Stange thing happened on the way to eat.
08-06-2017, 01:03 AM
#1
Pro
Thread Starter
Stange thing happened on the way to eat.
This maybe a little long but I want to describe the problem the best I can.
This is on a completely stock '92 LT1 Vette droptop.
OK, I was starting to notice the car not starting up as quickly like it normally does. Actually it was turning over longer than it normally has. (This car is a weekend sunny day cruiser)
Anyhow I took it out for about a 15 to 20 mile spin and she was running great! Then I stopped to grab a bit to eat. Came out about 45 minutes later and tried to start it and WOW it started hard and was running like Crap.
It seemed like it was running on about 5-6 cylinders at best and did good just to keep it going 45-50 MPH trying to limp home also the "check engine" came light on.
I got about 3-4 miles down the road and it's like I flipped a "magic switch".
She started running beautify and at the exact same time the check engine light immediately went off. She drove the rest of the way home flawlessly (about 15-20 miles). I Did notice when I got home though it still took awhile to crank back up but still ran great
So at that point I just felt like it was a fuel problem/pump. So, I grabbed the handy dandy fuel pressure tester and this is what it did:
On just turning on the ignition the pressure went up to 40 LBS and then quickly down to 5 lbs.
Then I cranked the car and she started and the pressure went back at 40 LBS and held steady while running.
Then I cut the car off and went straight back to 5 lbs not holding fuel pressure like it should.
I'm thinking fuel pump at this point but I had just replaced the pump a year or so before. So at this point I'm thinking the pump has gone bad again.
The first time I replaced it, it turned out the problem I was chasing was an unrelated problem (bad prom) but I changed it anyhow because it was 25 years old.
Just wondering before I change it again do Y'all think I'm barking up the correct tree going ahead changing out the fuel pump????
BTW I check the codes and the strange thing is no bad codes showed up or stored.......
This is on a completely stock '92 LT1 Vette droptop.
OK, I was starting to notice the car not starting up as quickly like it normally does. Actually it was turning over longer than it normally has. (This car is a weekend sunny day cruiser)
Anyhow I took it out for about a 15 to 20 mile spin and she was running great! Then I stopped to grab a bit to eat. Came out about 45 minutes later and tried to start it and WOW it started hard and was running like Crap.
It seemed like it was running on about 5-6 cylinders at best and did good just to keep it going 45-50 MPH trying to limp home also the "check engine" came light on.
I got about 3-4 miles down the road and it's like I flipped a "magic switch".
She started running beautify and at the exact same time the check engine light immediately went off. She drove the rest of the way home flawlessly (about 15-20 miles). I Did notice when I got home though it still took awhile to crank back up but still ran great
So at that point I just felt like it was a fuel problem/pump. So, I grabbed the handy dandy fuel pressure tester and this is what it did:
On just turning on the ignition the pressure went up to 40 LBS and then quickly down to 5 lbs.
Then I cranked the car and she started and the pressure went back at 40 LBS and held steady while running.
Then I cut the car off and went straight back to 5 lbs not holding fuel pressure like it should.
I'm thinking fuel pump at this point but I had just replaced the pump a year or so before. So at this point I'm thinking the pump has gone bad again.
The first time I replaced it, it turned out the problem I was chasing was an unrelated problem (bad prom) but I changed it anyhow because it was 25 years old.
Just wondering before I change it again do Y'all think I'm barking up the correct tree going ahead changing out the fuel pump????
BTW I check the codes and the strange thing is no bad codes showed up or stored.......
08-06-2017, 12:05 PM
#2
Melting Slicks
Member Since: Jan 2009
Location: Puyallup Washington
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I am no expert but from what I have read you should check the fuel pressure regulator or you may have one or more leaky fuel injectors. When you turn the car off it should hold the fuel pressure for quite a while. Find out why it is not before throwing money and parts at it.
08-06-2017, 12:42 PM
#3
Pro
Thread Starter
I am no expert but from what I have read you should check the fuel pressure regulator or you may have one or more leaky fuel injectors. When you turn the car off it should hold the fuel pressure for quite a while. Find out why it is not before throwing money and parts at it.
But the regulator yes I agree with you there and I want to change it anyway.
It's just the way it ran really bad upon first cranking and then all of a sudden and instantly it starting running so good again.
If it is the injectors and they are leaking,what the best way to check them?
08-06-2017, 01:18 PM
#4
Race Director
3 things can cause the fuel pressure to drop quickly after shutdown; a leaky injector, bad pressure regular or bad fuel pump. Pull he vacuum line going to the regulator and smell if there is any fuel in the line. You can use a mytivac to se if it holds vacuum. Pull the plugs to see if one is wet or black. That will show a leaky injector. Tape the pressure gauge to your windshield and drive around. If it drops under load, it could be the pump. Good luck.
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Smokeysvette (08-07-2017)
08-06-2017, 06:52 PM
#6
Melting Slicks
3 things can cause the fuel pressure to drop quickly after shutdown; a leaky injector, bad pressure regular or bad fuel pump. Pull he vacuum line going to the regulator and smell if there is any fuel in the line. You can use a mytivac to se if it holds vacuum. Pull the plugs to see if one is wet or black. That will show a leaky injector. Tape the pressure gauge to your windshield and drive around. If it drops under load, it could be the pump. Good luck.
