Need help: '72 911 Mechanical Injection problems

[Early_S_Man]

Jim,

It is not clear to me which pistons you have ... 2.2S or 2.4S, but that does not really matter for the MFI tuning issues you have! The higher c.r. pistons will raise BMEP, and improve torque and hp output ... but they have no effect whatsoever on airflow or tuning of the MFI.

I have always contended that the Solex and 'E' cams were different, but so close in peak hp and torque peak placement so as to be indistinguishible in the real world, whether on the road, or on paper. Unless you can measure your cams, and find that they are worn excessively ... or ground to the wrong specs, I see no reason to change back to stock 'E' cams!

What spark plugs and distributor are you using? The Bosch RS 2.7 replacement 0.231.184.004 distributor is generally regarded as having the best advance curve for high-output, high-revving MFI street engines. The ignition should be checked on a Sun [or equivalent] Analyzer to confirm consistent output across the entire rev range and all cylinders. The advance curve should be confirmed to be correct for your distributor's specs from idle to 6000 rpm ... without any variations or sticking! The timing light output should be rock steady at all rpms!

Overall ... my impression is that your engine isn't a highly-modified 2.4 ... just a bit 'optimized' here and there. It really isn't far enough outside the 'envelope' to present serious difficulty in MFI tuning or adjustment! Tuning should be done in a methodical fashion, just as presented in CMA, and without skipping around! A logbook should be kept noting all steps and changes made ... and any noticed changes in engine behavior during test runs, so that backtracking can be done in a logical fashion, should it be required.

Good luck!

[jluetjen]

Wow Warren! I just noticed that your post count is now up in the 5 digits!

...Very few if any have I not learned something from BTW!

[jimgolf1]

I agree, WOW. I can't tell you how much I appreciate all the advice on this board.

It has 2.4S pistons, '66 Solex cams, SSI's, point less dist, new CD box and none of the new parts have made a difference. The car is at Air Cooled Classics in Knoxville, TN. They are a good shop and they have worked and restored a lot of early cars, but this one has confused them. Gus at Pacific Fuel Injection rebuilt the pump, it apparently was switched by Bob Berry in Knoxville for a T pump a few years ago when it sat in his shop. After Gus rebuilt it back to E specs, it still ran the same, $1,100 later and nothing more than piece of mind knowing it wasn't the pump. If there is a crack or leak in the throttle bodies, no one has been able to find anything wrong. Frank Eibell had them rebuilt and the car ran the best after he tuned in back in '98, but it still had the little mis at idle. It is running the worse than ever right now and last year I had the engine and almost every part replaced or rebuilt.

The car is too embarrassing to even drive because it won't run evenly. I don't mind the faded paint, but it is a Porsche and it should be a good example of steller sports car performance. It's fine as long as you are accelerating all the time and hopefully make it to the next gas station.

I know it seems silly, but I figured if I kept replacing everything on the engine eventually I would find the problem and it would run like new again. Besides it has been in the family for it's whole life and I plan to pass it on to my kids. I may not be able to afford kids after I'm done.

[Grady Clay]

Jim,

Tyson Schmidt at TRE in Los Angeles. Some dyno time and well instrumented normal driving should locate the problem.

Milt is also correct; CMA assumes all new stock original components. Aside from being clearer about all the procedures, CMA2 needs to address non-standard issues and the geriatric condition of many components. The CMA procedure is the proper way to diagnose MFI issues. There is a lot more to it than what is in the original Porsche brochure.

You should get someone to get the mixture in the ball park before you head west. You will find 10 MPG no fun on a cross country trip. You can also ship it to TRE’s door, just disconnect the batteries by removing the ground straps and tell the shipper it is not running. Put the ground straps under the spare.

Keep us abrest of your progress.

Best,
Grady

[jimgolf1]

Well, everyone the Cams were the problem. Jack Lewis in Atlanta suggested I go back to the E cams instead of the Solex grind and it fixed the problem. The car runs great. I just want to thank everyone for their advice. Jim

[Grady Clay]

Jim,

Do you still have the “Solex” cams in hand? Can you get someone knowledgeable to measure the profile (camgrinder?) I’m with Warren in expecting very little difference between “Solex,” “Normal," and “E” cams. Not to the degree you were experiencing.

