1970 911E FI Problem?
 

I just purchased a 1970 911E Targa. The car has 110K miles on the original motor. The engine starts and idles fine (no smoke), but dies upon acceleration. The owner said it was intermittent at first and then the car couldn't be driven at all because once you step on the gas and let out the clutch, it chokes and dies. Is the problem the mechanical FI Pump or could it be something else?

sounds like a fuel flow problem. I suggest you clean the tank, replace the fuel lines and filters.

Tom,
Just a question...did you by any chance buy the car in Stockton, NJ?

Yes, the car was in Stockton, NJ. Do you know the car?

No, I spoke to the owner and was going to look at it, but it sold before I got there. The description of the car and it's mileage and FI problem sounded too coincidental. Sounds like you got a great buy, if his description was accurate. Are you in Hunterdon County , also?

Dave,

I'm in Mountainside, NJ (Union County), about 40 miles from Stockton. I actually just paid for the car today and haven't gone through it yet. I'm looking to have a local friend of mine, a retired porsche mechanic, look at it this week. I figured worse case it needs an injection pump, which I know is a big job. The car is in decent shape, it was always garaged, not much rust, the car was repainted in the late 70's so it's showing it's age and needs some cosmetic fix up. Had to have it towed because it wasn't drivable. Hopefully I'll have it on the road soon. Do you belong to any local clubs?

Good luck with your new baby! I belong to the Northern NJ Region PCA, but really haven't had time for club activities, and most of them aren't local to me.

You should read this thread in its entirety.
http://forums.pelicanparts.com/showthread.php?s=&threadid=173700&highlight=mfi+cu t+out

Lots of great suggestions for MFI. Once you get the fuel system cleaned, Move on to "check, measure and adjust".

Usually the pumps do not go bad. It could be out of adjustment for someone trying to compensate for other problems like bad thermostats, etc.

Other thing to try is to remove the side cover from the MFI and soak the entire pump in some b12 Chemtool. This will clean out all the old gas a varnish from the inside.

you should also go to this page.

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

and print out all the article. REad them, learn them, know them, live them. I will tell you that there are very few people that can tune an MFI system properly. YOu may have to take it upon yourself to fix the problem. Its not that hard and this board is really helpful.

Just to let you know, there is a search button in the upper right corner of the page. Make this your new best friend for tuning you car. you should be able to find the answer to your question there. It sometimes is much faster than waiting for an answer.

BTW, welcome to the life of a longhood. Glad to see another early 911 in careful hands. Once you get the car sorted you will absolutely love driving it. Those MFI 2.2E motors are great fun.

I agree, first order of business is to drain the fuel tank, remove the outlet fitting/filter screen, and clean the tank and filter screen.

This thread has info on fuel flow measuring.
“MFI thermostat spacers”
p. 1 end has CMA extension, p. 3 has nozzle, fuel flow, and fuel pressure.
http://forums.pelicanparts.com/porsche-911-technical-forum/169445-mfi-thermostat-spacers.html

“More Fun with MFI and LM1”
How to use protractors for correlation.
http://forums.pelicanparts.com/porsche-911-technical-forum/179707-more-fun-mfi-lm-1-a.html

Here is the thread listed above.
“MFI Problems”
http://forums.pelicanparts.com/porsche-911-technical-forum/173700-mfi-problems.html

Best,
Grady

Tom,

Sorry for being so brief earlier.

Welcome to the Pelican Forum and to the world of Porsche.
It is proper etiquette to post photos of the 911.

Jamie is correct; you should become your own diagnostician and expert with MFI. This Forum can help. There are many “expert” mechanics who can lead you down the wrong path. You want to know as much and have technical information as the best mechanics. If for no other reason, you can ask the right questions and properly interpret the answers.
With minimal mechanical skill, most of this is DIY stuff.

The Porsche document 4532.20 “Mechanical Fuel Injection - Check, Measure, Adjust” (CMA) is Porsche’s instructions for dealing with MFI. It is the best and only starting point. You will find on the Forum many worthwhile additions, clarifications, and extensions to CMA. The most recent production MFI 911 is 30 years old. CMA assumes all new parts so there are a lot of age and wear issues not addressed.
Here is CMA: “Mechanical Fuel Injection - Check Measure Adjust” (CMA)
http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf


I encourage you to read all the above listed threads in their entirety. You possibly should start yourself a digital or paper personal “MFI Manual.” This will be of immense value to you when discussing MFI issues.

When working correctly, MFI is the best fuel system ever for a 911 in terms of throttle response and power. It is tolerable at part throttle but never will give outstanding fuel economy. You have a street version of what Porsche used on 917s, 935s and more.


OK, OK,

Back to your issue.

I am a proponent of measuring and diagnosing first. You should perform the fuel flow and pressure tests listed in the links in the prior posts.

