No top end power, and also stalling. Just another day with a seven. <sigh>
09-30-07, 05:22 PM
#1
Full Member
Thread Starter
No top end power, and also stalling. Just another day with a seven. <sigh>
OK, first it's a completely stock 84 FB with a 12A and about 230,000 kms. The engine in it is one I baught from a local rotary specialist in november. He says he rebuilt it about four years ago and since then it had about a year of use than sat in his shop for about two.
I've had a stalling problem for a few months now. My car would stall pretty much any time I let out the clutch without giving it a little throttle first. If I got it up to even 1000 RPM and then let out the clutch it would pull away cleanly, but if I just let out the clutch and gave it a little throttle it would respond briefly and then fall flat on its face. Annoying but hardly serious. I messed with accelerator pump settings for months to no avail and I wasn't inclined to suspect the pump itself since I rebuilt the carb a little over a year ago and replaced the diaphragm. Since it was a miner problem it was low on my priorities list.
Now, however, my car has suddenly stopped making any top end power, and it seems to get worse by the day. A week ago it pulled strongly to 7500 RPM, which is as far as I ever take it. Now it often wont even rev past 6000 with no load. As I said, I rebuilt the carb about a year ago. I tried wiring the secondary throttles to the linkage to open mechanicaly, but that didn't do it. I checked my leading timing. My leading vacuum solenoid did break recently, but I just bypassed the vacuum line around and I'm now seeing vacuum advance at idle so I should also have it at redline, and yes, I did disconnect it before I set my timing. I even tried sitting the timing light in front of my windshield and revving it, the thing never stopped flashing. I did notice that revving it in the driveway, the fuel level in my rear float bowl drops from about half way up the window to about a quarter. The level in the front float bowl doesn't seem to change. I've replaced the fuel filter with no luck, and I just ran a volume test on the fuel pump and got about 1500 ml in one minute, just above the manual spec. My shutter valve is also dead, but I just blocked it off and I don't see what that could have to do with it. I'm getting really annoyed. I don't even know if these two problems are related. I'm thinking of buying a pressure guage and running a pressure check on the pump, and than a full ignition tune up, and than taking apart the entire exhaust to check for blockage, and than seeing if I can find anyone I can borrow a rotary compression tester from. I'm just totally lost.
I've had a stalling problem for a few months now. My car would stall pretty much any time I let out the clutch without giving it a little throttle first. If I got it up to even 1000 RPM and then let out the clutch it would pull away cleanly, but if I just let out the clutch and gave it a little throttle it would respond briefly and then fall flat on its face. Annoying but hardly serious. I messed with accelerator pump settings for months to no avail and I wasn't inclined to suspect the pump itself since I rebuilt the carb a little over a year ago and replaced the diaphragm. Since it was a miner problem it was low on my priorities list.
Now, however, my car has suddenly stopped making any top end power, and it seems to get worse by the day. A week ago it pulled strongly to 7500 RPM, which is as far as I ever take it. Now it often wont even rev past 6000 with no load. As I said, I rebuilt the carb about a year ago. I tried wiring the secondary throttles to the linkage to open mechanicaly, but that didn't do it. I checked my leading timing. My leading vacuum solenoid did break recently, but I just bypassed the vacuum line around and I'm now seeing vacuum advance at idle so I should also have it at redline, and yes, I did disconnect it before I set my timing. I even tried sitting the timing light in front of my windshield and revving it, the thing never stopped flashing. I did notice that revving it in the driveway, the fuel level in my rear float bowl drops from about half way up the window to about a quarter. The level in the front float bowl doesn't seem to change. I've replaced the fuel filter with no luck, and I just ran a volume test on the fuel pump and got about 1500 ml in one minute, just above the manual spec. My shutter valve is also dead, but I just blocked it off and I don't see what that could have to do with it. I'm getting really annoyed. I don't even know if these two problems are related. I'm thinking of buying a pressure guage and running a pressure check on the pump, and than a full ignition tune up, and than taking apart the entire exhaust to check for blockage, and than seeing if I can find anyone I can borrow a rotary compression tester from. I'm just totally lost.
09-30-07, 05:41 PM
#2
82, 83, 88, 82 RX-7again!
OK, first it's a completely stock 84 FB with a 12A and about 230,000 kms. The engine in it is one I baught from a local rotary specialist in november. He says he rebuilt it about four years ago and since then it had about a year of use than sat in his shop for about two.
I've had a stalling problem for a few months now. My car would stall pretty much any time I let out the clutch without giving it a little throttle first. If I got it up to even 1000 RPM and then let out the clutch it would pull away cleanly, but if I just let out the clutch and gave it a little throttle it would respond briefly and then fall flat on its face. Annoying but hardly serious. I messed with accelerator pump settings for months to no avail and I wasn't inclined to suspect the pump itself since I rebuilt the carb a little over a year ago and replaced the diaphragm. Since it was a miner problem it was low on my priorities list.
