CIS no start ad nauseum

patkeefe · 03-07-2006, 07:26 AM

78 SC CIS. Won't start. CIS pressures are good. I have a weak-ish spark, but I get no signal pulse from 7 to 31d on the CDI connector. I have battery voltage at 15.

Could the pulse generator be ok, judging from the spark, even though I detect no AC pulse signal on my meter? May be response of the meter doesn't allow the pulse to show. Also, tach moves OK when cranking.

Or, should I just rip it all out in a fit of anger, and put an MSD unit in?

Pat

patkeefe · 03-07-2006, 10:48 AM

Amazing what you can find when you take the old air pump bracket off. Like, the wires to the thermo time switch being fried and fused together, and the cable connector for the coax cable being overheated and falling apart. Now, to check the continuity on the coax cable...

patkeefe · 03-07-2006, 03:19 PM

After checking everything, I pulled off the new plus wires, and put on some old one's from my 2.4, and the car started. But I still have CIS issues.

System pressure is good at 70 PSI. My control pressure is 30 PSI, and, will not go up any when the engine warms up. Pressure bleed down is within reasonable limits. I am using the procedures outlined by Jim Williams in his very insightful CIS Primer. I have read every freaking post on CIS on this board (well, almost). This is not the usual failure mode of the warm up regulator.

The car hunts at idle until it gets warmed up really well, and still hunts a bit then. The car has always run rich. I can't find any vacuum leaks. I'm going to try and clean out the WUR and see if its blocked up or something. I hate to randomly change parts.

I love how Bentley says "change it with a known good one", like I have a basketful of 1978 SC Bosch warmup regulators lying around.

Pat

patkeefe · 03-07-2006, 05:55 PM

OK, the light is going on now. The warmup regulator has low control pressure, and stays low, because the electric signal to it is non-existant. I think it comes from the AAR, which makes sense, but the Bentley wiring diagram shows the system for a closed loop, and not the early SC open loop.

So, by having continual low pressure, the car always thinks its cold, and tries to richen, and never leans out on its own. I figured maybe the WUR had some sort of clog in it, and took it apart. The fuel passage was a bit clogged. I cleaned it out with carb cleaner and blew it out in the reverse flow direction with 30 PSI compressed air (the fuel passage). The WUR is an amazingly simple device, considering a new one costs $501.00. I'll bet it takes about 20 minutes to rebuild it, providing one has the parts. I could also make mine adjustable, which would make life easier.

So, now I have 45 PSI control pressure, which is too high at start up cold; borderline at 65 degres F per my charts. Maybe I can figure out where the power comes from for the WUR resistors, and get that working, and get the control pressures straightened out. I suspect the AAR has something to do with the problems. The decel valve is not working either.

Need to get the CIS fixed up, so I can get the turbo put on. Otherwise, I will never get it running right.

craigster59 · craigster59's Garage

Do you always talk to yourself like this working on the car? Been there with the CIS issues, just wanted to lend moral support and stick a different avatar on the thread.

ianc · 03-07-2006, 07:16 PM

Definitely take the time to make the WUR adjustable. I found that I needed to adjust mine in the winter to keep things running smoothly. It is a very simple device.

Post more detailed descriptions of the problems you're running into, and you'll get plenty of help,

ianc

jeff m · 03-07-2006, 08:29 PM

Well I have MFI, so I'm no CIS expert, but if you have always run a little rich and you haven't cleaned your Aux Air device then I would check it. It should be open when cold and closed when hot. These things get a lot dirtier than the WUR. It allows more air flow and thus more gas until things heat up.

Paulporsche · 03-08-2006, 03:54 AM

So what are your symptoms now that your cold cp is high?

patkeefe · 03-08-2006, 04:05 AM

Paul:
I did not have it running after I did the WUR thing. I need to find the voltage for the WUR first, and look at the air bypass. And, I have to go to work today (bummer). And, PCA meeting tonight (gotta get the DE forms in!).

I'm going to guess it may be too lean to run cold. I might take the WUR out first and revisit the inside of it, to see why I made the pressure go up so much.

The CIS is preetty amazing, in that it still remains functional even with so many components screwed up.

Paulporsche · 03-08-2006, 04:21 AM

You seem to be going about this the right way. If you get the ccp down to the correct level, the engine will probably start. You may have to revise your mixture setting. Checking the elec will help to get the WUR warmed up, although this will happen somewhat from the engine heat. See if your cold idle speed is up, which will tell you about the AAR. Many posters plug the decel valve line, whether working or not. Let us know what happens.

