no fuel pressure question
Thread Starter
Racer
Joined: Aug 2008
Posts: 367
Likes: 0
From: Sacramento ca
no fuel pressure question
I have no fuel pressure, there is no power to the wire that gives power to the pump. Is there a fuse? I saw a relay under the hood.
Also if there was an ignition switch / lockout issue is it possible that it would give no power to the fuel pump?
Any help would be great.
Thanks
Also if there was an ignition switch / lockout issue is it possible that it would give no power to the fuel pump?
Any help would be great.
Thanks
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,121
From: Dyer, IN
I have no fuel pressure, there is no power to the wire that gives power to the pump. Is there a fuse? I saw a relay under the hood.
Also if there was an ignition switch / lockout issue is it possible that it would give no power to the fuel pump?
Any help would be great.
Thanks
Also if there was an ignition switch / lockout issue is it possible that it would give no power to the fuel pump?
Any help would be great.
Thanks
You can check the fuse and relay with the schematic below. You need to make sure the fuel pump relay is engaging. To test the circuit from the relay socket to the pump connector, you can install a jumper wire in the relay socket. The jumper should be installed from 30 to 87 as labeled in the pic below. There should be a good ground on 85, and 12 volts is supplied by the PCM at 86 when the ignition is turned on.
Thread Starter
Racer
Joined: Aug 2008
Posts: 367
Likes: 0
From: Sacramento ca
so I do not know where to go from here, 30 has power, 85 does not have a good ground 86 does not have power when ign is on.
The car ran fine, then died, no fuel pressure. Any help would be great. Where does this relay get its ground? If no power from the PCM is it a bad PCM?
The car ran fine, then died, no fuel pressure. Any help would be great. Where does this relay get its ground? If no power from the PCM is it a bad PCM?
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,121
From: Dyer, IN
Any other important info you'd like to share? 
If you are checking at the relay socket(i.e relay removed), you should have the following(as label in the pic):
Measurements taken key to on position:
30 = O volts
86 = 12 volts ( for two seconds)
87 = 12 volts ( constant)
Measurement taken key to off position:
85 = Ground (should be low resistance i.e. .3 ohm or below)
No offense, but I'm questioning how you are taking the measurements, since all these things failing at the same time are unlikely....unless the car has been in an accident.
When you jump 30 to 87(of the relay socket), you should have 12 volts at the fuel pump connector.....unless there is a wiring problem.
There should be a ground at 85.....unless the ground is corroded at SP122 (located under the battery tray), or G105 (left lower side of block) is damaged.
There should be 12 volts at 86 when the key is first turned on, unless the PCM is not providing it.
http://forums.corvetteforum.com/c5-t...e-grounds.html
If you are checking at the relay socket(i.e relay removed), you should have the following(as label in the pic):
Measurements taken key to on position:
30 = O volts
86 = 12 volts ( for two seconds)
87 = 12 volts ( constant)
Measurement taken key to off position:
85 = Ground (should be low resistance i.e. .3 ohm or below)
No offense, but I'm questioning how you are taking the measurements, since all these things failing at the same time are unlikely....unless the car has been in an accident.
When you jump 30 to 87(of the relay socket), you should have 12 volts at the fuel pump connector.....unless there is a wiring problem.
There should be a ground at 85.....unless the ground is corroded at SP122 (located under the battery tray), or G105 (left lower side of block) is damaged.
There should be 12 volts at 86 when the key is first turned on, unless the PCM is not providing it.
http://forums.corvetteforum.com/c5-t...e-grounds.html
Last edited by lucky131969; May 28, 2010 at 05:00 PM.
Thread Starter
Racer
Joined: Aug 2008
Posts: 367
Likes: 0
From: Sacramento ca
I will check again.
The only thing that happened is that I was driving it and it died. When I looked at the fuel pump connecter on the fuel pump side the terminal that gets power for the fuel pump was pushed in. I replaced the end as I thought it was the issue.
I then checked the relays last night. I did not have someone help me so I may have missed the one that gets power for 2 seconds. I tried and tried and did not get a ground to register on the other one.
