Nostart on hot engine only ? (but does after some cranking (or resting and cooling off), and always starts cold easy)      

First, be aware that fuel vaporizes poorly cold and very good warm  and due to that fact  a hot engine does not like super rich mixtures.  ( DO NOT FORGET super secreUNFLOOD MODE, wide open throttle cranking, pre operators guide)
If you are nunning old spark components all this data below is useless,  with out spark there can be no fire.  ( forgot that 60,000 (100km) tuneup did you?)  Cap,rotor,wires. and plugs?)
This car runs under EFI , Electronic fuel injection.  see photo 2 below , to see how simple it can be.
As always , to  start this engine, you need the 3 basics good,  Compression, spark, then fuel,   Watch Scotty do his magic?

If the CEL lamp does not glow key on, the ECU maybe in Backup mode, or bad ECU. (sure, bad lamp) fix this first. Backup mode floods the engine. Sure check fuses first or all electric fails of any kind.
Hot soak no start failures are because of :    All the tests must be done at the failure point,  as we can not diagnose any running perfect car.  (no DTCs stored)
  • Lost 12vdc power to ECU, only HOT? (rare, but is possible as are a vast number of things)
  • Loss of spark  to 1 or more cylinders, do check them all (or weak spark ,due to a low battery or caused by a bad charging system,. Et cetera)   Never doing a 60k tuneup is the #1 cause of all no starts.
  • The total Loss of fuel  (fuel pressure now zero or below 30 PSI?)
  • Flooding ,  is too much fuel      Keep in mind, flooding causes are usually due to no spark or runnning very old spark plugs, cap,rotor and HV wires. or too high fuel  pressure, or wrong inputs to the ECU/PCM.
  • Starter spinning too slow?
  • Lost compression only hot ? (valve lash is set wrong, seen many cars never had lash set, ever, not even checked at the 60k mile new timing belt service) So when hot, the compression drops like a rock.  150 PSI is min.
  • Loss of hot start air supply? (ISC failure, IAC failure, or the Dashpot 8v only, is  dead) This causes flooding, but is caused by loss of air.
  • This one sensor  input to the ECU/PCM  is wrong?  The ECT must read correctly or the engine, will flood, if the wires fall off the ECT or it goes bad, open or to a very high Ohmic resistance.
  • The crank sensor (CKP) does not  end spark, but the CMP will on all Suzuki engines, the Cam sensor in the Distributor. (almost never fails) until the 1996 J18 sport engines, that love to fail hot soaked. (or J20 engine later) note1:
  • Dribbing injectors (leaking) more flooding and spark plug fouling.  see here for all injector issues.
  • It is possible for and injector to stick closed hot. (the injector balance test can find this, but is hard do to because, it starts working as it cools.) Get them pro serviced if all tests here pass.
  • The fuel pump regulator can fail many ways,  one way, is too  low fuel pressure, and starves of fuel, or fails with too much pressure, it can stick at 60 PSI and the engine will flood, no matter what you do.  A $20 fuel pressure gauge is easy to use.
  • Most engines may flood  in ECU failsafe, or backup mode for sure.  Scan the ECU or use the jumper clip test.
  • There are other odd failures, EGR stuck wide open (but snaps shut cold) or Catalyst melted and keeps stalling engine, but may or may not restart, but if a cold engine has full power and runs good cold,  its not the CAT.
The key to finding the problem, is testing quickly ,which of the 3 are failing, engine compression, spark, or bad fueling. BASICS)

note1:  The ECU on this car will flash code 41 (or 42 is bad spark) if the CMP sensor is bad, (the magic trick is crank for full 5 seconds with DLC diagnostic jumper in place)  Let the ECU tell you why the car fails to HOT SOAK start.
The same is true on all 1996+ OBD2 cars too.  (new codes are used )

Most modern ECU/PCM use fuel tables (AFR calibrations) for at least 4 modes of running , and for start up.  See this link for how custom ECUs are tuned.  See how it is done.

I mention this, because you need to know what mode the ECU is IN, before troubleshooting a problem.   The ECU is the engine contoller unit,  Spark and Fuel injection brains.
 All this information is covered in 1 book.     "How to Tune and Modify Engine Management Systems" By Jeff Hartman.  
This injection system is designed to operate from -40F and one at 200F. Coolant temperatures. (at least).  In the extreme, the air fuel ratio can be 10 times HOT.


ECU modes of operation:   ( a cold start , very cold engine) sequences through each step , in this order)  Switching fuel maps as it does.
  • Start up  (hot or  cold  ECT readings  )   The cold AFR can go as  rich as 4:1   and far  less rich at 70 . F.
  • Cold running  (can be optional or is only used on extreme cold weather)   or is just part of warmup cycle.
  • Warmup
  • Hot.

During this progression above , these sensors/actuators come on line : (MAP/MAF) ECT and IAT  at cold running, then the 02. when  the 02 sensor gets warm enough at 800F?.
When cranking (starting) the Air flow is fixed by the 3 fixed paths of Air, " IAT, ISC and Air bleed".  
The IAC device,  will be near wide open. cold.  and fully closed over 150F, hot. On the 8v motor the dash pot device adds lots more air (path 4).
The fuel tables are tuned for these 3 paths to create near perfect AFR.  
Flooding is caused by , too much fuel,  sure, but can be caused by  too much fuel pressure, or an ECT that reads too cold for reality or the loss of air supply .
Over fueling is cause by lies (inputs) to the ECU.  (sensor lies, or bad actuators.)    A bad actuator can be a leaking injector , bad Fuel pump regulator .  A bad input will be the ECT.
A stuck closed ISC?  or IAC.
An 8V engine with a stuck closed Dashpot ( never adds air for any hot or cold start)

When you start a hot engine the ECU behaves differently.  It should jump from Start up to HOT , in my list above.
It will see the ECT Signally  at lets say, 170F or more Temperature (coolant temperature)  The ECU adjusts the injection rates for less air.
If hot restarts are hard,  then you have too much fuel or too little.  (add air or add fuel to find out which , is lacking?)