Ron.G · 03-08-2006, 04:32 AM

I beleave the power to the WUR comes from the starter circuit (right on the starter) . You will not have voltage with just the key in the on position. You need the crank the engine over and then test for voltage.

I learned this from the PP board at some point or another.

patkeefe · 03-08-2006, 04:39 AM

Paul
Yup, when I bought the car the decel line was plugged.

Ron G:
Thanks! I'll check that right now before I leave for work.

patkeefe · 03-08-2006, 06:06 AM

I brought my remote stater out to the garage before work (she was a bit put out by this, LOL) Voltage appeared while it was cranking, just as Ron G said. The car started immediately, but stalled. After three or four tries, it ran ok. Cold control pressure was 40 PSI. I plugged in the wires, and control pressure went up to 65 PSI. No hunting was evident at all in the idle. A miracle!!

Now, whatever I did to the WUR has got it functioning as it is supposed to, but I sort of overshot the runway on the pressures. I'll take it apart as soon as I get a minute, and see what I did to cause the elevation in pressures. Maybe the little springs aren't seated correctly for the plunger. Then, it will be off to the AAR and the decel valve. And, I'll have to get a CO meter so I can get the mix set.

Does the rich/lean 3mm Allen screw in the fuel distributor effect the control pressure? I'll need to research this.

Pat

Gunter · Gunter's Garage

I cannot see how the 3mm Allen screw would affect control pressure.
To check the AAR, when cold, disconnect the air hose, use a small mirror and a light, look into the AAR and check for the halve-moon-shaped opening. With power applied to the AAR, this opening closes completely. Do you have power to the AAR when starting/running?
The special connector has a small wire clip which needs to be undone carefully with a very small srew driver/picking tool.
I have an extra connector to supply 12V to either WUR, or AAR, to make sure that the heater element works. If all is well, you can actually feel them warming up.
With engine running, I always thought that there is a constant 12V to the WUR. Am I wrong???

patkeefe · 03-08-2006, 07:51 AM

Yes, it looks like the 12V is continuous, AFTER the starter has been engaged. Just switching on the ignition provides 0v, as I found out last night.

I didn't know if the fuel enrichment adjustment (the 3mm allen screw) is in the circuit before or after the WUR. My guess is after, hence, probably does not have any influence on control pressure. I need to study the diagrams some more.

Huh · 03-08-2006, 08:35 AM

The 3mm allen screw only affects the slit size. That is not even in the circuit. Now the rise in pressure you talked about was probably from plugging in the wires. The wires send electricity to the bimetal arm in the control pressure regulator (WUR). I read the Bosche fuel injection and engine management book for the 3rd time recently. It is a good book to have. The WUR only is used during cold starts once warm the plate lift and plunger determines mixture. Now your lambda sensor and valve is used to determine mixture once warm. I think we have a compensation for WOT on our WUR that used manifold pressure to increase mixture.

Paulporsche · 03-08-2006, 02:56 PM

I don't think you overshot your control pressures at all. Your ccp should be 1.6 to 2.15 bar. That's about 23.5 to 31.6 psi @ up tp 10C (about 50F). You may have to knock the plug in a little to get that pressure down a little bit.

911quest · 03-08-2006, 03:53 PM

You said it would start and die have you checked the check valve on the fuel pump how about residual pressure over night?

patkeefe · 03-08-2006, 06:58 PM

The pressures I recorded last night indicated to me that I had 40 PSI cold control pressure. My WUR was at 65 deg F, according to my infrared temp gun. That seemed to put me at the upper limit, or a bit over, on cold pressure.

The residual pressure dropped off in accordance with the published values I have in the Bentley book, and the Jim Williams CIS Primer, so I don't see any issues there.

Paul, I found an old thread on building an adjustable WUR, which looks pretty simple. I like the idea of setting the cold pressure, as long as I can maintain the differential between cold and warm control pressures.

Tomorrow I can tweak this a bit, and get around to the air valve, AAR and the decel valve. Looks a bit cramped on that side, but I still have two fingers which have not bled in the past few days.

I appreciate everyones input on this.

Pat

Paulporsche · 03-09-2006, 08:46 AM

@ 65F your ccp should be between about 28 and 35 psi so you are just a little high. A simple knocking of the plug should bring it down. The relationship between hot and cold pressures remains the same no matter what the cold is set at. You can adjust it via a screw @ the bottom but usually this is not necessary.