When you changed the cams to E, what else was done? Are they OE 911E cams or regrind? What was the history of the Solex cams? Every little gruesome detail may shed some light here. You may be able to chart some new territory.

Best,
Grady

BTW, Thanks for following up on the Forum.
Too often a problem is solved and the feedback
is lacking. We all need to learn.
THANK YOU!

[jimgolf1]

Grady,

I had the original E cams ground to the '66 Solex grind by Web Cams about 6-8 years ago when I had Webers on the car. Don Ramsey has the Cams at his shop in Knoxville, 865-671-4914. I'm sure he would be willing to measure them. Jack Lewis recommended I go back to the E cam grind because he had experience the same problem when he would put different cams in his early race engines with mechanical pumps.

We didn't do anything else to the engine except put different cams with an E grind and it runs great without any hick ups. My understanding is that the cam grind in the pump needs to match the cams in the engine. Changing the ones in the engine seemed like a better solution.

Thanks,
Jim

[jluetjen]

Thanks for the great follow-up! You learn something new everyone -- at least here at Pelican.

[Bobboloo]

I'm with Grady. Thanks for the follow up. If people don't post the solution then the thread serves no purpose for the data base.

[jimgolf1]

Thanks. It did take a while, but the problem is solved. I will try to keep every posted if I learn more about the Solex cams. Anyone is welcome to them for $200 or best offer. They are in great shape with only about 8k miles on them.

Thanks,
Jim

[jimgolf1]

Well everyone, the problem still exists for my original owner '72 911 E Targa.

I replace the Solex ground cams with the originals and the problem is still the same. I thought it was fixed because the repair shop is at their limit of fixing my car. Now after all the trouble and money I have spent on chasing the problem, it looks like it may just have been cracks in the intake pipes.

Anyways, it doesn't look like this car will be seeing the streets anytime soon. The poor car has been in 2 shops for the last 6 years and it still won't run properly.

I'm going to take it to Jack Lewis in Atlanta as the next step and then out to LA to TRW if that doesn't work. I have faith in Jack's ability and I will keep you posted on the end result again.

Sorry for the false hooray.

Jim

[David E. Clark]

Originally posted by john_cramer
... I wouldn't spend another dime until you got the mixture analyzed. Search here for "LM-1" and "MFI."

I've never used the LM-1 but I have used the Gunson. Either way, I have to agree that getting the mixture right is where I would start. Other ideas I have read suggested here, like retarding the ignition a few degrees, have the potential to do more harm than good (especially if you don't carefully monitor that you are getting the proper octane. Remember, there is no computer to compensate on these early cars!). You also need to consider that retarding the timing will require a commensurate change in the dwell angle and resetting the throttle valve air flow which leaves you without a factory baseline for reference and still with a mixture problem!

If it were my car the first thing I would do is a leak down just to satisfy my curiosity that the engine was healthy. Once I got this assurance, I’d step my way through CMA with a particular emphasis on getting the exhaust emissions correct with whatever tester was available. From your description, it sounds to me like your car is not so far modified that CMA is irrelevant. There are a lot of folks on this board with a lot more experience than me but being a traditionalist, I have found that starting with a strict adherence to CMA is always wise. Good luck.

[304065]

Uh, wasn't Jack Lewis the one who suggested going back to the E cams?

Last Friday I removed my entire MFI system except the pump, inspected, soaked, cleaned, reinstalled and calibrated in three hours. It's so easy to do even a first-timer could do it.

If you have air being introduced into the cylinders from somewhere outside the normal induction path, then yes, it will require a lot more fuel to make the engine run. But what kills me is that a crack in the STACKS should be visible and probably not make that much of a difference, and a crack in the throttle bodies, or worn seals around the throttle shafts, should be detectable in a five minute inspection. You pour B-12 on the throttle plates and see if it leaks out immediately. You hold the TB up to a bright light and look for leaks around the plate. And if you think there's a crack, there are inexpensive powder-developer NDT kits that can tell you in about five minutes whether the TB is junk or not. A simple flow bench made from a vacuum cleaner and the standard synchrometer will tell you if the TB is leaking air with the plate all the way closed (throttle stop screw backed all the way out).