Codes are always secondary to basic troubleshooting.
08-07-2017, 12:17 AM
#7
Pro
Thread Starter
3 things can cause the fuel pressure to drop quickly after shutdown; a leaky injector, bad pressure regular or bad fuel pump. Pull he vacuum line going to the regulator and smell if there is any fuel in the line. You can use a mytivac to se if it holds vacuum. Pull the plugs to see if one is wet or black. That will show a leaky injector. Tape the pressure gauge to your windshield and drive around. If it drops under load, it could be the pump. Good luck.
When it cools down a bit I have a mytivac and that I know it's an easy change out anyhow. Like I said she's 25 years old now so a new one would be great for it anyhow and as I see so many regulators fail here on the forum anyhow anyhow.
I did go out and turn the key on and it went straight to 40 lbs and then in a split second went straight to 5lbs. Tried to start the car and she fired right up and ran great but as soon as I shut it down in a split second went to 5lbs again. If it is an injector it must be a really bad one to leak down that fast!
BTW, it has only does it this one time and never has done this before and she's always cranked up right away and always drove great.
Thanks for all the advise so far and please keep the future advise coming.
08-08-2017, 10:09 AM
#8
Pro
Thread Starter
Just as a follow up:
No injectors leaking and all show good. Yesterday I took it to a shop and they did a injector leak down test. Before that I tested the regulator with the mityvac and holds good vacuum and no signs of an external leak. The last thing I know would be to change out the fuel pump and I guess I'm going to give that a shot after I step away from it out of frustration. If that's not it I'm at a loss.
It seems like every time I fix something in this car something else likes to decides to go wrong with it and this is on a nice stock 92 42K mile convertible with the optional hard top. I swear if this pump doesn't fix it...I'm getting rid of it. I'm getting close to 70 years old so I can't work on it like when I was a youngster. I have two others Corvettes that serve me so well, a 92 coupe, and the '05 C6.
So if this one I can't get it running correctly she's getting sold! Sorry, I love Corvette's but this one is really testing my patients,
No injectors leaking and all show good. Yesterday I took it to a shop and they did a injector leak down test. Before that I tested the regulator with the mityvac and holds good vacuum and no signs of an external leak. The last thing I know would be to change out the fuel pump and I guess I'm going to give that a shot after I step away from it out of frustration. If that's not it I'm at a loss.
It seems like every time I fix something in this car something else likes to decides to go wrong with it and this is on a nice stock 92 42K mile convertible with the optional hard top. I swear if this pump doesn't fix it...I'm getting rid of it. I'm getting close to 70 years old so I can't work on it like when I was a youngster. I have two others Corvettes that serve me so well, a 92 coupe, and the '05 C6.
So if this one I can't get it running correctly she's getting sold! Sorry, I love Corvette's but this one is really testing my patients,
Last edited by Smokeysvette; 08-08-2017 at 10:13 AM.
08-11-2017, 12:05 PM
#9
Pro
Thread Starter
Just a follow up to what the cause was in my case and for anyone else who might run into this problem.
It was the fuel pump.
I installed a new pump and the car is now holding 41 lbs of pressure after sitting for at least 6 hours. I'm just glad it wasn't something more expensive like having to replace all the injectors. The fuel pump has an apparent one way valve in it that prevents the fuel from flowing fuel back into the tank. I took her out for about a 1/2 hour spin and she's running great and even noticed getting better fuel mileage too.
Sometimes when you get aggravated like I was in this case, you just have to take a few steps back and attack the problem when you minds clears up
Thanks goes out for those that helped.
It was the fuel pump.
I installed a new pump and the car is now holding 41 lbs of pressure after sitting for at least 6 hours. I'm just glad it wasn't something more expensive like having to replace all the injectors. The fuel pump has an apparent one way valve in it that prevents the fuel from flowing fuel back into the tank. I took her out for about a 1/2 hour spin and she's running great and even noticed getting better fuel mileage too.
Sometimes when you get aggravated like I was in this case, you just have to take a few steps back and attack the problem when you minds clears up
Thanks goes out for those that helped.
08-11-2017, 12:17 PM
#10
Melting Slicks
Member Since: Jan 2014
Location: Downers Grove Illinois
Posts: 2,474
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Just a follow up to what the cause was in my case and for anyone else who might run into this problem.
It was the fuel pump.
I installed a new pump and the car is now holding 41 lbs of pressure after sitting for at least 6 hours. I'm just glad it wasn't something more expensive like having to replace all the injectors. The fuel pump has an apparent one way valve in it that prevents the fuel from flowing fuel back into the tank. I took her out for about a 1/2 hour spin and she's running great and even noticed getting better fuel mileage too.
Sometimes when you get aggravated like I was in this case, you just have to take a few steps back and attack the problem when you minds clears up
Thanks goes out for those that helped.
It was the fuel pump.
I installed a new pump and the car is now holding 41 lbs of pressure after sitting for at least 6 hours. I'm just glad it wasn't something more expensive like having to replace all the injectors. The fuel pump has an apparent one way valve in it that prevents the fuel from flowing fuel back into the tank. I took her out for about a 1/2 hour spin and she's running great and even noticed getting better fuel mileage too.
Sometimes when you get aggravated like I was in this case, you just have to take a few steps back and attack the problem when you minds clears up
Thanks goes out for those that helped.
