Ok i've been reading up on hot start issues and trying to figure out what might be causing it, Id like to fix the problem and not do a switch.

When hot it won't start, however if I unplug the relay under the dash it WILL start. If I plug the relay back in when it starts it will keep running just fine.

Can anyone help enlighten me? I've been thinking the intake air temp sensor might not be working. When the car starts up cold it wants to stay idling around 1500k, it never drops back down unless I turn the car off after its warmed up and do the relay trick i mentioned above. After that the car seems to run faster and idles were its supposed to. I've heard bad grounds might cause this too, any thoughts? i've tried replacing the relay thinking that the relay may be bad but didn't change anything.

The car is a 88 turbo II, has no mods except for KN air filter and the resonator taken off and replaced with a straight pipe.

 

The items the ECU looks at are shown in the attached jpg.

ECU sees the start signal when the key is HELD to Start.

It uses the water thermo sensors input.

It looks at the rpms being under 500 rpm.

IF the water thermo sensors input to the ECU is b/t 0.4vdc and 5vdc when the engine is hot, then there is nothing wrong with that sensor.

IF the ECU sees the Start signal on its small plug then there is nothing wrong there.

You can look at the tach ans see if it's under 500 rpm.

The ECU uses a pre programmed START FUEL MAP that you cannot change by yourself. So if the items above are ok, then your out of luck.

OR you can play the silly game of changing out the fuel injectors and getting them cleaned. I doubt that will do squat for your problem.

I won't mention low compression being maybe the problem.

RTEK 2.0 using a Palm device lets one select the amount of fuel during START or in other words alterning the stk fuel start fuel map.

 

so let me get this straight.

May be the coolant temp sensor

maybe the injectors

maybe the ecm

or injectors?

I don't think it would be compression because I can start it right up with the relay unplugged then plugged in while trying to start it.

I think I'm going to try the sensor first

 

The switch works like a champ ! i have mine hidden in the center console lid. if my car doesnt hit after 2 sec of cranking then i use the switch ( quite often in this heat )

 

Even the Rtec doesn't 100% fix it. I still get hot start issues from time to time.
My rad temp sensor, the bottom one, wasn't seeing ground. I did a quick work around wire splice the other day. My guess is that it will still have problems. I still don't have a adjustable fuel regulator so some of it is to much fuel from my walbro.

My plan is to eventually put in a megasquirt and just say to hell with it.

 

i also have a walbro 255lph getting hot start issue.... i think it was when i plugged the thermo senser in hahahaha S4 T2 hackjob

 

so this might be a stupid question but how do you wire a switch in?