924Board.org

brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

Hello, and let me fill you in: 1977 1/2 924
We rebuilt the engine. New head, water pump, and new gaskets/hoses all around. As one of the injectors was leaking, we replaced all the injectors w/ new bosch ones, but before we did that, we (sorry, my father and I) took out the old fuel distributor which was leaking and had it rebuilt by a place that specializes with fuel distributors. Put it in (and new fuel filter), and the car ran okay, wouldn't idle right and would misfire. Pulled it into the garage, and all of the sudden the fuel pump started making a bunch of noise. Next time we tried to start it, wouldn't start. Turns out the fuel pump crapped out (or so we think). So, we started the next process: flush out the gas tank, add new fuel pump & prefilter, and fix the brakes. Surpisingly, the tank was really quite clean, besides a couple drops of water and some fine dirt. So we also did the brakes (no big deal) and the fuel pump. The old one looked brand new, but was quite small, but we got the right bosch one and put it in and the new prefilter.
So we finally flushed the lines out of the old gasoline that was still in the fuel lines. My father thought the fuel was coming out a little slow, but we continued on. Started it up, and ran pretty smoothly, but then started sputering.

Anyways, the essentials:
The fuel pump seems to be working immensly hard to pump the gas, making a bunch of noise and heat. If you push the accelerator pedal down, it just sputers at you. We took off the air filter and found the Control Plunger wasn't working properly; it seemed a bit stiff. We could get the engine to rev by pushing up the sensor plate ourselves, but the plunger just wouldn't push the sensor plate well by itself. We don't know where to look now, as we have put so much time into fixing this thing (three summers now) and really just want to get it running. Any suggestions will be greatly appreciated. Thank you!

Paul · Posted: Mon Jul 13, 2009 12:46 pm Post subject:

Time to get a CIS tester and verify that your system and control pressures are correct.

Once that is verified or fixed, then you will need an emissions gas tester to set the mixture.

DO NOT PLAY WITH THE MIXTURE UNTIL YOU CHECK THE PRESSURES.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Smoothie · Posted: Mon Jul 13, 2009 12:48 pm Post subject:

Assuming the fuel distributor was rebuilt correctly and the center plunger is actually not stuck...a blocked fuel return line through the WUR or beyond might account for both excessive backpressure on the plunger, and excessive backpressure on the fuel pump.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

We removed the fuel distributor and the plunger isn't stuck. We cleaned it to just make sure but didn't make a difference.

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

I believe that the steel fuel tanks have two fuel pumps. One internal and one external. Maybe you only replaced one when both are bad. I fixed this problem by upgrading to a bigger fuel pump off of a 951.
_________________
1980 924 NA
1982 931

Paul · Posted: Mon Jul 13, 2009 1:21 pm Post subject:

The sensor plate moves the plunger not vice versa.

You have checked for vacuum leaks correct? One leak can cause this problem.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

No vaccum leaks (replaced the vaccum lines and checked them all over), and only has one fuel pump. It does however have two accumulators. Because the whole lifter won't move right the car also now makes a whistling noise when you try to give it gas. My fuel set-up is the same as this one:
http://autoatlanta.com/model/924-76-79/201-12.htm

Nobbi · Joined: 24 Aug 2006 Posts: 1396 Location: Germany

What about the co2 screw and set up on your fuel distributor? Is it turned all the way to the left? If so, turn it two times cw. for basic start up.

Is the new fuel filter in the engine compartment installed in the right direction? Arrow pointing into the sky....?

Check fuel delivery, if you get 750 ml in 30 seconds, thats the minimum!
Bigger numbers are better.

Is your airfilter clean?

Did you replaced all of the rubber seal rings on the new injectors?
Replace them on a regular bases.(3 years)

Nobbi

_________________
NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1967

Paul · Posted: Tue Jul 14, 2009 10:36 am Post subject:

Stop everything else and check your system and control pressures.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

Well, the 924 is running nice and smoothly now, and none of the replies I have gotten were the answer (p.s., I know how to put a fuel filter on). With the help of the business that rebuilt my old fuel distributor, I found out that all it needed was to have the pressure regulator cleaned. The plunger valve was stuck, and was due to a few particles of fine dirt.
Thanks for all of your replys!

Paul · Posted: Tue Jul 14, 2009 11:36 am Post subject:

The CIS tester would have found that.....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Don't underestimate fuel filter confusion - the fuel filters on the 931's point toward the rear of the car when installed correctly!
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

Smoothie · Posted: Tue Jul 14, 2009 1:58 pm Post subject:

Well, actually I had it covered with the "or beyond" portion of -