I would not spend another nickel, especially chasing another set of 72E throttle bodies and stacks, until this inspection is performed, either by you or a reputable shop. Henry at Supertec, Matt at EuroMetrix, Bieker Engineering all can diagnose this problem or anything else wrong with the TB's or stacks, rebuild them if necessary and set everything up properly.

[Grady Clay]

Jim,

Where is the 911E now?

I’m sure the Forum can lead a willing shop through the procedures to solve this. There is no excuse for the 911 to be languishing like this. It needs to be driven.

Please review the history and the current symptoms. What are the recent diagnostics?

If your E were here in Denver, it would be driving within a week – extraordinary circumstances excepted. That would be determined the first day.

Best,
Grady

[jimgolf1]

Thank you very much for the responses. Here is a brief history of the car.

Original family car. No plans to ever sell it. I have been trying to chase this problem for over 10 years now. In the last years everything was rebuilt again; engine, trans, mech pump twice by Gus in SFO, rebuilt dist, went back to E cams from the Solex grind, new CD box, SS heat exchangers, S pistons (for the last 15 years with only about 10k miles on them), cam housing plugs removed and steam cleaned. The throttle bodies were rebuilt by Frank Eibell in FL about 7 years ago and the car has only been driven about 5k miles since then.

Mechanically the car is almost new. Last week they put a new fuel pump and lines under the car. Now the shop is saying the problem must be in the intake stacks, which was never mentioned during the last 2 rebuilds.

After all this work, the cars still has a little miss at idle and during a constant speed. It accelerates great. I agree that leaks in the stack shouldn't creat this problem.

Nothing against Air Cooled Classics, they are a good shop and Don Ramsey has been very up front with me about their limit knowledge when it comes to small details on the mechanical injection cars.

This car has become a big mistery and I can't wait to finally fix the problem. I would like to fix the car before I ship it out to LA, but if Jack can't fit it in I may just bring it to TRW. I talked with Jack Lewis today and he said he has had this problem before and it always seems to be in the pump.

Again, I thank everybody for their advice.

[Early_S_Man]

Jim,

Sorry to hear about the latest setback!

Based on your description that it has a constant miss at speed, and bad gas mileage ... I think a bit of sleuthing work to track down which cylinder(s) are not performing properly is in order. I suggest fitting six thermocouple probes to monitor the cylinder head temps and a USB-based thermocouple data acquisition module connected to a laptop to log and plot the data for a day or two of driving. It might not take more than a couple of hours of driving to narrow the problem, and the probes could be installed temporarily just for troubleshooting purposes.

Thermocouple probes for fitting under spark plugs are available at Aircraft Spruce:

http://www.aircraftspruce.com/menus/in/probesandsenders_cht.html

USB TC data acquisition module is available from Measurement Computing -- includes software:

http://www.measurementcomputing.com/cbicatalog/cbiproduct_new.asp?dept_id=414&pf_id=1692&mscssid=X750U5ETX4ET8K4BJ0M4T1WXJUMQ1FNA

Good luck!

[69911e]

What are you using for a pointless ignition? I hope it is not Pertronix, this can cause odd things at an idle.

[jimgolf1]

I don't remember what kind of points, but the change made no difference in the car. It ran exactly the same before and after. We have been chasing the problem with new parts for almost 2 years now. I think I have replaced or rebuilt just about everything on the car. It actually runs worse now after spending over $12,000 to fix the small oil leak and hickup.

I'm willing to ship the car wherever to get it running correctly.

[jimgolf1]

Well, I don't want to jump to any conclusions, but it looks like Jack Lewis was able to find and fix the problem. It turns out to be the distributor, even after being rebuilt had a defect in it. He put a used one in and the was able to set the timing correctly. The pump was set to the proper settings, it was out 11 clicks to rich. This was probably to overcome the fact that the cold start injection wasn't working. It would work, but it wouldn't turn on. The car is running great. In the end, it doesn't look like the fuel injection pump being rebuilt twice and engine rebuilt twice, not to mention all the other parts along the way were any of the problem.

I will include a few pictures when I get it out to LA.

Thanks for everyones help.

[jluetjen]