CIS Troubleshooting for Dummies

[Porschedave]

Hi

Thank you for that clarification. It seems to me. then, that my WUR has an issue. The current situation arose as I drove home from a DE day. The car ran fine all day. On the drive home, as I was on I5 there were a couple of large backfires that I associated with taking my foot off the gas. I stopped at a rest place and the car barely idled. However, back on the I5 at 3200 rpm the engine ran fine. I checked timing and the usual culprits but all looked good. I measured my pressures and found the system pressure was 4.7, the cold control pressure was 2 at 20 degrees C and the warm control pressure rose to 3.4 after about 2 minutes. However, the engine continues to backfire and run rough. I guess my question, then, is whether this resistance issue has made the engine run too lean and hence the backfire and idle issues. And I see at Pelican that you cannot purchase a new WUR so what are my options? Oh, and this is an 090 WUR from a stock '83 engine.
Thanks for helping.

Dave

[tirwin]

Dave,

I doubt the WUR is your culprit. The fuel pressures look ok. The resistance would only be an issue for the first few minutes of startup.

[Festive_Zombie]

Sounds like a vaccum leak? Did something loosen up during your DE?

[Porschedave]

Hi All

I sorted out the problem with my engine. It was indeed a vacuum leak. One of the rubber boots between the intake runners and the air box cracked. I replaced all of them and of course it was the most difficult and the last one to come out. The car runs great and I'm back at the DE events. Great times. Thanks to all who responded.

Dave

[Charles Freeborn]

Can I join the party here?

My '74 has run like a champ - and still does when warm - but is beginning to get crabby on cold starts - popping and bucking and so on until it's run for 30 or so seconds. I've begun to take it to DE events, so it's time to get serious about tuning and safety. I've read through all the materials I can find, including above, and am ready to embrace a complete understanding of how CIS works.

A little background: Completely stock '74S 2.7, originally a CA car, but now exempt on account of it's age. The long range plan is to upgrade to a 3.2 with Motronic, but that's at least a couple of years off. FD is # 0 438 100 004 and WUR 0 438 140 008. The fuel accumulator is showing signs of slight leakage - just damp on lower half - no drips....yet. Fuel pump seems fine, but we'll see when the pressure gauge is on it.

My plan is to pull the FD, clean and replace all o-rings and seals. Are there crush washers on the banjos? Inspect all other hoses and fittings and replace as needed. I will of course test all the fuel pressures before going in. I'm hoping that the WUR is re-usable, otherwise, as I understand, it can only be replaced and not re-built.

I'm all ears to criticism, advice and so on. Particularly the proper sequence of opening and closing the FD. I am quite experienced in mechanics and have access to excellent resources here in our town (Rothspont, Rennsport, and other racer friends and machinists), but this will be my first foray into the mysterious world of K-Tronic...

Many thanks in advance,
-C

[Festive_Zombie]

Verify potential vacuum leaks prior to checking the fuel system... A lot a small leaks combine to make one big one. And usually turns out to be the cheapest fix (if you don't have a blown airbox).

[Charles Freeborn]

Originally Posted by Festive_Zombie

Verify potential vacuum leaks prior to checking the fuel system... A lot a small leaks combine to make one big one. And usually turns out to be the cheapest fix (if you don't have a blown airbox).

Great advice. I'm not of the mind to solve a problem that doesn't exist... however I do believe in preventative maintenance - especially when it can avoid a breakdown.
-C

[jason2guy]

the cold start issue is either the CCP or AAR or both. to have a perfect cold start everything has to be right. u have to make the WUR adjustable, then you have to adjust it right. after that you can deal with the AAR and the 12v source for the WUR and AAR. the harness to those in my car was melted together on the inside and finally shorted out and created a bunch of chaos.

[Porschedave]

Hi
I agree with the above comments regarding air leaks. I had a crack in the airbox of my 83 engine. It probably began as small and over time got larger. When I finally discovered it and replaced the box I couldn't get the engine to start at all because the mixture was so out of whack. It had been adjusted and each time a bit more to account for the air leak.

A separate leak occurred when one of my intake runner boots cracked. That was a pain to find but when replace the car ran great. Go for the simple things first.

Dave

[NOLAsc]

Originally Posted by tirwin

1) Recommended Reading - post #3

2) The Pearls of Wisdom - post #4

3) Overview of Potential Problem Areas - post #5

4) Test Procedure for System, Control and Residual Pressures - post #6

5) Finding Vacuum Leaks - post #8

6) Fuel Delivery Problems - post #10

7) AAR, AAV and Decel valve... What's the Difference? - post #16

Thanks for this thread.

[willcall]

Subscribed. Some great reading here.

[tirwin]

Charles,

I haven't seen too many people tackle the job of rebuilding the FD. But I did see a thread recently where someone did just that so it can be done.

There are several places around that do the rebuild jobs. I believe Brian (RARLYL8) does rebuilds. (RarlyL8 Motorsports) There may be others around and it sounds like you've got some great local options!

Bosch was the original manufacturer of many CIS components. There may be rebuild kits for sale.

