Engine Red-lines on Start-up

[piscator]

Mike,

Thanks for your kind sympathy and photo offer. The woodruff key disappearance happened months ago. I replaced it before putting the engine back in the car. I’m probably being over-cautious, but after all the work that’s been done, every odd noise is making my hair standing on end! As you say, losing a part like that can be tough on the nerves!

I haven’t installed my new compressor yet, so I don’t think the A/C is playing a part in this case. Thanks for the tip though!

[piscator]

Tony,

Good point! I’ll do the flow test tomorrow and report back.

This evening, I’ve been reading the K-Jetronic Workshop Service Manual that’s available over on Rennlist. It really is fascinating how these systems were engineered! I found the section concerning the flow test and the shims.

I did not remove the primary pressure valve on the fuel distributor. I took the CIS off the engine at the intake runners, but didn’t disassemble anything, except to change fuel lines. I took the CIS off to clean the engine and check out the devil’s triangle under the shroud. The CIS went back on the engine, exactly as it came off – well, to the best of my ability, anyway.

I dropped the engine to refresh the suspension rubber and the project grew from there. But there was no engine rebuild or work done, other than installing the SSI’s and adjusting the valves; with a dial gauge and my fancy new Stomski jig.

Thanks so much for your help!

[piscator]

Tony,

That was smart of you to suggest the Flow Test!

The Porsch K-Jetronic Workshop Manual states the specification as: “minimum 1000cc in 30 seconds.” I did the test 3 times and got almost twice that: 1800 cc in 30 seconds. Well above the specification.

This made me suspicious of the pressure data that I posted, which was, in fact wrong! I tested my gauge against two others I had in the shop and discovered that my gauge was faulty. I replaced it and retested for System Pressure – 3 times.

I got System Pressures of 68 psi every time. The specification for System Pressure is 65 – 75 psi. So, it seems I don’t need the new fuel pump!

I’ll do the diagnostics the manual recommends under “Irregular Idle” but I really need to determine whether to start the engine and confront the tapping noise. I ordered the gaskets for the crankcase cover and will pull that down when they arrive.

Thanks again for your help and please jump in with any new ideas!

[boyt911sc]

Robert,

Your post #17 is misleading. The 42 psi. is not the system fuel pressure but the warm control pressure. Was this with the valve closed or opened? I would say it was opened. Based from your flow rate, your fuel pump is good contrary to what some people claimed.

Tony

[patkeefe]

Can you measure the cold control pressure with the apparatus you have? Are there any more vacuum leaks?

My guess is the tapping noise is nothing to be overly concerned about. Doubtful it is the Woodruff key. Maybe a loose valve adjuster?

[piscator]

Good Morning Tony and Pat,

Pat, I think you may be right about the tapping. It's like a consistent 1/8th note beat. Maybe I'm being too overcautious. Still, the gaskets for the oil sump arrived, so I'll drip that and see what I find. I even have a bore-scope on the way, but I'm not sure I'll know how to use it.

Tony, I’m sorry for that misleading post! You’re probably right, it’s very possible I left the valve open. Still, for whatever reason, that gauge is not consistent with the others and no longer comes down to zero. So it needed retirement, in any case.

Before anything else, allow me to ask if you, Pat, or anyone, can explain what the K-Jetronic Workshop Manual means when it states:

“...Bridge the safety circuit (see Electric Wiring Diagram) ...”

The manual says we need to bridge this circuit to do the warm and cold Control Pressure test, but this has me stumped because:

On the Electric Wiring Diagram (attached below) it reads:

“911, 911S, 911SC .(since 1976) Bridging the electric safety circuit . The electric safety circuit can be bridged by disconnecting the air flow sensor plug or by bridging terminals 30 and 87a with a fused (8 amp) jumper wire “

What’s confusing me is that the diagram shows terminals 30 and 87a on component “R” – which it calls “R = Thermotime Switch”. My Thermotime Switch has two terminals and doesn’t look anything like that!

