No combustion in rotor 2
11-16-12, 02:41 PM
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No combustion in rotor 2
I've got an 82 RX7, 44K miles, with a Racing Beat Holley Intake kit. It was running fine but one day it starting stumbling - it sounded like a rotor wasn't firing. Timing lite showed spark on all leads but when I pulled either or both wires off the rotor 2 plugs nothing happened indicating no combustion in rotor 2. Compression is fine, between 95-105. I originally thought it was a timing issue and thanks to the forum I found out that my timing pulley was mounted wrong. The timing, however, is OK. While doing all the work with the dizzy/timing, I found a bad plug, replaced it, reinstalled the dizzy and started it up - and it ran fine! I let it run for half hour and shut it down. I washed the car, let it dry, and when I started it up a couple hours later, same problem - back rotor not working. The last idea I had was a possible stuck jet. I disassembled the float assembly, cleaned the jets and float assembly and put new plugs in. No luck. Any ideas?
11-16-12, 06:03 PM
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Shoot a PM to Whitey85mtu
He is local, knowledgeable, and has a buttload of leftover parts (including engine parts) he's looking to get rid of (for free). He might be able to see something you've missed, or at least hook you up with parts needed for a rebuild.
Good luck...
.
He is local, knowledgeable, and has a buttload of leftover parts (including engine parts) he's looking to get rid of (for free). He might be able to see something you've missed, or at least hook you up with parts needed for a rebuild.
Good luck...
.
11-17-12, 10:58 AM
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Thanks for all the replies. In answer:
- I don't know Whitey85mtu and he doesn't show up in the member list.
- The 'bad' plug was not firing across the gaps but rather side electrodes to the base of the center electrode. It may have ignited the mixture but I was grasping for a possible solution. I pulled the leading wire and connected it to a spare plug (grounded the case) to watch the sparks. They looked fine.
- The dizzy cap is new and mounted securely.
- Both venturis are spraying gas and as I have said the jets are clean. However, when I rev the engine, though I can't be sure, both rotors seem to fire.
The fact that it worked fine for a while indicates an intermittent problem. What did I miss?
- I don't know Whitey85mtu and he doesn't show up in the member list.
- The 'bad' plug was not firing across the gaps but rather side electrodes to the base of the center electrode. It may have ignited the mixture but I was grasping for a possible solution. I pulled the leading wire and connected it to a spare plug (grounded the case) to watch the sparks. They looked fine.
- The dizzy cap is new and mounted securely.
- Both venturis are spraying gas and as I have said the jets are clean. However, when I rev the engine, though I can't be sure, both rotors seem to fire.
The fact that it worked fine for a while indicates an intermittent problem. What did I miss?
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11-17-12, 12:39 PM
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Yes. I removed the air cleaner and looked down the primary venturis - gas going in. And just in case flooding is an issue, I deflood (remove spark plug, MMO, etc) each time I try something different. Thanks, I'm taking all ideas - any others?
11-17-12, 01:05 PM
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A lot of screwing around with the dizzy, Check the dizzy plug and make sure all 4 prongs are exposed and making good contact and not pushed back into plastic plug housing also check the pickup inside and make sure the pickup has not been moved on the metal holder there should be around 30 thou air gap on the pickup to star . you could try swapping the two leading plug wires (just the spark plug end ) and see if the problem goes to the other spark plug .
Gerald m.
Gerald m.
Last edited by gerald m; 11-17-12 at 01:08 PM.
11-18-12, 12:13 PM
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My thanks to RotaryEvolution for being persistent about checking the venturis for fuel. What I initially saw was residue fuel from the accelerator pump needed to keep the engine running. Under regular idle it's very difficult to see atomized fuel in the venturis but since I had spark and compression the only thing left was lack of fuel. I used both carb cleaner and lo pressure air to clean out the air bleeds for the idle and main jets and voila! It’s running fine. I probably blew the obstruction into the main bowel so if the condition returns I'll have to do a more substantial carb rebuild. I agree, RotaryEvolution, I hate carbs.
11-18-12, 12:56 PM
#12
sounds very familiar, the hitachi carbs on the early sedans and REPUs were notorious for blocking the venturi passages.
a little compressed air and carb cleaner would remedy it for a while. best to just redo it and let the disassembled barrels sit and soak in a carb solution bath for a few hours and blow it all out persistently. an additional fuel filter also rarely hurts(just keep it away from heat or use a well built unit if you locate it in the engine bay). also never let a carbed engine sit for more than a few months without starting it up to circulate the fuel and keep the fuel in the bowls fresh.
and i still hate carbs.
a little compressed air and carb cleaner would remedy it for a while. best to just redo it and let the disassembled barrels sit and soak in a carb solution bath for a few hours and blow it all out persistently. an additional fuel filter also rarely hurts(just keep it away from heat or use a well built unit if you locate it in the engine bay). also never let a carbed engine sit for more than a few months without starting it up to circulate the fuel and keep the fuel in the bowls fresh.
and i still hate carbs.
Last edited by RotaryEvolution; 11-18-12 at 01:01 PM.
11-18-12, 03:16 PM
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Actually, the carb is a Racing Beat Intake kit with a Holley 4 bbl. I put it on ~1983 and this is the first issue I've had with it. Of course it now has 30 years of accumulated dirt and varnish. A friend of mine put the same system on his RX and the only problem he ever had was a stuck float. Even if you hate 'em it sounds like you're a carb guy. There's an excellent YouTube series on rebuilding 4 bbl Holley's at:
The RX is asleep now for the winter. A carb rebuild and hi beam switch failure are projects for next spring.
The RX is asleep now for the winter. A carb rebuild and hi beam switch failure are projects for next spring.
12-11-12, 06:00 PM
#17
My thanks to RotaryEvolution for being persistent about checking the venturis for fuel. What I initially saw was residue fuel from the accelerator pump needed to keep the engine running. Under regular idle it's very difficult to see atomized fuel in the venturis but since I had spark and compression the only thing left was lack of fuel. I used both carb cleaner and lo pressure air to clean out the air bleeds for the idle and main jets and voila! It’s running fine. I probably blew the obstruction into the main bowel so if the condition returns I'll have to do a more substantial carb rebuild. I agree, RotaryEvolution, I hate carbs.
Good to hear you got it working. I'm "Whitey85mtu", changed my name on here after DGRR11 (new nickname b/c I popped my motor).
I had a RB Holley 465, and had one hell of a time getting the secondaries to work properly. I ended up doing the "screw trick" to get them to actuate.
Where in Michigan are you located?
-Jim
12-12-12, 12:27 AM
#18
carb whisperer
The RB idle "jet" is a very very tiny .017" You can block that passage with a spec of dirt. Make sure youre running a good fuel filter, and when you do rebuild that thing blast it with some compressed air.
Good to hear you got it right for now, tho.
Also whitey, I envy your lack of secondary action. My current RB doesnt work with a power valve set up :C
Good to hear you got it right for now, tho.
Also whitey, I envy your lack of secondary action. My current RB doesnt work with a power valve set up :C
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