"A few more CIS questions"[Or a 20 year sleep].

[Sunroof]

Here is a photo of the inside of the 1973.5T fuel tank. Take a look at the bakelite swirlpot that collects the fuel. That hole in the center is where that large fine meshed filter (about four inches tall) screws in. Fuel must get past the mesh to get to the fuel pump. Any debris and the fuel pump struggles. Hope this helps.

[ossiblue]

Originally Posted by Sunroof

Did you say REDI-KOTE for your CIS tank? If that's the same as RED KOTE your going to have issues: trust me on this one. As you know the CIS fuel tank has the "bakelite" swirl-pot. That's the same material as the distributor and as such, will not let many coatings adhere to it forever! It was suggested that I use it rather then the POR tank coating treatment when I pulled my tank to have it boiled and coated. It was BAD advice for this tank. Well, the coating has dissolved off the plastic pieces and messed up my internal mesh tank filter (screws into the tank from the bottom) and that's like choking a chicken! I pulled the fuel level, looked into the tank with a flashlight and saw ribbons of red in the fuel! Damn! The car will start then stall, start then backfire, start then go a few blocks then stall, etc, etc. CIS has to have CLEAN fuel and this mesh tank filter can be the culprit here. Many overlook this item, which now I realize that for CIS tanks is a first look item when having fuel issues.

So by chance did you replace it when you had the tank cleaned and re-coated? If not, I would say its loaded with paint flakes, reduces flow and there you have it.

You have to drain the gas to remove. Folks fabricate this nut and bolt removal tool to get it out. Its on the board somewhere in the achieves. Simple R&R. By the way it will cost you about 56 dollars. Do not forget the gasket.

Good luck

Bob
1973.5T

This makes a great deal of sense^^. It would account for your dropping of fuel pressure at the accumulator, which is unusual, and your overall low pressures and lean running symptoms. It is certainly worth checking out, IMO.

[E Sully]

To check total fuel flow, the line in the picture is where all the return lines merge. This is where to check the total volume. If the tank coating is reducing flow out of the tank, your volume will be less than the 850cc in 30 second specification.
.
There is also a removable mesh screen in the bottom of CIS tanks that could be clogged reducing flow. If the return line to the tank is blocked from the coating, your system and control pressure would be higher.


In this picture, to check system pressure you must remove the lines to the TPS and the WUR and connect the fuel pressure gage directly to the fuel distributor. The fuel pressure gage would be dead ended for the System Pressure test with no flow through the gage.

Here is my thread on the CIS gas tank.
CIS Gas Tank
This is another thread that is similar to your situation. A few pages, but it has quite a few photos and expalnations that may help you.
Engine Backfires + CIS airbox Repair

[donlan]

Ossiblue and E Sully,Ed. Just re-read your posts? no's 4 and 5 about pressure gauge connections and I think I am going to have to find a few more fittings as I have it hooked up as per the "CIS primer for the Porsche 911" which is for a post '73 CIS. Thank you both. That bit slipped past me the first time.Will report back in the morning. Regards,Michael.

[donlan]

Everyone, Sorry I have been a bit busy these last 2 days but did manage to start a total fuel flow test on the return line to tank and I ran out of fuel ! I had put about 7 litres in the tank a couple of days ago. Will re-do in morning. Regards, Michael.

[donlan]

Hello everyone, Well I didn't have any luck at the industrial supplies shop so will be back to my mates lathe for some fittings then on with the testing. Regards,Michael.

[donlan]

Hello everyone, My mate was away . He came home yesterday and I gave him my request,now I am going away tomorrow and won't be back till next Tuesday.Will will report back as soon as I can after that. Regards,Michael.

[donlan]

Hello, I'm back [1200 km.trip mostly by bike to vintage races] and my mate hadn't done one of the fittings and can't do it till Monday.More waiting.Sorry.Regards,Michael.

[boyt911sc]

Michael,

Build or fabricate a small fuel tank with about 1 or 2 gallon (max.) capacity. This volume would be more than sufficient for your fuel pressure test while you are rehabilitating the OEM gas tank. Perform the pressure test without running the motor just the fuel pump. The FP should be tested and verified good before doing further work.

The experimental gas tank would have an outlet with a shut-off valve (optional) and a return line. I have a similar gas tank for my CIS bench tester which I use for my portable CIS gizmo.

You need to establish first that the fuel flow to the engine is unobstructed and sufficient to generate the needed system pressure plus return (extra volume). Get these pressure numbers and post them. Thanks.