The diagram also shows component “D” – which it calls “D = Electronic Relay”. This is where I’d expect to find terminals 30 and 87a, but the terminals on component D are numbered 1 – 5.

Am I reading this wrong or is there an error here? Does “Bridge the safety circuit” really mean “jump the fuel pump relay” or is it something else? Since I couldn’t figure this out, I proceeded without knowing whether my safety circuit is bridged or unbridged! :-)

Cold Control Pressure: following the Workshop Manual, I did the cold control pressure test –

Engine cold and not running
Power cable DISCONNECTED at the WUR/FPR
Gauge connected between the WUR/FPR and the center fitting on Fuel Distributor,
Valve at the pressue gauge, OPEN.

I did the test 3 times and found the results kinda surprising.

Result: 18 – 19 psi !!

I just don’t see how that’s possible. This engine ran beautifully before the drop and NOTHING has been changed! It seems awfully strange that the WUR/FPR worked flawlessly for 40 years and decided to quit while sitting out of the car for 8 months! Maybe I really do need to ‘bridge my safety circuit?’

Warm Control Pressure:

Engine cold and not running
Power cable CONNECTED at the WUR/FPR
Gauge connected between the WUR/FPR and the center fitting on Fuel Distributor,
Valve on the gauge, OPEN.

Result: 31 psi

AFTER, the warm test I checked the voltage at the cable to the WUR/FPR and got 11.96 V

I know this is too low, but how the heck do you get 14+ volts out of a 12 volt battery? I realize that they charge to a higher voltage, but I don’t think my battery is ever above 14 v consistently. Spurious current draws and minor flaws in the system knock that down to low thirteens.

I’m going to do the test again and try to supply the WUR/FPR with 14v.

Tony, before I sign off, let me thank you for your tremendous contribution to all of us! I spent a lot of time yesterday reading archived threads on CIS, Adjustable WURs, etc. Your comments were always clear, helpful, and intelligent. I learned a lot! Thanks!

All additional comments here are most welcome!

[pmax]

Pisca,
Yes, "bridging the safety circuit" means bypass at the fuel pump relay, refer to the Bentley, there's a pic. The fuel pump needs to be running for the cold/warm pressure tests. Use a fuse in the bypass just in case and when you're done, keep it in your glove box.

Sorry, can't find a good pic...

By the way, this thread has some great info CIS Troubleshooting for Dummies

... and if you don't have the Bentley, get one. Mine is used to shreds.

[timmy2]

11.96 volts at the WUR is normal, don’t worry about the 14 volts.

[piscator]

Hi Pmax,

Thanks much for that! I had a feeling that's what it meant. It seems odd that Porsche would make that kind of mistake in a service manual diagram -- mis-labeling BOTH the "D = Electronic Relay" AND "R = Thermotime Switch" !!

I'm enjoying learning more about the CIS and will check out the thread!

Timmy,

Thanks for the voltage information! I plan to re-check it, just to make sure my readings were correct and to see if it stays consistent.

So it seems that I did "Bridge My Safety Circuit" correctly. If that's so, then my cold and warm Control Pressures are way too low. It still befuddles me as to how that could happen with the engine just sitting here in the workshop!?!?

Hopefully, Tony will come by to provide his insights! And maybe an offer to fix my WUR?!?

[boyt911sc]

Originally Posted by piscator

Hi Pmax,

Thanks much for that! I had a feeling that's what it meant. It seems odd that Porsche would make that kind of mistake in a service manual diagram -- mis-labeling BOTH the "D = Electronic Relay" AND "R = Thermotime Switch" !!

I'm enjoying learning more about the CIS and will check out the thread!

Timmy,

Thanks for the voltage information! I plan to re-check it, just to make sure my readings were correct and to see if it stays consistent.

So it seems that I did "Bridge My Safety Circuit" correctly. If that's so, then my cold and warm Control Pressures are way too low. It still befuddles me as to how that could happen with the engine just sitting here in the workshop!?!?

Hopefully, Tony will come by to provide his insights! And maybe an offer to fix my WUR?!?

