<TOP>I have a '72 911E Targa with mechanical fuel injection.
It will start right up, but if I try to give it any gas it will loose power and stall. If I let it idle for 5-10 minutes it runs fine.
I don't know how you lived with it like that for more than a season. You should get the Bosch/Porsche MFI book "tune, test, adjust" or whatever it's called. You need to start at the beginning like the book says and check your ignition, compression, and other things and make sure they are right before you mess with the injection.
Then you might want to start with cleaning out the disks in the warm-up regulator by removing it and BEING VERY CAREFUL not to change the order of the disks which are not all the same.
You should also clean out the idle air passages on each intake. You can do it by removing the adjustment screw (count how many turns it is from closed first so you can re-install it). Then spray some carb cleaner down the hole and clean it out with a long pipe cleaner. The pipe cleaner will be REALLY dirty from carbon. Also clean the needle on the adjusting screw.
You can check for vacuum leaks with the car idling by spraying that carb cleaner around the base of the intake stacks — if you hit a leak the engine RPM will change. Maybe you can check for leaks on the head this way too by spraying through the ducting.
Also check the pump timing which will require a mirror to see the timing mark on the back of the pump. I hear it's not that critical but couldn't hurt.
After fixing all these wear items, if it still runs bad you can then do the adjustments — throttle linkage lengths, butterfly valve stops, pump vs. butterfly correlation, etc. Then you can set the part throttle and finally idle mixtures. Bob Spindel built a neat pipe with an O2 sensor which clamps onto your muffler and you read the voltage with a digital volt meter. It works good for the part throttle adjustment. I have an article I accumulated about using an O2 sensor for tuning if anyone is interested.
<TOP>First, check that your thermostat is working correctly:
Start motor and warm to operating temperature (180°C).
On the MFI housing behind the thermostat is a small triangular cover plate.
Remove this inspection plate and observe if the thermostat rod is pushing against the cam-shaped lever. This lever should not be able to move back further. (Use a small angled screw driver or similar to gently check the there is no movement). If there is, continue as below.
If you need to clean out the thermostat I would do it this way:
To remove the bottom screw on the thermostat cap, grab your air cleaner with your fingers while placing your thumb on the thermostat cap, remove top screw (cap is spring loaded).
Remove cap, set aside, (don't lose cap gasket, mine was broken so I made another
one — this thing will not work without the gasket, it's also a spacer).
Draw out the rod with elements — I would not take them off if it works!!
(There are 25 pairs of expansion elements (mounted like cymbals) fitted first, followed by three slightly larger flat washers).
Clean with carby spray cleaner, set safely aside.
Remove bottom screw on thermostat housing (kind of hard to get at), hold on to housing,
remove top screw, remove housing.
You should have a cross shaped gasket with a hole in the middle, and a metal spacer.
Should also have a small rubber "o" ring type gasket in the flange on injection pump.
Clean them up using parts cleaner or carby cleaner.
Next, hold thermostat housing, install rod with elements, spring seat, spring, and compress cap with your thumb, install screws.
Check for movement on thermostat rod...about 3/16" (4.75mm) or so..
Now reinstall thermostat.
The reason for installing the whole thing assembled is, if you install just the housing, and then the rod with elements, it gets warped and doesn't move right.
<TOP>Also, about adjusting the pump timing... In my newsgroup wanderings I read two posts at different times. In both posts, they said that the Porsche factory racers found that they could detect no difference in engine performance, no matter how the timing was set. I haven't noticed any difference myself in the adjustment, but I still set it anyway. Just a little tidbit I wanted to pass on. -Hans Achter <TOP>
From Rennsport (Visit for more great performance information)
Bosch Mechanical Fuel Injection is a splendid, if not inexpensive, performance induction system. It was used on the 911S and 911E from 69 to 73 as well as the 73 Carrera RS. Porsche used various types of MFI on factory racing cars from 67 to 84. This is a very complicated fuel delivery system that, if set up properly and in good condition, makes excellent power and throttle response.
The trouble is, few people anymore possess the necessary knowledge to make these systems run well and Bosch has little documentation available for the owner. Pacific Fuel Injection and Eurometrix are two of the most reputable re-builders of injection pumps and throttle bodies.
