PeteKz]

Ed, thanks for the reply. I've have peered inside my gas tank becuase I replaced the sender and looked around inside to see if there was rust on the bottom, and I inspected he swirl pot too.

I know I was low on fuel, as I was trying to get it really low before I drained the tank to check the strainer, but I don't think it was actually empty. At any rate, adding a gallon should have given it enough gas to start, but it took two more gallons and multiple attempts to get restarted. It could have been a combination of things, including the extra fuel filter, but that doesn't contain much volume. Anyway, I just won't run it that low again.