Robert,

I saw your post earlier with the factory diagrams and noticed the mistake. I wanted to call your attention to this blunder but my wife was calling to have lunch. And after lunch, saw you have discovered the blunder and that is good.

I will give you another advise when doing this type of electrical troubleshooting. Use a 12-volt test light to test for continuity, voltage, or ground. It makes the testing easy and simple.

If you need assistance in evaluating your WUR send it to me and will do it for FREE. Just take care of the shipping and insurance costs. BTW, what are the last 3 digits (0 438 140 xxx) on your WUR? Thanks.

Tony

[patkeefe]

Robert, I think the "safety circuit" is the airflow switch. So, if the car doesn't see airflow (ie, engine not running with the key on after it has been running, the switch will shut off the fuel pumps. I think it is the 85 circuit on the fuel pump relay.

[boyt911sc]

Originally Posted by piscator

Good Morning Tony and Pat,

Pat, I think you may be right about the tapping. It's like a consistent 1/8th note beat. Maybe I'm being too overcautious. Still, the gaskets for the oil sump arrived, so I'll drip that and see what I find. I even have a bore-scope on the way, but I'm not sure I'll know how to use it.

Tony, I’m sorry for that misleading post! You’re probably right, it’s very possible I left the valve open. Still, for whatever reason, that gauge is not consistent with the others and no longer comes down to zero. So it needed retirement, in any case.

Before anything else, allow me to ask if you, Pat, or anyone, can explain what the K-Jetronic Workshop Manual means when it states:

“...Bridge the safety circuit (see Electric Wiring Diagram) ...”

The manual says we need to bridge this circuit to do the warm and cold Control Pressure test, but this has me stumped because:

On the Electric Wiring Diagram (attached below) it reads:

”911, 911S, 911SC .(since 1976) Bridging the electric safety circuit . The electric safety circuit can be bridged by disconnecting the air flow sensor plug or by bridging terminals 30 and 87a with a fused (8 amp) jumper wire”.


(Edited)........

Robert,

Read the highlighted sentences above “Bridging the electric safety circuit”. This should be expressed as “By-passing the electric safety circuit”.

“The electric circuit can be bridged by disconnecting the air flow sensor plug.......” the word “bridged” is erroneous and should be replaced by “by-passed”.

Let’s reconstruct the sentences and insert the correct translation:

911, 911S, 911SC (since 1976). By-passing the electric safety circuit. The electric circuit can be by-passed by disconnecting the air flow plug or by bridging terminals 30 and 87a with fused (8 amp) jumper wire.

Most of the mistakes you will find in the original factory manuals or technical bulletins were caused by German translation to English. Majority of the readers will not find the errors unless the reader/s has a good understanding of subject. Re-read the re-constructed format and compare it from the original version. Which do you think makes sense?

Tony

[piscator]

Good Morning Gentlemen,

Greetings Pat!

I’m sure you’re right that it’s the air-flow switch. I’m learning a lot about this stuff! The link Pmax offered is an excellent tutorial. So is film he posted.

Tony,

Thanks for your generous offer! Before I take you up on that, I’m going to re-do the control pressure tests today, just to double-check that I didn’t do something in error (always the first likelihood).

The Cold Control Pressure @ 18 psi and the Warm Control Pressure @ 31 just baffles me. I find it too strange that the WUR should fail while sitting in my shop, on the engine, idle, for 8 months. Any thoughts on that?

“911, 911S, 911SC (since 1976). By-passing the electric safety circuit. The electric circuit can be by-passed by disconnecting the air flow plug or by bridging terminals 30 and 87a with fused (8 amp) jumper wire.

No question! Your rewording is far better! Your version clears up the confusion as to what gets ‘bridged.’ That’s where I got stuck, thinking there might be another terminal 30 and 87z on some relay or component I didn’t know about.

WARNING: Abstruse pedagogy ahead, proceed at your own risk!

I suspected that the error might be in the translation to English, but it seemed odd that the translator would use the term bridging in three locations, if it hadn’t been phrased that way in the German.