Injection pumps can be recalibrated to almost any engine size and camshaft. 2.7 RS-spec engines equipped with these systems continue to be quite popular since the requisite space cam for the pump is still available. Eurometrix can enlarge the throttle bodies to 40mm for larger engines as well. The larger plastic intake stacks as used on the "S" and Carrera RS engines are still available from Porsche as this is written.
Tall butterfly throttle stacks from the 73 2.8 RSR and 911 SC/RS are one of the good upgrades for engines used for racing purposes. These 50mm throttles work quite well for 3.0 litre and larger racing engines. Another upgrade to consider are the RSR throttle slides from the 74 3.0 RSR. These are being re-manufactured by Andial for racers as well as restorers. Other aftermarket throttle slides and fuel rails are available for the 3-bolt flanges used on 3.6-3.8 litre engines. You can even fit excellent quality aircleaners to these throttle assemblies. Typically, FI pumps used for racing are recalibrated to RSR-spec and the idle-cutoff solenoid is removed.
The early FI pumps are better suited for the RSR modification and the later pumps used on the 2.4 litre engines are better candidates for an RS-type upgrade.
From: hansey@worldnet.att.net
Date: Thu, 5 Aug 1999 22:11:1
I have the same car, and have dealt with the MFI quite a bit. Bruce Abbott certainly has some good advice; it will take some time to get familiar with it.
You might get some help from my experiences:
(When I had the MFI pump rebuilt and reinstalled it, the engine still ran like trash. There was still spark, and I could get a timing light to work, so I never suspected the coil. After lots of frustration, I finally noticed that the timing light would intermittently wink out when I revved the engine). It's easy to check the coil with a multimeter (see Haynes manual.)
It's "chock full of info" on MFI! He'll soon be posting the Porsche factory MFI adjustment manual, called the "check-measure-adjust" manual.
Hans Achter
73 911E Targa
From: Matt Beaubien <mbeaubie@gpu.srv.ualberta.ca>
Date: Wed, 11 Aug 1999 01:48:52 -0600
Hi all,
I'd like to thank everyone who sent me suggestions on what was wrong with the MFI on my '73 911E. A few discoveries have been made and thought I'd share them with everyone.
My cold start problem was in fact electrical. I ended up removing the electrical panel in the rear and cleaning every single electrical connection with contact cleaner and a brass-wire brush. She fired right up after reinstalling the panel.
Quite a few people suggested that my poor part throttle running and missing above 6k RPM may be a supply problem due to rust clogging the screen, lines, filter etc. I didn't really feel that fuel supply was a problem as it was fine at 5000 rpm at WOT.
I did some more investigating in the thermostat operation on the regulator. I removed the top access port to get a better idea on how it worked. It seemed that the thermostat never really moved that much. I levered the assembly with the engine running, and was able to see black
smoke for the first time. I then operated the throttle a couple times and noticed much better response than before.
To make a long story short, I started removing pairs of discs from the thermostat. I removed one or two pair at a time but it didn't make much of a difference. I then removed a whole bunch (~ half) and it seemed just right. Took it for a spin and it pulled to 7k+ RPM in the first
three gears, without missing at all. Perfect! This allowed me to go to a track the next day for a lapping session to get acquainted with the physics of 911's.
It then started to miss again occasionally at part throttle. This time it was a rich-miss. I could tell because giving a little more throttle opening would make it stop. When it was lean, more throttle would just make it worse. I'm now tinkering with finding the right number of washers to get it running properly. I'm thinking of threading the thermostat cap to allow me to adjust the preload quickly and easily.
(It seems that the spring or whatever in the regulator that presses against the thermostat is not strong enough. Removing discs reduces the load required to get enrichment happening).
For those of you that have had your MFI systems overhauled, can you let me know how much to expect money wise? Private or public emails are fine.
FWIW, my engine only pumps 135 psi on a compression gauge and burns a noticeable amount of oil. However, I was able to hit 6500 RPM in 5th which equates to 143 MPH (S+ numbers, no?). This was with the sunroof open and it was still pulling a bit. I have an RS-esque air dam and a duck tail which may reduce the drag a bit.
What a fun car...
Matt Beaubien
'72 911 E
From: pcowper@webtv.net (Peter Cowper)
Date: Fri, 20 Aug 1999 23:13:19 -0700 (PDT)
1974 911 . . . (with a fresh 2.4 S engine under the bench waiting for 2003 when my car drops off the California Smog Roles!)
