Help! C6 Hard to Start
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
Help! C6 Hard to Start
I've done several searches for similar starting problems, but haven't found anything with the same issue. My 2009 C6 with 16K miles is hard to start. Mostly when the car is cold. Left it with the dealer overnight so they could duplicate the srarting issue. No luck with it starting hard. No computer codes found. Car runs fine once it starts, but it may turn over for 10-15 seconds before it starts. Any suggestions? Should I start with new plugs? Anything else to consider?
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
I bet the fuel is draining back thru the pump. Connect a fuel pressure guage, run the engine and shut it down and let it sit overnight. If it is at 0psi in the am, crank it over and watch the guage. it should start after the pressure reaches about 40-50psi. Then tell them to put a pump in it.
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 25
From: Austin Texas
A local guy (name witheld by request) had the same problem with his '07, Dealer couldn't verify the no start since it always started for them cold or warm. No codes shown.
Solution? Seems that the owner occasionally had his foot on the gas pedal while trying to start. The ECM sees the gas pedal depressed as a "flooded" start attempt and shuts off the fuel! A simple solution that worked for him.
Solution? Seems that the owner occasionally had his foot on the gas pedal while trying to start. The ECM sees the gas pedal depressed as a "flooded" start attempt and shuts off the fuel! A simple solution that worked for him.
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
The ecm need to see the throttle angle past 80% to go in clear flood mode. It is designed to start with just the starter button and brake/clutch depressed, that's it - no throttle.
see below for clear flood mode
Clear Flood Mode
If the engine is flooded with fuel during starting and will not start, the Clear Flood Mode can be manually selected. To select Clear Flood Mode, push the accelerator to wide open throttle (WOT). With this signal, the ECM will completely turn OFF the injectors and will maintain this stage as long as the ECM indicates a WOT condition with engine speed below 1,000 RPM.
see below for clear flood mode
Clear Flood Mode
If the engine is flooded with fuel during starting and will not start, the Clear Flood Mode can be manually selected. To select Clear Flood Mode, push the accelerator to wide open throttle (WOT). With this signal, the ECM will completely turn OFF the injectors and will maintain this stage as long as the ECM indicates a WOT condition with engine speed below 1,000 RPM.
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
A local guy (name witheld by request) had the same problem with his '07, Dealer couldn't verify the no start since it always started for them cold or warm. No codes shown.
Solution? Seems that the owner occasionally had his foot on the gas pedal while trying to start. The ECM sees the gas pedal depressed as a "flooded" start attempt and shuts off the fuel! A simple solution that worked for him.
Solution? Seems that the owner occasionally had his foot on the gas pedal while trying to start. The ECM sees the gas pedal depressed as a "flooded" start attempt and shuts off the fuel! A simple solution that worked for him.
thanks-
Don
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
You can also disconnect the breather hose behind the tb and spray some 2+2 into the plenum ( about 2-3 seconds). Put the hose back on and crank it. If it starts and stalls, you GOT a fuel delivery problem.
This is the only explanation I can think of for an long extended crank with an engine that runs perfectly normal within 15 seconds after it starts.
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
Get that fuel pressure guage on there. I looked it up, key on engine off pressure should be 55-62psi. On a 1 line system, if the pump leaks back, the injectors have to purge the air from the line and rail. On the older 2 line sytems, the air would go back to the tank much more quickly via the return line. I have changed inline filters on other 1 line cars and it takes alot of cranking to get them refired.
You can also disconnect the breather hose behind the tb and spray some 2+2 into the plenum ( about 2-3 seconds). Put the hose back on and crank it. If it starts and stalls, you GOT a fuel delivery problem.
This is the only explanation I can think of for an long extended crank with an engine that runs perfectly normal within 15 seconds after it starts.
You can also disconnect the breather hose behind the tb and spray some 2+2 into the plenum ( about 2-3 seconds). Put the hose back on and crank it. If it starts and stalls, you GOT a fuel delivery problem.
This is the only explanation I can think of for an long extended crank with an engine that runs perfectly normal within 15 seconds after it starts.
Thanks for the help on this Marty!
Don
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Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
You were exactly right! Pressure gauge showed that the pressure wasn't holding after shutting the car off. Reads 62 psi when it starts andas soon as it shuts off, drops quickly to 0. Called the local servicemanager and he said to bring it in next week and they would fix it. Just wish they were a little less dependent on computer codes when they troubleshoot a problem like this!
Thanks for the help on this Marty!
Don
Thanks for the help on this Marty!
Don
It's a shame you got such a weak effort from your dealer.
Safety Car
Joined: Sep 2008
Posts: 4,296
Likes: 156
From: Location: Location: kAnSaS
One thing to take into consideration is when you hook up the pressure tester the first time it will read zero because you just bled the pressure off.
The best way to see if its leaking down is to leave it on over night, if its low and wont start and then you see the pressure rise and it starts then theres your problem.
2 things commonly that cause hard starts is the pressure bleeding off and the crank sensor glitchy. good luck with it
The best way to see if its leaking down is to leave it on over night, if its low and wont start and then you see the pressure rise and it starts then theres your problem.
2 things commonly that cause hard starts is the pressure bleeding off and the crank sensor glitchy. good luck with it
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
One thing to take into consideration is when you hook up the pressure tester the first time it will read zero because you just bled the pressure off.
The best way to see if its leaking down is to leave it on over night, if its low and wont start and then you see the pressure rise and it starts then theres your problem.
2 things commonly that cause hard starts is the pressure bleeding off and the crank sensor glitchy. good luck with it
The best way to see if its leaking down is to leave it on over night, if its low and wont start and then you see the pressure rise and it starts then theres your problem.
