Please help, I’m at my wits-end!
 

I recently completed an engine drop in my ’76 Carrera 3.0 to undertake some gearbox work and ever since, the car has been running appallingly.

The confusing thing is that car was running fine before the engine drop (albeit with some minor snatchiness and some barely perceptible bucking and surging), with the only additional work undertaken at the time being the replacement of the fuel lines.

The problem is that the car is now running very, very rich and any adjustments to the mixture (using the allen key adjustment screw) result in the engine running too lean. The car is experiencing bucking and surging, particularly through the 2,300 – 2,600 rpm rev range, but also pretty much anytime you are using anything less than about 80% throttle. It also pops and crackles quite a bit under trailing throttle and misses badly at about 5,500 rpm.

Now I’ve had the car to both a local specialist Porsche tuner and the local Porsche Center (both at great expense – over 8 hrs labour each), both of whom have been unable to diagnose or improve the performance of the car, but they have confirmed the following:

1. The CIS has no air leaks (pressure/smoke test).
2. All CIS ancillaries have been tested and are apparently ok (WUR, accumulator, etc)
3. Fuel pressure and delivery is spot-on for all cylinders.
4. The ignition system is in good condition, with the points, condenser, rotor button and cap are ok and new plugs have been fitted.
5. Ignition leads ok (only 3 yrs and 20,000 kms on them).
6. Timing is OK (but strangely the timing marker fluctuates a couple of degrees at idle when checked with a timing light).
7. Compression on all cylinders is within acceptable margins (10%)
8. A valve adjustment has been completed.

Another item of interest is that the car has two different camshafts fitted; one a Carrera 3 (930 105 148 10) and the other a late model SC (930 105 147 08). I have been told that these cams, although from different eras, are essentially the same and both have been correctly set with “1 ML lift on inlet valve @ TDC overlap” to quote the receipt from the specialist.

For my part, the only aspect I can think of is that possibly the air-metering valve in the CIS may be sticking, but everyone reckons they have checked the CIS and its all operating ok.

So some $1,600 later, I am reaching the limits of my patience (and budget) given that the issue is no closer to resolution. It is in complete desperation and much anticipation that I seek your assistance with this problem.

"2. All CIS ancillaries have been tested and are apparently ok (WUR, accumulator, etc)"

Have they checked to see if there is power to the WUR?

Is there any way two lines are crossed? Line to wur going somewhere else. You might want to check each line carefully. schamp

CIS can be a very frustrating system to troubleshoot and it can be very expensive to just start replacing parts. Since it ran OK before the engine drop and bad afterwards, I would concentrate on something that could have been re-connected wrong when putting the engine back in rather that a failed component.

You mention that fuel pressure and delivery is spot on, but have you checked control and system pressures and operation of the WUR?

Good luck.

Mike

on my 77, the vacuum to the WUR comes from the thermo time valve, check that 12v is applied to yours if u have one. after about 30sec of power, it should open allowing vacuum to lean out the mixture via the WUR. put a vacuum gauge on it and check for vacuum.
check all the elecrical connections to the cis.

Just a thought... You say timing varies at idle, you might take a look at your distributor and see that the shaft is not loose and that the flyweights are free.

I was thinking just what AZ1977911 has stated. My 76 2.7 was running exactly as you have described, and was running pretty well before I took it down for a month for an extensive tune up.

So, this past friday, I pulled the distributor, took it apart & cleaned, then re-assembled and replaced & regapped the points. The difference in performance was like night & day. No troubles throughout the RPM range.

If you pull the dist., check for vertical play in the gear shaft. I have read that there are bushings or shims that can be used to rebuild these. And be sure that you thoroughly clean the weights and they are free to move. Also clean & lube the advance plate.

this all worked for me! goodluck.

69911e and Schamp both mentioned this - the electrical plugs for the WUR and the Cold Start Valve are the same and can be easily mixed up. The result is that the Cold Start Valve has power all the time (runs very rich), and the WUR only has power when the key is in the start position. The Cold Start Valve is only supposed to get power during starting, and the WUR is supposed to get power all the time. Pull the WUR electrical plug (it's the easiest to get to) and see if it has power only when the key is in the start position - then you'll know that they are reversed.

