1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

carb issue

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Old 10-28-23 | 12:17 PM
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nightli's Avatar
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From: Kingston, Ontario
carb issue

Got a 1985 rx7 base model this last month and doing lots of maintenance, got it to run a few times but it stalls out many times and need to play with choke before getting it to idle good enough to stay on, it mostly just turns on runs for like 2-5 seconds then shuts off, ive already replaced fuel filter and fully cleaned out the gas tank and put a new strainer in, have 15 gallons of fuel with pre mix 2 stroke in it, ratio of .75 oz per gallon and a bottle of seafoam. so only problem can be fuel pump or carb as the other issues are already fixed or replaced. ive taken some videos of the car running when ive got it to after playing with it long enough, it seems like the driver side barrels left one dribbles more than the right one (sorry for bad terminology im new to carbs) and even dribbles for a little bit after the car stops running as well. sorry i couldnt get a better angle in the video, if i put the choke in more it wouldve most likely stalled as it has before when ive tried. also not sure if this means anything for the fuel pump maybe being too weak but when the car runs the fuel filter doesnt hold very much in it (might be normal i just dont know, first time having a clear fuel filter on a car) also the passenger side barrels the left one dribbles and the right doesnt really let anything out at all. also not sure what the triangle shaped thing on driver side of carb is but when ive checked it seems like its running better when its full and pouring out a bit, and when the car runs rougher and lower idle and nearly dying its been like less than half full, not sure if thats how its designed or what but pointing out as much as i can think of since im so new to this and need help knowing the issues and if i can do anything to get it to run good enough to drive it to a storage garage im putting it during winter to work on it (tow truck cant get it in i have to drive it in) its only 10 mins away so if it runs crappy but drives that good enough, cant do much more than idle the way it is tho and takes like 20 mins of starting and stalling to get it to do that even... if anyone has more questions feel free to ask, thank you.
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Old 10-28-23 | 12:35 PM
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From: KC
Have you checked the fuel pressure and fuel volume? The factory service manual has a fuel volume test. Fuel PSI should be around 4.

Factory Service Manual can be found here.
http://www,foxed.ca
Old 10-28-23 | 12:59 PM
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i have the manual as well, do you know what page or section its in?
Old 10-28-23 | 01:06 PM
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Originally Posted by nightli
i have the manual as well, do you know what page or section its in?
It's in the fuel section. Don't know the page number from memory.

One thing that really impresses us here on the forum are new folks that dig in and do some research or search in the service manual before posting a question. This helps us rule out what you might have already done. Most of us old timers will know the answers from experience and will respond as such. Your doing a good job with what you've done. You would not believe how many times I'll just open the service manual and read it. You run across something and think, wow, I didn't know that.

Last edited by KansasCityREPU; 10-28-23 at 01:13 PM.
Old 10-28-23 | 02:54 PM
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yeah ive been looking through it alot as well and bookmarked most important pages too, just didnt notice a way to check voltage or even think of it yet, i just checked the voltage going to the connector and got my brother to hold the key starting it while i have the meter hooked up, it was showing me high 10's and low 11's on the volt meter, the connection had a little bit of blue corrosion so i cleaned it but seems the same result.
Old 10-28-23 | 03:20 PM
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Since you already have one thread basically the same as this one, it's easier just to have one thread.
Old 10-29-23 | 11:49 AM
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Since it's an 85 there's a fuel cut relay underneath the steering column under the dash just above the driver's foot well. Small cylindrical metal thing with a 6-pin connector. This was added in (I think) 83 to make it so that the fuel pump only rums when the engine is running, and cuts off if you flip the car so that raw fuel doesn't pour out of the now-upside-down carb. Previous years just ran the fuel pump as long as your ignition was in the last position before cranking.

This makes it harder to test fuel pressure and volume without the car running. The good news is that you can just unplug the relay and jump two of the wires in the connector together (they're in opposite corners but I can't remember which ones - search for fuel cut relay on the forum or look in the wiring diagram).

So you remove the relay, jump the wires, then when the ignition is in IGN position you'll hear the fuel pump going if you listen carefully.

Then just follow the Factory Shop Manual procedure for testing volume. I'm not sure how you'd test pressure without a gauge though.

Make sure you've got the Factory Shop Manual and Wiring Diagram off Foxed.ca and not just the Heynes manual. As good as the Heynes is (I use it a lot for quick reference) the FSM has many more detailed procedures and specs in it.

From the sound of it though, and personal experience, I'm betting that your carb is a bit gummed up if it's been sitting for a while. Mine needed a rebuild after sitting for 4-5 years in the previous owner's driveway. Either that or there's some kind of vacuum leak.

Rebuilding the carb is ... Well it's not super hard, but if you haven't removed all the emissions equipment (rat's nest, air pump, air control valve, shutter valve) it's a lot more complicated to remove and has like a dozen extra bits on it that make the rebuild a bit more involved. There's an awesome carburetor manual on foxed.ca, and there are lots of good threads on here about removing emissions stuff. Search for remove rat's nest, and also look up shutter valve, and ACV. There's a word doc I wrote years ago about stripping the Nikki carb to simplify it down, but I don't have a copy anymore. So if anyone here still has a copy, please share it!