Tony

[rockreid]

Originally Posted by donlan

Ossiblue and E Sully,Ed. Just re-read your posts? no's 4 and 5 about pressure gauge connections and I think I am going to have to find a few more fittings as I have it hooked up as per the "CIS primer for the Porsche 911" which is for a post '73 CIS. Thank you both. That bit slipped past me the first time.Will report back in the morning. Regards,Michael.

your pressure readings are the same as my 73.5 CIS. I was having a difficult time getting the proper System Pressure readings because I used the CIS Primer test gauge hookup. It turns out with the fuel pressure gauge connected to the FD without the Throttle Valve fuel line being connected my fuel pressures were fine all along.

As it turned out,my no-start condition due to no fuel delivery to the injectors was due to the Air Sensor Plate screw being so far out of adjustment.

[donlan]

hello everyone, Well my mate got the final fitting finished this afternoon.I went and picked it up [about 30 km.round trip] and hooked it all up as per Tony and Ed's advice,as noted by Rockreid and here are the readings... System pressure. 70 PSI. 475 KPA. Cold pressure. 25 PSI. 175 KPA. Warm pressure. 40 PSI. 275 KPA. Residual pressure. 30 secs. 150 KPA. 2.30 Min. 50 KPA. Will have to do fuel flow in morning. Will make a small tank as your suggestion Tony. Regards,Michael.

[donlan]

Hello, Did the fuel flow test and got.. 1160ml./30secs. Regards,Michael.

[boyt911sc]

Originally Posted by donlan

hello everyone, Well my mate got the final fitting finished this afternoon.I went and picked it up [about 30 km.round trip] and hooked it all up as per Tony and Ed's advice,as noted by Rockreid and here are the readings... System pressure. 70 PSI. 475 KPA. Cold pressure. 25 PSI. 175 KPA. Warm pressure. 40 PSI. 275 KPA. Residual pressure. 30 secs. 150 KPA. 2.30 Min. 50 KPA. Will have to do fuel flow in morning. Will make a small tank as your suggestion Tony.
Regards,Michael.

Michael,

The test results look good. But have a question to ask you. Was the test done with the engine running or just the FP running? Could you extend the residual pressure test to 20 mins. or 30 mins.? The FP volumetric flow rate is very good.

Tony

[donlan]

Tony, Motor will not run ! [fires but won't run]. The pressure test is for as long as there is pressure ! [when I did the original pressure test in February it would hold pressure for an hour,70 kpa./10 psi. Regards,Michael.

[E Sully]

Was the fuel pump flow rate checked with fuel tank from car or Tony's small tank suggestion? While using a small tank will test fuel pumps ability, you would need to check with cars fuel tank to make sure car is able to flow enough gas. Small tank will not show you if there are obstructions preventing enough fuel flow under normal conditions. I would also recommend removing the fuel strainer from the cars gas tank to see that the strainer screen is clear.
I still wonder about the engine itself. As mentioned earlier, you show a '72 engine type 911/51 which is a 911E, MFI. This would lead to questions as to whether it is set up to work with a 1973 cis intake. An "E" camshaft would not be correct for it. Any pictures?

[donlan]

Ed, Tests have all been done with cars normal fittings [apart from fuel pump]. I havn't tried the emergancy tank as yet. I have had the strainer out a couple of times to check if any of the tank treatment has come adrift and so far so good. Motor has no pump drive on front of l/h cam? When I purchased car motor looked like it had been in car for years [no recent activity on nuts or fittings etc.] and I have driven it approx.1206 miles in U.S. and here. My mistake was not starting the motor on a regular basis. [the 20 year sleep]. Will take some photos and get them posted. Regards,Michael.

[donlan]

Ed, A few photo's. Michael.

[rockreid]

my 73.5 CIS no-start was due to the adjustment screw being very far out of whack. After chasing fuel pressure ghosts, I lucked out and figured the fuel was simply not being delivered to the injectors.

Place your injectors into little bottles to watch for fuel pattern. Lifting up the Air Sensor Plate should give you a squeal of fuel and spray. You should feel resistance as you lift up the plate. If you do not feel resistance, then it must be either a stuck FD piston, or the air adjustment screw.

My symptoms were a quick start then the engine dying- a sign the engine was getting initial fuel from the Cold Start Injector but the real injectors not delivering fuel.

[donlan]

Rockreid, thank you for that. That's what mine is doing+ a backfire. Will go and try that right now. Regards,Michael.

[donlan]

Rockreid,