How does my fuel pressure sound?
93 LT1, stock. Been desperate trying to figure out a hard starting problem when letting it sit for a while.
So I did a test yesterday just because. Key on, engine off, 42 psi. It leaked 10 psi after 10 minutes. Is that good? Or should I look into probable causes? |
Sounds like one or more of your injectors has a slow leak which can cause your problem.
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..... I would look elsewhere .....
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Originally Posted by 1993C4LT1
(Post 1594186710)
93 LT1, stock. Been desperate trying to figure out a hard starting problem when letting it sit for a while.
So I did a test yesterday just because. Key on, engine off, 42 psi. It leaked 10 psi after 10 minutes. Is that good? Or should I look into probable causes? |
Originally Posted by aklim
(Post 1594188867)
Clip off the return line hose, pressurize it and see what happens. If it holds pressure, FPR
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Originally Posted by 1993C4LT1
(Post 1594189091)
thank you. And what if it doesn't hold?
Fuel pressure is always 42 at key on. That doesn't mean a thing to me that the fuel pressure is always at 42. How do you know that something isn't leaking and the pump is keeping up? Even if we do a WOT run and see it is at 42, it tells us the pump can keep up. |
I mentioned it's always 42 at key on, because I thought it would eliminate the fuel pump. I hate to sound like a beginner, but what do you mean by clip and clamp? I would assume to get some pliers, and put something over the return and or feed line that won't damage it?
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Originally Posted by 1993C4LT1
(Post 1594186710)
93 LT1, stock. Been desperate trying to figure out a hard starting problem when letting it sit for a while.
So I did a test yesterday just because. Key on, engine off, 42 psi. It leaked 10 psi after 10 minutes. Is that good? Or should I look into probable causes? |
Originally Posted by 1993C4LT1
(Post 1594189344)
I mentioned it's always 42 at key on, because I thought it would eliminate the fuel pump. I hate to sound like a beginner, but what do you mean by clip and clamp? I would assume to get some pliers, and put something over the return and or feed line that won't damage it?
http://www.sears.com/craftsman-hose-...B&gclsrc=aw.ds |
anything above 30 minutes sitting, with the engine warm, it's hard starting. It always fires up perfect on cold starts. To make it simple, anytime the engine has been ran for a period of time, it's hard starting. But say I shut it off when it starts on a hard start, and attempt to start it, it fires up fast. Am I making sense?
@bjankuski |
I found this thread, and OP has the exact same problem as me. Even the same bleed down rate. Except my car always passes emissions, and I've had this problem(hard start) since I bought my 93. And I don't have 140k on my car, I have 81k miles. Unfortunately, he didn't say whether he found the problem/fix.
https://www.corvetteforum.com/forums...s-problem.html |
..... Key on fuel pressure is the most important pressure there is to a running engine ... why would it matter to your no-start condition if the pressure leaks down a few pounds when the key is off for ten minutes ? .....
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Originally Posted by C409
(Post 1594190126)
..... Key on fuel pressure is the most important pressure there is to a running engine ... why would it matter to your no-start condition if the pressure leaks down a few pounds when the key is off for ten minutes ? .....
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Originally Posted by 1993C4LT1
(Post 1594190498)
I hear you. Except I don't have a no start condition. I have a hard starting condition when the engine is ran up to temp, and I let it sit for about 30 minutes or more. That is why my fuel pressure matters to me.
Live well, SJW |
Originally Posted by 1993C4LT1
(Post 1594189760)
anything above 30 minutes sitting, with the engine warm, it's hard starting. It always fires up perfect on cold starts. To make it simple, anytime the engine has been ran for a period of time, it's hard starting. But say I shut it off when it starts on a hard start, and attempt to start it, it fires up fast. Am I making sense?
@bjankuski Sometimes you can pull the intake bellows off the throttle body and hold the throttle wide open and you can actually hear the injectors dripping fuel, it will sound like a very slight hiss. |
Originally Posted by bjankuski
(Post 1594191188)
More then likely this is a leaking injector problem. When the car is warm it does not need much fuel to start and if you get too much fuel in the cylinders it will flood and be hard to start. Your fuel pressure is fine but the slow drop in pressure combined with the hard warm start tells me that the injectors are leaking into the cylinder and after 1/2 an hour they have leaked enough fuel to make it hard to start. You can check this by flooring the car before you start to crank the car on a hot start and see if the car starts quicker. (obviously let off on the gas as soon as the car starts) If it starts quicker some or all of the injectors are leaking down into the cylinders. Confirm this theory and then decide on the next step.
Sometimes you can pull the intake bellows off the throttle body and hold the throttle wide open and you can actually hear the injectors dripping fuel, it will sound like a very slight hiss. |
Originally Posted by SJW
(Post 1594191082)
Look elsewhere for the cause of your hot hard start problem. Fuel pressure is not going to be the fault. Does it puff black or blue smoke when it does eventually start up?
Live well, On cold starts, no smoke. On hard starts, very small amount of blue smoke. When running, no smoke. I belive the blue smoke is due to bad valve stem seals. SJW
Originally Posted by bjankuski
(Post 1594191188)
More then likely this is a leaking injector problem. When the car is warm it does not need much fuel to start and if you get too much fuel in the cylinders it will flood and be hard to start. Your fuel pressure is fine but the slow drop in pressure combined with the hard warm start tells me that the injectors are leaking into the cylinder and after 1/2 an hour they have leaked enough fuel to make it hard to start. You can check this by flooring the car before you start to crank the car on a hot start and see if the car starts quicker. (obviously let off on the gas as soon as the car starts) If it starts quicker some or all of the injectors are leaking down into the cylinders. Confirm this theory and then decide on the next step.
Sometimes you can pull the intake bellows off the throttle body and hold the throttle wide open and you can actually hear the injectors dripping fuel, it will sound like a very slight hiss. |
Originally Posted by 1993C4LT1
(Post 1594191308)
I'll give it a try. I wish I could lift the fuel rail, prime it, and inspect for leaks. But with the fic injectors, not possible.
When was the last time it was inspected by FIC? |
Originally Posted by aklim
(Post 1594191548)
Why is it not possible with FIC injectors? They are injectors like all others unless you are talking about the fuel injection retainer which they no longer use?
When was the last time it was inspected by FIC? |
Originally Posted by 1993C4LT1
(Post 1594191572)
Yeah because they no longer use the retainers. I have never sent them to him for inspection. I bought these injectors September 2015. It makes sense that they could be leaking. Because on hard starts, it doesn't idle perfect. But will idle perfect after about a minute.
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