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I got my car on the road this spring, and it was running great. After a couple months it started to have trouble Idling, and backfiring when i let off the throttle. Eventually it was idling very rough, and wouldn't idle for more than a couple seconds without the choke on. I did the rats nest removal, and it got rid of the backfiring, but still wouldn't idle well. I noticed the accelerator pump was leaking, so i pulled the carb out to replace that. I figured, while I've got it out, I might as well do a full rebuild. I also followed the steps to strip off the unnecessary stuff. When i put the carb back in, it wouldn't start. I de-flooded the engine and got it started. it will run for a couple mins but it makes TONS of smoke and smells VERY rich, it also seems very weak. It takes a couple seconds to rev up near redline, and i tried driving it, but it doesn't have nearly enough power to safely get into traffic. Over a period of a couple mins it gets weaker and weaker, until I have my foot on the floor just to keep it at idle. The plugs are black after this, and I have to clean them and de-flood the engine to get it started again. It is very tricky to get it started. As far as I can tell there isn't gas flowing into the intake when the throttle isn't open(it doesn't seem to be flooding without running/cranking). I had new needles and seats in, so I switched back to the originals, no improvement. I tore back into the carb and noticed one of the gaskets was upside down. I thought that must be the problem, but it didn't help.
I bought a used carb off a local guy, which supposedly was working when he took it off, but it still doesn't work. The fuel level in the bowls looks like it's above the sight glass, so i'll have to see what's going on there. I might just put my other carb back on. -At least I'm positive my old one was running good a couple months ago.
Any suggestions which I should proceed troubleshooting with?
If it's flooding that bad so you have to "keep your foot to the floor to idle" and you don't see gasoline in the intake manifold I'd suggest looking else where for your issue. What kind of ignition are you using? How long have you had the car? Is it a regular driver or a weekend cruiser?
The thing that I keep getting hung up on is that, it at least ran before i rebuilt the carb. Although, it is possible that this is just coincidence.
It was a daily driver for the summer. I drove it to work everyday for about 2 months. i have been trying to fix it for the last 2 months.
It is all stock ignition. I replaced the cap and rotor. It gets a good spark on all plugs. I haven't checked timing -I have never done that before.
The carb that is on right now has the float bowl vent solenoid removed and the hole plugged, but the passages clear. The carb I had on yesterday, had the solenoid in it. You could hear it click/actuate when I connected it with the ignition on.
I will take some pictures tomorrow and try to post them right away.
If it ran before... DON'T MESS WITH THE TIMING OR IGNITION!!! Its probably fine.
I hate to say it but it the carb was probably fine before you tinkered with it. The idle fuel adjustments can sometimes "wander".
To address your current problems though. Seems like you have typical flooding issues. Its a battle is all I've got to tell you. If you win you'll be the happiest clam on the beach.
So the consensus seems to be keep looking at the carb...
I have worked on a couple carbs before this, but it was always just a matter of cleaning everything, even if repeatedly. A 1991 Yamaha 2-stroke snowmobile, and my 1973 Honda CB350. and they were much more simplified carbs.
I think I'll switch back to my previous carb which had proper fuel level in the sight glass. It's a pain because I have to switch some the throttle linkages between carbs, because the one I bought was missing a couple pieces. Is it normal to see problems like this when the fuel level is correct in the sight glass?
I was thinking about trying it with the return line just running through a brand new hose to a jerry can, to eliminate the possibility of a blockage in the return line causing issues. But I don't think that makes sense. I think it would only be gravity and venturi effect moving fuel from float bowl to the intake. If it was a pressure issue I would think that would show up as the float bowl overfilling. Right???
Any ideas what can make it run rich, other than the adjustment screw? -Because I have tried playing with that...
There have been lots of things I initially regretted taking apart, but they have proved to be valuable learning experiences. Failure is not an option. Even if I found a perfect working carb, I would probably end up taking it apart to see what is different from my old one, to try to find the solution(hopefully not resulting in two useless ones). Not knowing what the problem is, would consume me. Putting it back together without knowing what I did to fix it would be nearly as bad as not being able to fix it. Sorry no pics yet. I will post some tomorrow. -Let me know if there's anything particular i should focus on.
P.S. My wife is getting tired of it not moving from the driveway, and it is a touchy spot in conversation, so this is the best place for me to vent my frustration. Haha
No, running return gas to a jerry can isn't a problem... but just blow out the return line to clear any blockage.
Yes, you should be able to see dripping into the barrels of the carb when the carb is flooding at idle.
Do this....
Take the carb off.
Get a 2.5# fuel pump/regulator. Make it work off the car with a spare battery.
Hook up a temp fuel pump situation in an area that's easier to work on. ie a bench.
Run the temp fuel pump to and from a jerry can.
Set your float height on the bench. (like bench syncing CB350 carbs)
After you get it nailed; then put the carb back on the intake.