I will take the battery and tray out to look at all ground connections as I guesse that may cause an issue.
I need to spend more time on it and I appretiate the diagram as it shows me what should be there.
The only thing that happened is that I was driving it and it died. When I looked at the fuel pump connecter on the fuel pump side the terminal that gets power for the fuel pump was pushed in. I replaced the end as I thought it was the issue.
I then checked the relays last night. I did not have someone help me so I may have missed the one that gets power for 2 seconds. I tried and tried and did not get a ground to register on the other one.
I will take the battery and tray out to look at all ground connections as I guesse that may cause an issue.
I need to spend more time on it and I appretiate the diagram as it shows me what should be there.
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Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,121
From: Dyer, IN
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,121
From: Dyer, IN
Pro
Joined: Jul 2000
Posts: 580
Likes: 0
From: Washington, USA
Are you sure about this? What was the final solution to the bad ground? (sorry if I didn't read it properly in the thread)
I went through this and found out the pump was not bad, after buying a new one. If you want a C5 application walbro 255 let me know.
I went through this and found out the pump was not bad, after buying a new one. If you want a C5 application walbro 255 let me know.
Instructor
Joined: Apr 2008
Posts: 164
Likes: 0
From: McKinney TX
I know this is an old thread, but maybe someone can help me.
I have an '01 C5 and only have 5 psi fuel pressure with the key on. It has a Racetronix fuel system with the harness that runs power direct to the pump. It was installed by the previous owner and I tried contacting Racetronix to get instructions or a wiring diagram and never heard back from them.
The car ran fine for a long time after I bought it. It just quit on me one day and now no fuel pressure.
Fuse and relay both tested good.
On the factory fuse block I measured voltages and I have no voltage on 87 where I should have constant 12V.
I do get 12V on 86 when I turn the key on.
Does anyone have info on how the Racetronix stuff is wired in?
Any ideas would be appreciated.
I have an '01 C5 and only have 5 psi fuel pressure with the key on. It has a Racetronix fuel system with the harness that runs power direct to the pump. It was installed by the previous owner and I tried contacting Racetronix to get instructions or a wiring diagram and never heard back from them.
The car ran fine for a long time after I bought it. It just quit on me one day and now no fuel pressure.
Fuse and relay both tested good.
On the factory fuse block I measured voltages and I have no voltage on 87 where I should have constant 12V.
I do get 12V on 86 when I turn the key on.
Does anyone have info on how the Racetronix stuff is wired in?
Any ideas would be appreciated.
Last edited by FordDefector; Jan 2, 2012 at 05:40 PM.
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,121
From: Dyer, IN
I know this is an old thread, but maybe someone can help me.
I have an '01 C5 and only have 5 psi fuel pressure with the key on. It has a Racetronix fuel system with the harness that runs power direct to the pump. It was installed by the previous owner and I tried contacting Racetronix to get instructions or a wiring diagram and never heard back from them.
The car ran fine for a long time after I bought it. It just quit on me one day and now no fuel pressure.
Fuse and relay both tested good.
On the factory fuse block I measured voltages and I have no voltage on 87 where I should have constant 12V.
I do get 12V on 86 when I turn the key on.
Does anyone have info on how the Racetronix stuff is wired in?
Any ideas would be appreciated.
I have an '01 C5 and only have 5 psi fuel pressure with the key on. It has a Racetronix fuel system with the harness that runs power direct to the pump. It was installed by the previous owner and I tried contacting Racetronix to get instructions or a wiring diagram and never heard back from them.
The car ran fine for a long time after I bought it. It just quit on me one day and now no fuel pressure.
Fuse and relay both tested good.
On the factory fuse block I measured voltages and I have no voltage on 87 where I should have constant 12V.
I do get 12V on 86 when I turn the key on.
Does anyone have info on how the Racetronix stuff is wired in?
Any ideas would be appreciated.
Instructor
Joined: Apr 2008
Posts: 164
Likes: 0
From: McKinney TX
I replaced it and ran the car for a while and the fuse didn't get hot and had good stable fuel pressure.