I think the part number you posted is the Bosch number. If you do a Google search for "Bosch -your part number- rebuild", you might find a kit.

Try that and report back on what you turn up.

[Charles Freeborn]

These folks have parts and do re-building:
DeLorean parts, Delorean fuel distributor, CIS fuel injection Parts, Delorean parts, Porsche Mercedes
And I've also heard very good things about this shop:
CISFLOWTECH

There is also a great deal of useful information, including a link to the factory training manual here:
http://jimsbasementworkshop.com/CIS/

I'm going to have at mine myself first, and if I get in a pickle I'll box it up and send it out.
-C

[aseem]

Thanks for a great thread.
I find myself often referencing the Bosch K-Jetronic manuals that i have downloaded: "Bosch*Technical Instructions K-Jetronic" and "3299223 Bosch Kjetronic Fuel Injection Manual"- Unfortunately, I can't fint the site where I downloaded them, but a google search should locate them.
Try 3299223-Bosch-KJetronic-Fuel-Injection-Manual-
and http://www.usefulstuff.pwp.blueyonder.co.uk/myfiles/KJet.pdf

This is also a useful site: 911 CIS Primer - Index


Thanks again for a very informational thread.

[boyt911sc]

Originally Posted by tirwin

1) Recommended Reading - post #3

2) The Pearls of Wisdom - post #4

3) Overview of Potential Problem Areas - post #5

4) Test Procedure for System, Control and Residual Pressures - post #6

5) Finding Vacuum Leaks - post #8

6) Fuel Delivery Problems - post #10

7) AAR, AAV and Decel valve... What's the Difference? - post #16

Tim,

Your work has benefited many and I put off my hat to you. I received an email an hour ago from a member stating that his test data was the opposite of what you suggested. Refer to item #4 (above) about Test procedure.........Some where in the 'The Day Before' paragraph, you mentioned about the values of the heating resistance for WUR-090.

25 - 26 Ohms when warm.......
9.5 Ohms when cold........

It should be the other way around. Higher resistance reading when COLD and lower resistance value when WARM/HOT. I'll sent a PM. Thanks.

Tony

[Bob Kontak]

Originally Posted by Porschedave

I agree with the above comments regarding air leaks.

Charles,

I fought with bucking, rising idle when warm and a non-stop putt-putt mini backfire from the exhaust for over a year in the 2010 time frame. Ran great but not quite right.

I finally (e.g., exhaust gasket changing among other stuff) took a can of starting fluid to the base of the intake runners and found the leak to be the #4 runner base gasket at the head.

This was after I had pulled the engine for a trans rebuild and resealed what I could on the engine while I waited. I think I just did not tighten the runners correctly.

Mind you, I later did the comprehensive boyt911sc pressure test to find air leaks and found a few minor ones. But leaks at the base of the intake runners are stinkers. They are so close to the action.

[timmy2]

Figured I would post this here for all to find.
When you completely rebuild your system and are starting over with unknown richness the Porsche manual provides this tidbit of information to get you going again.
I wrote some basic directions in another post, and here is the text from the manual as well.

Injectors pulled and in jars.
1. Bleed fuel lines by lifting sensor plate many times. Ignition on, pump running.
2. Use 3mm hex wrench to turn mixture screw 1-2 turns counterclockwise (should stop all flow)
3. Make pump run continuously by pulling air flow safety switch off. Ignition on.
4. Turn screw clockwise until the injectors just barely eject. From this point turn the mixture screw back 1/2 turn counterclockwise.
5. Run engine to operating temperature and adjust idle and CO to spec.

Personally I would jumper the fuel pump relay socket instead of pulling the air flow safety switch.

Here is the text:

[boyt911sc]

Originally Posted by timmy2

Figured I would post this here for all to find.
When you completely rebuild your system and are starting over with unknown richness the Porsche manual provides this tidbit of information to get you going again.
I wrote some basic directions in another post, and here is the text from the manual as well.

Injectors pulled and in jars.
1. Bleed fuel lines by lifting sensor plate many times. Ignition on, pump running.
2. Use 3mm hex wrench to turn mixture screw 1-2 turns counterclockwise (should stop all flow)
3. Make pump run continuously by pulling air flow safety switch off. Ignition on.
4. Turn screw clockwise until the injectors just barely eject. From this point turn the mixture screw back 1/2 turn counterclockwise.
5. Run engine to operating temperature and adjust idle and CO to spec.

Personally I would jumper the fuel pump relay socket instead of pulling the air flow safety switch.

Here is the text:

Dennis,

This is a very good piece of technical information that would surely help many CIS troubleshooters. And I completely agree with you about using the FP relay instead of the AFS switch. One other thing you could add to above instructions is the importance of verifying or confirming the absence of unmetered air in the system which is commonly over-looked. This is the Achiles' heel of CIS.

Tony

[timmy2]

In addition to the aforementioned unmetered air (vacuum leaks) I found this chart in a factory manual that may help others with troubleshooting.

[kach22i]

Okay, I have this excellent thread bookmarked, just hope I can find it when I need it.

My CIS can always be improved upon.