rkhanso

My son's recently traded for '81 RX-7 has some issues. We had to put intake/exhaust gaskets in.

Putting a vacuum gauge on the intake manifold, the needle bounces quickly between around 10-30. It can also backfire some when starting it.

We've adjusted the timing to what appears to be correct (the timing marks aren't obvious on the pulley)

When the timing light is on L1 and L2, the strobe is steady.
When it's on T1 and T2, it's erratic. Sometimes it won't flash for a while, sometimes it's 'fairly' steady, but then goes back to erratic again.

It smells to be running very rich, and there's a strong odor of 2-stroke snowmobile type exhaust. The OMP is connected to the primary bowl port on the Holley carb. It also has a Racing Beat intake manifold.

It sounds like it's missing all the time.

The rear rotor plugs were more black than the front rotor. The front had a little more brown to it than the rear.

Any suggestions?

Thanks.

rkhanso

Here are a couple videos showing the vacuum gauge and the timing light. It takes a while for them to load.

Vacuum Gauge

The first strobe in the timing light video is one of the trailing plugs. The middle 2 strobes are both of the leading plugs and the last strobe is the final trailing plug.
Timing Light

Spark Plugs

prophetjohn

iTrader: (1)

sounds like you have a trailing ignitor / coil giving up on you.

KansasCityREPU

iTrader: (9)

Also make sure the distributor to stabbed correctly. There is an alignment dimple at the bottom of the distributor and aligns with a mark on the gear.

rkhanso

I got the trailing spark fixed....just cleaned up the back/grounding of the igniters. Good spark on all 4 plugs now. I just need to find those timing marks to adjust the ignition timing. I'd like to find those marks on the pulley before taking out the distributor.

I looked in the carb while it was running and see a fair amount of gas leaking into the carb. No idea if this is normal as I haven't had a car with a carburetor for 25 years.

Here's a video looking inside the carb while it's running.

VIDEO

rkhanso

What should the vacuum gauge do on these rotary engines at idle?

I've searched the FSM (for a '80 model - all I could find online) and didn't find anything mentioning vacuum gauge results. Searching online I found a Holley video on Youtube, but it stopped before it came to the explanation for my results.

MosesX605

While I've never used a Holley on any RX-7 that I've owned but that seems like way too much fuel dumping down those primaries.

rkhanso

I purchased a carb rebuild kit and new floats last night. They should be here on Monday. (I'll hope for tomorrow though).

Still wondering about that vacuum gauge. I sprayed some sea-foam in the carb last night. Boy did that smoke up the neighborhood. A neighbor came by to see if everything was OK.

When I sprayed into the rear primary throat, the engine stumbled. When I sprayed into the front primary throat, nothing happened. I'm guessing that means the trouble is in the front rotor.

After that, I poured a bunch of sea-foam in the front throat, turned the engine by hand and let it sit overnight. I'll see if there's any improvement after work today.

DivinDriver

iTrader: (15)

It looks from the video that the right-side bore (front rotor?) is getting a lot more gas than the left is. Might just be appearance in the video rather than fact, but fuel flow on both rotors should be equal for obvious reasons.

Plugs look pretty wet, too. Coupled with the rich smell you mentioned, I think rebuilding your carb and tuning your mix will probably help you out. I would hazard a guess that you are running pretty rich.

rkhanso

I removed the lower spark plugs on each rotor, put fingers in front of the hold and cranked the engine. The front rotor had considerably less pressure than the rear. I don't have a compression tester yet. Was going to pick one up on Monday off Craigslist.

I remembered the 'steam' cleaning method so thought I'd give that a try. Kept the engine running until it was hot and then removed the hose from the distributor trailing ignition diaphragm to the port at the bottom of the carb (the one at 45 degrees). Put the hose end into some water a little bit at a time, keeping the engine running between doses of water. It seemed to help. The car started running better.

I ended up putting about 20 oz of water through the engine. Was thinking about running another bottle through. Is this a bad idea? After the water ran out, I did run some ATF through the same hose, though only a few quick ingestions worth.

I'm wondering if there's still some cleaning out that needs to happen. Has anyone else who'd done this remember how much water they went through?

KansasCityREPU

iTrader: (9)

Harbor Freight as a standard compression tester for $21.99.

Search results for: 'compression tester'

Running the water was fine. Using ATF on an engine that runs is not so good. It can swell the seals. I only use ATF when I can't get an old engine to run because it has really low compression or to free a stuck seal.

rkhanso

I used some more water for 'steaming' the engine.
Adjusted the carb a little (still need to put a kit in it).
It's idling pretty good now. Hoping this decent idle means that it doesn't have a bad seal in the engine. The vacuum is still fluctuating and it still has hesitation and backfire on acceleration.

Here's the video listening/watching the idle.

rkhanso

I rented a compression tester from O'Reilly today. The rear rotor has 115 psi (I was by myself so I couldn't use the release to see what the 'pulsing' psi was for each rotor.

The bad news....the front has zero. It's amazing to me that the thing idles so nicely on just 1 rotor.

Wondering if there might be any chance that I can resurrect this thing from the dead by some miracle cure (ATF again, water again, sea-foam again), or if there's no chance.

Or, is it possible to rebuild just the one rotor? Trying to save some $$ for my kid.

Or, better to just sell it to someone that might have parts or the know-how to rebuild it.

Any opinions?

rotaryjunkee

That is way to much fuel going into the carb.
Did you check the level of the floats? Do you have a fuel pressure regulator on the car? Holleys only want 6psi of fuel. And start with a base tune on the carb by setting the idle air mixture screws at 1 1/2 turns out and tune it from there. If the one rotor has 0 psi, then I would remove the exhaust manifold or header if it has one and check the apex seals see if they are stuck or if you can push them in and they dont come back out, then it might need new apex seal springs, if your on a budget. If the apex seals are stuck then proceed with whatever suggestions the archives say. Thats what I would do if this was my car.

Sent from my samsung gs4 using RX7Club app

rkhanso

I think we're just going to call it a day on that car. Don't want to stick any more money or time into it. I'll be putting it in the for-sale section.