From: Terri & Marko <ciganovic@bigplanet.com>
Date: Thu, 21 Oct 1999 17:21:29 -0400
I recently asked listers if they had any luck using this approach,aparently no one did — so I
thought I'd try various techniques/chemicals...after many failures I won!!!!!
So, here is what worked for me. I used a 1 litre ultrasonic cleaner (large jewelers or graphic type) — must be capable of heating solution to 150º+ F.
The solutions are simple and available at any hardware store... mix 1/2 turpentine + 1/4paint remover + 1/4 acetone, bring to temp.150º+ .
Soak injectors vertically for 2 hrs. Invert and soak for 2 hrs. Lie flat (roll back/forth) for 1hr.
The screens will be perfectly clean (there will be a small amount of residue on bottom of
ultrasonic bowl).
I cleaned same and repeated process — IT RUNS FANTASTIC!! You will have to lean the mixture on the pump behind the shroud approx.3-4 turns or to your liking respectfully.
From: Bob Spindel <spindels@aol.com>
Date: Mon, 25 Oct 1999 11:13:45 -0700
Kevin,
The sockets are made to pop off the balls. Just wedge a large screwdriver blade between the ball and socket and twist, or use an open-end 10mm spanner in a similar manner.
The length of only one rod is critical: the rod between the MFI pump and the accelerator linkage. It should be 11.4 cm +/- a few 1/10th millimeters from balljoint centre to centre. With that one set right, the lengths of all the others fall into place.
Essentially, you adjust the length of all the rods so that the butterflies are closed and each is just resting on it's stop. The "correlation" will then be right. You don't need the protractors.
Bob Spindel
'72 911T
'73 911T (being restored)
spindel@apl.washington.edu
From: AnalogMike@aol.com
Date: Wed, 27 Oct 1999 11:15:07 EDT
That number is the correct pump for a 2.7RS. They are 0408 126 XXX :
>> I also have the part number for the stack (911.110.312.1R). Does that look consistent with an RS? <<
That # is not in the MFI book, it would be in the factory parts book but I have that at home so can not check. The S and RS have bigger stacks than the T and E, they should be the same as your '73S.
My '72S stacks had "S" written on them with yellow grease pencil at the Factory I think (wonder if the concours guys check for that?).
>> Also, a more basic question, does the Carrera RS have different stacks than a '73 S, how about throttle plates? There seems to be a lot in common between the '73S and the '73RS so far. <<
Yes, they are almost the same engines. Only real difference is space cam in MFI pump, and
pistons/cylinders. However the MFI book says that the RS features "throttle valve casing with enlarged bypass bores for idling air; recognizable by Solex part number on front surface".
So I guess the throttle valves are slightly different, though it should be easy to bore out the S idle air passes a bit if idle is too low.
Good luck, sounds like you are putting MFI back on your '73S ?
Regards,
Mike Piera
AnalogMike@aol.com
MFI cold start problem?
From: Mike Piera
>> I have a '72 911E Targa with mechanical fuel injection. It will start right up, but if I try to give it any gas it will lose power and stall. If I let it idle for 5-10 minutes it runs fine.<<
You can check for vacuum leaks with the car idling by spraying that carb cleaner around the base of the intake stacks — if you hit a leak the engine RPM will change. Maybe you can check for leaks on the head this way too by spraying through the ducting.
Also check the pump timing, which will require a mirror to see the timing mark on the back of the pump. I hear it's not that critical but couldn't hurt. After fixing all these wear items, if it still runs bad you can then do the adjustments — throttle linkage lengths, butterfly valve stops, pump vs. butterfly correlation, etc. Then you can set the part throttle and finally idle mixtures.
From: Josh Pinkert <flusherino@yahoo.com>
Last night I pulled my heat exchangers so that I could rotate my motor on the stand and have better access to the underside of my motor (cleaning time!!!). It was a piece of cake... judiciously used PB Blaster on the bolts and they came right off (although the muffler bolts were really rusty).
Upon looking at the exhaust ports, all of them were uniformly caked with a dry soot, except for #2. Before I dropped the motor, I had replaced the plugs, cap, and rotor and after subsequent test drives (and an examination of new and old plugs) I concluded that plug #2 was fouling. Now that I have a chance to look at the exhaust port for #2, I see that it’s all wet.
