My car starts fine when the engine is cold, one turn. The problem is that once the engine is warm it won't start at all until the engine cools down.

My Mazda dealership has looked at all kinds of solutions. First they check my fuel pressure regulator and found that it needed replacing. This though did not solve the warm start problem. Next they checked the fuel pump and it is fine. They have also check all my wiring and it checks out fine. They are now telling me that they think it might be an ecu problem. They want to test this by getting an ecu that they know is good and plug it into my car to see if this helps.

Also they check all the vaccum lines and they are fine.

Anyone have any ideas as to why I might be having warm start problems. I think my dealership is running out of ideas.

 

While getting dynoed at KDR, I mentioned my hot start problems to Dave. Since I had good compression we knew it was not an engine issue. He replaced my leading coil and that seemed to help a lot. I'm not too sure what the leading coil does, but you should look into this. Also, check your compression and air and water thermosensors. Good luck.

 

On an FD HOT start problems ar generally caused by 1 or both of 2 things -
1, a Weak / Failing Battery and/or
2, LOW COMPRESSION

the FIRST THING the Dealership should have done is CHECK the Compression (it says so in the FSM)
Even when my compression was way LOW installing a NEW Battery solved my Hot start problems (until my coolant seal went) HEAT KILLS Bateries & a HOT battery puts out LESS voltage than a Cool One (COLD like below 0degf will reduce a batteries voltage also but is not as hard on the battery as excessive HEAT) The FD gets VERY HOT under the hood, which is why MAZDA but the battery in a full batery box (you do still have the box & Lid dont you :-) ) w/ it's own cooling air supply.

If it starts cold it is not a Fuel Pressure problem, could be ECU but not likely. Can also be weak Starter motor But that would also probably cause hard Cold starting also.

 

Thanks for the input.

The battery was replaced with a new one about 3 months ago. The battery is still in the factory box with the lid so I don't think that is the problem.

My compression is below Mazda specs, mid 6's for rotor one and mid to high 6's for rotor two. Right now I am in a fight with my warranty company over this issue. Hopefully, but not likely, I will get a reman engine.

I will get on to Mazda about this compression problem possibly being the problem with the hot start. Maxpesce by chance do you know where in the factory service manual it talks about compression being a problem with a hot start.

I will also get Mazda to check the leading coil, air and water thermosensors.

I also have no mods on my car.

Thanks

 

This is an outside suggestion, as I'm sure the low compression is the likely culprit, but don't forget the FPR is activated via vacuum, and this vacuum is supplied through a solenoid, one of the ones in the rat's nest. These solenoids are known to have intermittant problems working properly when they get hot, especially as they age. It's a bit of a bitch, but you might want to make sure the solenoid is actually opening correctly on warm startups. This would entail providing an alternate voltage source to the solenoid and a hand vacuum pump, or just blowing through tube to make sure it opens properly. The real problem is getting at the solenoid while the engine is still warm. Ouch!

Anyway, likely not the problem, but it is in the signal path, and should be ruled out in any case! You can also of course pull the solenoid and pop it in the oven and then test it. Test it about 200F or so...

 

I was going to mention the FPR Solenoid as well...it's the one on the rack closest to the firewall.

 

spurvo thanks for the suggestion about the solenoid for the FPR as being the possible problem. I will check that out.

 

Dubs and I are synchroneously wavelengthed.

 

Re The Battery - Check the terminals for corrosion and tightness. The may not have been cleaned well when the battery was installed.

RE Compression Lo > mid 6's is low enough to cause the hot start problem MAZDA lower limit for compression is 8 for 93's and 7 for 94+'s
iirc the compression check is the 1st item in the troubleshooting check list for Hot Start problems - I will have to check when I get home.
fwiw I fought the Low Compression Need reman Battle w/ my warrenty co and lost - if the commpression is equally low on all 3 faces of each rotor the will claim it due to Normal Wear, if the #'s ar low ononlw 2 ot the 3 faces you can argue "Broken Motor" as in broken apex seal.

 

I used to have that problem and getting new terminals for the battery fixed it