Owen

iTrader: (1)

Float bowls fill all the way up but there's no leaking.
(The stock Nikki is deadheaded, only way I could get the pressure gauge to read.) I hope the fuel isn't getting dumped straight into the engine, doesn't seem that way. But it doesn't want to start either...

No matter what I do, I can't get the floats adjusted to where the bowls only fill half way! I guess a rebuild is in order but...don't know what year carb it is...Am I SOL?
https://www.rx7club.com/1st-generation-specific-1979-1985-18/need-help-asap-id-ing-nikki-576938/

perfect_circle

that sounds like your needle and seat. the needle valve closes off all of the fuel from getting to the floatr bowls when thr floats tell it to.

Kentetsu

What do you mean by "deadheaded" ? I'll take a guess and say that you have no return line hooked up? If so, then that is the issue (most likely). You will also need to have the little "bullet" restrictor in place in the return line, because without it you won't show any fuel pressure hardly.

If the floats are stuck, try tapping on the top of the carb with a screwdriver handle or something like that.

Owen

iTrader: (1)

But the bowls are full....???

vipernicus42

iTrader: (4)

It doesn't matter if the bowls are full, he's right.

Think of the inside of your carb like the inside of a toilet tank. The float raises with the water (fuel) level until it gets to the point where it closes the valve (needle and seat) and stops more water (fuel) from rushing in.

If the valve (needle and seat) don't close properly, the float can go as high as it wants and it won't make a difference.

You should NEVER adjust your float levels unless you have extremely good reason to. They don't come out of adjustment on their own very easily. If I were you, I'd get a nice accurate ruler, check the carb manual, and spend some quality time making sure you didn't mess up your float level. Then remove the floats, pull out the needles. Blow out the seats with compresed air, replace the needles and floats. Then move the floats up and down their full range gently by hand at least a dozen times each. This should solve your problem.

This problem is very common right after carb rebuilds because the needles and seats stick until they wear themselves in. When it starts doing that, often just a tap on the fuel bolts will fix it, but sometimes you have to take the top off the carb and move the floats by hand again. Ask me how I know.

Jon

vipernicus42

iTrader: (4)

While deadheading your carb is possible without many problems, you should consider the fact that your guage sucks. I had a Mr. Gasket 0-15psi guage that wouldn't read at all, or read about 1psi, then I got an actually ACCURATE guage and found out that I was really running 5.5psi.

What fuel pump are you using? Do you have a regulator?

Don't trust guages that parts stores sell with the 0-15psi range. They suck nuts.

Respeed has an amazingly accurate guage, but it's not cheap. The only one I'd trust though.

Jon

Owen

iTrader: (1)

Yes, the return line is currently capped. Not the best setup but do-able per information on this site.

Fuel pressure is at 3psi or so deadheaded. Return line is non-stock. Should I switch back to the return system and put a restrictor in? I don't have the stock line anymore...I did try pinching the line and that still didn't show pressure on the gauge.



This baffles me, how does a stuck needle cause a leak if it's stuck in the closed position? Or do they normally stick half way? Even then, the float should be pushing it up while more fuel enters the bowl right?


More info: I tested the floats in a bucket of water and they're not sinking. Adjusted the float tabs, cleaned out all the little needles/screws, and jet things at the bottom of the bowls, turned the airhorn upside down and did the blow test, which passed. The last install, BANGED on the banjos and it stopped leaking and the bowls stopped at full. I'll try draining from the holes below the windows and turn on the pump again.

Also, I tried gutting the vent solenoid but it just made it worse so now its back to stock. I'm gonna have to do another teardown I suppose, 12 times yesterday, what's 10 more, right?

Thanks everyone for helping me with this.

vipernicus42

iTrader: (4)

For info on the stock carb I recommend reading these archived threads by Sterling:

https://www.rx7club.com/1st-gen-archive-71/intake-nikki-carburetor-rebuilding-tips-238032/
https://www.rx7club.com/1st-gen-archive-71/intake-carburetor-troubleshooting-flooding-problems-238029/
https://www.rx7club.com/1st-gen-archive-71/intake-carburetor-troubleshooting-acceleration-problems-238028/
https://www.rx7club.com/1st-gen-archive-71/intake-carburetor-troubleshooting-high-rpm-power-loss-238027/
https://www.rx7club.com/1st-gen-archive-71/intake-write-up-mech-seconds-accelerator-pump-mod-37243/
https://www.rx7club.com/1st-gen-archive-71/intake-carb-crap-nikki-mods-62678/

The second one deals exclusively with flooding problems.

Here's an article from Paul Yaw's site about how critical fuel pressure is and the innacuracies of standard automotive fuel pressure guages:
http://www.yawpower.com/fueldel.html

The first two parts listed on this page are the fuel pressure guage I was talking about and a quick-disconnect valve which lets you have the guage only connected when you want to tune.
http://www.mrcmfg.com/respeed/catalo...e859ef7ef141bc

Jon

Owen

iTrader: (1)

Thanks man, my reply to Kentetsu might have answered some of your questions, but I've done the adjustments you mentioned above also. I didn't want to take apart the carb but had to...:-( I used dial calipers to set the levels.

My confusion is, ok, the needle isn't seated properly, so the bowl filled up. At one point, the needle SHOULD seat, but it kept overflowing into the carb bores. My guess is a problem with the needle tip or needle seat itself, hence my wanting a rebuild kit. Still no luck on that tho.

I know for a fact when my needles go up, they usually don't come down. Which is why I asked the needle sticking half way question. The design sucks IMHO, there should be a spring at the needle seat. The way it is now, the spring moves up and down in the needle which is stuck. Can/should the spring be stretched to lengthen it?

Owen

iTrader: (1)

Yeah, cheap *** gauge! But when I deadhead the carb...I get a reading...I need to look into that restrictor thing.

Fuel pump is a Facet Posi-Flow electric, had it already and it works. FPR is the Holley 1-4psi one.

I wonder if Napa has accurate gauges, I know summit sells them but they're the 1-15psi range.

Owen

iTrader: (1)

Thanks, yeah I've read all those and have them saved to disk, LOL. AP is ok, good strong streams, banjo filters very clean. I'll try and find another gauge locally.

Rx7carl

You can deadhead it if you control the pressure, so with your FPR you should be ok. Is the vent solenoid working?

Rx7carl

The needles may be sticking in the bores or there may be trash keeping the tip from seating properly, or they may be flat worn out. I replied in your other thread about rebuild kits. Dont mess with those springs, it wont help. The pressure of the fuel will open the needles when the float drops.

Owen

iTrader: (1)

Yes, the vent solenoid is working, strangely enough...

I just know it's the needles, thanks for your other reply in my ID thread.

Quick question, I know the specs for setting floats off the car. But say you have a car like a drag racer with a lot of rake, that would tilt the carb and mess up the settings won't it?

Gotcha on the springs, I even tried small spacers between the plunger and needle body to try and get more leverage! It shoulda worked...in theory???

Sterling

How much rake?

Owen

iTrader: (1)

I don't know...it was just a hypothetical question!:-)

perfect_circle

i dont think you would see enough of that to make a difference unless you were getting the tires off the ground, at which point you probably wouldnt be using a nikki anyway. probably boosted efi.

Owen

iTrader: (1)

yeah it was just a thought. i read here that the carb should be level. and then thought about my 13b intake mani with its angled neck and base which the carb bolts to; and wondered why it wasnt flat?

Owen

iTrader: (1)

BTW, it stopped flooding after a rebuild and some 3-1 oil on the needles. Still couldn't get fuel pressure to read unless I deadheaded it.

Next problem is, it won't start! I'll start a new thread.