Excellent feedback guys!

I'll start checking these items tonight, but it will probably be the weekend before I get a chance get to have a decent shot at them again. Both are very plausible solutions.

Once again thanks for your feedback.

Hi Sheldon,
just saw this thread. I guess that means you won't be running her at QR this weekend - bummer! Hope you get her running again soon.

I recently had a similar problem. At appropriate fuel mix the car was hesitating and surging although mine was in the 200 - 3000 range. The timing and all other components seemed to be spot on. When running the mix super rich the car was smooth but obviously something was amiss. The entire injection system was removed & tested. Six new injectors required along with various sleeves & seals. Still the problem persisted.

The fuel distributor was tested & seemed to be ok but when a distributor off another car was swapped on the problem vanished. The distributor was sent back to the tester ( a company in melbourne I believe) they still couldn't find a fault with it. It turned out that the 'flow rate' or whatever setting they tested it at didn't show any problems but once the unit was tested at a variety of rates it was found to be all over the place. So it was basically tossed & a new one slotted in.

It's now running perfectly with no surging snatching or anything of that nature. Interestingly going back through the receipts of the previous owners it's been an ongoing issue for about 10 years. We've finally cracked it :) , although the bill wasn't pretty.

Given yours was ok before the rebuild it's probably not a worn part like mine but it highlighted to me the problems with 'testing' or fault finding. Most places seem to test only at certain reference points which might not reveal everything that's going on. I racked up 6hrs in labour before the problem was isolated, although those 6 hrs did reveal other things that were fixed while we were in there. Good luck with it.

Gavin,

I'm up to 16 hrs of paid labour and probably as many unpaid so far. This time around!

You comments about the distributor and the fact the it had been an on-going, long term issue for you ring true with my car also. The PO had spent many $'s at the FI specialist too. I have had to run my car very rich in the past to mask the bucking and surging issue (mainly because another specialist told me this was 'normal' for a C3 - what cr*p), and because no-one seemed to eb abel to get rid of the problem totally.

I will see if I can get my hands on another distributor and see if that works too. Thanks

Lets hope it's easily & quickly solved. If it is the distributor try & see if you can get one rebuilt. I was lucky with the mechanic having the necessary bits & only having to purchase some. An entire distributor is pretty pricey if bought new. My experience with the unpaid labour has been close to yours. While the maintenance on these things is not inexpensive it's nice to see mechanics not charging for every minute & giving you a reasonable go. This is the third time that Bob Whymms have saved me a fair whack of money by going down an alternative path rather than just replacing everything in sight with new parts. A big thumbs up again for their work.

Ok guys, I've found two more symptoms:

1) The spark plugs in cylinders 1-2-3 are very sooty compared to those in 4-5-6 (refer photo below); and
2) Following on from suggestions from T77911S and 69911e I checked to see if there is power going to the WUR. Surprise, surpise, there does not appear to be aby power going to the WUR (engine was warm, almost running temp).

Questions:

1) Why is this affecting one bank and not the other?
2) Why would the WUR not be getting any power?

Any ideas?

Forgot the pic in my haste...

http://forums.pelicanparts.com/uploa...1163315001.jpg

Well look like a might have been a bit premature about the no current situation, just checked on a friends SC and got the same result.

I tried to see if there was current by disconnecting the cables to the WUR and the putting the multi-meter probe into the pin (on the cable connector) and the earth probe on the fan hosing, with both the ignition on and ignition off. Using both methods, there was no sign of power to the cablke on either car (both warm).

Is this the correct way to test the current on the WUR?

Weird that you have no power to WUR. I recall going over my CIS that there should be power when engine running, but I can not recall if I have measured it with the connector on an with the multimeter pins pushed in. I'll check tomorrow how I did it.

This said I would have also gone with the Distributor, giving the fact that he moves around, that is not normal, he should go to roughly 21 BTDC with vacum line attached but at Idle I have never seen it move.

Then I saw your next post and the spark plug on one side, that can not be induced by disitributor, he would affect all 6 randomly.

