Accelerator pump adjustment

Allenk · 07-24-2002, 04:46 AM

Yes another question. My 911 t was butalized by an uncaring ........and I'm just trying get things right. My accelerator pumps/linkage has obviously been toyed with some pumps not even being engaged. I have a Haynes that gives a breif desciption on how to set the linkage but I'm confused. What is the best way to set the finger adjustment screws? When should the pumps begin working? Is it when any throttle is given, or at 1/3 throttle etc....

T Bird · 07-24-2002, 05:55 AM

Allen
You have Zeniths in that car, no? I have no practical experience with Zeniths, but on Weber 40 IDA 3Cs, the accelerator pumps begin discharging fuel as soon as the throttles are activated. Can't believe it would be any different for the Zeniths.

Have you tried the factory workshop manual? There is material in there on setting up Zeniths. I have never bothered to read it though. If you don't have access to the manual, let me know and I'll look tonight and advise.

Good luck.

Allenk · 07-24-2002, 06:04 AM

I do have Zeniths and I don't have access to the factory manual so any info would be appreciated. I think you are right in that they should activate right away. I have 2 couple of parts carbs that activate slightly into the throttle being applied but I'd like to sure. Thanks again

Allenk · 07-24-2002, 07:58 AM

So is the setting a volume specific setting determined when at WOT. Right now if I press the throttle linkage the accelerator jets begin to squirt right away. Is this too early?

T Bird · 07-24-2002, 08:30 AM

No, it's not too early. You measure by placing the vial directly under the nozzle and having an assistant in the car press the accelerator pedal to the floor. Use an assistant-- you will get better results than if you try to activate the throttle linkage by hand from the engine compartment. Withdraw the vial and read the results. You can do this on the bench too, with the carb partially disassembled. Measure for each throat. The specified quantity reflects the amount of fuel discharged when the throttle moves from fully closed to fully open.

Allenk · 07-24-2002, 09:01 AM

Got it! Thanks people.

T Bird · 07-25-2002, 04:08 AM

Allen
Here's the procedure out of the factory workshop manual:
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1. Turn the self-locking adjusting screws ("a" shown in picture) at the pump shaft lever until the 3 actuating fingers on the pump shaft are positioned vertically (straight up and down).

2. Loosen adjusting screws ("b" shown in picure) on the actuating fingers.
CAUTION- To prevent inaccurate readings, do not adjust the injection quantity while the engine is hot.

3. Turn in adjusting screws of accelerator pumps for cylinders #1 and # 4 until they lightly touch the pump plungers. Tighten lock nuts.

4. Check discharge quantity in cylinders #1 and #4 with measuring tube P 25a. Nominal quantity is 0.5 +/- 0.1 cc per stroke. Activate lever once or twice before taking measurement. If the discharge quantity is too high, turn the adjusting screws on the actuating fingers farther in. Adjust as necessary.

5. Adjust the other accelerator pump screws as described above in paragraph no. 3. Recheck discharge quantity and correct if necessary.
NOTE- Fuel should flow from the injection tube as soon as the accelerator pump is actuated. If fuel does not flow immediately, the pump inlet valve may be defective.
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The factory workshop manual pages relating to these Zeniths (SF 46-SF 68) cover the following: description of operation of each circuit with schematics; carb specs; procedures for adjusting idle speed, auxiliary enrichment system, accelerator pumps, and float level; removing and installing carbs; an exploded diagram of carbs with numbered description of each part; and, how to check the micro switch.

If you want copies of these pages, send me a private message with your fax # and/or address and I will fax and/or mail to you.

Frankly, after reviewing this material, it's no wonder many of these Zeniths have been junked in favor of Webers!

Formerly Steve Wilkinson · 07-25-2002, 04:50 AM

What makes a nice measuring vial, by the way, is the barrel of a small medical syringe. Remove the needle (and the plunger, of course) and plug the tiny hole, and it'll have a lip around the top so you can wrap a length of soft wire around it, to dangle it into the carb.

All you need to do is find a friend who takes insulin.

Stephan

Allenk · 07-25-2002, 06:27 AM

Good one! I actually was a Veterinary Tech for a while and can get one from the VEt I worked for.