Odd engine starting issue

[98GSX S2K-03]

I have had a weird problem when trying to start my 98 GSX after it has sat for an hour or two.

If the engine is cool, it starts fine, no issues. Turn the engine off and then restart it a short time later, no problem. But if I try to start the car and hour or two later it will not start right up. It always does fire eventually, it just needs to turn over for about 3 to 4 seconds. What's even odder is that if the car sits for hours or longer it will start within a half second of turning the engine over.

In summary, I only have problems after the car has sat for an hour or two. I am planning to sell the car and would like to correct this.

I think I remember reading something about bad coolant temp sensors causing weird problems, any advice?

Thanks

 

[sergiosdsm]

Ive got a few suggestions for things to look at
1. check and make sure you have good spark and fuel
2. go to a local autozone and have them hook your car on a obd2 scanner and see if you car has any stored codes.
3. If no codes appear you can test your coolant temp sensors by following this:
http://www.vfaq.com/mods/wayback/BradBauer/misc/temp.html

good luck and I hope this info helps you out

 

[boostcrazyawd]

my car was doin the same thing and it ended up being the coolent temp sensor the wire was broke on it so i would def check that out.

 

[eclipsh]

Check to see if someone disconnected the Fuel Pressure Solenoid (or maybe you did). It also sounds like potential vapor lock in the fuel system. Reconnecting the FP solenoid can alleviate this.

EDIT: getting terms right

 

[98GSX S2K-03]

First off, I have no codes. I have software that allows me to connect my notebook to the OBDII port.

Regarding the vacuum lock, (or Vapor lock) this is exactly what I was thinking. I am glad someone else was thinking the same thing. From what I know about vapor lock is that the fuel becomes super heated and evaporates or goes into a gaseous state. Common on cars with a carburetor and not so on fuel injection. But our 4G63 engine bays do seem to get quite hot.

The question then is, what do I do about it?

Also, I don't recall this happening before I replaced my factory injectors with AMS 580cc's. But if I had a bad injector the engine should just run like crap until the bad injector began to fire.

My other thoughts were that I was getting a sensor that was nut functioning when it sat hot and idle. For example, the cam angle or crank angle sensors. Without ether of these the ignition would not fire.
Thanks

 

[eclipsh]

Thanks for the correction, meant to say vapor lock. It does happen on our cars. I had it happen to me a couple times this summer when I disconnected my fuel pressure solenoid on the advice of a fellow tuner. Turns out he was wrong and it was a bad idea.

Incidentally, that was after I installed 780cc injectors on my system so there may be something to the larger injectors contributing to vapor lock. There isn't enough data here to be sure.

Did you check your fuel pressure solenoid? I never received a code on my vapor lock incidents but they went away immediately after reconnecting my FP solenoid.

As far as a sensor not working while the engine sat hot... tough to say. My only thought on this is: if heat were to disable sensors on your engine I suspect they would be blinking out whenever you ran the car hard, even with the engine still running = random engine dieing. Plus if it were hot sensors failing, cranking a few extra times shouldn't cause them to cool down enough to work.

I really think you have a case of vapor lock.

It also couldn't hurt to check the coolant sensor functionality like the other guys said.


Just noticed your mods list. Do you have any sort of after market fuel pressure regulator to control that 255 pump? The stock pressure regulator can't handle the load so your fuel pressure levels bounce all over the place. You can fix it by switching to a 190 pump or getting a regulator.

 

[98GSX S2K-03]

I just checked the solenoid and found that it was connected. However, I did find that one of the terminals was highly corroded. It was as green as the Statue of Liberty. I cleaned it up and now just need to drive it and then let it sit for the hour or two. I will keep you updated.

 

[98GSX S2K-03]

Didn't work. I am going to remove the hose going to the fuel pressure regulator during the next hot start. This will confirm that the solenoid is not the problem.

 

[gvillegsx]

Sounds just like my problem that I had. Car would start, but after sitting it would take a bit and sometimes wouldn't start. Turned out to be the coolant temp sensor, sounds like you have the same symptoms I had. good luck.

 

[eclipsh]

Didn't work. I am going to remove the hose going to the fuel pressure regulator during the next hot start. This will confirm that the solenoid is not the problem.

No actually, that won't. By removing the solenoid from the system you are guaranteeing that the fuel pressure will be low, not high. The fuel pressure regulator decreases or increases fuel pressure based on air pressure from the line. Pressure rising causes fuel pressure to go up. At start the car is pulling vaccume so the fuel pressure is lower, not higher. The FP Solenoid cuts the vaccume to the FPR during hot starts, Raising the fuel pressure to try and overcome vapor lock.

Regardless, it didn't fix your problem.

Try the other sensor mentioned above.

 

[Phil97GST]

haha im on the same boat as you, its been like a month or so for me now and i still can't figure it out, i installed a new starter. so no luck.

 

[98GSX S2K-03]

Which sensor?

1.) Engine Coolant Switch

2.) Engine Coolant Temperature Sensor

3.) Engine Coolant Temperature Gage Unit

I believe the first one is for the fans and the third one is for the gage cluster.

So my assumtion is that I should replace the second one, right?


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[eclipsh]

I haven't priced those sensors lately but it should be easy to test. The manuals all want you to remove it and stick it in hot water and use a volt meter to test it. Dunno why they don't just get the car hot and test it but you sure could. Just follow the coolant temp sensor test in any Haynes/Chiltons/factory repair manual. Can't help you on which sensor it is though