So I guess I would be going to the only item that can effect one row only and that is unfortunately the fuel distributor, which could correspond with your earlier comment on the allen key not accepting your inputs. Or by assembling you have accidently blocked the intake runners on one side.

Another thing that is weird is that emission testing comes back positive. I am using a LM-1 for datalogging and tuning of my CIS with RPM converter and in-equality of taht sort will definetely show up in the exhaust gasses and in the A/F ratio.

I too had an experience with P-mechanics charging me enough only to find that the car was still running as crap. I since then decided to invest my money in a LM-1 (250USD) and a fuel pressure measuring kit (75USD) a strobe light (80USD) and a multimeter (10USD). Thats all you need to troubleshoot CIS and ofcourse a lot of time...;o)

And should I forget this site http://members.rennlist.com/jimwms/CIS/CIShome.html

Good luck.

Michel

He He. It's me. Yes I registered again. When I saw you on today, I thought I'd try and help out some others.

It doesn't sound like you're getting any confident responses that address the problem. Maybe it's just a process of elimination. Try borrowing parts from others like me before spending too much more.

Cheers

Kent

Just joining in here. I don't know much (I guess I could consult the manuals I have), but should there be any power to the WUR when the car is.... warm? Seems to me I've seen here a couple of deals where one side was sooty. Have patience and a free bump.

Indeed not Milt. The power to WUR should be (or can be ) zero when the engine is on temperature as the Bi-metal strip in the WUR will have leaned teh fuel out thanks to heat radiated from the engine. But when stone cold he should have volt reading.

I do not believe the WUR interacts with only one side of the injector, I believe it interacts on the fuel quantity delivered especially when cold prior to the fuel distributor on top. As the WUR acts continuously also after warm-up I think it can not act on one side alone. Warm-up regulator is a bad name I think.

Michel

looking at the wiring diagram, power is applied to to the WUR, thermo time valve and aux air reg. from the fuel pump relay. the power should be there when the key is on. lack of power here will effect all plugs the same.so u may have 2 problems. i didnt see a thermo time valve on the 76 diagram that i have but there is one on my 77.
also, use a "test light" for trouble shooting power, it is much easier to use than a multimeter.
does the fuel dist. have screws beside each of the fuel line connections? if so, they adjust the amount of fuel to that injector.
you could have bad injector seals on 4-5-6 making them run leaner than 1-2-3.
check the fuel flow on injectors 1 and 4, should be equal.
u could even swap 2 or 4 fuel lines on the fuel dist, if they will reach, put in new plugs and see if the "bad plugs" move. the dist is very expensive, try everthing before u spend the money on one.

T77911S, the pressure for each line were apparently checked by both specialist tuners and were found to be good, although given some of the other aspects overlooked/incorrectly set maybe its worth checking again. I’ll have to check tonight to see if there are adjustment screws on the fuel distributor, but I can’t remember seeing them in the past (although I must admit, that without gauges etc, I’m reluctant to adjust anything on the FD). I’ll also re-check the fuel injector seals on the right-hand bank as well.

Swapping the fuel lines is interesting, as I put new ones on when had the engine out. Any chance of an air lock or something coming into play here?

Also, I have an option of buying a complete CIS system for around $200-300 and I am seriously considering buying one of these and just transferring bits and pieces on a one-by-one basis until the problem is resolved.

Given Milt's comments about the engine being warm when I tried to test the WUR for current, I had another go this afternoon with the engine stone cold.

The result was that with the ignition off, there was no current measured. With the ignition in the start position (could hear the fuel pump buzzing), I could only measure 0.1 volts! Now to measure this I was pushing the multi-meter probe hard into the connector as 'arrowed' in this picture:

http://forums.pelicanparts.com/uploa...1163412821.jpg

Also, why is there a spare 'male' connector on my CDI (photo below):

Oops, forgot the second photo:

http://forums.pelicanparts.com/uploa...1163413147.jpg

So goven that I seem to have another problem (left bank running richer than right), is it safe to assume there is something wrong with the WUR (no current) and that this is the reason why the car is running so rich (about 5-6% CO2 level)?

