12a Power Loss
 

Hi all, I've got a 1980 5 speed RX7. It's a project car my little brother bought for $500 and I'm quite impressed with it for that price.

Previously, the car would pull slowly before 4K RPM. When it hit 4K it would practically die and then come back to life when it hit ~6K and never exceed 6K. After a little carb cleaning, a seafoam treatment, a new belt, and fresh gas it has consistent power all the way up to 6K RPM. I can hardly get it to pass that when sitting in neutral. It also takes a while to get there. I have a missfire and ordered new plugs today, which arrive tomorrow. Is there anything else that causes power loss throughout the powerband and then will prevent me from exceeding 6K RPM? I believe my fuel is doing what it should and last I checked my secondaries were working, I will probably go mechanical when I rebuild the carbs anyway.

tl;dr
Low power; will not exceed 6K RPM; occasional missfire.

start simple ...

(1) check the timing
(2) fuel filter/fuel pump

I've already checked the fuel pump and replaced the fuel filter. My fuel pump does make a constant clicking on/off noise. When I asked here on this forum all anyone said was "I think the sound just annoys you". So I'm guessing it's fine. I have plenty of fuel when I remove the hose from the rail in the bay. Like I said, I believe the fuel is doing what it should. I'll be checking the timing tomorrow.

I would think it could also be distributor related, but that's just my 2 cents.

Could you provide me with a link to a little info on our distributors. Like models, replacements, inspection, etc? I really don't know much about distributors. The cars I work on and my personal car all are coil-on-plug so I've never had to work on a dist cap.

All the info you need is right here. This site has all the manuals on every generation.

Better start reading :)

Dude... thanks. The Hayne's manual kinda sucks.

Here's an update.
After replacing the spark plugs I found that one plug was the wrong plug entirely. It was a motorcycle plug or something. The other 3 weren't even gapped. It runs quite a bit better now but still has a choppy idle and struggle to pass 6k RPM. I noticed it dumping out fuel from the exhuast at idle. I assume it does the same while driving. I put like 4 gallons of gas in it and after just a few trips up and down my 1/4 driveway and some figure 8s in a gravel parking lot I ran out of fuel. Would running way to rich cause the slow acceleration? Also, the air pipe injection line is rusted out and seems to dump fuel out of whenever I start the car.

By the way, checked the timing and it was perfect. Just had to move that vacuum thing on the rotor slightly.

Another update. After rebuilding the carb it idles amazingly at 500 RPM and starts at -32F weather very easily until it warms up. Then it will die. It'll start right up pretty easy afterwards until I drive it. I can pull through first gear pretty slow and then by the time I hit 2nd it will be hard to start. Even if I deflood it I really struggle to get it started until it's cooled down. Is this the igniters?

When you checked the fuel flow did you also check the flow going through the carb and out if the return.

Sounds like fuel issue with running too rich all the time and then when you hit the AP and open
the secondaries the thing dies and floods. Is it a stock OEM pump or after market?
Nicholas P. brings up a good point, make sure the return line is not clogged and also has the
small restrictor in it as well. Check your bowl site glass and see if the fuel level is at 1/2 on
both bowls.

Added those to my list! Going to pull the tank and check for debris and try to clean it the best I can. Wouldn't mind just putting a fuel cell in the trunk...

I've cleaned out fuel in my tank twice and I still end up cleaning my carb after two months. The only way I can get mine not to sputter is when your idling. Turn screw to rich no restriction. Then start to turn lean, as throttle goes down raise idle screw and eventually sputter will go away. Just don't turn two much you will go too lean. It helps with start ups too. This is of course if your jets are clean, mesh screen is clean,, and no restrictions.

I am wondering about apex seals at this point. If it gets had to start after the engine gets loaded with the vehicles weight I would think internal at this point... just my thoughts since I lost an engine to this same thing. that is what mine did it was an 92 RX7 with a 12A N/A engine. lost power idled ok but once I put a load on it it would fail, and then let it set awhile and it would start again, then finally it would not start anymore, what I would do if it were mine is take and warm the engine up get it to fail and put a compression tester on it and turn the engine over and check the compression after fail, see what it is and then let it set for a while and test again once its cooled, I would bet you will have a huge difference in compression. just remember to take the Schrader valve out of the compression tester since your testing a rotary and not a piston engine... hope this helps

After running the RX7 long enough for me to not be able to start it I quickly removed the gas feed from the carb with the pump running and saw it was barely dribbling anymore. It must be debris in the tank, right? I'm going to pull it, fill it with rocks or BBs and tumble it for a while to get all the debris out.

After cleaning the tank I ran it for a couple hours and it never stalled. Only acts starved for fuel at 6 or 7k. My throttle linkage is getting stuck open sometimes too, not that big of a deal.

Sounds almost normal now. You may need to clean out the carb as debris could be
clogging some things up since your tank had these issues. Even at its best it will
rev freely up to 8K but there will be no extra power after about 6900 rpm, in fact
power will actually drop off at that point with a stock ported 12A.

You may want to just run some seafaom through it and drive it on a tank with some
in it for awhile and see if it gets better. Don't forget to keep an extra fuel filter,
you tanks probably still going to give off debris over time unless you lined it or
something.

The tank actually looked pretty good inside. It was still shiny and I didn't see much if any debris come out. I blew out all the lines with compressed air. I just cleaned and rebuilt the carb last week. It's probably still running a bit rich from my crazy exhaust leak and I haven't readjusted the carb since cleaning the tank.

well, it sounds like you're making steady progress. it should be just a matter of time.

Did you replace all of the fuel hoses? Old hoses usually break down from the inside out.

Here's another update. I swapped the coil packs and now it runs like a freaking champ. Still hesitates somewhat occasionally but I can rev all the way to 7K easily. My secondaries keep sticking open which is probably due to me welding mechanical secondaries and leaving the stock vacuum control hooked up. I'm going to remove the rat's nest, replace the fuel filter again and eventually fix my horrendous exhaust leak. It's steadily returning to a daily driver!

All right, it's running out of fuel. Running it between 4-6.5 rpm in neutral bouncing the throttle it will drain the bowls by the 3rd or 4th time I hit 6k. When cruising it'll run for about 3 minutes at 2-3k before the bowls are empty.

Here's a few symptoms I'm experiencing:
Bowls draining and not refilling without turning the car off and letting it sit for a minute.

The fuel tank acts like it wants to implode. Removing the gas cap it will make a large sucking noise and if I just in the car with engine off I can hear the tank "popping" like it's expanding.

I will check the fuel pressure tonight and replace the pump if needed. As well as the fuel filter.

Maybe your vent is clogged? Start up without the gas cap on & see if the problem persists.

The vent is that tube that follows the filler neck right? How could it get clogged?

I left the gas cap partially open and it never stalled and I never heard the tank pop. The cap itself doesn't seem to have a vent. Is my charcoal canister bad?

Will this gas cap work?
http://www.oreillyauto.com/site/c/de...3355&ppt=C0333