So, you need to clean the fuel tank (I expect.)

Remove the large plate from under the front suspension. This may take some Ez-Off and coaxing (force.) If you intend to test drive it with the plate off, you must reinstall the two larger bolts and washers.
Drain the fuel from the center, lowest, fitting. Properly dispose of the old fuel; you don’t want to put it back in the 911.
There is a large brass fitting to the left of center with a central hose. Remove the hose without scratching the fitting.
With a large box wrench, loosen the fitting. I don’t think you can remove it with the tank in place but it is easier to loosen with the tank firmly attached to the car.
Loosen both clamps for the big filler hose, remove the breather hose, and unplug and remove the fuel level sender.
Now you can remove the tank mount brackets and remove the tank.
Clean the screen fitting with carb cleaner first, lacquer thinner, and compressed air. Use a brass wire tooth brush. If you need to replace it, only use the brass version, not plastic.

Do a search on fuel tank cleaning and such. There are lots of options.

Reassemble in reverse order. You will need a new gasket for the fuel level sender and new O-ring aluminum seals at all the fittings. Inspect for any damaged/old hoses, replace if even suspicious. Fuel or vapor leaks are obnoxious to smell and very dangerous.

Some “while you are there” issues might be to replace the fuel hoses and Y-fittings at and around the electric fuel pump. I prefer stock OEM parts, including clamps.

I would not (yet) replace the MFI filter or the electric fuel pump.

With fresh, high (110) octane fuel, repeat the fuel pressure and flow tests.


How long has the 911E been sitting? There is some good info here on how to protect a 911 engine on start-up:
“Winter Storage Checklist”
http://forums.pelicanparts.com/porsche-911-technical-forum/183215-winter-storage-checklist.html


Regularly update this thread (don’t start a new one) as you make progress. You can easily find it using your screen name and keyword MFI in a Pelican search. This Forum moves about three +/- pages per day.

Best,
Grady

Thank you all so much for your warm welcome and expert advise. This information is so helpful. I printed it out and will be working on the car very soon. I will get back to you with the results and will post pictures as soon as I can get the car out of the garage, maybe sooner!:)

The car has been driven only 60K miles in the past 26 years and was only driven to local shows during the summer months in the past few years, so it did a lot of sitting in a garage.

Tom,

I’m going to add some about jacking and supporting your 911 when working under it. Excuse me if I duplicate your skills but there are many others who lurk here.

The two major safety issues here are the jacking and supporting the car and dealing with gasoline.

Always block both front and back of both tires on the opposite end of the car. In this case, additionally apply the parking brake. Leave it in neutral (you may want to turn the ignition on and you don’t want the car to jump if you forgot it was in gear.)
To lift the front of the car, it is best to jack under the suspension A-arms. Position the jack inboard so it can’t slip. Many make custom wood inserts for the jack, cut to fit the suspension.

Large, heavy, broad base, sturdy jack stands are a must. Keep them set as low as comfortable for you. For your project it is best to place them at the front of the A-arms. Make sure the floor surface is flat and secure and everything is “settled in” and not ready to tip.

Always have redundancy for the jack stands. I usually suggest 2+ tires and wheels under the main chassis of the 911. The tunnel is usually very strong and somewhat out of the way for your project. Once everything is in place put the jack under the front tow hook member as a third safety.

If at all practical, leave the front tires on.

Remember, you are going to be under the 911 wrestling with balky bolts and fittings. We don’t want to read any obits or worse.



Gasoline is probably the most dangerous substance we normally come in contact with.

Disconnect the battery ground first. Make sure the ground cable can’t touch anything.

When you drain the fuel tank, do it outside, away from your house. It is easiest to siphon the fuel after removing the fuel gauge sending unit. I have a 3’ piece of 5 mm brass tubing from a hobby/crafts shop and a small siphon from an auto parts store. When I get everything I can out, I pour in a quart of solvent and siphon it out (the gasoline mixes with the solvent.)

If you are really concerned, give the tank a short blast with a CO2 fire extinguisher or drop in a small piece of dry ice. 62 liters of air-fuel at ideal stoichiometric ratio is a powerful explosive.
One thing people tend to forget is in normal operation a fuel tank has just liquid fuel and fuel vapor. The air has been purged by the vaporizing fuel. When working on an “empty” tank is when there is danger.

When you have the car up in your garage and spill some fuel while dealing with hoses, fittings, etc. get out and clear the fumes. Do you have any open flame heaters, hot water heaters, gas clothes dryers, etc. in the garage?

I am a whimp when it comes to fire safety. On track, I wear two layers of Nomex underwear, two layers of Nomex sox, a Nomex balaclava, Nomex & leather gloves & shoes, Nomex lined helmet with collar, and a four-layer Nomex driver’s suit. A burn injury is devastating.

Best,
Grady