Mazda RX-7, rought to start, concerned about hot start: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Feb. 7, 2010 9:21 p.m. Jeff Dork

So the RX is ready for it's first race. I tried to start it Friday, but no luck. I wasn't surprised, it had been about a month since it cranked. I put the battery charger on and waited. Today I went out, and after some cranking (about a couple of minutes worth actually) it started up. I ran it until it was at full temp and pressure, then revved it up a few times. After about 15 minutes I shut it down.

My concern/question is twofold. First, can I do anything to make it easier to start? It's prepped for IT7 so a lot of the carb crap has been blocked off or removed. It has no choke. Is starter fluid an option to make it crank easier?

The second issue is hot starts after doing autocross runs. I've heard the rotaries can have trouble there. Any thoughts or suggestion on how to make this easier?

I'm going to start it up everyday this week before the Sunday event. If you are in LA (lower Alabama) come by the Wiregrass SCCA autocross.
Feb. 7, 2010 9:51 p.m. jwdmotorsports HalfDork

I never had any hot start issues out of my FBs. Autox or daily driving.

I have heard of a lot of issues hot starts on FCs and flooding issues.

As for easier starting, rotaries don't like to sit. Start it more often.
Feb. 7, 2010 9:55 p.m. bamalama Reader

I always put the fuel pump on a switch. Makes it a lot easier to clear out the engine.
Feb. 7, 2010 10:02 p.m. aussiesmg UltraDork

Pull the plugs, turn it over a few times, put them back in and Bob's your uncle
Feb. 7, 2010 10:19 p.m. P71 SuperDork

If there is any hot start issue, it's from heatsoaking the starter. Cold start is because of no choke.
Feb. 8, 2010 7:00 p.m. sevenracer New Reader

I use starting fluid sparingly and try to avoid it altogether.

Make sure your starter, cables, battery and connections are in really good shape.

You should do a compression test both hot and cold, just to know where you stand.

I don't know what kind of seals you have, but if you're running single piece carbon or ceramic seals you'll lose some compression when hot.

If it's really bad, you can put a little MMO or motor oil down the primaries of the carb to help with hot starting.
Feb. 11, 2010 10:36 a.m. Jeff Dork

So I assume when you pull the plugs and gas runs out the leading and trailing spark plug hole that it's flooded ?

Got them all pulled, cranked it over a bit (had fire extinguisher at the ready) and am now letting it dry out. I'm guessing I need to be more judicious with the fuel pump early on. Maybe just on for a few seconds, switch off till it starts to catch, then switch it on again.

Rotary guys, anything else?
Feb. 11, 2010 1:13 p.m. bamalama Reader

Jeff wrote:

I'm guessing I need to be more judicious with the fuel pump early on. Maybe just on for a few seconds, switch off till it starts to catch, then switch it on again.

Rotary guys, anything else?

Try it with the pump off first. If it hits, switch the pump on then.

Unplug the coils next time you crank it over with the plugs out. I forgot. Once.
Feb. 11, 2010 11:16 p.m. sevenracer New Reader

Sometimes the float needles stick and cause the bowls to overflow into the bores. Should be pretty obvious if this is happening - with the air cleaner off, you should see it and smell it. It's a bad idea to run the fuel pump when the car's not running.

You don't need the fuel pump on to start the car if the float bowls have fuel in them. You will need the pump to run the car more than a few seconds.

I usually pump the gas pedal 3-4 times as I hit the starter, keeping it floored on the last pump til it lights off.
Feb. 12, 2010 9:54 p.m. fastmiata Reader

Wire your fuel pump as separate circuit so that you can kill the pump and let the car run out of gas every time you want to turn it off. That was our standard procedure with the RX3 and it worked.
Feb. 12, 2010 10:13 p.m. Jeff Dork

So I tried the plug clean up, seafoam and oil in the carb, and some gumout and starter fluid for good measure. I got it to kick over and run for maybe 15 seconds, then it would stop when it ran out of stuff to burn. I'm now guessing that the carb initially flooded the engine right before it gave up the ghost and stopped working because it seems like it's not getting fuel.

I'm going to check the filters and lines to see if I'm getting gas to the carb. If that looks good, time for a carb rebuild or just rebuilt one from Sterling.

Thanks for your help and encouragement. Any further suggestions are appreciated.
Feb. 12, 2010 11:25 p.m. Toyman01 Dork

My FB with no choke is a real pain to start if the temp is below 40 and it has been sitting for more than a day or two.

Starting procedure.

1: Pump the gas 10-12 times and fire it up. 2: Keep pumping gas. 3: After it stalls, go back to step one. Repeat. Repeat. Repeat.

After the fourth or fifth try I can usually keep it running by continuously taping the gas. After a few minutes it will idle. And 5 minutes later you can put it in gear and go. It will stall at the stop sign at the end of my street so I never pull out in front of anyone. Do NOT shut down before it is fully up to temp.

The Abomination with the12A and the Deltoro carburator is like a combination lock. If you don't know the combination it isn't going to start. Fuel pump for about 5 seconds. Choke set to about half. DO NOT touch the throttle. It will start and fart and spit fire out the exhaust. TURN ON THE FUEL PUMP(I have been known to forget this step). Once the temp hits 160 it's drivable. To shut it down, turn off fuel pump. When it starts to spit and miss-fire, shut off ignition, other wise it will flood.

Carbureted cars can be a trick to start some times. You just need to figure out the proper procedure.