So, my 85 RX7 race car just doesn't like to hot start. It is a second gen. motor, non turbo with a weber 48 IDA. I'm running twin MSD boxes as well. It starts fine cold but once hot it is a difficult start. I almost couldn't get it to start when I was running my small odyssey battery so I upgraded to a mondo one with 950 cranking amps and that has improved it some. Any ideas or thoughts?
How hot is your carburetor getting? Do you have a header? Is it wrapped and/or coated? What does your fuel system consist of?
Have you checked the compression?
^This^
They like to flood as well. Pull the plugs and see if they're soaked.
I've had to resort to pull starting a few RX7's in my day. Hook it up to a truck, tow it at about 20 mph in 3rd to clear everything out and bingo, we have ignition. Hardly ideal, but hey we were kids and you do what you gotta do.
How new are the plugs? also check compression.
New motor, new Weber, new everything. Compression good. Underhood heat is not bad, certainly not boiling fuel because it will not hot start easily even when the hood is open. I'm a little perplexed but the new battery has made it significantly better.
Are the Webers side draft and sitting above the engine?
The Abomination runs a Dellorto side draft. It has a tenancy to flood the engine when hot if you don't run the bowls mostly dry. Probably due to fuel expansion from heat. SOP for a hot shut down is kill the fuel pump, run the engine until it starts to stumble, kill the ignition. As long as I do that it will hot start fine. I keep meaning to fab a heat shield to mount between the engine and carburetor.
Toyman01 wrote: Are the Webers side draft and sitting above the engine? The Abomination runs a Dellorto side draft. It has a tenancy to flood the engine when hot if you don't run the bowls mostly dry. Probably due to fuel expansion from heat. SOP for a hot shut down is kill the fuel pump, run the engine until it starts to stumble, kill the ignition. As long as I do that it will hot start fine. I keep meaning to fab a heat shield to mount between the engine and carburetor.
Carbs sit above but that sounds like a similar problem. I may try the shield route as I am running RB headers and no wrap so it may have fuel expansion. Good tip, definitely worth trying.
Running the carb dry was SOP with my ITA RX3. Even with a heat shield the heat was incredible under the hood.
The Dellorto on mine sits right on top of the engine. There might be 3/4" clearance between the block and the bottom of the carb.
I guess that'll help when pitting. I just hope I don't stall on track or anywhere not near my paddock area
Didn't some X1/9s come with a fan that blew cold-ish air onto the carb to fix a similar problem? I know this adds weight but it might be worth considering a similar kludge, err, "fix"?
It is kind of embarrassing to spin one in the middle of a autocross course and then spend 5 minutes trying to get it started. Fuel pump off, throttle on the mat, mash the start button. Eventually it will start...eventually.
Just don't flood it cold. The choke on mine stuck at full choke at the last autocross. It took me an hour to get it to fire. Made for an interesting first run since I didn't get to walk the course. 
Toyman01 wrote: It is kind of embarrassing to spin one in the middle of a autocross course and then spend 5 minutes trying to get it started. Fuel pump off, throttle on the mat, mash the start button. Eventually it will start...eventually. Just don't flood it cold. The choke on mine stuck at full choke at the last autocross. It took me an hour to get it to fire. Made for an interesting first run since I didn't get to walk the course.
Mine doesn't have a choke, yet cold starts at 40 degrees and above are no problem. Autocross is how I knew I had a hot start issue as I stalled in the que line and it took a long while to restart. THe car is really set up for road racing but I have been autoXing it for the last month just to sort it out as it is a fresh motor and suspension. Gonna make the last changes next week going to the Re-Speed setup with Koni Yellows all around replacing the Tokico Illuminas and RB springs. Doubling the spring rate, expecting a much flatter steering response.
1)A stainless heat shield between the intake manifold and the exhaust 2) An insulator gasket/seal between the carb and the intake manifold 3) Check compression when hot
I had hooked up a switch to kill the fuel pump on my S4 FC for this exact reason since its original engine had some compression issues. Also made a good additional anti-theft measure on the convertible. 
Is this engine new or rebuilt?
If rebuilt, (and to a lesser extent if new) the engine will have lower compression. it needs time for everything to "seat".
Before I got my injectors cleaned (2nd gen) I had to shut the fuel pump off every time I knew I was going to re-start it in teh near future.
If it does die on track, keep the fuel pump off and try to start it. Once it coughs, turn teh fuel pump back on. it should catch OR it should start with the next turn of the key.
Rob R.
wvumtnbkr wrote: Is this engine new or rebuilt? If rebuilt, (and to a lesser extent if new) the engine will have lower compression. it needs time for everything to "seat". Before I got my injectors cleaned (2nd gen) I had to shut the fuel pump off every time I knew I was going to re-start it in teh near future. If it does die on track, keep the fuel pump off and try to start it. Once it coughs, turn teh fuel pump back on. it should catch OR it should start with the next turn of the key. Rob R.
Rebuilt (new) motor. I had considered that the seals may not have fully seated causing low compression but there is little I can do about that until they break in.
I have a fuel pump shut off switch already, just hadn't been using it.
Good advice, thanks.
bruceman wrote: 1)A stainless heat shield between the intake manifold and the exhaust 2) An insulator gasket/seal between the carb and the intake manifold 3) Check compression when hot
On my list
Hot starts back in the '80s were only a problem with the injected engines. Since your car has a carb, it shouldn't have a hot start issue. And seals should not need breaking in. Is there a return to the tank fuel line as found on the stock version? Have you tried lowering the float level?
The seals do need to wear in slightly if they are new and the housings are new or different. Of course, I would think that would be more of an issue with cold starts.
Most of the time, when a car starts fine cold, but not hot, it is an electrical problem, usually solenoid related. Check the cables, connections, and the starter. If the problem improved with a new battery, it probably doesn't have anything to do with carb/fuel issues.
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