kumiko44

iTrader: (1)

In need of a little help from people who know fb's really well, so I came to the one place I knew I'd find great help

My '83 is having issues. Major issues. We finally got it running again yesterday, it'd been sitting in my yard for the last 6 months or so due to no insurance. I had a friend of mine rebuild the carb, since the last one crapped out after the rats nest was removed, because someone decided silicone would work instead of using a proper gasket. Now the problem is, the one that is currently sitting on my car is meant for a street-ported engine (it's my friends old carb, it's a 79).

So the issue we ran into yesterday was, when the float bowls are full the car runs fine, but as soon as they start to empty, the car will bog and die out. Let it sit for a few minutes, and it runs normally again. I'm thinking that maybe because it's meant for a ported engine, and my 12a is completely stock, that it's dumping too much fuel into the engine and causing it to flood? Is this possible?

Also, when we managed to limp the fb home, he tried to start it, but the fuel pump made this weird gurgling noise on a couple of attempts before the car started again. My brother heard the same thing when he attempted to start it mid-week. I have NEVER heard the fuel pump make that sound before. It's an aftermarket pump (carter if I'm not mistaken). Any reason it would be doing this?

Sorry for the novel guys I just want my little fb running normally again.

84stock

iTrader: (5)

check the fuel filters

Rx-7Doctor

iTrader: (13)

Perform a fuel pressure/volume test.

kumiko44

iTrader: (1)

Thanks guys, I'll do those asap and let you know

gregrx73

I agree with Rx-7 doctor. First carry out a volume test before pressure regulator and then after the pressure regulator. This will help to see if you pump is working properly. Reguardless install a new fuel filter like 84stock said. Set the pressure regulator to 2.3 - 2.6psi. Do this and you should be fine. We ran these stock carbs on a ported engines in Calgary for racing and they ran pretty good. I had my bad experiance with fuel delivery and hate to hear that someone else is having the same problems as I had.

Is the ventury tubes larger than stock?

Gregrx73

brando54009

sounds like half of the pump might be burnt out

orion84gsl

iTrader: (5)

Is the carb a completely stock or was it modified? What size are the jets? If it hasn't been modified than there is no reason it would not work perfectly on a stock port engine. Definitely sounds like the fuel can't keep up with the engine.

kumiko44

iTrader: (1)

The carb has been modified for a ported engine. Like I said in my post, it's almost like there's too much fuel for the car to handle. As soon as the throttle pushed, it bogs and then dies. I bought a new fuel filter today, so that'll be going in tomorrow after work, providing I can find a tutorial on how to change it.

I'm not entirely sure about the venturies, it was my friend's carb that he gave me because my previous one died.

Kentetsu

It can be very hard to tell the difference between flooding and starving. Does it seem to run better with the choke on?









.

EDSRX3

Do you have any details how the floats were set up? Did you check the needle and seat? If you are dealing with silicone, a dab in the right place could limit fuel flow past it!

Rx-7Doctor

iTrader: (13)

Quit screwing around and perform the test that I recommended please. :-)

You don't a need tutorial on how to change a fuel filter on a engine with a Carburetor. Pinch off the line that comes from the tank to the fuel filter. They make a special tool for this but in a bind (but not recommended) use some vise grips or have a bolt ready to insert into the end of the hose (After you remove the hose and are not using vise grips or pinch off tool) to keep fuel from spilling everywhere. Undo the clamps, removed the filter. Install new one making sure arrow is pointing towards front of vehicle (towards the carburetor). Reinstall clamps. Perform fuel quantity/pressure test.

Specifications for "Minimum" fuel specifications are in the FSM (Factory Service Manual). Link is in my signature. Also their is the procedure to replace said fuel filter. As well as troubleshooting guide. Also in my link is the carburetor service manual. It also will have more on troubleshooting. :-)


Your quote-
So the issue we ran into yesterday was, when the float bowls are full the car runs fine, but as soon as they start to empty, the car will bog and die out. Let it sit for a few minutes, and it runs normally again. I'm thinking that maybe because it's meant for a ported engine, and my 12a is completely stock, that it's dumping too much fuel into the engine and causing it to flood? Is this possible?


Now examine that statement. If you were flooding the plugs would be fouled and soaked with fuel. Also the fuel bowls "Start to empty", they don't empty when you are "Flooding". :-)

kumiko44

iTrader: (1)

I appreciate the help, but I'm new to rotaries and mechanics in general, so a lot of what I say comes from the friend who's been helping me or my brother. My being new to this is the reason I posted here in the first place. This is way over my head so I figured I would ask people that knew a hell of a lot more than me.

That said, I am not screwing around as far as the test goes. I was reading the manual I have and it said to use a pressure gauge (which I need to purchase) and to replace the filter before either test to ensure the results are not just caused by a clogged fuel filter. Is this wrong?

Ken: It will start and idle semi-normally with the choke on, though it still feels rough. Not as violent as when a rotor blows, but that same sort of rocking motion.

Rx-7Doctor

iTrader: (13)

Sorry I am lecturing or trying to be hard on you. You have to remember that those of us who have been around these cars for a long period (me, almost 1/4 century) know most of the more common things to look for based on the information that is posted.

In many cases you may have more than one issue going on.. In order to properly diagnose you have to start at the most common and go from there.

