Need help: '72 911 Mechanical Injection problems
 

I have a one owner '72 911 E Targa with some interesting fuel injection problems, I think.

I have rebuilt or replaced everything on the engine several times. The car is currently at Air Cooled Classics in Knoxville, TN and they have tried everything. Gus even rebuilt the pump twice. I had the engine rebuilt twice, rebuilt the throttle bodies in FL at Frank Eibell's place, rebuilt distributor, SSI heat exchangers, S pistions and solex cams. The main problem is a hiccup at idle or constant speed. The gas mileage is very poor also, around 10 mpg.

I am living in the LA area right now and would like to bring the car out here to drive.

I am looking for advice and who in the Atlanta or Los Angeles areas I can send the car to for diagnosis and repair. Please help.

TRE in LA.

Tyson Schmidt at TRE in Los Angeles.

What's the mixture? Have you tried an LM-1 data logger to see what the mixture is doing? You can search here for more info.

Can you give us detailed info on this problem and its history?

The car has always ran very strong on acceleration. It is definitely running rich, but I can't find anyone in TN that can adjust it. The best guy in Knoxville, TN is Robert Berry, but he is a crook. Air Cooled Classics has done great work for me, but they just don't have anyone there that know the early cars in depth. Everytime they try to lean it out, it pops more. Bruce Anderson drove it about 5 years ago and said it was one of the stongest 2.4's he had ever driven. It just misses a little and feels like a hiccup, sometimes backfiring. My Dad said when he bought the car new, it got about 17-26 mpg, not it gets around 10-12. I have replaced just about everthing except the whole engine at this point, which may be next. We did put Webers on it about 20 years ago and I rebuilt the fuel injection and put it back on about 10 years ago. It has 135,000 miles total and about 300 on the last total rebuild in June '04.

<b>Randomly replacing parts isn't a valid method for troubleshooting an MFI system!</b>

The best thing you can do for your car is to plan on doing your own work ... begin by downloading, printing, and reading all of the MFI documents on the following Pelican page:

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

As you familiarize yourself with the MFI system, build a special service info binder & library, and gather some specialized tools and test equipment, including a Gunson Gastester. Do a search of the Pelican archives ... there have been many threads on practically every aspect of the MFI system, including troubleshooting, tuning, and repairing. It wouldn't hurt to gather threads and info on the CDI system as well!

The central, and single most important document is a factory MFI publication called <b><i>Check, Measure, Adjust.</b></i> There is a specific, ordered list of tasks to be followed in order to rectify MFI system performance.

Try retarding your ignition timing a few degree`s . Also which muffler are you using ?

Kurt Williams

My best advice, being a fellow MFI owner, is to follow Warren's suggestion. Without deviation.


PERIOD.

Do some searches and read his replies and you will see. He is the MFI MAN!!

Warren is a very smart and well informed mechanic. However, the admonition to go get the CMA is getting tiring. (to use Warren's bold type to make a point...)

The CMA doesn't tell you anything about what to do if a car is not STOCK.

And, as sensitive as the MFI is supposed to be with regard to having the valves adjusted exactly right and the ignition spot on, one would figure that if the exhaust has been changed, it would have some kind of DRASTIC effect.

Now, I don't belittle the CMA and I don't belittle Warren. That would be foolish. I have learned from the CMA and I have worked the procedure.

(more bold ;) ) I have the same problem as jimgolf1. I have never had a stock muffler either. It took me the better part of 3 days to find 950 RPM idle. So, chasing the problem jim has, I make a part-load adjustment and I'm back above 1300 at idle. That was 2 clicks richer.

Jim, we can't tune out the pops at idle if the switches aren't closing, can we? What we need is some honest help. But, contrary to what your mileage is telling you, I think you need to go richer on the part load. Only a tester will tell you if that's correct. Mine is on the way.

