Darth Linux

After a rebuild, my 73 Nikki shoots gas out of the nozzle where the upper small venturis are instead of the accelerator pump nozzles when I depress the gas pedal. The accelerator pump got a new diaphragm, the inlet and pump nozzle check ***** are in place- everything seems ok, but it's squirting gas from the wrong place.

Any ideas on why this may be happening? I'm thinking that perhaps the accel. pump isn't even working and the carb is just drawing gas out of those low speed venturis as a matter of operation.

If that's the case, then what would cause an accel pump to not squirt? the lever actuates the diaphragm, the spring is in place . . . I have no way to really test things out other than when the car is idling with no load on the engine. thanks in advance

Dave
73 RX-2

Sterling

Well, my immediate reaction to the first paragraph was that your carburetor is indeed...
...possessed.

The acelerator pump (AP) circuit is completely unattached to the main circuit. So the AP can't be causing the boosters to get fuel. (The small "mini venturis" in the big bores are boosters)

The AP nozzel is located in between the primaries. Test it with the engine off. As long as there is fuel in the fuel bowl behind the AP housing where the diaphragm is, then you should see a squirt of fuel shoot evenely from both sides of that nozzel, directly into the center of each primary venruri.
Simply operate the primary throttle shaft by hand while you look into the carb.

If you rebuilt the AP with a new diaphragm and clean ***** and wieghts, and there's a gasket under the nozzel, then there's not alot that can go wrong.
Possibilities include;
A crooked wieght ubstructing the checkball,
a piece of crap is lodged between the check ball and it's seat causing a bad seal to occur,
the nozzel is clogged with ****,
No fuel in the fuel bowl.

Check out my site for help. Just click on the picture in the signature, and click the next one as well.

The leaky boosters are a different problem - unfortunately you have more possibilities to check.

First, fuel pressure should be no more than about 3.75 psi +/- .5 psi.
I do not know what the float drop is for a 73 Mitsubishi Nikki. But if you futzed with it, shame-shame! It can screw you all up unless you know the specs and what you're doing.
Let's assume you did not...

The fuel level should be half way up the glass in a later Nikki. I assume it should be that way with an earlier carb as well, however I do know the floats have more volume. (For this reason, I dont think you can set drop by later Nikki specs.)

So see if one is "lazy" on the fuel level.

If they are full, then your needles are not seating.

See my website.

If they are where they're supposed to be, even roughly, (IE if it isn't flooding...) then there's another problem...

Upon idle, the main circuit shouldn't even be open to pressure drop. At such low RPMs there simply isn't enough air flow to create the pressure drop within the venturis to allow the fuel to be pushed out of the fuel feeder into the booster by atmospheric pressure acting on the resevoir.

But if your resevoir is not vented to recieve atmospheric pressure, it can be depressurized ever slightly enough to overcome the buoyancy of the floats, letting in more fule...under pressure, which causes the fuel to surge out of the feeder tube. If the carb is'nt vented, it will flood because of this, and the most puzzeling thing to people is when the turn off the car and the damn thing is still spilling fuel!
...simple siphoning action.

Another possibility-
Your idle circuit is'nt functioning at all, and you're basically running idle off of the main circuit.
Kind of far fetched, but possible, though perhaps not for you. You would've been cursing about the crappy quality of your idle first and foremost.

So look through my site, especially the troubleshooting Nikki part, and with any further questions, PM me to return to this thread.

Good luck and keep us updated.

Darth Linux

thanks Sterling. I'll check out those things you listed. There are some things in your list that don't exactly apply to the older Nikki, but I'll detail those in a later post. I'm going to go work on the carb at the moment and see what I can do.

Darth Linux

UPDATE:

My AP actually works. It's just that my carb was idling on the primary circuit, so when I blipped the throttle, I didn't see gas coming out of the AP nozzle, just fuel out of the nozzles for the boosters.

Why is it idling on the primary circuit you ask? Well, I've had this carb/engine apart for over a year and a half, and when I put it all back together, I put the insulator spacer UNDER the drip tray rather than on top of it. RX-2s have a drip tray under the carb to catch gas and oil, and it dumps it out a little hose that leads to the wheel well. Above this is a resin spacer about a 1/4" thick that the carb sits on. When I put it all back together, I forgot which order it went on and put the spacer under the tray. So, my linkage didn't have enough room to return to a real idle position cuz it was binding on the tray.

Once I get things swapped around, I'm pretty confident I'll be able to actually set the idle.

Now, to clear up a few things about early Nikkis:
*they don't have the weights over the checkballs for the AP inlet and outlet circuits. not sure why, but they don't.
*they don't have any sort of venting solenoid, so they must be vented in some sort of "natural" fashion i.e. through the bowl cover.

one last thing - I had to futz with the float bowl level because someone else had messed with them thinking that you set the level the same as on the RX-7 float . . . which you don't . . . anyway, previously, the floats were preventing gas from filling the float bowls even 20% - which explains why I had NOO power and when I blipped the throttle the AP did nothing but dribble. It dribbled cuz there wasn't any fuel in the bowl!! DOH!

anyway, thanks for the advice. Some careful thinking after reading your post and some troubleshooting got my float levels straightened out, the AP nozzle was tested successfully and I found some binding in my linkage.

happy rotoring!

Darth Linux

UPDATE 2:

ok, I'm still having problems. I can't get it to idle low enough to actually set the speed and mixture. It seems to be binding on something. I'm not sure if it's the accelerator pedal cable or the hand throttle cable that is binding so I'm gonna take the hand throttle off for now.

also, my float level is off again. I set it when everything was cold and the gas was in the middle of the sight glass. I got it running and fully warmed it up and the gas went to the top of the window and started floading the engine through the secondary boosters!!!

It may because I messed with the bi-metal spring thingy in the fuel return line. My book says that the writing on the bi-metal spring should face up. Well, guess what, mine doesn't have any writing on it. It was installed with the bend pointing down which seats the little needle valve. My brain at the time told me this was backwards because I wasn't sure if the strip would get straighter as it warmed up or more bent . . . If I messed it up when I reveresed it then perhaps that is what was causing the flooding because the fuel return valve was stuck closed. Thoughts?

Also, I'm really confused about the float drop adjustment. If I'm holding the bowl cover upside down and the floats are resting on the needle valve, does increasing the space between the top of the float and the bowl cover raise or lower the fuel level in the bowl?

thanks in advance
Dave

Sterling

I don't know about a bimetal spring.
Widening the space lowers the fuel level.