Just to be pedantic about it, I turned to GoogleTranslate to find that the German for “bridging” is “Uberbruckung.” In German the word emphasizes ‘getting over’ or ‘getting around’ something. It appears to be synonymous with the English word “reconciliation.” Understood in that manner Uberbruckung seems to carry the connotation of your English word choice “by-passing.”

In English, the word “Bridging” certainly implies ‘getting over’ – but the stronger connotation, I think, is the sense of ‘connection.’ We use “bridge” to mean ‘connect one side to the other.’ The word’s connotation of ‘getting over’ seems a secondary meaning.

So the translator might have, correctly, chosen ‘bridge, bridging’ to represent “uberbruckung” – not knowing that, in English, it would lose it’s sense of ‘getting around’ or ‘getting over.’

What, to me, seems more egregious is the mislabeling of the components in the diagram. “R = Thermo-time Switch” and “D = Relay” are not terms requiring subtle translation. The German “Electrisches Relais” is correctly translated as “Electronic Relay” but it’s mislabeled component “D” when it should be component “R.”

If component “R” had been correctly labeled as “Electrisches Relais” in the original German document, it’s hard to imagine that the translator chose “Thermo-time switch” as the best English equivalent; simply by looking it up in his German/English dictionary! It’s more likely it was mislabeled in the original German document as “Thermo-Zeitschaltuhr.“

Isn‘t this fun?! Of course, it’s all conjecture on my part. I’m not a language scholar and I don’t speak German. If one our German speaking Pelicans finds himself bereft of absolutely anything more useful to do, maybe they’ll clarify some of this. ;-)

O.K. Time to go re-check the control pressures. I’ll report back later.

As always, thanks for the help!

[patkeefe]

Robert
Lower control pressure when warm is a good sign Your engine may have always operated at this control pressure and you may not know it. I believe there is a control pressure chart in the Bentley manual that you can refer to.
On my last iteration of K-Jettonic, I had nothing but a warm-up regulator and an auxiliary air valve. All the other crap was gone by this time.
I tend not to look at the translations rather I just read the wiring diagram.
Tony is pretty sharp with the CIS stuff

[piscator]

Pat, I was an English major, so I look at the language first! ;-)

BTW: The Control Pressure tests in the Bentley are done with a running engine. The test in the Porsche K-Jetronic Workshop Manual is done with the engine off. The manual also states that engine temp is “not important.”

Tony,

I installed a new battery in the car and re-tested the fuel pressures. No significant changes.

System Presssure (specification is 65 – 75 psi): My reading = 68 psi
Cold Control Pressure: (temperature 27 C, so specification is 25 – 30 psi): My reading 20 psi
Warm Control Pressure: (specification after 3 – 5 minutes, 39 – 46 psi): My reading 32 psi

New battery static voltage just under 13 v
Voltage to the WUR = 10.96

Should I conclude from this that the WUR needs adjustment or is there something else to check?

Lastly, IF a new fuel pump delivered 75 psi how would that effect the cold and warm Control Pressures?

Oh, and I forgot to answer your question, my WUR is a 045.

Hope you're enjoying the weekend!

[boyt911sc]

Originally Posted by piscator

Pat, I was an English major, so I look at the language first! ;-)

BTW: The Control Pressure tests in the Bentley are done with a running engine. The test in the Porsche K-Jetronic Workshop Manual is done with the engine off. The manual also states that engine temp is “not important.”

Tony,

I installed a new battery in the car and re-tested the fuel pressures. No significant changes.

System Presssure (specification is 65 – 75 psi): My reading = 68 psi
Cold Control Pressure: (temperature 27 C, so specification is 25 – 30 psi): My reading 20 psi
Warm Control Pressure: (specification after 3 – 5 minutes, 39 – 46 psi): My reading 32 psi

New battery static voltage just under 13 v
Voltage to the WUR = 10.96

Should I conclude from this that the WUR needs adjustment or is there something else to check?

Lastly, IF a new fuel pump delivered 75 psi how would that effect the cold and warm Control Pressures?

Oh, and I forgot to answer your question, my WUR is a 045.

