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75 Carrera CIS Fuel Pump questions

Hello everybody, I have been following the Forum for some time and it is a fantastic resource.
Recently I have purchased a 75 Carrera CIS (I will say the car was a 7 out of 10) and I'm slowly working on the little bits to make sure that it runs without a single issue.
Thanks to the forum I have been able to repair the original VDO clock (working like a charm now) installed the Sherwood Lee's gate shifter kit (what a change on the old play of the transmission) and now I'm working my way into some of the common "Gremlins" of the CIS K-Jetronic system.
The car starts from cold with very little effort, but the hot start is not great.
I have exchanged the WUR (it made the car run better), I have cleaned the injectors on the ultrasonic bath so the car is really performing amazingly now BUT the hot start is still an issue.
Next is to remove and clean the Fuel Distributor (ordered a repair kit from American Precision Machinery) but I was wondering if I should also change the Fuel Pump.
It was exchanged 2 years ago, but it does not seem to be the correct part for this car (see attached pictures).
Any help will be highly appreciated it.



Old 06-08-2020, 12:17 PM
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Faulty Fuel line return check valve or fuel accumulator can cause poor hot starts.
Test your residual fuel pressure with a gauge yet?
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Old 06-08-2020, 02:09 PM
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Typically hard hot starts indicates a bad check valve, I believe on a 75 the check valve is in the banjo fitting.
Old 06-08-2020, 03:13 PM
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Many thanks for the information, highly appreciated it. I have another question regarding the pump which as you can see is starting to rust. Would it be possible to clean it and paint it with some water based anti rust paint ? Thanks in advance.
Old 06-09-2020, 10:25 AM
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Old 06-10-2020, 12:42 PM
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One of the thing I see is that terrible wiring repair at the pump. It's not your problem but it must be repaired. The hot start issue is most likely the fuel accumulator.
Old 06-11-2020, 04:17 AM
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Agreed, missing or bad check valve on the fuel pump. Not the original pump there. Also it appears that you are missing the shock pad under the pump. You can add an aftermarket check valve inline there.
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Old 06-11-2020, 06:40 AM
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P/N for banjo fitting w/checkvalve is 911 608 901 00, if it needs replaced.
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Old 06-11-2020, 01:50 PM
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I have a suggestion re: this "Side Outlet" Pump. Junk it and go with a new CIS "Flow-Through" pump from Bosch.

First, this will allow you to eliminate the Fuel Feed Hose being routed through the Left Frame Rail. You no longer use the Banjo with the check valve in it that requires a hose clamp in (4) places, and the later design pump allows crimped fuel line to the accumulator.

Lots of failures of the old design (too old & worn, and rebuilds do not last). According to our host, new Old style pumps are now just under $800 from Porsche, while new "Flow-Through" pumps from Bosch are $100.

I am happy to help with a new, crimped one-piece Feed Hose (E-85 Rated) from the new Pump to the Accumulator. Yes, it is expensive with it's special order fittings, but it will last as long as the rest of the car, and it's new pump.

For info, please email me.

Len.Cummings at verizon.net


Last edited by BoxsterGT; 06-13-2020 at 10:24 AM..
Old 06-13-2020, 10:22 AM
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Hi Len you got message. But going with a new CIS "flow-through" pump will mean I have to remove the pump from the back and put it in front?
Why a new "old style" Porsche pump is $ 800 ? Yeah, I know all about Porsche trying to get our $$$ but is it so much better ? Thanks in advance.
Old 06-16-2020, 01:30 PM
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Mounting the pump up front is preferred but is a lot of work.

The Flow-Through pump can be mounted in place of the original, and with it's check valve part of the Pump body, a new Feed Hose can be crimped and routed between the rear crossmember and the firewall, as all later 911 models have.



This requires some special order fittings, but eliminates (4) hose clamps on a High Pressure hose and reduces the risk of a fuel leak and fire..


Len.Cummings at verizon.net

Old 06-16-2020, 04:24 PM
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Old 06-23-2020, 01:19 PM
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niushork -

Pump does not have to go up front, although it is the best location, as a pump is a better pusher than a puller.

Email me and I can give you details on this. Here is a typical Fully crimped one-piece E-85 Rated Hose to use with the new "Flow-Through" Pump....



It is routed up between the firewall and the rear crossmember.

Len.Cummings at verizon.net

Old 06-23-2020, 02:07 PM
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Welcome to the forum. I know I have found lots of help here.

I do not suggest attempting repairs on the fuel distributor until you have verified the following;

- Ignition is working correctly (many ignition issues masquerade as CIS issues)
- Fuel pump operating correctly.
- Check valve and fuel accumulator operating correctly.
- CIS system pressure
- Cold and warm control pressures for the WUR
- Idle CO content and speed are correct

The fuel distributor is one of the most "bulletproof" components of CIS. Consider sending it to a specialist if you determine that it does have trouble...
Old 06-23-2020, 05:05 PM
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Quote:
Originally Posted by fanaudical View Post
Welcome to the forum. I know I have found lots of help here.

I do not suggest attempting repairs on the fuel distributor until you have verified the following;

- Ignition is working correctly (many ignition issues masquerade as CIS issues)
- Fuel pump operating correctly.
- Check valve and fuel accumulator operating correctly.
- CIS system pressure
- Cold and warm control pressures for the WUR
- Idle CO content and speed are correct

The fuel distributor is one of the most "bulletproof" components of CIS. Consider sending it to a specialist if you determine that it does have trouble...
Thanks for your reply.
- Ignition is working properly
- CIS system pressure correct
- WUR is brand new
- CO content and speed are correct
- Fuel Pump seems to operate correctly

I have ordered a brand new fuel accumulator so that would be my next check area.

Any other ideas ?

Old 06-25-2020, 06:17 AM
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