Check the flow rate of your fuel on your return line going to the gas tank. (Not the same as pressure or flow to injectors) That the problem reared it's head after fuel line replacement is suspect. Just because a fuel line is new doesn't mean it isn't be defective.

I had a similar experience once with my Benz. I had a fuel line replaced and shortly thereafter it started experiencing bucking and the motor dieing. I took it back to the shop and specifically mentioned that the problem occurred after the fuel line was replaced. They in their infinite wisdom chose to ignore this crucial piece of info and proceeded to start replacing parts at my expense without permission to no avail. When I asked if they had checked fuel pressure and flow rate they said no so I immediately told them to not touch the car anymore.

I had the car towed across town to a reputable shop. Problem turned out the new fuel line was defective. It had an obstruction.

I'm not saying this is your problem or for that matter your only problem because it seems like you have more than just one issue going on but it wouldn't hurt to verify flow rate from the fuel pump.

The WUR should be recieving current while the motor is running. On the earlier motors it recieves current as soon as the ignition is on but on later versions the motor has to be running for it to recieve current. (this prevents preheating the element by accident on cold mornings)

The connector shown in the picture for the WUR has one side that is ground the other side is the hot lead.

The WUR is basically a valve that bleeds off fuel pressure from the system as the motor warms up therby leaning out the fuel mixture to the proper warm running condition. It is not bank specific and has nothing to do with what could be causing the spark plug soot problem.

For the shop to confirm it's functioning should mean they checked pressure for cold and warm running conditions and confirmed it is working.

The fuel and electrical systems are not bank specific. That one bank of spark plugs is sooty and the other side clean makes me suspect cam timing. Is this a recent development or has this happened in the past?

In the picture of your CDI the extra terminal is redundant. Nothing to worry about there.

Start with fuel delivery and confirm that it is up to spec. Also check for fuel contamination.

Once fuel delivery is confirmed check spark. Each plug should be giving a good spark.

Keep in mind that if you find the initial source of your problem it will still take a while to get the idle readjusted since the mixture screw has been messed with.

bobby is correct, the WUR treats all cylinders the same. no voltage to the WUR will make it run rich. fix the power problem and see what youve got after that. i still think you may have an air leak on 4-5-6 or the injectors arent spraying enough fuel for what ever reason. the injector seals are easy to replace. i may have missed it, but what is the condition of the injectors..cleaned and check?
nice pics by the way

Sheldon,

Bobby has voiced a thought I had also... You are running two different camshafts; can you identify if the sooty bank is the SC cam rather than the C3? I'd be trying to ascertain that the two shafts are truly identical. Do you know if the timing of these cams is identical also? If you can satisfy yourself that the cams are "identical" then you may have to re-time them - in the abscence of carbies or ITB's, I reckon that is the only answer to one bank being different to another. (If you need the tools - I've got 'em)

Cheers

I've been assured that the cams should be identical and that they are at the correct timings. From memory, the plugs were ok in changes undertaken prior to this (except strangley plugs 3 &4 were showing some signs of running rich). If all elase fails (no leaks from injectors etc), I guess that I'll have to pull the cams out and have them analysed. Keep in mind though that the car was running essentially ok prior to the engine drop.

This weekend I'll conduct more tests on the WUR and look more closely at the wiring loom as it does show some signs of deterioration in several areas. I think there are two issues at hand, wiring and air leaks. Exactly why they have chosen this point in time to fail simultaneously is anyones guess.

Similar problems in my '73 - after a fortune in swapped parts, it turned out to be an inline (fuel) pressure regulator ($19). Check the fuel pressure to the CIS before you mortgage the house...

George

Sheldon

Time to drop back a bit and look at this.

First figure out if the changes for the worse were coincidence or a result of pulling your engine out and replacing the fuel line. Did you disconnect both fuel lines down by the transmission, or just one. If just one, I guess you couldn't have gotten them hooked up wrong. The fuel lines are tough to replace - sure no dirt got in when you were pulling it through? Fuel filter OK? And how about fuel delivery: disconnect the fuel line (maybe at the fuel filter?) and run the fuel pump, dumping the fuel into a container so you can measure flow. Time a few seconds or a minute's worth and measure the output and compute the rate. I don't recall fuel flow rates, but it ought to work out at least to say 69 to 80 liters/hour with no resistance involved as a pure guess. Someone will have a spec for this.