Hope you're enjoying the weekend!

Robert,

Based from the fuel pressure data you have collected, here are my comments:

System fuel pressure within spec. but on the low side. Set it to 70~72 psi.
Warm control fuel pressure is too low @ 32 psi. Set it @ 42 psi. (Without vacuum)
Cold control fuel pressure @ 27°F (33~39) psi. Not (25-30) psi. Yours @ 20 psi is too low.

What is your WCP (with vacuum)?

What CIS problems are you experiencing now? Unless you install a good working WUR-045 the engine will never run well. I could lend you a WUR-045 that you could use and try in your motor. Send the WUR back to me after the tests. You would have the chance to see the difference how a good WUR performs compared to yours.

Lastly, a 10% increase in system pressure (68 psi. to 75 psi.) will have a very small effect on the control fuel pressures. Try it to satisfy your curiosity.

Tony

[pmax]

Originally Posted by piscator

The link Pmax offered is an excellent tutorial. So is film he posted.

Glad to know those were useful. The link to the film is courtesy of our turbo powaa' friend, Raw' !

WARNING: Abstruse pedagogy ahead, proceed at your own risk!
...
What, to me, seems more egregious is the mislabeling of the components in the diagram. “R = Thermo-time Switch” and “D = Relay” are not terms requiring subtle translation. The German “Electrisches Relais” is correctly translated as “Electronic Relay” but it’s mislabeled component “D” when it should be component “R.”

Fun read. English major did you say ? Typos, mislabeling are not unheard of. Confirming w/a Pelican search is advisable and a practice I adhere to. The CIS well is deep here and goes back more than a decade.

BTW the 045 WUR has a vacuum port which adjusts the CP. You can use a hand vacuum pump to test it.

[piscator]

Good Morning Tony & Pmax

Tony,

Thanks so much for your assessment! I may take you up on the loaner WUR! I'll send you a PM after I’m finished futzing around with this one..

The CIS problem I had with the engine running, was that the RPMs would climb to about 4,000 and then dive to about 1,000 RPMs -- climb and dive, climb and dive, climb and dive – six to ten times – and then stall out. Operating the throttle I could keep the engine running, but that didn’t stop the fluctuation. Releasing the throttle, the engine would do it’s up and down ‘death dance’ and finally cut out.

I don’t have a warm control pressure with vacuum, because I haven't run the engine since I started hearing the tapping sound. I do have a hand vacuum pump, so I’ll try Pmax’s suggestion and test with vacuum this afternoon.

When I heard the rhythmic tapping sound at the right rear of the engine, I shut it down and started panicking over the possibility that I’d just found my lost woodruff key!

As you suggested, I dropped the sump and started exploring with my just-purchased bore-scope. Exploring the crankcase, what I can see of the timing chain, and running the scope into the accessible oil return tubes – I haven’t found my woodruff key, or any obvious damage.

I’ve attached some photos taken with the Endo-scope, but they’re not very good, mostly because I don’t know what I’m doing! I don’t know whether to take the valve covers off and continue exploring with the scope – or should I call it a day, regarding my lost woodruff key??!!

Pmax,

The film was especially helpful, so thanks also to ‘powah Rawk!’

And thanks for the vacuum tip, I’m going to try that.

Glad you enjoyed the abstruseness! English major, yup. Two majors actually, graduated with honors in history. Lifelong student, which means I just haven’t grown up! :-)

Thanks to all!

[boyt911sc]

Robert,

You don’t need a running motor to do the tests. All you need is to test run the FP with the pressure gauge hooked up and a hand held vacuum pump. This is pretty common and basic procedure for CIS troubleshooting method. I am surprised you don’t know this one.

Tony

[piscator]

Hi Tony,

I'm still learning! I'm most familiar with the tests in the Bentley book, which are done with the engine running. The hand-held vacuum test that Pmax suggested is in the Porsche/Bosch Workshop Manual that I downloaded from Rennlist, just last week. I didn't know about it before that.

I'm going down to the shop to do that test now.

Any comments on my lousy photos or whether I should start the engine again?