[86911TLCAB]

1978 3.0 engine

I presurrized the fuel system (YES!). All 6 fuel nozzles are pulled out and in containers. When i lift the air plate, the puimp comes on, there is good resistance in the plate itself. But I am not getting any flow from the nozzles. I took one of the nozzles off and the fuel is flowing out. But nothing coming from the nozzles. Is this right or should fuel be spraying out? Thanks

[86911TLCAB]

I got the answer...something not right again...lets try swapping fuel pumps...Thanks Jeff..

[William Miller]

It all works on pressure. Do you have a set of CIS gauges?
The manual should tell you how much pressure it takes to push the pintle of the injector open. Something around 2 and a half bar?

Sounds like you have some of the electrons flowing now!

[86911TLCAB]

Bill I do electrons flowing and i have guages. I really didnt have enough gas...(ran out gas already)...put some more in and fuel started to flow. Charged the oil system...got good oil pressure.

Went to start the car and it seems like it wants to start, but then dies right away...almost as if it is getting killed. I keep wondering if its the rpm limiter switch?
How does that work? It is obviously providing a signal to the fuel pump to die if the rpms are to high. But should it do the same if there is no rpm or if it isnt even there. Engine did not have such a switch before (or if it did I am unaware of it).

Can i jumper pin 87a to 30 and try and run the car or is that only for testing. I was thinking if i cut the red wire between 87 and 86 and then that might be enough to eliminate the power which would go to the switch. But that is providing voltage to the switch. How is the signal getting back from the switch to the pump telling it to shut off. How do i tell the fuel pump relay to forget about the rpm limiter? Not sure this is the culprit and might take you up on an offer to borrow one, but first trying to wire it out to see if it is the cause. Car just acts like it wants to start, then dies. after that the starter will turn, but it wont engage unless i wait a minute or so and then try again. Any thoughts? will continue tomorrow. Thanks.

[William Miller]

Starter is a completely independant circuit, but remember the power to the cold start valve comes from the auxilliary contact on the starter. (Little yellow wire with stripe.)
You have to look very closely at the terminals at the starter and if you can get them clean, they are numbered. I think Bently Manual has a good picture.

I don't think there is any safety device to prevent the starter from turning. So, you need to diagnose the reason it cuts out. Clean terminals on the started and the ground strap (Both ends) while your under there.

After last weeks look at the diagram and describing the fuel pump relay diagram. (GO back and read that description while looking at the diagram. THE OTHER THREAD)
I recall, but not sure that 3 things were connected on the ground side of the fuel pump relay coil. The contact on the air plate. (lifting the plate opens the ground and lets the pump run) The alarm system wire. (Did you find this?)
Also is the RPM Limiter switch. I'm not an Engineer, so I'd just be guessing at how that part of the circuit works. I do believe that when the Fuel pump relay is NOT energized "normal" condition, the power should flow thru it to the fuel pump only while the ignition is in the start position.

I'm guessing you had the fuel pump relay jumped out when you lifted the plate and saw the fuel flow?

BTW, if you have the injectors still disconnected, it might be good to flow a few gallons of new gas through the system and out the injector tubes, just to get some of the old crud out, instead of pushing the crud into the injectors. Those CIS injectors have a tiney filter screen where the fuel enters. I understand that they are not serviceable, but I've heard that there are services out there that ultrasonically clean them. Once you get a good fuel flow on the hose, hook them back up and see how well they spray.
Careful with the gas

It sounds like your making slow and deliberate progress! Sometimes slow is good because when your done, you'll know almost every part of your car and fixing one symptome at a time is soo much easier!

[86911TLCAB]

Well had the running today. However not by itself. I appear to have a lot of pressure on the air plate. When i try to lift it with the car in the on position to get the fuel pump to start, the pressure seems to build and then it becomaes very hard to raise. Only way i was able to get it running was to manually raise and let go the air plate while someone else was starting the car. It would catch and then i had to continue to raise the plate with my finger to get it to run. Didnt hold it up, just lifted it slightly and let it go and then kep repeating thatcontinuously to keep it running. Either i am low on vaccuum or fuel pressure is so high it is somehow affecting the plunger preventing the plate from lifting on its own. It did run a couple of times by itself for a few seconds or so, when i had relived the pressure in the fuel system for one reason or another. Am getting very close. I have spark, I have fuel. Now must determine what is causing it to be so hard to lift. When it runs it sounds good and no backfires...so thats a good sign...Any thoughts and posibble causes? Thanks...

[William Miller]

Here's an answer to your PM: A Copy

The valve goes on the leg between the "T" and the WUR. With the valve closed, you are reading "System" pressure which is regulated by the "regulator" built onto the side of the fuel distributer. This is the pressure that goes to the fuel injectors. The system pressure is adjusted by adding or removing shims. The fuel pump actually pumps the fuel continuously in a loop from the fuel pump thru the filter, accumulator and fuel distributer and back to the tank thru the return line. The regulator has a needle and spring that restricts the flow creating pressure on the side before the needle.

The "control pressure" is what counter acts the force of the air meter plate lifting up. More control pressure prevents the plate from lifting and leans the mixture. Lower control pressure alows the plate to lift easier with the same flow of air which makes the mixture richer. Simular to the system pressure regulator, the WUR aka "Control Pressure Regulator" restricts the flow of fuel as it returns to the tank. The difference is that the WUR is made to modify the control pressure based on Time, tempature and (on a few years) Manifold pressure.

If the engine is very cold, stone cold (Not run for 12+ hours or so) when you start it the control pressure will be very low. As the WUR itself warms up from the engine heat, the control pressure increases steadily.

At some point in the development, the electric heater element was added to speed up the time that the control pressure increases. (Actually, different cars have different WUR part numbers where these things heat up at different times. At some point, you should check the part number stamped on the unit to make sure it still has the right one in there.)

In addition the one you should have has a vacuum connection on it. This vacuum effects the diafram inside the WUR and when you open the throttle quickly, manifold vacuum drops quickly. With the drop in vacuum, the WUR makes the mixture richer. Since there are several points where the vacuum hose could be connected, it is very important to get them in the right spot. The vacuum line from the WUR first goes to the Thermovalve. (This is a porsche specific part as far as I know and it is not manf by Bosch)
The thermovalve should be closed on a cold start and then it opens after several seconds (something like 20-30) So while this is closed, no vacuum can get to the bottom of the WUR so it will make the mixture richer. Remember that I mentioned before that you might not have the wires for this unless it is part of the engine wiring harness. (If so you are golden!)

To test the valve, simply blow into the vacuum hose and it should be closed. (It has to be cooled down and no power. Put power on it and after several seconds it should open up.

Once you get the engine running, you can run the engine with the gauges hooked up and watch how pressures change over time.

Remember that during warm up from a stone cold situation, many changes must take place to make the engine run smoothly. Thus there are many devices that were designed to help this happen.

I once wrote down a "Sequence of events" which is not in any literature that I have seen.


BTW, the fast idle comes from the AAR which should slow it down gradually over time. Like the WUR it heats up from the engine temp and it has an internal heater like the WUR that speeds up the rate at which the idle slows to normal. Check that the electrical plug on top of the WUR has voltage. (I think that one should be easier to get to.) If not, find out why. If so check the AAR next. they are on the same circuit..

Are you familiar with Jim Williams "CIS Primer"
I assume at one point Jim went thru the same learning curve. He has a web page dedicated to Porsche CIS. Its very good.

There still might be a link somewhere on this board, but there certainly is on Rennlist.com

Search CIS PRIMER on Dorkiphus.