Kurt, thanks for that suggestion. That will make my idle go back down while I search for the sweet spot in the mid range.

edited for spelling

THANK YOU ZEKE!! I have been waiting so long to here someone say that. CMA is great if you are driving a car that has been in a time capsule, but even rebuilt, these systems are over 30 years old.

There are so many good ways to begin chasing your problems, the best of which is probably a Dyno with an A/F meter, or the LM-1 data logger that John mentioned. You will be able to see what your engine mixture is doing at load and see what is happening when the hesitation you described occurs.

Learning to do your own tuning is also good advice. Many Porsche mechanics dont know this stuff and dont care to learn. The tools are cheap, (or easily made) and as long as you make note of the changes you make to the mixture, you can always start over.

Paul

I know and used a guy in Gulfport MS that is very good with the MFI,
HE tuned mine prefect, and he is honset.

I agree that chasing the problem with parts is not a good answer and that is why I'm ready to move on to a real professional. I wish I could work on the car myself, but I am working in LA and don't have the time go back to TN to work on the car and no tools with me in LA.

I have SSI Exchangers, stock muffler, no smog, Gus at Pacific Fuel Injection rebuilt the pump (very expensive) to the specs of the engine with S pistons and solex cams (reground stock E cams by Web Cam) I did like the stock grind better.

What do you think about Jack Lewis in Atlanta? Frank Eibell in FL had it running the best a few years agowhen I lived there. It has always had a tick at idle since I put the fuel injection back on, installed the S pistions and Solex cams. I'm not even opposed to putting new E pistons and cams in if I could just get to run like it did originally.

Thanks for all the advice, I'm glad I found this forum.

Jim,
I am telling you This guy in Gulfport is a Porsche super star.
He has worked on some of the cars for guys on this board.
And he is very reasonable, Is name is Mr Howard
228-865-0180
YOu will not be sorry!

I talked with Jack Lewis in Atlanta last week and he suggested that going back to the original E Cams made the most sense. After all, there is a reason they made 3 different injection pumps with 3 different cam and piston set ups. I am taking out the Solex cams, let me know if you need some, and putting in the E's. I will let you all know how it works.

Uhh, I wouldn't do that.

The Solex profile is identical to the early E. According to others here, there is no difference between the early E and the late E. Call Gus Pfister and ask him whether there's a different space cam in the MFI pump for a 2.2E vs a 2.4E, I'd be willing to bet the space cams are the same in profile (All the 2.4 space cams are slightly wider, but the profile is the same as the earlier T, E or S.)

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

Those of us that have worked on the MFI's ourselves (I started with a '72 E) will tell you that you really need a gas tester to determine what is going on. I recommend the Gunson gas tester as it is relatively inexpensive and is quite accurate. If you do a search on my screen name and "gunson" you will find a couple of threads regarding this subject.

You say the more you lean it out the more it pops. Pops from where? If from the intakes you are too lean. If from the exhaust then too rich.

The cams I have are the '66 Solex grind. A mechanic suggested this from Bruce Anderson's book back in about '92. It seems like most of the problems started when I put the cams in. It's hard to tell since that was also the same time I rebuilt and put the fuel injection back on the car. Since then I have replaced just about every part except the cams. I already have the cams ordered and I think it drove better with E cams.

Anyone know what would be a reasonable price to reseal a '72 911 engine and trans, no rebuild, just seals for oil leaks?

Bad regrind perhaps? Who's to say that the cam timing is correct from lobe to lobe?

Also, how is it misfiring? Through the intakes or exhaust?

Also, double/triple check your ignition timing. I got caught with this (simple) item one time. It can be relatively easy to mess up with all the various markings on the pulley and lots of spark wires to choose from... :-)

John, I maintained that for a long time in the absence of any reliable proof of the difference. Camgrinder has finally convinced me of the difference based on his direct measurements of the different cams with his equipment.

True. I think that the important thought here is that there are many different levels of experience on the board, ranging from having read every post over the last 5 years to newbies. Many like to jump from newbie to tap the experience of the vets right off the bat. I know that I do all the time. The discipline is valuable when working with the MFI. If you don't KNOW why something is doing what it does, start at the beginning -- straight out of CMA.