Seeing you stating that the fuel bowls are running out, the fuel pump is making weird noises and the engine bogs is pointing towards fuel delivery at this point. Other things may also be causing the "Full" problem but lets not over complicate things and start at the most basic and easiest. :-)

Yes, you do need a fuel pressure gauge to test pressure. However you can test fuel volume.First thing you have to do is change the fuel filter.This is done as to eliminate any possibility that the filter is a restriction and give a false account of the true volume. Also inspect the hoses at the fuel pump and make sure they are not kinked, therefore causing the fuel pump to not operate properly. Ensure that your electrical connections at the pump are clean and tight to ensure you have proper ground and power to the pump.

Then get a suitable container such as a metal can or glass Pyrex that shows how much it holds. Disconnect the fuel feed hose from where it goes into the carburetor. The next step is better if you have 2 people. Someone has to hold the hose into the can and record how much time goes by. Of course the pressure test is supposed to be performed first but if you don't have a gauge yet this test will give you some insight. Anyways you should see approximately 1.48 QT's of fuel expelled in one minute. The other person if you have available is the one that can turn the key to the on position to activate the fuel pump. :-) On position (not start position). To prevent accidental starting of the engine you can also disconnect the coil wires. :-)

Note:
Friends are great but if they do not have "First" hand knowledge of the vehicle in question or have a lot of "On hand" experience with general Automotive Mechanics then it best to take what they say with a "Grain of Salt". :-}

Kentetsu

Kumiko, is the car driveable at this point? What I meant when I asked about the choke was whether it actually drove better with the choke engaged than without it.

Like this; driving along and the car starts showing symptoms. Pull the choke out and see if it improves the situation or worsens it.

That is a very easy way to tell whether the problem is related to too much fuel, or too little.

kumiko44

iTrader: (1)

Ken, the car is barely driveable, and it doesn't run any better with the choke pulled out. I would say it stays about the same.

doc, thanks for the clarification on how to do the test the car's frustrating me so I'm sorry I snapped. The friend that is helping me has owned a few fb's himself and is very knowledgeable about them and how they work (especially the carb aspect), but he lives quite far from me and doesn't always have time to come help me out, so I figured I would be proactive and search for the solution myself. This week I will go to canadian tire or something and see if I can rent one (Lordco *auto parts store* wants $129.99 for the guage).

trochoid

iTrader: (6)

I'll keep this simple.

The modified carb was modded to provide more fuel and air to the ported engine. If anything, yours should be running a tad richer since most ported engines pull less vacuum. It cannot run rich enough to empty the fuel bowls.

You don't need an in dash fuel pressure gauge to do the test. You should be able to find an inline gauge for 10-20 bucks at most parts stores.

You have a fuel supply problem, period

Common causes are plugged fuel filter, fuel pump going South. kinked fuel line, cracked fuel line sucking air or a crap/rust in the fuel tank that's plugging up the supply/draw tube inside the tank. Cut open your fuel filter. If it's full of rust chips, time to have the tank cleaned and resealed/lined. Lastly, are you sure the carb rebuild was done correctly?

Personally I don't bother with pressure or supply tests, but then I've worked though almost every starvation issue there is. Did run into a new one this weekend though. The front bowl was filling/flowing fine, rear bowl was dry as a bone. That one's simple rebuild the carb, free up the float and install new needles.

From what you've posted it sounds like the fuel pump is toast but start with the filter first.

Good luck

ian65

I had exactly the same problem 10 years ago on a 1st gen. Mine was caused by rust in the fuel tank going down the lines.
The fuel filter by the pump will catch most of the rust but not all of it.
On my car, tiny specs of rust made their way down the line and clogged the fine gauze filters that sit under the banjo bolts when the fuel lines connnect to the Nikki carb.
The fuel flow will keep up with demand on tickover / low revs but under load or when you boot it, the float bowls will empty quicker than the fuel can get through the filters.
Leave it to sit and the bowls slowly fill back up
Cleaned the tiny filters out on my car and never had another problem ( although I did change the gas tank)
Worth checking them.

kumiko44

iTrader: (1)

Thanks I'll check that too My road test to get my Novice license is tomorrow, so I've been practicing most of the week, hence no updates. I'll be doing this soon though

DivinDriver

iTrader: (15)

With adequate fuel delivery, your bowl levels should stay constant no matter what engine speed is. The whole point of the float and needle system and the bowls is to keep the same amount of fuel depth over the jets at all times.

If your bowl levels drop when the engine is under load, it's pretty much got to be a fuel delivery problem.

j9fd3s

iTrader: (3)

the fuel volume test is very easy and takes like 2 minutes.

the wife gave me a juice container that just so happens to be marked in CC. pull hose off carb, put in container, turn on pump; i unplug the main fuseable link, and turn the key on, that way i can hold the container and turn the pump on at the same time.

even the PP engine is a 30 second 1500cc test, i'm not sure what stock is, maybe half that?.... its not that much fuel. pour the gas back into the tank when finished.

ideally the battery is fully charged, but the engine is cool, hot engine parts and spilled gas are not a good combination.

kumiko44

iTrader: (1)

Filter is changed, pump is shot. In the process of acquiring a new one. Thought I would update