1976 2.7 with running issues ...

[Hil911]

Hi
My CIS 911 runs terribly. It's not bad at idle but as soon as I put my foot down it bucks, misses and backfires. I don't want to bore you with all the stuff that I have done but the injection has pretty much been covered. I even rebuilt the fuel distributor. I measured injector output and checked spray patterns and whatever.

Soo .... I have moved onto the ignition. New distributor cap, new leads, new rotor. Points are good. Distributor advances when you suck on the pipe or when you rev the engine. I wonder whether the timing flash is a bit irregular and weak. Maybe it jumps around a bit but I have nothing to compare it with.

I looked at the CDI unit and it seems OK, so I am wondering about the HT coil. Funnily enough I got stranded in Golden in British Columbia when the coil in my VW bus died ... anyway, I measured the resistances in the HT coil. The primary winding is about 0.4 to 0.5 Ohms which is probably OK, but I got 0.729 KOhm for the secondary winding, as I measured it with an ordinary multimeter. Does that sound like toast? Has anybody else had something similar?

Any suggestions will be gratefully received!

Cheers - Hil-Down-Under

[Hil911]

Well, I thought about this more as I lay awake in the night. I also saw a posting which made my coil resistances look normal, although another post showed much higher resistances for the secondary winding - 2.5 KOhm.

One thing that puzzled me is that the misfiring is much more sensitive to throttle position than to RPM. The ignition system has no idea what position the throttle is at, although the symptoms may be more obvious under load.

So, back with the CIS. I'm going to test the vacuum functioning of the WUR over the weekend.

Fingers crossed.

Hil

[Hil911]

Sorry - not strictly true above. There is the vacuum function on the distributor.

Hil

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[T77911S]

post the part number on the warm up reg (WUR).

there is a vacuum port on the WUR that goes to a thermo time valve (TTV) then to manifold vacuum. you may or may not have the TTV, but the vacuum line needs manifold vacuum.
if the TTV is bad or the WUR is not connected properly, it will run like crap.

idle will be good, steady speed driving will be good but acceleration will be like you say you have now.

[ossiblue]

Your symptoms are consistent with a lean condition which could be due to a faulty vacuum at the wur, as mentioned by T77911S, or from an out of adjustment wur. In your initial post, you did not mention the fuel pressures of your CIS. Too high pressure will result in the lean condition you describe. Just so we follow the most likely lead, please post your fuel pressures--system, cold controlled, warm controlled, and residual. If they check out, then the problem lies elsewhere.

[al lkosmal]

Checking the fuel pressure(s) as described by ossiblue, should be your next step. This check is one of the basics to gaining an understanding of how well your CIS system is working...and to helping pinpoint system issues.

regards,
al

[Hil911]

Sorry for my slow reply and many thanks for your suggestions.

I checked the control pressure to the fuel distributor and it starts fairly low and climbs as the engine warms, pretty much in line with the specs.

HOWEVER - the ignition distributor was onto the top port on the manifold (i.e. atmosphere) and the WUR was onto the lower one - the distributor port. AND looking at older posts and diagrams, my WUR was piped the wrong way so that ATM was to MAN and MAN was to ATM. Makes you wonder about the last garage that worked on the engine (out of the car).

I DO know that my system does not hold pressure, which may be partly due to a broken check valve, which I have ordered. I put a bicycle pump onto the inlet pipe and I can hear bubbling in the fuel tank. Not sure about the accumulator at the moment. However this shouldn't really cause poor running, I think.

I have made another discovery reflecting on the previous garage. When I got the car, I checked the timing using the marks they had painted/emphasised on the pulley. It was good. I have only recently realised that they had painted and used the WRONG marks! They used the 30/35 advance marks. So the engine was going to 70 degrees advanced at 4000 RPM. Not a recipe for a smooth-running engine.

Right now I am cleaning up the fuel distributor and will then try again. I'm pretty optimistic ...

Hil