If this all checks out, it is unlikely that the fuel line was the problem. But you have a fuel problem.

Then recheck everything you had to disconnect in order to take the engine out. There aren't many of these, and I don't hold out much hope. But who knows - maybe somehow the 14 pin connector got messed up and that affects WUR current or something.

If all seems OK (you think it is now, I gather), and you don't think anything got dislodged or busted during the engine R&R, then put aside thoughts that the R&R was involved, as at that point it may be best to assume coincidence. Unless somehow in the process you got dirt into the fuel lines downstream from the fuel filter.

So now what. Well, you say it ran OK before, but then contradict that by saying the previous owner had had to fiddle with the fuel system, and maybe it didn't run all that well.

Now what? Well, does your spark distributor check out pretty well? Advance (and retard, if it has that too) work OK? Etc. Sure, that isn't apt to affect right vs left side, but so what - it could affect running generally. Always best to check the spark side of things before the fuel side.

Were those plugs new - replaced when you had the engine out? If not, why not put new plugs in to see if they quickly start looking like this batch?

Next, myself, I'd follow the suggestion of your mate and swap fuel distributors to see if something in there is causing the problem. If something went wrong in there it is almost impossible to fix. He says he had very similar symptoms.

Adjusting fuel distributors: there are adjustment screws next to each of the six fuel lines, but they each have a cap over them so they don't look like screw heads. And for good reason - most of us don't fuss with them as they set something mysterious called the differential pressure for each fuel line.

But there is a test you could perform yourself without instruments:

Get six baby bottles - clear glass (or plastic) with fluid graduations on the sides (or raid a chem lab). Pull all six fuel injectors. Stick each one in a bottle. Run the fuel pump and, with the air cleaner off, push up on the fuel metering plate. Then compare bottles to see if each one has about the same amount of fuel. If the right side ones that correspond with the really sooty plugs (and one of those left side ones doesn't look so hot) have a lot more, maybe you are onto something.

Of course, the two left plugs with white insulators might be running quite lean due to a problem with their fuel supply, and the overall fuel supply has been richened over time to try to compensate. You could try to adjust those two until their flow was the same as the others, I suppose. Adjustment involves pushing on a spring that pushes on a little diaphragm inside the fuel distributor. I understand that these diaphragms can go bad. If a hole developes, the one affected doesn't do its job. Most of us never fiddle with them (I never have, but a buddy once did to fine tune his fuel flow - said it didn't make a noticeable difference). Substituting a known good fuel distributor might be preferable to doing this.

The WUR should have +12V all the time the engine is running. When the engine is hot this is redundant, because conducted engine heat should keep the bimetal strip bent and doing its job increasing the control pressure. Without this current you will still have a rich mixture to start up with, but it will stay richer than it should longer until things heat up.

However, surely the shop tested the WUR and found that control pressures at cold-start and over the warmup period and for warm running were within normal limits?

If this CIS stuff is confusing, follow Michel's advice and look at Jim William's rennlist site: pictures, diagrams, explanations, Bosch troubleshooting chart.

I'd not worry about the "mismatched" cams. The SCs only had one cam grind, so the fact that you have one from the original motor and one replacement from a later motor (is that how you read things?) ought not to matter. (Though one might wonder why a cam had to be replaced at all.) Cam timing is easy to check, however, so if worried you should do that at some point to see if both cams are properly set. If one side is out some, it isn't all that hard to reset it - it can be done with the engine in the car, though with some effort, like removing the muffler and some sheet metal, and jacking the car way up from the rear to keep the oil in the case.

Bottom line - swapping in a known good fuel distributor may be the quickest way to get a handle on what is or is not causing the problems. After you are sure your spark distributor is working well - which you could also do as a swap job if you have someone nearby who can lend you his. And you did do the "glow in the dark" plug wire test, right? But a fuel distributor fault sounds to me like the thing that would be hardest for a shop to find. And maybe just sitting around while the transmission was being worked on was just the amount of time needed for something to corrode in there.

