Weber 32/36 DFEV problem. Tuning help needed.

[16vDigiGti]

To start off I will just say i searched the sh!t out of the web and vortex before making this thread.

I recently rebuilt my Weber 32/36 DFEV and have been having some problems.

When I took it apart, i removed the main jets it had in it(a 137 and a 140) and installed a 130 in the primary main port and the 137 it had in the primary into the secondary port. I didn't touch the idle jets nor the air jets.

It was pretty much a complete rebuild, i replaced the pump diaphragm, the choke diaphragm, and the economizer assembly. I also replaced the fuel needle assembly and noticed that the one on the carb before was a "200" and the one that replaced it was a "175"

I made sure to have the float level at 12mm at fuel shutoff and 26mm at full droop.

I also set the carb at the reccomended baseline settings as per the redlineweber website.

See:
http://www.redlineweber.com/ht..._.htm

I did the lean best idle tune and got it to idle nice but as soon as the engine gets warm the idle raises to about 1400 and wastes too much gas.

What am i doing wrong?

TIA

[chickenfriend]

You said, "I did the lean best idle tune and got it to idle nice but as soon as the engine gets warm the idle raises to about 1400."

This step is incorrect. The lean-best idle tune can only be carried out on a warmed-up engine.

The choke should be fully open (plates vertical) and the fast idle cam disengaged. The radiator fan should have cut-on at least once.

Your warmed-up idle should be between 850 and 900 rpm, but closer to 850 if you are having problems with run-on or dieseling. Check your timing at this point and re-adjust as necessary.

Throttle plate action should be smooth all the way down to the base idle speed setting; if the plates bind constantly or occasionally, make sure the throttle shaft nut is not too tight. If the nut is ok, then you will have to pull the carburetor and re-center the plates in the bore; I would do this with a warm caburetor and locktite the plate screws afterwards (it is not necessary to remove them).

The idle speed and mixture at at warm-up is controlled by the fast idle cam and the choke: the "lean-best" setting is not a player in the first couple of minutes.

After you set the lean-best idle to a warm engine, post back if you are still having problems

[16vDigiGti]

Timing is at 8* BTDC @ idle.

I will set the lean best idle again and post up later.

Thanks for the help.

Modified by 16vDigiGti at 11:38 AM 9-27-2008

[16vDigiGti]

Ok i redid the lean idle adjustment while the engine was warm and it all was well. then i came home and the car was off for a few hours. it cooled down then i went to start it and the idle was waaay too low so i adjusted it to 850. once it warmed up it was at about 950 so i lowered it a little to about 900. all seems well so we'll see tomorrow when i go to start it.

[chickenfriend]

Sounds like your fast idle cam needs adjusting and/or your choke. Both ensure reliable cold starting.

The fast idle cam holds the thottle plate open for a faster idle from a cold start. When the engine is warmed-up, a tap on the accelertor petal frees it and the thottle plate will return to the setting you have your idle speed screw at.


Modified by chickenfriend at 11:11 PM 9-28-2008

[B4S]

Yeah, I wouldn't worry about the too-low idle at warmup if you're not using the choke. My mikuni idles at 800 cold/1100 warm, no choke.

[16vDigiGti]

how do i set the idle cam? i searched but found no settings.

[chickenfriend]

When the engine is cold, rotate the throttle cam with your hand, or use the accelerator petal. Roll your window down or open the door if you use the petal so you can hear things under the hood.

Slowly depress the petal, and about 1/3 of the way, you should hear a click. That is the cam setting itself. All is well in your world when you hear that sound. I think there might even be two steps to the cam, I can't remember, but if so, additional rotation would produce a second click.

When the engine warms up, the cam keeps the throttle open until you depress the petal again to release it. The idle should drop immediately and substantially when you do.

Once the engine is warm, the action of the choke disables the cam system. In other words, the choke and the cam work together like one happy family.

The choke needs to be properly adjusted. If I recall, if the choke setting is too far out, the fast idle will not work.

You can begin to learn about the fast idle cam by finding the vertical arm lever whose bottom has a 90 bend that slips into the throttle/accelerator cable cam. It's the piece that has a little dog-leg bend about half-way on it. Follow it up to the top and you will find the fast idle cam and the adjusting screw.

It might be a good idea to remove the carb and spend some quality time playing with the mechanism until you understand how it works, because the mechanism is a bit hard to see since it is under the choke, assuming you have the electric choke.


Modified by chickenfriend at 12:18 PM 9-29-2008

[16vDigiGti]

I found my problem: worn acc. pedal bushing

i popped in a new one i had as well as a new acc. cable and all is good. I will wait to see if this solves the problem. old acc. cable was sticking and not letting the throttle go back to rest position.

[chickenfriend]

I guess I am bumping this aging thread since I came across it in a google search regarding float level adjustment for a Weber DFEV carburetor.

Just thought I would add in here that after a little frustration, I finally located an official-looking Weber Carburetor Factory Calibration Chart on a webpage, and it states float level for a DFEV or DFAV should be 46.5/36.5mm.

I checked mine and it matches these specs exactly (give or take that 0.5mm )

This is not the same setting as for the DGAV or DGEV, indicated by the same chart as 35/51 for a plastic float or 51/41 for a brass float.

The measuring process is to hold the top vertically with the float hanging down. Tilt the top so the float hangs out to the max, and measure the distance from the bottom of the float to the gasket surface, this s/b 46.5mm. I use the depth rod on a slide caliper to make this measurement, because it is fairly easy to do it that way.

Now, tilt the top back toward vertical, and watch the tab on the float bracket, which rides inside the hanger that is on the needle valve. When the tab swings over and first touches the ball on the needle valve end, take the other measurement the same way, gasket surface to bottom of float.


If the top is tilted past this point of first contact, then the lever begins depressing the spring--loaded ball and the float will not be in the correct position to do the measurement.

I also noted that Weber had not tightened down all the way one screw on the power valve diaphragm. People say to check out these carbs when new for stuff like that, quality control problems, probably a good idea.

I remember I shaved off about 3 threads at the end of the fast idle screw to make it smooth because the threads were hanging on the fast idle cam. The threads are not needed there for anything, I'd say they used a wrong screw.

I might add, all the settings show by that chart (http://www.mgexperience.net/article/...librations.pdf) match my stock jets, except the order of the primary and secondary emulsion tubes. The only thing I changed was the idle jet combo, stock it was 60/55, and I went to 55/50, which gives me 1.5 turns out on the idle screw to a lean-best mixture. Engine is a 1.7L.

I am still trying to remove one of the emulsion tubes to check the size. It is stuck good. The other one was clean, so at the risk of tearing up the tube, I might have leave it alone.

There is a F50 emulsion tube on the secondary side. According to the chart I referenced, the other tube should be a F66, although the chart indicates the F66 should be the secondary, which must be a typo. I located another official Weber diagram that indicates the F50 should be the secondary emulsion tube.