My question is... is there an easy way to tell if it's oil versus fuel? If it is fuel, I'm not worried. Just retune it. If it's oil, then I'll have some problems to deal with. How difficult is it to pull just one cylinder? It would require pulling the head from that side, so I'm looking at a good investment in tools, plus I'll have to re-time the cams, right?
Josh Pinkert - '72 911T
Josh@Pinkert.com
From: Bob Spindel <spindels@aol.com>
Date: Thu, 23 Mar 2000 13:52:25 -0800
The through-the-stack popping at idle is reduced mostly be getting the throttle linkages adjusted correctly. If you're off even a teensy bit on one stack — pop pop! A good way to go about it is with a warm engine at idle, start popping (bad word!) off the links, checking to make sure they are adjusted so as to present no preload to their respective butterflies. This includes the link to the MFI pump itself (which should be exactly 11.4cm, ball-to-ball, this is critical) and the main link from each set of stacks to the accelerator rod.
The backfiring-through-the-exhaust can be minimized by adjusting the MFI pump for part load adjustment. A simple way to do it is lean the pump out (clockwise, I think) a lot. Get it to the point where it is so lean it idles poorly, and backfires like a banshee when you let up on the accelerator at speed. No need for walls here, you'll hear it if it's lean enough. Then start enrichening it a few clicks at a time until it idles nicely again, and doesn't backfire, and allows smooth acceleration through the 2500–3500 rpm range. All three of these will happen at the same setting. The switch from way too lean to just about perfect occurs over a very few clicks — maybe 3 or so.
you do need something to allow you to determine how much air is being drawn in. I use a device called a Unisyn, which has been around forever. I'm not sure what they cost these days, but I'd be surprised if they were more than $25 or $30 (although they're probably worth $10). There are all sorts of fancy tools available. I've seen some with gauges on their faces that
cost nearly $100, but they are big time overkill. The Unisyn just has a tube with a little ball in it that rides higher or lower depending on the air flow. One just adjusts the bleed screws until the ball rides at the same level for each cylinder. The bleed screw adjustment is pretty fine in
that it takes a fairly whopping adjustment to make much change. With them all at 3 turns out you're probably very close, even pretty equal on most, but usually there will be one or two cylinders that are off enough to start popping through the stacks.
The procedure of taking a reading in all six and then finding the mean and adjusting to it will certainly work, and maybe it can be quicker that way. It's very scientific of course — Germanic — but overkill. The object is simply to get all the intakes equal. You can read fancy vacuum gauges, or look at little balls. Same result. When they are equal, you may wind up with the idle a bit high or low, in which case you just decrease or increase each screw the same amount to get the idle where you want it.
I'm sure you have the linkages set correctly, and I'm probably misinterpreting your words, but to be doubly certain you don't want to set them to just evenly close the butterflies alone. There are stop screw adjustments on each of the butterflies to do that. Disconnect the linkages and set the stop screws so that the butterflies are all just closed when they rest on the stops. Then adjust the linkages so that when you pop them on they don't move the butterflies off their stops. The bleed screws then simply allow you to account for very small differences in each butterfly/stack. If all the intake stacks and butterflies where accurate, precise devices, you wouldn't need the bleed screws.
One more thing. If you have one cylinder that consistently fouls, like Josh's #2, double check the linkage/butterfly/air screw on that one. It's often the probelm.
Hope this helps.
Bob Spindel
'72 911T
'73 911T
spindel@apl.washington.edu
From: jhunt@huntinter.com
Date: Sun, 26 Mar 2000 23:49:0
The cam in the MFI pump is matched to the cams in the engine. Changing your cams can cause rough running. But that can be okay for increased performance. (I had a "T" pump with "Solex" cams, switched to an "S" pump and found it runs much better).absolutely no effect no matter how far I adjust them out/in).
2) Frequent backfiring through the stacks — primarily from cyls 2 & 5.
-- No idea (see Bob Spindel’s previous post)
3) Lots of backfiring through the exhaust — mostly when decelerating but not always.
From: AnalogMike@aol.com
Date: Mon, 27 Mar 2000 09:42:15 EST
PorschePoor@hotmail.com wrote :
> After spending the last 6 months rebuilding my 2.2S motor...
> Question: If adjusting the air screws on the TB's doesn't change idle
> speed one whit, despite running them out past ten turns from stops, am I
> correct in assuming that the fuel at idle is too lean?
