'94 LT1 hard to start - help
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
'94 LT1 hard to start - help
My '94 with 116k miles on it started acting funny recently. When I go to start it in the morning it's fine, but after it's been running (even after sitting for a few hours) it's hard to start. It acts like the timing is way retarded because it's turning over fast and starts spinning up faster but never quite getting where it needs to be. Takes a good 5-8 seconds to start. I'm pretty sure this is a coincedence, but it started doing this immediately after I took it to get two new tires on so my first thought was that the guys jacked it up and crushed a fuel line or something but I got under and didn't see any problems. Any insights?
Thanks.
Thanks.
Pro
Joined: Dec 2008
Posts: 658
Likes: 0
From: Lubbock for now, headed for Oklahoma
Or a leaking fuel pressure regulator(starting to sound like a broken record). They tend to rupture the diaphragms and let the vacuum source draw fuel into the intake. Pull the vacuum line, plug the intake side, and start it a few times. You should see the quick restart return and no doubt some fuel from the vacuum line connected to the regulator.
G/L
G/L
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
get a FP gauge on there and check that you have adequate pressure, I can't remember but I am thinking around 40psi.You should first check for error codes. Easy procedure you can do yourself. There are so many things that can cause problems like this, and your computer can store a plethora of error information. All you need is a short piece of wire to short 2 of your ALDL pins together, and error codes will display on dash:
http://www.corvettebuyers.com/c4vettes/codes.htm
How doe's the engine run once you get it going? Any change in performance now as opposed to when you did not have this long cranking problem?
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Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
Wow, CF never sends me updates for some reason that there were more posts. I just checked the module and it was good (at least at that moment). Since it's an intermittent problem I wouldn't be surprised if it was at fault though. Guess I'll check fuel pressure now. I'd be surprised if that is the problem though since I can turn the key and let the pump stop and it'll still do it.
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
get a FP gauge on there and check that you have adequate pressure, I can't remember but I am thinking around 40psi.You should first check for error codes. Easy procedure you can do yourself. There are so many things that can cause problems like this, and your computer can store a plethora of error information. All you need is a short piece of wire to short 2 of your ALDL pins together, and error codes will display on dash:
http://www.corvettebuyers.com/c4vettes/codes.htm
How doe's the engine run once you get it going? Any change in performance now as opposed to when you did not have this long cranking problem?
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
No codes thrown. What is the correct procedure to test the fuel system for either a leaking fuel pressure regulator or leaking fuel injector (I assume it will be pressure fuel system and see if pressure drops in some time x).
Thanks.
Thanks.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
Turn the key on check pressure
Turn the key off watch the gage see if it falls and how fast
or you can just smell the FPR vacuum line for gas if you smell it it is toast.
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
Ok. Checked fuel pressure. Turn the ignition to on (not running) and pressure pegs to 40psi. Turn off and it has lost about 10psi in 5 minutes. How do I determine where the leak in the system is? Is there a way to isolate whether or not it's the fuel pressure regulator or an injector?
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
Pull the vacuum line from the FPR if it smells like gas it is bad. If not then you need to pressurize the rail and pinch the line at the gas tank to eliminate the FP check valve if it still drops then it is probably a stuck injector.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Ok. Checked fuel pressure. Turn the ignition to on (not running) and pressure pegs to 40psi. Turn off and it has lost about 10psi in 5 minutes. How do I determine where the leak in the system is? Is there a way to isolate whether or not it's the fuel pressure regulator or an injector?
1) remove plastic injector covers on each side
2) remove fule rail retaining bolts
3) carefully wiggle fuel rail and injectors upward until all eight injectors pop out of their ports.
4) put something under fuel rail assembly to suspend it above intake
5) put glass container under each injector to catch fuel
6) Ignition on to prime system to 40psi
7) Ignition off ....... Observe to see which injector(s) are leaking fuel
Note: 10psi drop in 5 minutes is too much, something is bleeding down too fast, either injector(s) or FPR.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
You can use a 5 gal white bucket and stick the injector assembly into it to check for leakage short sweet and neat.
Thread Starter
Racer
Joined: May 2003
Posts: 348
Likes: 1
From: Hermosa Beach, CA
What are the symptoms of a failed FPR? In my head, I'm able to convince myself it's a fuel injector due to it being hard to start after it's been sitting allowing fuel to drip into a cylinder. Is it because you're drawing fuel in through the vacuum hose?
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
When the diaphram in the FPR ruptures fuel is pumped via the vacuum line into the intake after shut down. Since it is flooded at that point when you try to restart before the fuel evaporates it will spin up and almost fire for a few seconds. A leaking injector will act a little different but similar because 1 cylinder is flooded unless you have multiple injectors leaking. Very Rare
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