Now, however, my car has suddenly stopped making any top end power, and it seems to get worse by the day. A week ago it pulled strongly to 7500 RPM, which is as far as I ever take it. Now it often wont even rev past 6000 with no load. As I said, I rebuilt the carb about a year ago. I tried wiring the secondary throttles to the linkage to open mechanicaly, but that didn't do it. I checked my leading timing. My leading vacuum solenoid did break recently, but I just bypassed the vacuum line around and I'm now seeing vacuum advance at idle so I should also have it at redline, and yes, I did disconnect it before I set my timing. I even tried sitting the timing light in front of my windshield and revving it, the thing never stopped flashing. I did notice that revving it in the driveway, the fuel level in my rear float bowl drops from about half way up the window to about a quarter. The level in the front float bowl doesn't seem to change. I've replaced the fuel filter with no luck, and I just ran a volume test on the fuel pump and got about 1500 ml in one minute, just above the manual spec. My shutter valve is also dead, but I just blocked it off and I don't see what that could have to do with it. I'm getting really annoyed. I don't even know if these two problems are related. I'm thinking of buying a pressure guage and running a pressure check on the pump, and than a full ignition tune up, and than taking apart the entire exhaust to check for blockage, and than seeing if I can find anyone I can borrow a rotary compression tester from. I'm just totally lost.
I've had a stalling problem for a few months now. My car would stall pretty much any time I let out the clutch without giving it a little throttle first. If I got it up to even 1000 RPM and then let out the clutch it would pull away cleanly, but if I just let out the clutch and gave it a little throttle it would respond briefly and then fall flat on its face. Annoying but hardly serious. I messed with accelerator pump settings for months to no avail and I wasn't inclined to suspect the pump itself since I rebuilt the carb a little over a year ago and replaced the diaphragm. Since it was a miner problem it was low on my priorities list.
Now, however, my car has suddenly stopped making any top end power, and it seems to get worse by the day. A week ago it pulled strongly to 7500 RPM, which is as far as I ever take it. Now it often wont even rev past 6000 with no load. As I said, I rebuilt the carb about a year ago. I tried wiring the secondary throttles to the linkage to open mechanicaly, but that didn't do it. I checked my leading timing. My leading vacuum solenoid did break recently, but I just bypassed the vacuum line around and I'm now seeing vacuum advance at idle so I should also have it at redline, and yes, I did disconnect it before I set my timing. I even tried sitting the timing light in front of my windshield and revving it, the thing never stopped flashing. I did notice that revving it in the driveway, the fuel level in my rear float bowl drops from about half way up the window to about a quarter. The level in the front float bowl doesn't seem to change. I've replaced the fuel filter with no luck, and I just ran a volume test on the fuel pump and got about 1500 ml in one minute, just above the manual spec. My shutter valve is also dead, but I just blocked it off and I don't see what that could have to do with it. I'm getting really annoyed. I don't even know if these two problems are related. I'm thinking of buying a pressure guage and running a pressure check on the pump, and than a full ignition tune up, and than taking apart the entire exhaust to check for blockage, and than seeing if I can find anyone I can borrow a rotary compression tester from. I'm just totally lost.
10-02-07, 09:41 PM
#6
Full Member
Thread Starter
Thanks jeff and troichoid. It's nice to have two of the boards most knowledgeable members helping me out. I changed the fuel filter when this first started, no improvement. It now wont rev past about 4000 even in the driveway out of gear, so I've taken it off the road until I solve this, after replacing my clutch slave on the street outside my work. It failed rather dramatically yesterday. I seem to be having one of those weeks with my car.
I just tried looking down the carb whilst reving it to about 4000 at full throttle briefly. I'm seeing two nice big clouds in the primary venturis and two smaller streams in the secondaries as they just begin to open, yet the engine doesn't pick up any rpm. I'm thinking ignition now, but I still plan to open up the carb eventually if I can't solve it.
Also, just to ease my mind, I plan to run a compression test. Does anyone know where in Vancouver I can buy/rent a rotary compression tester?. For that matter, does anyone in Delta or Surrey want to sell/rent/loan me a tester? Thanks again guys.
I just tried looking down the carb whilst reving it to about 4000 at full throttle briefly. I'm seeing two nice big clouds in the primary venturis and two smaller streams in the secondaries as they just begin to open, yet the engine doesn't pick up any rpm. I'm thinking ignition now, but I still plan to open up the carb eventually if I can't solve it.
Also, just to ease my mind, I plan to run a compression test. Does anyone know where in Vancouver I can buy/rent a rotary compression tester?. For that matter, does anyone in Delta or Surrey want to sell/rent/loan me a tester? Thanks again guys.
10-06-07, 12:39 AM
#7
Full Member
Thread Starter
Wow, just found out how expensive a compression tester for a rotary is. 
looks like i'll need to make do with a standard one and just take out the check valve. At least now I have a long weekend to work on the car.
looks like i'll need to make do with a standard one and just take out the check valve. At least now I have a long weekend to work on the car.
