hard to start when warmed up

[Supraboy89]

im having issues starting my car once its warmed up. i have checked the VSVs and they look good and i have replaced the ecu temp sensor and it still does the same thing. when it finally fires up it barly wants to run and it reads very lean on the wideband but after it runs for a min it runs great. any ideas?

 

[jetjock]

Rest pressure...

 

[585Soup]

http://www.toyota-supra.info/forums/mkiii-supra/11747-car-wont-start-hot.html

there's a thread in there about cleaning the intake valves and injectors.. also, check your plugs and plug wires.

 

[585Soup]

And if all that checks out, wouldn't hurt to do a compression test on it.

 

[Supraboy89]

also what is the sensor for that is below the ecu sensor

 

[GC89]

Rest pressure...

+1 good chance it is vapor lock

also what is the sensor for that is below the ecu sensor

which 'ecu sensor'?

 

[Supraboy89]

+1 good chance it is vapor lock



which 'ecu sensor'?

the one below the green plug one that looks like the one for the guage

 

[GC89]

the one below the green plug one that looks like the one for the guage

AC temp switch.

Test the FPR & resting fuel pressure per the tsrm http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=71

 

[jetjock]

Actually iirc it is for the gage. That's why (along with the ECU sensor) it's on the engine side of the thermostat. Been awhile though so I could be wrong.

 

[GC89]

JJ your right, aux and ac fan sensors are on the t-stat housing.

 

[Supraboy89]

Actually iirc it is for the gage. That's why (along with the ECU sensor) it's on the engine side of the thermostat. Been awhile though so I could be wrong.

the one for the gauge is on the housing right. or is mine in the wrong spot for the gauge because if i rember mine has allways been on the housing. all i know is that the gauge sensor looks a little different then the one i am talking about

 

[jetjock]

The gage sensor belongs on the engine side of the thermostat. It's the one-wire device located directly below the TCCS coolant sensor (all ECU sensors are two or more wires). The reason these sensors are on the engine side is so they can better monitor engine temp regardless of thermostat position. Pretty standard stuff.

Even if yours is in the wrong place that alone wouldn't cause your symptoms. You really ought to be checking rest pressure. That should always the first step when encountering hard hot starts.

No way to do that? Here's a tip: Look at the top of your fuel dampener. Pop off the plastic cover if still there. Jumper the fuel pump on in the diag block and observe the little screw on top of the dampener. It should be standing proud. Now unjumper the pump. If the screw quickly falls you're losing rest pressure.

 

[Supraboy89]

The gage sensor belongs on the engine side of the thermostat. It's the one-wire device located directly below the TCCS coolant sensor (all ECU sensors are two or more wires). The reason these sensors are on the engine side is so they can better monitor engine temp regardless of thermostat position. Pretty standard stuff.

Even if yours is in the wrong place that alone wouldn't cause your symptoms. You really ought to be checking rest pressure. That should always the first step when encountering hard hot starts.

No way to do that? Here's a tip: Look at the top of your fuel dampener. Pop off the plastic cover if still there. Jumper the fuel pump on in the diag block and observe the little screw on top of the dampener. It should be standing proud. Now unjumper the pump. If the screw quickly falls you're losing rest pressure.[

i have a fp gauge and it holds when the engine is off even if it sits for like 30+ min i mean it will loose a few psi but it holds for a while. and i guess i didnt pay it much attension but makes sense about the temp sensor belonging on the engine side. also does anyone have pics so i can tell which sensor is which because one has a rivit holding the terminal on and the other looks to be covered with like a plastic on the terminal.

 

[GC89]

how many psi of fuel pressure are you getting?


3rd post has a good pic

http://www.supramania.com/forums/sh...t-working...&p=1295730&viewfull=1#post1295730

 

[Supraboy89]

how many psi of fuel pressure are you getting?


3rd post has a good pic

http://www.supramania.com/forums/sh...t-working...&p=1295730&viewfull=1#post1295730

28psi at idle with vac line on a aeromotive afpr

 

[suprarx7nut]

Rest Pressure. Interesting. Never heard that term before. I have very similar symptoms to OP periodically, but thought it was because I have an open element filter in a hot engine bay.

I'll have to check my FPR tonight.

Thanks for the knowledge JJ!

 

[jetjock]

You bet. Toyota calls it residual pressure but I tend to use Bosch terms. After all they pretty much invented EFI. Keeping the fuel under pressure prevents boiling and vapor formation. Same principal as the cooling system.

 

[jesse_rc1991]

i have the exact same problem as you except im a aristo 2jzgte. Starts great cold, after i drive it around and come to stop and let it sit for a few min and try to start it, it hesitates and im lean at 17 afr on the wideband for about a min then all is good. On mine though all fuel system is new pump, afpr, fuel injectors, fuel filter, fuel hanger even feed and return lines. i have a fuel pressure gauge installed on my Aero FPR and im at 38 when i shut it down and then it starts to creep slowly down to zero over about 3 min. I even had the FPR return line clamped after shut down and it still does it which leads me to think either injectors or fuel pump, but ive already replaced the pump twice because of this with a denso mkiv tt pump. Weird thing is when i had the new pump out of the box before installation i smoke tested the outlet port and it began to bleed down as well on a new pump! shouldnt check valves prevent this. I hope it is fuel drop related because ive checked everything else i can think of related to this problem.

 

[jesse_rc1991]

any update on this OP?