YellowIROC305

Wow it's been over a year since i've had to post any problems here at thirdgen. Yesterday I went to start my 305 '86 IROC-Z. It would crank, but wouldn't start. Finally, I found I could start it by cranking it with the pedal all the way to the floor. It slowly comes to life, sputtering, with a lot of smoke comin' out the exhaust. You gotta keep some pedal in for about 20 seconds or so before it smooths out. After that, it idles fine, and while driving, it runs perfectly! I was initially thinking it was a bad fuel pump, but the engine doesn't even make a hiccup while driving around. When you turn the key before start, you can hear the fuel pump relay click and the fuel pump prime as it should. Another thing that stumps me is that NO CODES were thrown. That should eliminate any bad sensor right? It seems that it's only this hard to start when the engine is cold. If I let the car warm up, turn it off, and restart, it starts up perfectly. Any ideas? I don't want to have to get another starter on top of the problem because I have to crank it so much to start.

IROCThe5.7L

I'd get a fuel pressure gauge and make sure your don't have a leak somewhere (injectors or regulator).

xbcrguy182x

I would recommend changing your fuel filter. Im having a problem just like yours and I changed the filter today and it kinda went away...lol But it helped...I need 2 starts to get it running...

Damon

When you start with the pedal on the floor you are engaging programming in the ECM they put in there for clearing out a flooded motor. It is the electronic equivalent to carburetors that would mechanically pop the choke open about 1/2 way if you put them wide open while cranking on a cold engine. In short, it's running the injectors very lean when you crank it over while wide open. I beleive I read somewhere the target A/F ratio is around 25:1 under those conditions.

Maybe something is leaking fuel and flooding the motor out when you try to start it normally. Or maybe the CTS is giving bad readings and telling the ECM it's -40F outside when you first go to start it.

YellowIROC305

the oil does smell a bit like fuel...so there probably is a fuel leak. would make sense because the longer the car sits, the harder it is to start. Let it run, shut it down, immediately restart it....starts right up. Shut it down for about 5 minutes (like when im filling it up at the gas station), hard to start but it still starts a lot quicker than when, say, the car sits overnight. what would be the best way to find out what's leaking (if anything)?

IROCThe5.7L

It sounds like leaky injectors. I had the same problem, and it would always start quicker when I gave it 80% throttle (flood mode, the injectors don't fire). After sitting, 3 of my 8 injectors would keep dripping fuel, flooding out my engine.

Start small and check your fuel pressure regulator. After it has been ran, pull the vaccum line off of it and check to see if it has fuel in it. The next step would be to check your fuel pressure after the car is turned off. It should hold pressure for a while. If it doesn't, you got a leak somewhere (I'd bet injectors).

When I had leaky fuel injectors, these were my pressure readings:




After I seen my fuel pressure dropped off too fast, and my regulator was fine, I took apart my intake, and took out the bolts holding my fuel rail down. Then I lifted the rail up, exposing the injectors. I primed the fuel pump and waited. Sure enough there were a few that dripped every minute or two.

Francis

HI, just wondering how you went?

I know this might seem silly, but I would of gone down the parth of a bad spark plug lead or spark plug. I've seen them not wont to work when cold, then once there is a bit of engine heat though them they come good. Interested to see what it was or how your going with it.

YellowIROC305

i decided to check the fuel pressure regulator first. i started the car, let it smooth out, ran it for a while, and shut it down. Then, i disconnected the fuel pressure regulator vacuum line from the intake and guess what! Slow, steady stream of fuel out of it. I let it all run into a cup, waited an hour or so, reconnected the line to the intake, and the car started up perfectly! SO...leaking FPR it is! Now here's my new question:

How easy is this to replace. I know I can get one at autozone for like $40. The replacement involves taking the whole intake off right? Do I need to take the fuel rails off as well? I think I also read somewhere that you can replace just the bad diaphram? Is this possible or does the whole thing gotta go? I really appreciate the help already given, I'd like to get this done tonight.

IROCThe5.7L

If I were you, I'd get an adjustable one. The only thing that needs to be takin off is the plenum. The runners and fuel rail do not need to be touched. You are going to need a special bit due to the regulator screws having nipples on them.

Francis

I know the adjustable ones are better, but for the effort and on a stock or mild engine, where keeping it neat and simple is what you want, I'd just replace the part with a genuine one. you should get years of use out of it, and it should be fairly straight forward to fit.