Adding 10% throttle or Wide open throttle (magic unfood mode)can cause the engine to start more quickly  or instantly . ?  Yes, then you lack AIR supply. or have flooding issues.
Many will say car starts great cold, so how can it flood warm?  ( please, study fuel vaporization effects on both a cold or hot engine,  a complex subject , not covered here.)
Keep in mind the ECU is programmed to start at - 40C,   It can, and will flood any engine, if the ECU sees the wrong coolant temperatures. (a bad ECT) The car starts great in ALASKA just for this one feature (fuel tables/temp)

The ECU does not know that your injector (s) were leaking,). , if the injectors leak, then it will be hard to start hot.
The ECU is a computer, a simple computing controller, processor and as such if the inputs are wrong it will calculate wrong or it will use the wrong fuel tables,  This is called, GIGO, in the business, Garbage in , Garbage out)
The ECU will guess wrong (calculate wrong) with a bad ECT, or fuel pressure is WRONG or the Injectors are leaking or clogged. It has no magic way to know these things are wrong,
Same with IAT, (8v) same with OBD1, oxygen sensor "O" stuck at 0v or 1v. (hot) The old OBD1 cars  love  to go too rich (with bad 0) (a design weakness cured with OBD2)

Injector leaks are (another lie to the ECU, it is)
Do the fuel pressure leak down tests. To find  injector leaks ,or fuel pump issues !
If you have a 1.8L or newer engine, (bigger) the CAS/CMP , cam angle sensors are notorious  for hot start fails.

BLAME:
Causes of hot start fails:  See all the sensor  tests, here.
IACstuck open , (failed) will only cause, fast idles starting. but on a hot motor this might fool the ecu, you'd know its bad because at all times hot, the IDLE RPM would be insanely too high. like 2500 ?
ECT Bad? May cause hot restart flooding.  (reads too high in ohms for reality )  if it opens circuit or fails to read near 300 ohms hot, it is bad. and then motor will love to flood.
Just pretend the ECT is a choke,  ( It really is , at all start up's)
ISC stuck  (jammed)  (clean it. and test it)  The ISC must be free to move and must open with 12vdc applied and must close with 12vdc removed.
If the Water coolant supply through the ISC or IAC are blocked , you will have both actuators fail, and starts up can be hard. (try starting with 10% throttle to offset the error with air supply)
A engine coolant flush every 2 years solves that rare failure (coolant blockage).
The CMP likes to hot soak fail on 1.8L motors, Sports Suzuki Sidekicks, and on the old 89/90 the dizzy ignitor or VR device like to fail hot too.  The 91-98 1.6L never have hot soak electronic failures..(robust is the word)
A dead CKP sensor (96+) will not cause a starting issue.
The TPS not signally IDLE , may cause cold starts to fail. The TPS must be calibrated.
Dribbling injectors sure can cause a nice hot start flood.

PRESSURE:
The fuel pressure is too high, causing harm starts to be too rich. FP-REG fail? ( not noticed  cold?, because the car and out door temperature and fuel seem to like too rich.  as they say , magic happens)
I will not try to get into vaporization effects of gasoline at different temperatures, but ever try to start a hot lawn mower with the choke lever , stuck on?   Bingo.
The biggest mistake is assuming you know what is wrong before troubleshooting.  Start with a tune up , and learn to read the spark plug tips.

If the fuel pump can not hold pressure (a bad check valve or leaking injectors) you will have a slow start. (delay until 30 PSI is reached)
So,  key on 5 times, one,off, on.....  now you have full pressure, now start.  does that help ?  yes? then do the pressures tests in the FSM , it will fail , I bet.  The residual pressure tests will fail.

See the 8 tests for the fuel pump system?,   and just do the first 4 tests, and the Residual Pump test, this test finds leaking injector(s).

Keep in mind it takes 9000 gallons of  Air to burn 1 gallon of fuel.

Last,  the wrong  Fuel
Gasoline refiners produce fuel with a slightly lower volatility rating (called "Reed vapor pressure") during hot summer months because lower volatility fuel is less likely to boil and cause hot starting problems. (vapor lock)
End hot start fails.

Comment: there are only a few tricks that can be done, with no tools.   You can't fix cars with out any tools. 
You can check spark plugs for free. (almost)

Photo section:  Got good spark at all cylinders?  or are they black and packed with  carbon, carbon is a perfect conductor of HV, electric current and effectively shorts the plug out. (the car below has 60 PSI fuel pressure and floods at the drop of hat)
Photo #1      So cazlled,  Fouled spark plugs and fuel soaked, and flooded.

Photo  #2  ( as simple as I can make it ! )


CAS = cam angle sensor or CMP, in Suzuki Jargon. VSS is veh. speed sensor.
The 1996 has  CKP sensor that does not prevent starting the engine, on this Suzuki , like it can on other cars.

A Jargon list here.


rev 2   ++++ 4-16-2011