I opened up my original carb to look for any issues. I think I had my primary and secondary jets switched. When I went to put them back in, I put the first one in the wrong position because thats how I had them laid out from disassembly.
EUREKA!!!!!!
So I reassembled it with them in the proper positions, switched the throttle linkages back to carb that was running well this summer, and put it back in the car.
Nothing! I checked for spark and noticed I wasn't getting spark on the leading plugs L1 & L2 (bottom). I already had put a new rotor and cap on, and I tried switching the cables, but they weren't the issue. I tested the resistance across the terminals on the coils according to the FSM and got 1.3Ohm's -in spec. I cleaned and tested the ignitors,and reassembled everything. I am now getting spark on all 4 plugs , but it doesn't seem quite right. Sometimes the spark isn't at the tip of the electrode, it is down around the ceramic. The plugs look like they are in good shape and I have cleaned them thoroughly. Based on this, I will see if I can get a new set of plugs tomorrow.
I was very excited when the car started in the first 5 seconds, and much easier. But it still runs rough and weak, but most notably only for less than 10 seconds, then it dies. It is particularly consistent: when starting you can feel it fire a couple cycles, but if I don't put my foot to the floor it won't actually start. When it does start, it will run for 3-10 seconds and it dies abruptly. Any suggestions what to look at now?
Check the connections on the J-109s. They are the ignitor boxes on the side of the distributer. If you were moving things around (swapping caps) they could have been jarred out of there sockets.
Check the connections on the J-109s. They are the ignitor boxes on the side of the distributer. If you were moving things around (swapping caps) they could have been jarred out of there sockets.
I cleaned all the connections and reassembled everything after I reassembled the Ignitors. They are well seated in place. Any other suggestions?
weak spark... try swapping coils. Just swap the wires from front to rear. If your leading coil is bum and your trailing coil is hot this is a quick test to check it. (I know it passed the resistance test, but a try is as easy as pulling two wires).
weak spark... try swapping coils. Just swap the wires from front to rear. If your leading coil is bum and your trailing coil is hot this is a quick test to check it. (I know it passed the resistance test, but a try is as easy as pulling two wires).
It back-fired through the carb(i think this is called spitting?) i didn't have the filter bolted on and it popped it off the carb. Another time I actually had a pretty decent flame out the top.
I noticed one of the vacuum lines to the dizzy was completely kinked, straightened that out. Still won't stay running.
I think i may have misled you with that bit about "weak spark", unless it's an intermittent problem. It's dark outside now, and i can positively tell you all spark plugs are getting a good solid spark on all cylinders. I didn't actually try switching them because they all had a good spark.
Also I think I overstated how long the engine runs. It will start with the throttle floored and start to rev up, but it will die abruptly after 1-5 seconds.
It sounds like now i'm dealing with a lean condition?
What are your fuel levels in your bowls? Level the key in the on position and check the fuel level with a flash light. The fuel should be right in the middle. You'll see the meniscus on either end of the sight glass.
Key on, fuel pump pumping, the fuel levels are good. That is why I went with this carb. The rear one was a pain to get a picture of, but you can see for your self:
You can't keep it alive even when pumping the peddle?
From the fire shooting up from the intake I think you have fuel delivery. You're sure the plug wires are routed properly? I've made this mistake, and it threw me for a loop when I did.
EDIT: whats going on with your rear primary jet hole?!?
I checked to make sure the wires were routed properly. i will double check tomorrow.
I'm assuming that below the rear sight glass, you think you are looking at the holes for the primary and secondary jet holes. I'm not sure what the hole on the left side of the rear sight glass is, but in that picture, the primary jet hole is directly below the sight glass. the secondary jet hole is just to the right of it hidden in the shadows.
I can do a compression test tomorrow. I haven't done that yet because i've been fixated on the carb, since it was working fine until i started messing with that.
....I can do a compression test tomorrow. I haven't done that yet because i've been fixated on the carb, since it was working fine until i started messing with that.
That's why I tossed out bad engine since normally RX7's blow apex seals, sit, get sold, then the new owner inherit the problem unknowingly.
BUT in light of the backfiring I'd do a compression test before more money/time invested.
I wonder if I should start a new thread since my initial problems are totally different from what I'm dealing with now. It no longer appears to be running rich, I haven't had to de-flood the engine in days, the plugs aren't dripping wet when I pull them, and they're not Fouled blacker than coal.
Originally Posted by Jeff20B
Backfiring through the carb on a rotary means broken apex seals. That could be why it won't run for you unless it is floored.
Failure is not an option, I NEEEEEED to know what the problem is. I'm not OCD, but sometimes it feels like i'm bordering on it, when i need to find out how something works, or in this case doesn't work.
I doubt it will shed any new light on the situation, but here's a pic of what the 2 plugs looked like after it died last time:
They are the 2 leading plugs, they aren't exactly the same, But they're both infinitely better than when I started.
10-29-16, 05:18 PM
