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Starting issue when car is hot

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Matt's Gsx

Probationary Member
22
0
Apr 15, 2010
Camphill, Pennsylvania
I'm having an issue starting my car when it's hot meaning it was just running and when I go to start it again it doesn't start. I've changed cam angle sensor, coil packs, spark plugs, transistor pack, resistor pack for injectors, tried different ecu, and even checked the whole wiring harness. It has enough power to start but won't fire. But if the car is cool it'll start just fine. If anyone knows what it could be please, let me know asap. Thanks.
 
Vapor lock. Cool the fuel rail.

Why do you think it would be vapor locked? If the car runs fine you should be able to fire it right back up in like 2seconds. How could it vapor if your shutting it down and then firing it right back up right away? The fpr is at about 40-42psi. It's getting spark but were not 100% if the injectors are firing. It drives perfect but if you shut the car off after a drive or even if it just let it sit there and idle for just ten minutes and shut it off it will not start back up until fully cooled down. It's acting as if its not getting fuel or its not igniting at the right time. We swapped almost every sensor out and ecu and nothing.
 
Last edited by a moderator:
Well, I say it because that what it was on my car. (And it acts like it's not getting fuel because it isn't.) Heat from the head is always being transmitted to the fuel rail. When fuel is flowing, the fuel cools the rail. Not optimal, but alright. As soon as you turn the engine off, the rail heats up to head temp, boils the fuel, and you can't restart.

You can cool the rail by spraying water on it. When I needed to restart my car hot, this is what I'd do. A better fuel pump and letting the car sit for a moment with the key in the "on" position before trying to start could also solve the problem.
 
What does leaving the key in the on position do? It doesn't run the fuel pump.
 
Well, I say it because that what it was on my car. (And it acts like it's not getting fuel because it isn't.) Heat from the head is always being transmitted to the fuel rail. When fuel is flowing, the fuel cools the rail. Not optimal, but alright. As soon as you turn the engine off, the rail heats up to head temp, boils the fuel, and you can't restart.

You can cool the rail by spraying water on it. When I needed to restart my car hot, this is what I'd do. A better fuel pump and letting the car sit for a moment with the key in the "on" position before trying to start could also solve the problem.

I understand your point. But just letting it run for even ten mins is not making the motor to full hot temp. I mean its getting warm but its not getting boiling. And constantly cranking it over is putting fuel to the rail. It's like the fuel and spark like the timing its being altered in some way like how when a coolant temp sensor goes bad.
 
What does leaving the key in the on position do? It doesn't run the fuel pump.

Oops. That might be true, stock. I can't remember. I had a rewired fuel pump (doesn't everyone? tee hee) and it ran when the key was at "on."

I understand your point. But just letting it run for even ten mins is not making the motor to full hot temp. I mean its getting warm but its not getting boiling. And constantly cranking it over is putting fuel to the rail. It's like the fuel and spark like the timing its being altered in some way like how when a coolant temp sensor goes bad.

I have no clue what you're on about.
 
I'm having an issue starting my car when it's hot meaning it was just running and when I go to start it again it doesn't start. I've changed cam angle sensor, coil packs, spark plugs, transistor pack, resistor pack for injectors, tried different ecu, and even checked the whole wiring harness. It has enough power to start but won't fire. But if the car is cool it'll start just fine. If anyone knows what it could be please, let me know asap. Thanks.

It probably your Engine Coolant Temp sensor. Once it goes bad your car won't start after running for awhile.
 
Hey guys the fuel pump was bad but did not solve the problem does even body els no what it could be
 
It sounds to me like a electrical problem. I also had electrical problems when it was hot out never really figured out the problem just decided to run a new wire from my starter to ignition switch and it fixed my problem. I highly doubt this is your problem but ,I had a nissan that was hard on starting because it had a bad oxygen sensor.
 
ECU can cause this problem also .... been there and done that with hot restarts...

What I've done in the past with preventing vapor lock on other cars is to head to Home Depot and get some of that copper pipe foam insulation, wrap the line inbetween filter and rail with that stuff and see what happens ... doesn't do too bad...
 
I solved vapor lock by adding a phenolic spacer between the head and intake mani. If the intake stays cool, so does the fuel rail, it seems. Between the spacer and the water injection, my intake was cool to the touch at the *end* of a run.
 
Though this is resolved, I just want to add that these symptoms can also be caused by unplugging the Fuel Pressure Solenoid, by having a bad FPS or by not having it's vacuum line hooked up the FPR.

OP, just for the archives, what was it that fixed the issue?
 
Good to hear ya solved the issue. I am curious to read how you fixed it. My Talon likes to act up on hot starts, but what i found that helps with my issue is turning the key to the on position and turning my a/c on to kick on the a/c fan. I let it run for about 30-60 seconds and she start right up.
 
Hey I'm having problems starting my car when it's over 200 degrees. I've changed the coolant temp sensor three times and it's still doing the same thing. But when I take another sensor and plug it In outside of thermostat housing and it starts up. Does anyone have any ideas?
 
Well since u are plugging another sensor in wouldnt that tell u that the sensor is bad?
Hit yourself.

When you say you changed it does you mean you keep putting used ones in or a brand new one? How's the actual thermostat?
 
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