car wont start once engine is warm

90 LS. automatic. new fuel filter, spark plugs, oil, replaced MFR. car turns on fine when cold. get to your destination and turn it off and 5 minutes later when you go to start it it starts and dies instantly and when you try to restart it, it just cranks and cranks and the s3 light is flashing and check engine light stays on. let it sit for a few a couple minutes and you try again. this time the s3 light and CEL turn off. you start it and this time hit the gas. get it reved up to 3000 rpm and let it drop down and now the car stays on. any ideas as to what the problem may be will be appreciated.

possibly coil or igniter. check for spark when problem is occurring
and it never stalls while driving?
can you hear the pump prime when problem is occurring?

igntior?? could you explain this part to me please LOL
car never stalls while driving. once its on it stays on no matter what
and i do not hear the pump prime 0r the MFR turn on either. which is why i replaced the MFR. it takes me a few tries of turning the key completly off and the on again for it to allow me to turn it on. sometimes it will die again but usually if i give it gas it will turn on.

disregard the igniter and coil.
check/clean your thermostat housing ground cluster to start with

fuel pump could be going out

^^since he says he doesn’t hear the mfr click, it’s gonna be a power or ground issue. or ecu

oh very true…missed that part.

Sounds like your new MFR might be bad. Stranger things have happened. Where did you get the replacement?

Don’t rely on the fact you cant hear the pump prime. I have never been able to hear mine in 3 years. Pull the back seat up and put your ear directly to it, then have some turn the key. That’s the only way I can hear mine and even then it’s not loud.

the MFR is not new. it is a used one. i can always hear the pump prime when its cold. when its warm and i get back in the car. i turn the key. hear the pump prime. turn key and it turns on but then it just dies. then when i try to restart it. the s3 light starts flashing and the car fails to start. i wait a few minutes and try again. and it usually starts. other times i have to keep trying over and over again. eventually it starts… i can hear the MFR every time except when it dies on me and the s3 light starts flashing… on only two ocasions since the problem started has it not started when its warm. then i had to hop on my bike and get to work lol i really appreciate all the help everybody…ill try cleaning the thermostat housing cluster and i am probably just buy a new MFR just to be sure. ill let you all know if it happens after that

check/clean that ground cluster. also, check for codes. since the s3 light is also flashing, and i am assuming tcm grounds in the same location, it is a good possibility the ground is bad

What is S3. I am having a simular problem. When mine heats up it does and wont start till it’s cold. I have a new build on the car with a honda data ecu. I don’t through any check engine lights or anything. I replaced the ignition, coil, new cap and rotor about 1 1/2 years ago along with a main fuel relay, fuel filter and pump. When my car wont start I checked for spark and yes I have spark. I can hear my fuel pump when I turn the key on but only when the car is cold. Is the ground what is on the thermostat housing? Mine is tight and it’s clean. Any other grounds I should check? How do I replace the ground wire on the thermostat?

Thanks

It’s almost definitely your main fuel relay. Try running your car at home until its warm and won’t start then remove the mfr and put it in the freezer for a couple minutes then reinstall it. If it works you’ve found the problem.

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sorry incublu… Rollinmyda I bought a new main fuel relay at napa and put it in and this was the first time out testing the new MFR. Still does it

I thought you said you replaced it 1 1/2 years ago, did you replace it again recently? Or you haven’t driven the car for 1 1/2 years? I’m not saying 100% that its the mfr but the heat related onset of the condition is a red flag for me that just screams mfr. There are some parts I would buy from auto parts stores but I don’t think thats a part I would. I always try to stick to OEM on the important stuff.

Yeah so the car has been finsihed and tuned about 1 1/2 years ago. I have replaced fuel pump, filter, MFR that time too. I just replaced the mfr on sunday and drove it t work monday and yeah it died on me and I coasted in the parking lot. Well it still wouldn’t start even after sitting there for 6 hrs. My buddy owns a shop in Utah and he gave me a OEM one and that still didn’t work. I am taking it to his shop so he can figure out what the deal is because I have no clue now. lol

If its dying while you’re driving it that actually doesn’t sound like the mfr. Usually it just causes the car to not start when its hot. Good luck!

yeah it’s at my buddys shop. I dropped it off today and he said he will look at it Thursday. I’ll let ya know what is up when I find out.

when was the last time you replaced the o2 sensor?

do you have a 90-91 or 92-93

Fouled o2 can cause running issues when the car is warm, but not show up when it is cold. Reason why is the sensor on say the 90-91 doesn’t start sending a readng until the manifold reaches operating temos or 300 degrees farenheit. Typically you get rough start, no start, rough idle type issues when the thing starts reading as it is tossing off the A/F ratio.

92-93 has a re heated o2 sensor… only difference tho is that the sensor will start reading sooner than the 1 wire sensor on a 90-91…