For vacuum leaks, those are WAY easier to locate if you've removed the rat's nest and shutter valve and blocked off the ACV. If the shutter valve and ACV are properly removed and blocked off with no leaks, and the vacuum line for the brake booster is in good shape, then there are no vacuum leaks at the Intake Manifold. Then you just have to block off all the ports in the carb spacer with vacuum caps (except one that runs your ignition VAC advance) and that takes care of leaks there and you're done.

So yeah, if you can, do the emissions removal. Makes tracking VAC leaks and removing/rebuilding the carb WAY easier.

Good luck, happy learning!

Jon
​​

Last edited by vipernicus42; 10-29-23 at 11:54 AM.
Old 10-29-23 | 11:56 AM
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Oh ****, you're in Kingston? That's only like 2hrs away from me, I'm up in Ottawa. I know the weather is starting to turn wintery (I just put my 84 in storage for the winter yesterday), but I'd totally come down and offer to help you out in a couple weeks if you've got somewhere to work on it. Or in the spring if you don't and you have to tarp it for the winter. PM me.
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Old 10-29-23 | 06:00 PM
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I re-read your post. A few more notes:

It won't run without the choke until it comes up to operating temperature, so that part is normal. Usually with these cars we start it, pull the choke to hit about 2,000-2,500, then when it warms up the magnet in the choke **** let's go and the spring pulls it in so it drops to idle.

​​​​if you can visibly see gas dripping into the carb, that's too much, and it might be why you have to take "20 minutes to start". My guess is that one of the float needles in the carb is stuck slightly open and raw gas is pouring into the carb. The car runs until there's too much raw fuel then it floods out. One way to check this would be to pull the spark plugs and see if they're wet, or covered with very dark soot.

If this is the case, it's not a big deal. My carb does this literally every spring after being stored for the winter. If you take the blue airbox off the top of the carb you'll see two large bolts on the driver's side where the fuel tubes connect. Smack each of them a couple of times with a hammer (or whatever hammer-like device you've got, I've used the head of a ratchet sometimes when that's all I brought to storage with me). That should knock it loose.

You can clean the spark plugs with a wire brush. They're pretty robust.

Also, for future upgrades : New battery cables will get that starter spinning faster and the spark plugs sparking better, both of which make it WAY easier to start when flooded. In fact I've never had flooding issues since replacing mine, even in the spring when raw fuel dumps into the carb barrels.

I hadn't read your line about storage earlier... Yeah I can't make it down to K-town before the snow hits, so best of luck! Maybe you can tow it as far as you can then get 2-3 friends to help you push it the rest of the way?

In my experience if you're having this much trouble getting it started you'll probably have a few more things to do before it's fully road worthy. But maybe not

Good luck,

Jon
Old 11-14-23 | 11:53 AM
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I actually have everything else fixed up on it so far at least to get it operating, full gas tank cleaning, redid entire brake system basically and a lot of other things too long to list so after this carb rebuild it should be road worthy but i just started tearing down my nikki carb and upon opening it up the floats are filled with greenish grey powder, and defenitely clogging up the channels in there, looking it up on google shows its old ethanol atleast is what people say but heres some pics of it, defenitely see why it ran so crappy and was a pain to get started.. also my bad for late reply got so reoccupied recently and just got a chance to checkup o this topic, i appreciate the help and offer to help, defenitely looking like a spring time activity lol, i dont wanna reinstall this thing in the cold on the street, still looking for a garage to rent but people want way too much so might just be parking it in the nearby park free parking for winter



Last edited by nightli; 11-14-23 at 12:06 PM.
Old 11-15-23 | 11:06 PM
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Yikes, that is a LOT of crud in there!

Scrape out what you can then get a can of carb cleaner and go nuts on it to try and dissolve and remove what's left.

If you unbolt the two fuel tubes the bolts should have little screens on them. Check the state of those to see if that crap came up from the old tank and clogged those screens too.

Once the main body is as clean as you can get it, remove the bolts that allow you to slide in a thin flat screwdriver to remove the main jets. Those are the little brass things at the bottom of the bowls. Clean those up well, they're probably clogged, and spray the hell out of the holes where they went with more carb cleaner.

Following the carb manual from foxed.ca you can find the chapter for your year-ish and that will help. Do you have a rebuild kit handy?

Do not, under any circumstances, attempt to adjust the level of the floats or use the needles/seats that came with the rebuild kit. The floats are factory set at the right level and if you try to bend/change them you'll never get them back to the right spotm The stock needles and seats have a much smoother surface than the cheap ones in the kits. If you swap them out for the new ones they are just going to constantly bind up and flood on you. So basically leave the air horn section alone except for cleaning it with carb cleaner and checking out the strainers on those bolts for the fuel inlet/outlet tubes. Concentrate on the main body.

I like to print out an extra copy of the page in the carb manual that lists all the air bleed tubes etc... And lay each one down on the sheet in the appropriate spot as I take them out. Don't forget that there are a couple of checkballs, weights, and springs in some areas. Don't lose those.

Good luck.

Jon
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