Another CIS nightmare need advice.
 

Another thread about a non running cis 911

1976 911 with cis injection. Car will not crank and run unless I lift up on sensor plate and hear injectors whine for a few seconds. Car then cranks and idle speed goes up to about 4k for a second then drops and car shuts off within 2 or 3 seconds.

Parts replaced.
-new fuel pump
-6 new injectors
-rebuilt warm up regulator
-new spark plugs
-new plug wires
-new msd cd unit
-fuel tank removed cleaned and reinstalled

I have temporarily straight wired fuel pump to battery to make sure pump is running which it is.

I do have a set of cis fuel gauges. Any thing else I can check or try before hooking them up?

What should be system pressure, cold an warm control pressure and residual pressure on a late 75/early 76 911? Thanx L

you should've used the gauges before replacing parts. there's lots of info about using them, google Jim CIS primer for a start

OK - I will keep my input brief as there are smarter guys out there. They are going to want the bosch number on the new WUR.

S/B 0438 140 033 for the 1976 model year.

One work of advice. Play tennis with them. If they ask you a question, return the volley at your earliest convenience with a clear and concise answer.

Don't respond with another question if that makes sense. These guys are worth hundreds and hundreds of dollars in YOUR pocket and they will find your issue if you just use the standard communication model.

Good luck.

Here is the graph for the 033

http://forums.pelicanparts.com/uploa...1379701984.jpg

Just a comment to make communication easier. You use the word "crank" in the context of the engine firing and running, I believe. If that's the case, a clearer term would be "fire" as "cranking" is generally understood to be the engine turning over via the starter motor.

You've already been "scolded" for not doing your fuel pressure check first. Seriously, when dealing with CIS issues (after eliminating spark and compression), depending on the symptoms, checking the fuel pressures is usually the first step as it is the easiest way to eliminate components as a problem without having to replace them in the hopes it fixes the issue.

With that said, here's what I see going on: The need to lift the sensor plate points to a loss of residual pressure. How would you know there is a loss or from where is the pressure being lost? That's where you fuel gauge/testing comes in.

The fact the engine fires after the sensor plate is lifted, revs to ~4K then drops and dies indicates 1) your cold start injector is working but 2) your cold control pressure may be too high to sustain running, or 3) you have a massive air leak from a hose, connection, air box, or one of the warm up components found on 76 CIS engines, or 4) you are not getting adequate fuel to the injectors, or 5) some combination of all of the above.

If this sounds daunting, it really isn't if you take one step at a time and systematically diagnose your problem. Given your symptoms, I'd suggest you hook up your fuel gauge and check the system pressure, cold and warm control pressures, and the residual pressure @ 5 min. intervals up to 30 minutes, and report back your results. This will be the first step and will give us a clue on how to proceed further.

You have a 76 CIS with several components that can contribute to your problem but you are trying to eliminate one component at a time, beginning with the fuel delivery system. You can get your pump to run with the key in the "on" position by either unplugging the wire from the air flow sensor (found in the engine compartment) or by removing the red fuel pump relay and jumping sockets #30 and 87a with a wire.

Report back your results, using the chart Bob posted for cold pressure, and we'll move on from there.

Here are the numbers from the cis pressure tests I just finished.

-system pressure 80 lbs 5.5 bar
-cold control pressure 32 lbs 2.2 bar
-warm control pressure (checked for 10 minutes continious) 37lbs 2.5 bar
- residual pressure (10 minutes) 17 lbs 1.1. bar
(20 minutes) 7 lbs .5 bar

temperature 80 degrees

Warm and cold pressures are ok. Residual is not ok. You have a small leak somewhere. Mine will hang well above 20psi for a long time.

Did you see the graph I posted?

80F is 27C.

Per Schumi; for your future reference:

911 CIS Primer - Index

Fuel pressures........
 

Lcox,

The system fuel pressure is too high @ 80 psi. While warm control pressure (if it is really your WCP) is too low @ 37 psi. These values could be tweaked or adjusted. But you have to locate the main problem: vacuum leak. Keep us posted.

Tony

Yes - That is correct. I read the darned CCP graph again for WCP rather than the stated amount. Argh.

Thanks for posting the graph and all the input.

I'll try to find obvious big vacuum leaks to start with .

Any additional input appreciated. L

In post #3 I asked you to communicate.

You ain't done f**k-all as far as doing that.

You are on your own agenda and that is what pisses folks off that help out.

I'm out.

I hope Bob's tough love doesn't turn you off. Helping others can be frustrating at times, he does like to help.
I may have a different opinion than Ossi on the residual fuel pressure. Loss of residual pressure will be compenstated for by lifting the air plate to get the pump running, but there is also another effect. The injectors will start spraying. When I first bought my car I knew nothing about the way the parts worked together. I did know that to get it to start cold I had to lift the plate for a couple seconds to give it a slightly richer start mixture. Later I found out the cold start valve was not working. Residual pressure is not as big an issue with my year since the fuel pump starts as soon as the key is turned on. From your description, first you prime it by lifting the plate to give the engine a rich mixture. It burns through that fuel and stalls out. To me that sounds lean, not sure the cold start valve is working, also check thermo time switch. You may have some air leaks to plug.
Why not start with the high system pressure, I would remove the cap off the pressure regulator on the fuel distributor, and check the spring, cylinder, and bore are clean and move smoothly, and the o ring is in good shape. Shims are used under the spring to adjust fuel pressure, so you could try different thickness's till you get it down to spec.
Checking the flow rate will tell you if enough fuel is passing through the system. It should be 850ml in 30 seconds. Check it after the point where all the return lines join together before it returns to the tank.
Control pressure may change once you adjust your system pressure, but at the moment it sounds like cold pressure is good.
Here is a picture of the pressusre regulator on my fuel distributor, yours will be slightly different but similar.
http://forums.pelicanparts.com/uploa...1379878834.jpg