All this is easy for a guy like me to say - I do my own work, own the CIS pressure tester (and ought to own an exhaust gas tester), and so on.

Walt Fricke

the lack of power to the WUR may be amplifing a problem you had all along, so fix that first.
i asked about the screws on top of the fuel dist. thinking maybe somebody turned them not knowing what they are doing, if u do have them, dont mess with them.
u said u replaced fuel lines to the injectors, lets go back and look there. i cant see 3 bad fuel lines, but u never know.
swap 2 of the lines on top of the FD or u can swap the left side injectors for the right side.
u dont need to pull the cams to check them, just put a dial gauge on them. if u havent done it before, just make sure u understand how to read the dial gauge, mine were set up 15* advanced because somebody read the dial gauge backwords. ( the needle moves in a CCW direction as the valve starts to open so u have to read the small numbers that go in a CCW direction)

Okay. When you drop the engine, you disturb two things - hoses and wiring. Sounds like you have a wiring problem with the WUR - hot wire 12V to that right away, and see if that changes anything. The WUR works all of the time - it's not really a "warm-up regulator."

The other thing is the most basic element of these systems - vacuum leaks. Spray some carb cleaner around the hoses, and the injector ports, and see if the engine idle increases even slightly. If yes, you have a vacuum leak, and that could be the cause of your problems...

-Wayne

check the connector to the relay board, u may have put it on 2 pins off, remove it and reconnect it

Thanks for the feedback evryone, this why this board is as good as it is.

I will systematically undertake checks of all the items listed here over the next week or so (unfortunately my schedule is very tight for the next few weeks), but I will keep you all posted on how I go.

Thanks again everyone, particulalry T77911S and Walt Fricke for their very detailed an considered responses.

IS this the cause of my CIS Issues??
 

Hi guys,

Well I went and pulled the CIS out of my car this weekend in readiness for sending the fuel distributor away to be rebuilt. Guess what else I found whilst pulling things apart!? A CRACKED AIRBOX and no gasket between the FD housing and the airbox! Have a look at these photos:

Underneath the airbox near the inlet manifolds:
http://forums.pelicanparts.com/uploa...1165036957.jpg [img]

Same again:
http://forums.pelicanparts.com/uploa...1165036973.jpg[/img]

And again. This one opened up quite a bit with just a little pressure:
http://forums.pelicanparts.com/uploa...1165036995.jpg

And again:
http://forums.pelicanparts.com/uploa...1165037015.jpg

I can't believe this, no gasket betwen the airbox and FD alloy housing!
http://forums.pelicanparts.com/uploa...1165037034.jpg

I know these couldn't have happened just because I pulled the engine out (unless the airbox took a big hit - which it didn't to my knowledge), but they must be contributing significantly to my problems. I still think that I should send the FD away to be tested and more than likely rebuilt.

What are you thoughts guys?

It's hard to tell from the photos but if your airbox is cracked then that's obviously not a good thing. I guess it's possible that it could have cracked when R+Ring the motor.

What's a little more common though is splitting the rubber boot that goes from the throttle body to the air meter on top of the motor. It's in a very handy spot for grabbing a hold of when your trying to get the motor back in the car. They get old and less pliable with age and tend to split when you try to use them for a handle.

How did you arrive at needing to send out the fuel dizzy. Was the system pressure off? Were the pressures to the injectors off?

fix what u know is broken first, then see what works and does not work.

The cracked airbox needs to be fixed first. That will solve the majority of your problem.

How could a reputable shop not catch a cracked box like that? I would want some answers and maybe credit back some labor. Hope a new box and WUR with power will be your fix.

Good find on the cracks.
Wait with rebuilding the FD until you have a new airbox and gasket.
Check the rubber boots for the intake runners and replace if necessary.
Check the gaskets between runners and heads.
With a new airbox, readjust the mixture and confirm that the WUR and AAR get power.
Don't mix up the connections for Cold Start Valve, Warm Up Regulator, Airflow Sensor Switch, Auxillary Air Regular.