CIS Fuel Distributor Leaking

[outlaw912]

Car wouldnt start and I discovered my 73.5 CIS Fuel distributor plunger was stuck. I removed the distributor, opened it, cleaned it up and loosened up the plunger. Upon numerous attempts to reassemble my car fills the exhaust system with fuel and the distributor leaks from the seam. Clearly I didn't assemble it properly or damaged it in the process. Do I even attempt a rebuild on my own or am I stuck sending it away to CIS flowtech?

Anyone have any experience to share here?

[patkeefe]

CIS fuel distributer cleanout w/pics

[Ronnie's.930]

I've never rebuilt one, but this "Made in the USA" company sells repair kits and assembly tools that look interesting.

http://stores.ebay.com/Cis-Jetronic?_trksid=p2047675.l2563

[Reiver]

Send it to Larry at Flowtech....he's the only Bosch authorized rebuilder of WUR's/ Fuel Heads in the US. Bosch Germany sends him WURs/Fuel heads from Germany for him to rebuild.
He is also the only guy with all of the original Bosch parts supplied from the factory.

[tkmoore]

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[T77911S]

send it to larry. its not much more than the ebay rebuild kit and it is done right
if it is leaking you either damaged the metal shim or you have dirt on it.


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[groovydude]

Larry was extremely helpful for me when I had WUR issues, and the rebuild was reasonable.

[fritzgator]

+1 on Larry, he just did mine a couple weeks ago.

[outlaw912]

Thanks guys

I'll send it out for repair and let you know what happens

[outlaw912]

I did my own rebuild on the fuel distributor as I'm likely doing an EFI conversion anyway and didn't want to spend the money on a rebuild. Plunger runs smoothly inside but when I turn on the fuel pump I get full pressure to the injectors and almost immediately hydrolock the motor. The plunger is all the way at the rest position. Is it possible to screw up the distributor to allow full fuel flow to the injectors even when the plunger is at the rest position?
Any ideas?

[yundar]

I realize this thread is a little over four years old but I stumbled across it as I am having the same problem. Outlaw912 did you ever arrive at a solution? I am getting fuel through the distributor no matter what the adjustment is at and flooding the engine to the point of hydro lock in a very short time each time.

[E Sully]

Do you have a CIS pressure gauge set? Does the plunger in the fuel distributor move smoothly? Are you getting fuel in all the cylinders or just some? You could check to see if you may have some bad injectors, maybe opening at too low a pressure?

[yundar]

Hey Thanks, I do have the gauge set but from what I have been reading I am confused on what control pressure is on KE-Jet. Sounds like with the lambda system the bottom side off the fuel distributor is different? I have removed the fuel injectors and bench tested them and they are within spec. Yes, the flooding is in all cylinders equally.

[E Sully]

Jims CIS page is always a good reference.
911 CIS Primer - Index
I have the first generation CIS, so I cannot help with the later Lambda system, but I would make sure the air flow plate and fuel distributor piston are set correctly.

As you can see in the diagram, if the piston does not drop to the correct starting position, fuel can flow to the injectors prematurely. This can be caused by a sticking piston or improperly set air flow plate.
And of course, using the pressure gauges to get system and control pressures in spec must be done.

[RarlyL8]

Pull the fuel distributor and check the piston for free movement. You'll know real quick if the piston is the problem.

[tirwin]

Originally Posted by yundar

Hey Thanks, I do have the gauge set but from what I have been reading I am confused on what control pressure is on KE-Jet. Sounds like with the lambda system the bottom side off the fuel distributor is different? I have removed the fuel injectors and bench tested them and they are within spec. Yes, the flooding is in all cylinders equally.

Can’t help on the FD but I can help with fuel pressures. System pressure is your baseline fuel pressure. If it is out of spec (usually too weak) then the other pressures don’t matter. System pressure is higher than control pressure — generally system pressure is in the 4.5 bar range and warm control pressure is in the 3.5 bar range. Broad generalization — don’t get too wrapped up in the specifics.

The control pressure is variable and measured in two states: cold and warm.

Picture a see saw in your mind. As air going into the intake pushes up on one side, the other side is pushing down on the plunger in the FD. The control pressure is the resistance against the downward plunger force.

The lower the control pressure, the lower the resistance. Higher control pressure, higher resistance. Lower control pressure, more fuel. Higher control pressure, less fuel.

On a cold start, you need a richer mixture so the control pressure is lower. Once the engine warms up, the mixture leans out to normal (close to stoich). Under load, you need more fuel to make sure you don’t go lean. This was accomplished in different ways over the years. Measuring CCP and WCP is making sure the mixture is correct in these two states.

The WUR “bleeds off” system pressure to act as a CCP and WCP regulator.

[boyt911sc]

Yundar,

Your FD is already leaking at the seams but this will not cause your flooding problem. The flooding could be caused by either a stuck plunger or one or more of the six (6) viton 0-rings inside the FD have been compromised.

Remove all the six (6) fuel injectors from the fuel line/s and place the ends of the fuel lines into suitable containers. Test run the FP for a couple of seconds and observe for any fuel delivery. There should be no sign of fuel delivery at this point.

Regardless if the plunger is stuck or o-rings are defective, the leak around the seam has to be corrected. Avoid using this FD unless you have corrected the leak/s.

Tony

[E Sully]

Not sure yundar has the leak at the seam issue, or just the flooding issue. If just flooding, it may be able to be fixed without opening the distributor, just freeing the piston and adjusting air plate.
On the right of the picture are the o rings Tony is referring to.

As you can see by this old fuel distributor I bought to rebuild as a spare, it can get a little ugly inside when left to sit for years. There are rebuild kits available on Ebay. They include a new metal diaphragm and o rings. It takes careful assembly to get the o rings to stay in place when putting the 2 halves together. With a little care many can be restored, if this is your problem.



The main fuel pressure issues can be taken care of by making sure the o ring is in good shape, and spacers are used to adjust spring pressure.