I have this annoying problem. I am wondering if other Camaro/Firebird/Trans Am owner have the same thing...

Cold start... fires right up, I barely have to bump the key and she comes to life.

Hot start... say the engine is all warmed up after a run, situation " Let the car sit for 5 minutes or less" .. starts right up, again I barely have to bump the starter...

Hot start.... different situation, the engine is all warmed up " Let the car sit for more than 5 minutes and she is cranky to start, will have to spin her over and over before she catches, strong smell of unburnt gas (most likely due to the fact that she has to crank over so many times)

I was thinking that since the gas lines on the 87 5.7 L run very close to the manifolf that after sitting for a longer time it would heat the gas in the line and vapor lock me....I am not sure if the 88-92 5.7L's have the gas lines ran this way or not (pretty sure they don't)

Anybody have this problem? Anyone know what the cause/cure could be??

 

I've been battling with this problem for over a year now and I have tried every possible thing, including having the injectors cleaned and flow tested and leak tested, replacing every possible sensor that would have to do with fuel (cold start injector switch, CTS, IAC valve...), and the list goes on. There is two scenarios here, I fall under the second one for sure...you could fall under either one or both.

1) Leaking injectors or leaking cold start injector. Run a couple containers of Valvoline Synpower (two in one full tank will do) and see if they might be leaking do to poor atomization (bad spray pattern).

2) The only thing left is something that is best left until it dies...the fuel pump. Based on all the research that I've done here is what I've learned in a nut shell...The fuel system is designed to hold a certain amount of pressure in the system for a designated amount of time. The purpose of maintaining this pressure is for the warm starts, when the cold start injector is being bypassed by the ECM. A certain amount of pressure is needed so the system doesn't have to fully reprime itself everytime the ignition is started. The module that does this has to do with the fuel pump. I believe it's like a check valve kinda deal.

Due to the cost of changing the fuel pump I'm just gonna put up with the nuisance for now. I'm 99.999999% sure it the fuel pump that's the problem, but just for the faint chance that it's not, I'll wait till I really have no choice but to change it. My suggestion for now is this...just get used to doing a double start. When you go to start the car, turn the key and you'll hear the fuel pump cycling, once it stops, turn the key for a crank or two then turn it back. Wait a second and turn the key again. It almost always starts on the second try, sometimes the third. As long as you don't sit there and let the starter crank and crank then it won't harm anything for now.

 

The fuel pump was replaced approximately 1 year ago...and you are right about the expense... not something a backyard mechanic can sensibly handle... rear end needing to be dropped, tank removed, blah blah...

I am leaning towards your scenario #1 .. I need to get a fuel pressure guage so I can see what is happening to the pressure after the car is stopped....

Vader makes a couple of very good points as well....


"Your symptoms are classic for a leaking injector(s) or pressure regulator. You should monitor the fuel pressure after the car is turned off. Pressure that drops off within ½ hour after shutdown may indiacte a leaking injector. It is also possible that the diaphragm in the fuel pressure regulator has a small hole that is allowing fuel to relieve through the vacuum fitting and line on the regulator into the plenum. "

I will put up with this nusiance for now and when I get my garage bulit next summer I will be able to tackle all of the smaller annoying problems over the course of the following winter... I will keep this post in my IROC Library of good tips and tricks

 

I've been told twice now that it's a imple fix - something to do with moving a solenoid or something. It's in the tech article section, I think...

https://www.thirdgen.org/newdesign/tech/solenoid.shtml

might not be the same thing as yours, I'm not sure...

 

No, it's not the starter solenoid in this case. I guess unless you've experienced it, it's hard to really put in writing.

 

I know about the "heat soaking" of the starter and it isn't that, starter spins the engine fine... it's a leaky injector or something like that, fer sure.... I will fidn it when I get my own place to "tinker" with my car. And when I do I will post it for the world to see!! hahaha

 

I have been having that samew problem in my 87 iroc 350 tpi as well. I got a fuel pump relay but i ahvent had a chance to go for a dirve to see if it worked if its not that it could aslo be the mass air flow sensor?? best of luck

 

Nope, I've replaced both the FP relay, MAF power relay, burnoff relay and the MAF and it made no difference. So don't waste your money on a MAF unless you absoloutely have to...way too pricey of an item to experiment with.

 

Mine was doing the same thing 2.8l multi port and after about a month it left me stranded at the Gas station. Car was running great and I pulled in to get gas, filled er up jumped in to start the car and nothing but starter motor cranking the engine for about a half hour. Finally had to get a tow to the shop. Simple $500 later and a new fuel pump and everything is fine again.

Hope this is not your problem. I can't explain why it only did it when the engine was hot other than possibly vapor lock causing too much backpressure for faulty/week fuel pump to overcome.

 

The only thing that I can think of is when the engine is hot, the cold start injector is not being used and the ECU treats things a bit differently depending on the temperature of the block. I'm not sure about Stan's case here, or any of the others. But I'm positive mine is the fuel pump, as there is nothing else left to replace that I haven't done. I'm just gonna wait till it dies and hope that I'm not far from home when it happens. I've got a brand new Holley FP sitting at home in the basement ready to go...pick it up from ebay for $65 still in the box.

 

Irocker, the fuel pump goes when it wants to go... mine luckily died while I was doing a coolant flush in the driveway...

If you know your pump is on its way, then I suggest you do it before it dies somewhere in the middle of nowhere...

Keep a rubber mallet handy if it does die in the middle of nowhere...

 

I know that is the proper thing to do, but due to the expense of the repair it's not worth doing till it dies. For all I know it could last a week, it could last another year. I have CAA... it's a PITA to have to get towed, but it's not that big of a deal.

And a rubber mallet?!? Dude, what for?

 

I had this exact problem on my car last year... during the winter I took the plenem, runners, and fuel rail off to polish them. I got the injectors cleaned and flow matched, changed the IAT sensor, cleaned the EGR valve, installed an AFPR, mild porting on the plenum, cleaned the TB throughly, and installed my performance resource chip.... anyway, one of those things fixed it, because my car starts up in less than 3 seconds every time.

IROCKER, you mentioned something about the ECM treating the condition as hot, and not using the 9th injector.... maybe performance resource fixed the problem in the chip?

Maybe having higher fuel pressure helps it start easier? But IROCKER has an AFPR too, and he still has hard hot starting?

thats all I could think of... I wish I could have changed each thing individually, but its hard to do that.

I'd try the performance resource chip, because if it works, great and you also get some more performance.. if it doesn't solve the hot starting problem.. you still get performance out of the chip

 

The chip must have changed something then...I too did everything that Nathan mentioned up above and more and the car is still doing it. It did start a little better for the first month or so, but it was still pretty cold out in March.

I'm hoping to try out a chip next spring so we'll see if that helps.

 

The rubber mallet is for if the pump does die, you can still "massage" the pump back to life with carefully timed hits to the tank area...

I managed to avoid having my car towed when the pump died.