Need help: '72 911 Mechanical Injection problems

[jimgolf1]

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.

[poorsha]

TRE in LA.

[304065]

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?

[jimgolf1]

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.

[Early_S_Man]

Randomly replacing parts isn't a valid method for troubleshooting an MFI system!

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 Check, Measure, Adjust. There is a specific, ordered list of tasks to be followed in order to rectify MFI system performance.

[pjv911]

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

Kurt Williams

[DonDavis]

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!!

[Zeke]

Originally posted by pjv911
Try retarding your ignition timing a few degree`s . Also which muffler are you using ?

Kurt Williams

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

[Paul Thomas]

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

[deoxford]

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

[jimgolf1]

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.

[deoxford]

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!

[jimgolf1]

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.

[304065]

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."

[Rot 911]

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.

[jimgolf1]

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?

[Mr Beau]

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... :-)

[jluetjen]

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.

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.

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.

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.



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.

[Bobboloo]

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.

[Walko]

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