Still needing help!!
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Hello 383vette,
I do know these facts.
The car is designed so that the fuel pump will run for two seconds after the key is turned on.
Once the car is running oil pressure goes up, over 5 psi and the car continues to run.
If the oil pressure goes below 5 psi the car shuts down.
In 1984 the minimum pressure was 10 psi.
And the link you sent me seems to support me. The C4 , 1985 until ?, Corvette requires 4 psi of oil pressure to run the fuel pump.
I do know these facts.
The car is designed so that the fuel pump will run for two seconds after the key is turned on.
Once the car is running oil pressure goes up, over 5 psi and the car continues to run.
If the oil pressure goes below 5 psi the car shuts down.
In 1984 the minimum pressure was 10 psi.
And the link you sent me seems to support me. The C4 , 1985 until ?, Corvette requires 4 psi of oil pressure to run the fuel pump.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
I have an 84 also. If the fuel pressure sender is disconnected, the car still runs. Look at the fsm of an 84 Vette (I have 2). There is nothing that shuts the fuel pump off if the fuel pressure drops. The fuel pump relay is energized when the ignition is on and the motor running. The ecm has no clue what the fuel pressure is. Also, I never sent you a link. You need to do some homework before spouting off.
Racer
Joined: Dec 2017
Posts: 250
Likes: 41
From: Sydney NSW
Perhaps you should read this article on engine start sequence published by Grumpy's Performance. Note the third paragraph regarding Initial Crank Action.
http://www.corvetteactioncenter.com/...uence-802.html
http://www.corvetteactioncenter.com/...uence-802.html
Strange..
Burning Brakes
Joined: Jan 2017
Posts: 961
Likes: 237
From: Diamondhead Mississippi
St. Jude Donor '17-'18-'19-'20-'21-'22
Burning Brakes
Joined: Jan 2017
Posts: 961
Likes: 237
From: Diamondhead Mississippi
St. Jude Donor '17-'18-'19-'20-'21-'22
If you look closely at the diagram for the ECM it says Fuel Pump Control (During Start Only). This tells me that once you release the key from the start position and let it go to the run position the ECM circuit opens and the Oil Pressure Switch closes to keep power to the Fuel Pump while the engine is running (as long as there is oil pressure)
Drifting
Joined: Feb 2013
Posts: 1,464
Likes: 48
cdm747 ,.
If I seemed rude to you in my reply. It was unintentional. I did think that your post was to the others and not to me. Sorry for an misunderstanding.
My 1984 would read the oil pressure as 9 psi and shut off. Now I had a new fuel pump and relay in the car. So I believed everything was operating as it should. I eventually bought fittings and put a mechanical gauge to test the oil pressure. Which at idle was close to 20 psi. But, the dash read 10/12. If it went to 9 the car would stall. I did purchase a new oil pressure sender. It still read low. So that is what happened.
If I seemed rude to you in my reply. It was unintentional. I did think that your post was to the others and not to me. Sorry for an misunderstanding.
My 1984 would read the oil pressure as 9 psi and shut off. Now I had a new fuel pump and relay in the car. So I believed everything was operating as it should. I eventually bought fittings and put a mechanical gauge to test the oil pressure. Which at idle was close to 20 psi. But, the dash read 10/12. If it went to 9 the car would stall. I did purchase a new oil pressure sender. It still read low. So that is what happened.
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Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
At s107 there are 4 lines. 1 is to the fuse then to the pump. 3 other points on the junction. 1 from the oil pressure sensor and 1 from the fuel pump relay. What is the 3rd from?
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
If you look closely at the diagram for the ECM it says Fuel Pump Control (During Start Only). This tells me that once you release the key from the start position and let it go to the run position the ECM circuit opens and the Oil Pressure Switch closes to keep power to the Fuel Pump while the engine is running (as long as there is oil pressure)
Burning Brakes
Joined: Jan 2017
Posts: 961
Likes: 237
From: Diamondhead Mississippi
St. Jude Donor '17-'18-'19-'20-'21-'22
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
My thought is that B2 gives it the power as does the oil pump. There is also a 3rd option for a prime only, hence the 2 second pump run when you turn it on
Burning Brakes
Joined: Jan 2017
Posts: 961
Likes: 237
From: Diamondhead Mississippi
St. Jude Donor '17-'18-'19-'20-'21-'22
How long did you leave it disconnected. I would think it would run for a while until the fuel pressure went down to zero and the fuel in the lies ran out. I am sure you have a lot more experience with this than me, i am just looking at the schematic and how I Interpret it. Hard for me to test anything as my car was just painted and is still being worked on.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
How long did you leave it disconnected. I would think it would run for a while until the fuel pressure went down to zero and the fuel in the lies ran out. I am sure you have a lot more experience with this than me, i am just looking at the schematic and how I Interpret it. Hard for me to test anything as my car was just painted and is still being worked on.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
cdm747 ,.
If I seemed rude to you in my reply. It was unintentional. I did think that your post was to the others and not to me. Sorry for an misunderstanding.
My 1984 would read the oil pressure as 9 psi and shut off. Now I had a new fuel pump and relay in the car. So I believed everything was operating as it should. I eventually bought fittings and put a mechanical gauge to test the oil pressure. Which at idle was close to 20 psi. But, the dash read 10/12. If it went to 9 the car would stall. I did purchase a new oil pressure sender. It still read low. So that is what happened.
If I seemed rude to you in my reply. It was unintentional. I did think that your post was to the others and not to me. Sorry for an misunderstanding.
My 1984 would read the oil pressure as 9 psi and shut off. Now I had a new fuel pump and relay in the car. So I believed everything was operating as it should. I eventually bought fittings and put a mechanical gauge to test the oil pressure. Which at idle was close to 20 psi. But, the dash read 10/12. If it went to 9 the car would stall. I did purchase a new oil pressure sender. It still read low. So that is what happened.