2 things commonly that cause hard starts is the pressure bleeding off and the crank sensor glitchy. good luck with it
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
Update -
Dealer has had the car since Monday afternoon. I told the service writer what I saw with the fuel pressure gauge. He says ok, but writes up the service ticket to say "Customer says car is hard to start." Tells me not to worry about it - the mechanics will check it out and do whatever necessary to fix it. Tuesday afternoon and no status call from the service writer. I call and he says- I'll go check... Comes back on the line and gives me song and dance that they found that they needed to replace the fuel pump. Hmmm! Good call. Well- we need to keep it until tomorrow because it's a big job to replace. Will be ready Wednesday afternoon....
Fast forward to Wednesday afternoon--- get a call from the service writer--putting everything back together, but they're running out of time and won't be done until Thursday afternoon. Tells me that to replace the fuel pump that they have to remove the whole drive train from the engine back to the transmission!
Is it possible that GM would design something as stupid as that? 2-1/2 days to replace a fuel pump? Sounds like BS to me...
Dealer has had the car since Monday afternoon. I told the service writer what I saw with the fuel pressure gauge. He says ok, but writes up the service ticket to say "Customer says car is hard to start." Tells me not to worry about it - the mechanics will check it out and do whatever necessary to fix it. Tuesday afternoon and no status call from the service writer. I call and he says- I'll go check... Comes back on the line and gives me song and dance that they found that they needed to replace the fuel pump. Hmmm! Good call. Well- we need to keep it until tomorrow because it's a big job to replace. Will be ready Wednesday afternoon....
Fast forward to Wednesday afternoon--- get a call from the service writer--putting everything back together, but they're running out of time and won't be done until Thursday afternoon. Tells me that to replace the fuel pump that they have to remove the whole drive train from the engine back to the transmission!
Is it possible that GM would design something as stupid as that? 2-1/2 days to replace a fuel pump? Sounds like BS to me...
Le Mans Master
Joined: Feb 2006
Posts: 5,762
Likes: 4
From: Chandler Arizona
Update -
Dealer has had the car since Monday afternoon. I told the service writer what I saw with the fuel pressure gauge. He says ok, but writes up the service ticket to say "Customer says car is hard to start." Tells me not to worry about it - the mechanics will check it out and do whatever necessary to fix it. Tuesday afternoon and no status call from the service writer. I call and he says- I'll go check... Comes back on the line and gives me song and dance that they found that they needed to replace the fuel pump. Hmmm! Good call. Well- we need to keep it until tomorrow because it's a big job to replace. Will be ready Wednesday afternoon....
Fast forward to Wednesday afternoon--- get a call from the service writer--putting everything back together, but they're running out of time and won't be done until Thursday afternoon. Tells me that to replace the fuel pump that they have to remove the whole drive train from the engine back to the transmission!
Is it possible that GM would design something as stupid as that? 2-1/2 days to replace a fuel pump? Sounds like BS to me...
Dealer has had the car since Monday afternoon. I told the service writer what I saw with the fuel pressure gauge. He says ok, but writes up the service ticket to say "Customer says car is hard to start." Tells me not to worry about it - the mechanics will check it out and do whatever necessary to fix it. Tuesday afternoon and no status call from the service writer. I call and he says- I'll go check... Comes back on the line and gives me song and dance that they found that they needed to replace the fuel pump. Hmmm! Good call. Well- we need to keep it until tomorrow because it's a big job to replace. Will be ready Wednesday afternoon....
Fast forward to Wednesday afternoon--- get a call from the service writer--putting everything back together, but they're running out of time and won't be done until Thursday afternoon. Tells me that to replace the fuel pump that they have to remove the whole drive train from the engine back to the transmission!
Is it possible that GM would design something as stupid as that? 2-1/2 days to replace a fuel pump? Sounds like BS to me...
Edit #1: OK, I just found the schematic. Yes, the check valve is back at the pump, so they do have to pull the tanks. And if it's an auto, they have to drop the tranny to get the tanks out. Sounds like an absolutely terrible design from a maintainability standpoint.
http://forums.corvetteforum.com/1566299770-post6.html
Edit #2: Here's everything you EVER wanted to know about the Corvette fuel system:
http://www.hessh.de/Corvette/FuelTankSystem.pdf
Note it says: When the engine is shut off and the turbine pump stops, a reverse flow check valve (W) maintains pressure in the system to ensure rapid pressure buildup during the next startup cycle.
Last edited by glennhl; Mar 24, 2010 at 09:21 PM.
Thread Starter
Instructor
Joined: Nov 2009
Posts: 225
Likes: 2
From: Hampstead NC
Well to close out this thread- picked up the car this afternoon. Car starts immediately after pushing the start button, which is what I had always expected. The service writer apologized for not realizing how long it would take to replace the fuel pump. He said that they hadn't had to replace one on his watch... The paperwork indicates that the drive line had to be dropped and the left fuel tank removed to replace the fuel pump module. He told me that the warranty work allowed 13 manhours for the replacement. From now on, I will simply request a replacement ride when I leave the car for warrranty work.
Thanks for all the replies and the information provided. This has been a continuing learning experience to say the least!
Thanks for all the replies and the information provided. This has been a continuing learning experience to say the least!
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
Well to close out this thread- picked up the car this afternoon. Car starts immediately after pushing the start button, which is what I had always expected. The service writer apologized for not realizing how long it would take to replace the fuel pump. He said that they hadn't had to replace one on his watch... The paperwork indicates that the drive line had to be dropped and the left fuel tank removed to replace the fuel pump module. He told me that the warranty work allowed 13 manhours for the replacement. From now on, I will simply request a replacement ride when I leave the car for warrranty work.
Thanks for all the replies and the information provided. This has been a continuing learning experience to say the least!
Thanks for all the replies and the information provided. This has been a continuing learning experience to say the least!