> If the problem lies in adjusting the pump, is there any base point to start
> from similar to the TB air mixture screws? (i.e. screw in until stop is
> reached & back out 5 half turns). <<
Not that I know of. When I got my last pump rebuilt, it was not even close to a setting that would allow the engine to run, even though Hans said it would run fine without adjustment.
If your pump's main setting (mid range mixture) is set extremely rich or lean, the idle air screws will not do much of anything. Also the pump's idle screw will not do much — you need to set the "part load" (remove allen bolt in front of pump and use a long thin screwdriver) before setting the "Idle mixture" (this special tool stuck through the fan). You do have the Bosch/Porsche
CHECK/MEASURE/ADJUST manual??? (I can copy if you need it).
> This is all rather frustrating as the fuel system worked fine before I
> pulled the motor, and I didn't touch the pump other than to remove and set aside.
That points to something other than the pump. You must follow the manual and check each component before blaming the pump. As the manual says :
"Remember, the injection system is not a separate component, as, for example, the generator. It should be thought of as part of the engine. No matter how well the injection system is adjusted, it cannot make up for problems in the operating condition of the engine. Always begin injection work by checking the engine's basic tune."
The checking sequence is:
1. Air cleaner cartridge (rubber gaskets in place? filter clogged?)
2. Compression loss (what is your compression? Maybe the cams are not timed right???)
3. Spark plugs (are they all firing correctly? some new plugs are DOA)
4. Dwell Angle
5. Timing (are you 180 degrees off, or off a tooth on the distributor? Check that at TDC your distributor rotor is pointing to the #1 notch on the distributor case.)
6. Fuel pressure and flow: should be about 10PSI at the pump, you can TEE in a cheap gauge for a quick reading.
7. Injection nozzles: when you rebuilt the engine you should have had the injectors tested/ cleaned.
8. Injection timing: not hard to check and adjust close enough suing a mirror, as per manual.
9. Correlation (lengths of throttle rods etc)
10. Exhaust emission test:
a) part load — I could write a book about ways of doing this…
b) idle — never seemed to make much difference on many engines.
NEVER DEVIATE FROM THIS SEQUENCE (or Hans will poke you with a long cheesehead screwdriver).
Good luck!
Regards,
mike piera
From: PROTURNER@aol.com
Date: Mon, 27 Mar 2000 10:32:34 EST
throttle rods. I can't believe that 5mm plus or minus is allowable... get them all as exact as you can. Do not worry to much about the angles of the throttle cams... getting the rod lengths correct will take care of that problem. You might also need to time the pump to the camshaft...requiring some mirror work!
After all adjustment is done, you will need a very small screwdriver of some length to adjust the idle mixture and lean/rich mixture control on the pump. (All this is in the manual). It took me a couple tries to digest the information and make sense of the procedure, but after setting it up, I've had zero problems — with the exception of adjusting the richness depending on seasonal cold... once in the winter, returning the setting for summer if it gets cold enough in New Orleans.
From: Bob Spindel <spindels@aol.com>
Date: Mon, 27 Mar 2000 10:34:41 -0800
I also think you're setting’s way too lean, but not because of the way your air bleed screws act (or don't act), rather because of all the backfiring. The bleed screws actually make pretty minor changes in idle even when everything else is correct.
You can also manually open the throttle by moving the linkage, thus letting in more air while keeping the gas the same, thereby leaning the mixture. If the idle smooths out, or speeds up,
you're too rich. When you're close to perfect, the idle will get worse when you do either of these.
I don't know if there's a rough rule as you suggest. I do know that the mid-range adjustment is by far the most critical, and if you have it right the idle adjustment can be way off and things will still be okay. I also know that the mid-range adjustment is very fine. Each click is 1/6 turn, and the right setting is within +/- 2 – 4 clicks or so. That's less than a full turn. And the screw itself is pretty dang long with a very fine thread, and you can probably turn it a zillion times from stop to stop.
Doing what I wrote above ought to get you close, then do what I posted before, which is lean out the mid-range adjustment until you start to backfire like a banshee — sounds like you're already there — and then richen it as I described.
Hope this helps.
P.S. John Hunt suggested if you're in the Pacific NW you should contact Chris, at Chris' German Auto in Bellevue, WA. I agree, he's excellent. (Coincidentally, I'm in Bellevue too!)
Bob Spindel
'72 911T
'73 911T
spindel@apl.washington.edu
