Orb

iTrader: (3)

I have an 85 GSL with the 12A engine.

Here's the symptoms...

When I give it full throttle it will usually but not always rev up to about 6-7k slower then it should. When it does it sounds like it's running on only one rotor. Like a 4 stroke dirt bike vs a 2 stroke. Usually it will top out at 7k rpm with the throttle full open. After a few seconds it'll then kick in and regain power and sound like it should.

When it kicks in the two secondary venturi's open about 1/4" from fully closed.
Sometimes it'll kick in at 4k, sometimes at 5k but usually it'll top out at 7k and run and that rpm for 1-5 seconds before the secondaries open and it regains it's power.

When on the freeway it'll act up and I have to pump the pedal a few times for it to work. At times just holding the pedal down for a few seconds will fix it, other times I have to pump it.

It does it regardless of what gear I'm in.

At 2k+ rpm the primary fuel jets have very visible fuel flow and as they should increase flow with increase in rpm.
When the secondary venturi's do open up they also have good fuel flow into them so it's not a fuel pump or filter problem as I originally suspected the pump.

I'm not sure exactly when or how much the secondaries are supposed to open but it seems as though the actuator for them (Or whatever opens them) is the cause of the problem... But I'm not an expert on the subject.

Could be a problem with the... Yea, I'm confused...

I hope I explained it clearly enough.

Thanks,
Orb

trochoid

iTrader: (6)

The secondariues open under vacuum load, they are not supposed to open up when looking down the carb, with the car stationary, unless you have done the mechanical secondaries mod.

The sputtering sounds like there is an ignition breakup on one rotor. Overall, constant lack of power may mean the cats are beginning to plug.

Welcome to the Club and thank you for such a clear and concise 1st post.

Orb

iTrader: (3)

I was having a closer look at it last night and I think it is the secondaries.
Here's why...

While looking into the carb I would push the throttle and noticed that when it acts up, the secondaries stay fully shut. When it does not act up, I can notice the secondaries open up as I advance the throttle.
And it's consistant in that when I push the throttle and the secondaries open, the engine revs as normal. But about 40% of the time the secondaries will Not open at all and it will sound like it's bogging and top out at 7k rpm until the secondaries do finally open it again runs fine.

In summary...
Here's the play-by-play.
Car in N
Advance throttle,
Primaries open,
Secondaries remain closed,
Engine revs to 7k in about 4 seconds and won't go faster,
1-4 seconds passes,
Secondaries open,
Engine revs past 7k rapidly.

Here's the play-by-play when the engine is working.

Advance the throttle from idle to full open.
Engine quickly revs up,
Secondaries start opening at aout 3k rpm,
Engine revs from idle to 8k in aout 1.5 seconds,
Secondaries opperating properly...

I have not done the mechanical mod to the secondaries btw.
There being opperated by vac.
Problem is I'm not sure where to start troubleshooting it.
The Haynes book doesn't go enough into detail.

I hope this clarify's the problem.

Thanks,
Orb

inuissus_cendi

If I were you I'd just do the mechanical secondaries mod. It'll solve your problem and make your car alot more fun. Just my 2 cents.

Orb

iTrader: (3)

Yea, I think your right. Would probably be a good idea. Now to figure out how. lol

inuissus_cendi

try this one. Sterling is the man, he knows everything there is to know about these carbureators. https://www.rx7club.com/showthread.p...ch+secondaries

Orb

iTrader: (3)

I wired the secondary making it open up full when the primary is full open. Starts opening the secondary at about 1/2 throttle and both hit full open at the same time... Well, the secondaries go almost vertical but about 5-7 degrees shy of vertical.

Anyhow it fixed the problem I was having.
Thanks for the tip.

Haven't removed the vac actuator yet though. Will this weekend and see if I can't mod the AP as well.

Thanks again.
Orb

t-von

iTrader: (8)

Bringing this one back.

Any more details on this? I'm currently having problems diaging this for a local 1st gen owner. As much knowledge as I have about rotary's in general, I'm NO carb expert. Anyways light throttle car runs fine and idles perfect however, as soon as I go WOT, it bogs. When it's bogging , there a bit of black smoke out the exhuast. I originally suspected that the secondaries weren't opening. Well I removed the filter housing and manually went WOT and never saw the secondary plates move when the engine was off. I then fired the engine up and manually went WOT again and the secondaries opened about 1/4 turn. The weird thing is, the engine doesn't start bogging till the secondaries open. I thought well "may the secondaries aren't opening enough" so I manually opened them myself along with the throttle and the engine bogged even worse when I opened them fully. I can see plenty of fuel being dumped from the secondary jets but I can't tell if it's too much fuel. The teeter totter linkage is missing the spring so I will have to address that. Can anyone help me with this?


I've also checked the vacuum advance with my timming light. The timming appears to be advancing till it starts bogging. Customer already replaced the fuel filter and the exhaust is only a few years old with no precats but ya never know about those aftermarket cats.

t-von

iTrader: (8)

Anyone?

j9fd3s

iTrader: (3)

will it free rev, and only bog under load? what is the condition of the cap and rotor? the wires should be under 16k ohms per meter, and new is about 7k.

i've had the experience where the stock ignition is fine, but it doesn't have any extra capacity, so its sensitive to things like bad wires and stuff.

t-von

iTrader: (8)

I should have mentioned this earlier. In free rev it will rev fine at 1/2 throttle and hit red line. As soon as you give it more throttle, it starts bogging and wont go over 7k. The engine has gotten very dirty since I last rebuilt it 3 years ago. Power steering pump or lines has taken a dump and gotten oil all over the ignition system. So that could be making things sensitive as you say under more load. It runs so well at idle and light cruise, I didn't think much of the possible oily contamination. I'll give it a good engine bay cleaning and check the cap and rotor and see what happens. I have enough parts laying around from my old 1st gen to test with.

j9fd3s

iTrader: (3)

ohm out the wires, it matters

t-von

iTrader: (8)

Will do!