Now many of us have found (worked) our way to the advanced class since things have changed on our. My car has 2.0S pistons, but E cams. Someone else has a sport muffler and Solex cams. If you have a pretty good idea how those things will change the combustion process, you're ready to try being artful with the settings. Let's be honest, it can be done. Porsche and Bosch did it before the age of computers! But it is a rubecs cube with each variable affecting the others, any many of the settings have only limited adjustment range -- so be warned!

As a starter as far as I know the following is an accurate (but simplified) conceptual drawing of the adjustments.

http://forums.pelicanparts.com/uploa...1113860046.jpg

Keep in mind that the thottle position and temperature will move the map in a 3rd and 4th dimension which is not shown here. As far as I undestand it the relationship with the throttle is controled by the 3D spacecam and is thus fixed for our purposes, and the temperature setting is also not adjustable.

So assuming everything else (cam timing, ignition timing, fuel flow, etc, etc) is working as it is supposed to what can you do? Here's my current working strategy -- but I don't do this for a living. If TRE or Henry Schmidt weigh in and dis-agree with me. My money's on them being right!

1) Figure out exactly what the issue is that you're trying to fix. Run-on? Pinging? Popping from the exhaust? Popping from the intake?, etc. Make sure you understand the rev range when it occurs so that you have an idea what adjustment range you're working in.

2) Develop a couple of theories for the problem(s). Keep in mind that there are many adjustments that may come into play in addition to the MFI, ignition timing being one, cam timing being another. My car has some run-on since I retarded the ignition due to the disappearance of 94 octane in my area. It also pops under deacceleration when warm and the hand throttle is off, with an occasional hesitation on tip-in.

A) Run-on: Preignition due to carbon build up from the fuel from last fall. I'm running Techron through it now that seems to help.

B) Still, retarded ignition means higher temperatures which increases the likely hood of this phenomenon. Did I retard it too far?

C) Popping on deaccelleration.
a) Does the fuel cut-off switch work?
b) Is it adjusted correctly?

D) Hesitation on part-throttle tip-in on in the mid-range (below 4000 RPM) Am I rich or lean right now?

3) One by one make check and confirm that everything (such has the cut-off switch in my case) works.

4) Make targetted adjustments (and the needed offsetting adjustments elsewhere). So if my car is a touch lean on tip-in, which adjustment affects that? If I move the part-throttle setting, I'll need to redo my idle speed and richness (keeping in mind the limited range of adjustment) to recover the off-idle performance that may result from moving the part throttle adjustment.

and so on...

As far as I know there are no silver bullets, but there are a lot of limits. Since much of our driving is done in the 1500-4000 PRM range, we're also limited by the space cam geometry which which fine tunes this range of the engine. So at the end of the day, you may be limited by the space cam. But before you throw up your hands and resign yourself to that fact, there are still a lot of "free" adjustments that you can make if you know what you're doing.

You say the pump was rebuilt to run with the solex cams so that profile shouldn't be an issue.

Besides, replacing the cams is a return to the shotgun method of repair. You need a better method.

First on the list should be diagnosis. This means a combination of CMA followed by a gas tester. Or take it to Tyson. he can diagnose it for you. By the way, he had a MFI car with the solex cams that he recently sold so he's been down the road with a mix and match MFI setup.

Having read most of teh articles on MFI I must agree that CMA is the point to start with.

My own experience with poor mileage and poping was rectified when I changed the brand of gasoline.

The gas made 30 years ago wasn't as dense as the modern gas/fuel.

Michael

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 <b><i>CMA,</b></i> 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!

Wow Warren! I just noticed that your post count is now up in the 5 digits! http://www.pelicanparts.com/support/smileys/pray.gif

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

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.

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

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

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!

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

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

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.

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

'72 911 E with Solex cams
 

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

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.

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.

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

'72 911 E Targa running rough
 

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.

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!

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

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.

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.

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