Car wont start hot

carfanatic89 · 10-03-2008, 06:30 PM

30 psi. and hold that for 3 hours. The vsv's are working and the fuel pump regulator is recieving vacuum. I have built alot of engines and fixed many of my friends vehicles, but their easy to fix problems. Nothing like wont start when hot and will when cold. Makes no sense, Im just frustrated with this car ive been trying to find out whats wrong with it for over a year now. I have taken the car to toyota, and they couldnt find anything. The school im going to has a toyota program and they are clueless as well. Just because I want to get a reliable car inorder to get a relaible job doesnt mean im a shitty mechanic. everything else as far as maintenance has been done by the book. Nobody can help me with the problem and im currently on 3 forums to find the problem.

TheMark3 · 10-03-2008, 07:16 PM

So the 30psi on the fuel rail is stable - meaning the same reading when it is hot, cold, running well, running like crap?

The vacuum solenoid valves are working - under what conditions were they tested? Back in the day I had a 280Z that acted similarly. A temperature sensor was faulty but bench tested OK - meaning it had the right resistance cold and hot - but it did not remain correct under prolonged heat. The end result was that the engine was enriching the mixture until it thought it warmed up - which it never did. It was eventually found after sitting on a diagnostics machine for about an hour.

TheMark3 · 10-03-2008, 07:36 PM

Another thought is to monitor your fuel trim and see what the engine thinks is happening with the fuel mix while this is happening.

...or stick a wide band sensor in the exhaust and see if it is rich or lean for yourself when this happens.

I would also recommend the NKG plugs - even a cheap set until you get this solved. When my 280Z was running as I described in my previous post - the NKG plugs were the only ones that could shake off the rich mixture - the rest would just foul until they died.

carfanatic89 · 10-03-2008, 08:39 PM

Thanks that was more helpful, I just took off the timing cover to make sure the cam gears haven't jumped a tooth. everthing checked out and I started it and ran ok. The fuel pressure is to high right now to crack the line, ima let it bleed off some pressure. Then ill put the guage back on to check and get a fuel curve of all conditions and see what I find. As far as a wide band goes, do they make a wideband sensor that will bolt inplace of the old sensor to run a guage and send feedback to the ecm. If so can you tell me where I could buy one. I have ngk wires on right now. I have to wait till next paycheck to get ngk plugs. Im also going to put on a new intake. I think the old ones fine, but it is old and has some stress cracks in it and might be letting un-metered air in the engine. Thanks again, I know im really close to find out whats wrong with her.

dfarah · 11-14-2008, 01:59 AM

Quoted on Dan:Thanks that was more helpful, I just took off the timing car covers to make sure the cam gears haven't jumped a tooth. everthing checked out and I started it and ran ok. The fuel pressure is to high right now to crack the line, ima let it bleed off some pressure. Then ill put the guage back on to check and get a fuel curve of all conditions and see what I find. As far as a wide band goes, do they make a wideband sensor that will bolt inplace of the old sensor to run a guage and send feedback to the ecm. If so can you tell me where I could buy one. I have ngk wires on right now. I have to wait till next paycheck to get ngk plugs. Im also going to put on a new intake. I think the old ones fine, but it is old and has some stress cracks in it and might be letting un-metered air in the engine. Thanks again, I know im really close to find out whats wrong with her.

Having a very high fuel pressure is quite normal according to your situation. Where are you planning to buy your plugs?

10-03-2008, 06:30 PM	#1
carfanatic89 3" Exhaust Join Date: Apr 2007 Location: Waco Posts: 164	30 psi. and hold that for 3 hours. The vsv's are working and the fuel pump regulator is recieving vacuum. I have built alot of engines and fixed many of my friends vehicles, but their easy to fix problems. Nothing like wont start when hot and will when cold. Makes no sense, Im just frustrated with this car ive been trying to find out whats wrong with it for over a year now. I have taken the car to toyota, and they couldnt find anything. The school im going to has a toyota program and they are clueless as well. Just because I want to get a reliable car inorder to get a relaible job doesnt mean im a shitty mechanic. everything else as far as maintenance has been done by the book. Nobody can help me with the problem and im currently on 3 forums to find the problem. __________________ Supra Engine Powered Dragster

10-03-2008, 08:39 PM	#4
carfanatic89 3" Exhaust Join Date: Apr 2007 Location: Waco Posts: 164	Thanks that was more helpful, I just took off the timing cover to make sure the cam gears haven't jumped a tooth. everthing checked out and I started it and ran ok. The fuel pressure is to high right now to crack the line, ima let it bleed off some pressure. Then ill put the guage back on to check and get a fuel curve of all conditions and see what I find. As far as a wide band goes, do they make a wideband sensor that will bolt inplace of the old sensor to run a guage and send feedback to the ecm. If so can you tell me where I could buy one. I have ngk wires on right now. I have to wait till next paycheck to get ngk plugs. Im also going to put on a new intake. I think the old ones fine, but it is old and has some stress cracks in it and might be letting un-metered air in the engine. Thanks again, I know im really close to find out whats wrong with her. __________________ Supra Engine Powered Dragster Last edited by carfanatic89; 10-03-2008 at 08:48 PM.

11-14-2008, 01:59 AM	#5
dfarah Stock Join Date: Nov 2008 Location: Fargo Posts: 5	Quoted on Dan:Thanks that was more helpful, I just took off the timing car covers to make sure the cam gears haven't jumped a tooth. everthing checked out and I started it and ran ok. The fuel pressure is to high right now to crack the line, ima let it bleed off some pressure. Then ill put the guage back on to check and get a fuel curve of all conditions and see what I find. As far as a wide band goes, do they make a wideband sensor that will bolt inplace of the old sensor to run a guage and send feedback to the ecm. If so can you tell me where I could buy one. I have ngk wires on right now. I have to wait till next paycheck to get ngk plugs. Im also going to put on a new intake. I think the old ones fine, but it is old and has some stress cracks in it and might be letting un-metered air in the engine. Thanks again, I know im really close to find out whats wrong with her. Having a very high fuel pressure is quite normal according to your situation. Where are you planning to buy your plugs? Last edited by dfarah; 11-15-2008 at 12:44 AM.

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10-03-2008, 07:16 PM	#2
TheMark3 Stock Join Date: Oct 2008 Location: Boston Posts: 9	So the 30psi on the fuel rail is stable - meaning the same reading when it is hot, cold, running well, running like crap? The vacuum solenoid valves are working - under what conditions were they tested? Back in the day I had a 280Z that acted similarly. A temperature sensor was faulty but bench tested OK - meaning it had the right resistance cold and hot - but it did not remain correct under prolonged heat. The end result was that the engine was enriching the mixture until it thought it warmed up - which it never did. It was eventually found after sitting on a diagnostics machine for about an hour.

10-03-2008, 07:36 PM	#3
TheMark3 Stock Join Date: Oct 2008 Location: Boston Posts: 9	Another thought is to monitor your fuel trim and see what the engine thinks is happening with the fuel mix while this is happening. ...or stick a wide band sensor in the exhaust and see if it is rich or lean for yourself when this happens. I would also recommend the NKG plugs - even a cheap set until you get this solved. When my 280Z was running as I described in my previous post - the NKG plugs were the only ones that could shake off the rich mixture - the rest would just foul until they died.