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10-06-07, 04:19 AM
#8
Unless you've done the mechanical secondary mod, you should not see any fuel flow in the secondaries while free reving in the driveway. They only open under load in stock configuration. Fwiw, the rear fuel bowl supplies the accelerator pump.
10-06-07, 02:52 PM
#9
Lives on the Forum
If you have the idle set correctly (rpm) and see vac advance while idling, then you probably have the vacuum line running to the wrong nipple at the base of the carb. This will throw things off, and increase the chance of stalling when coming off idle. Use the nipple farthest forward at the base of the carb.
It also sounds like you have a pretty big vacuum leak, so check that out.
Clogged exhaust, maybe. More likely you just need to rebuild the carb. Good luck!
It also sounds like you have a pretty big vacuum leak, so check that out.
Clogged exhaust, maybe. More likely you just need to rebuild the carb. Good luck!
10-07-07, 01:13 AM
#10
Full Member
Thread Starter
Let me rephrase Trochoid. At about 4000 or 5000 RPM (Can't tell for sure as I'm doing it under the hood), full throttle I'm seeing the secondaries just crack open and a very small but steady stream of fuel in the secondary venturis. Is this normal?
Also, my vacuum lines are all hooked up exactly as per the diagram in the factory service manual, I've just bypassed the the solenoid valve. I assume the solenoid normally closes off vacuum at idle in the stock configuration, but now I have it all the time. It's a problem, but I plan to remove my rats nest in future anyway, and then I'll run it to venturi vacuum as has been suggested elsewhere. I'll be looking for vacuum leaks also. I've removed the carb and I'll be opening it up tomorrow. Here's hoping I find a hopelessly clogged fuel inlet screen or a plugged main jet or something.
I also tried turning the engine over with each leading plug pulled out in turn. I get one nice strong puff for each turn of the eccentric on both rotors, and from what I understand that means I at least don't have a blown seal.
One other thing, I took off my cap and rotor to clean them and messed with the dizzy a little. The trailing pickup seems to move freely over a fairly wide range within the distributor body, but the leading pickup only moves about half as far. Is that normal? I'm wondering if this might a problem of insufficient spark advance.
Also, my vacuum lines are all hooked up exactly as per the diagram in the factory service manual, I've just bypassed the the solenoid valve. I assume the solenoid normally closes off vacuum at idle in the stock configuration, but now I have it all the time. It's a problem, but I plan to remove my rats nest in future anyway, and then I'll run it to venturi vacuum as has been suggested elsewhere. I'll be looking for vacuum leaks also. I've removed the carb and I'll be opening it up tomorrow. Here's hoping I find a hopelessly clogged fuel inlet screen or a plugged main jet or something.
I also tried turning the engine over with each leading plug pulled out in turn. I get one nice strong puff for each turn of the eccentric on both rotors, and from what I understand that means I at least don't have a blown seal.
One other thing, I took off my cap and rotor to clean them and messed with the dizzy a little. The trailing pickup seems to move freely over a fairly wide range within the distributor body, but the leading pickup only moves about half as far. Is that normal? I'm wondering if this might a problem of insufficient spark advance.
10-14-07, 06:50 PM
#11
Full Member
Thread Starter
Woo Hoo. I know what's wrong with it. After hours of work breaking loose bolts that had rusted solid, I was finally able to pull apart my exhaust system, and I can't believe my engine even ran at all with so much blockage. The first cat is actually completely empty, leading me to suspect someone hollowed it out before I bought the car, while the second and third cats are blocked and highly degraded. I'm probably just going to hollow out the remaining two cats and run it that way until my emissions run out and I have to buy new ones. Also, a test in my driveway, minus exhaust system, produced an immense amount of noise and a lovely quick rev up 6500 RPM. Sweet. Also, I've learned that an unmuffled rotary sounds absolutely evil! Now I'm going to have to buy a cool exhaust system for this car. Damn!
10-14-07, 06:56 PM
#12
congrats on figuring out the problem. I was going to suggest that it's the cats, as this happened to my little brother's car. 1989 Merkur Scorpio. 85k miles. dead cats. the thing wouldn't break 25mph on his way home from work. Dropped the cat and it ran like a banshee. hollowed out the cat and absolutely no problems now. Congrats on fixing it, and get yourself a RB exhaust. Sound and flow amazing. Only keep your cats sitting around for when you have to renew your emissions.
10-14-07, 06:57 PM
#13
I wish I would of seen this thread when it came out. We have a thread on this subject somewhere that has a complete check list of everything that can and will cause your sympton. :-)
Of course using the search function with the key words loss power/ no power, etc would of probably got you more info when you needed it. :-)
Of course using the search function with the key words loss power/ no power, etc would of probably got you more info when you needed it. :-)
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