Quick Fuel Pressure Question
Thread Starter
5th Gear
Joined: Oct 2006
Posts: 5
Likes: 0
From: Victoria
Quick Fuel Pressure Question
Am working on a blokes 87 vette,
Its been around a couple of workshops trying to fix a problem.
Was told it was running way rich at idle and wouldnt pull at any throttle. The last workshop tested the fuel pressure and decided to drop it to about 35 psi to drop idle richness but made driving worse.
Now I have it and am planning to up the pressure and give it a full tune.
Just wondering what idle pressure is normal and what is a good full load pressure. Am thinking high 40's to low 50's.psi
Motor has been worked a bit by the sound of it and std injectors.
Thanks
Its been around a couple of workshops trying to fix a problem.
Was told it was running way rich at idle and wouldnt pull at any throttle. The last workshop tested the fuel pressure and decided to drop it to about 35 psi to drop idle richness but made driving worse.
Now I have it and am planning to up the pressure and give it a full tune.
Just wondering what idle pressure is normal and what is a good full load pressure. Am thinking high 40's to low 50's.psi
Motor has been worked a bit by the sound of it and std injectors.
Thanks
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
43.5 PSI or around that with the vacuum connection off, and blocked at the plenum. Idle and off idle should probably be pretty close in terms of pressure with the vac disconnected.
Where are you from?
Where are you from?
Thread Starter
5th Gear
Joined: Oct 2006
Posts: 5
Likes: 0
From: Victoria
Thanks.
Going to have a play with it on the dyno this arvo to try and dial in some throttle response at least. I havent checked the timing yet either so thats first up because the last workshop said he didnt know what to set it at and just wound it back to 8 deg btdc. I'm willing to bet he didnt have aldl terminals grounded when he checked it.
From south west Vic, down near Warnambool 3 hours from Geelong.
cheers
Going to have a play with it on the dyno this arvo to try and dial in some throttle response at least. I havent checked the timing yet either so thats first up because the last workshop said he didnt know what to set it at and just wound it back to 8 deg btdc. I'm willing to bet he didnt have aldl terminals grounded when he checked it.
From south west Vic, down near Warnambool 3 hours from Geelong.
cheers
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
No worries mate. Somewhere between 6-8 degrees BTDC should be fine to start with. Im not sure what the factory setting is, but its one of those 2 (i think its 8)
Do you have a service manual for this vehicle?? If not you probably should get one even if its only a Haynes.
I say this because of your willingness to bet he didnt have the ALDL terminals grounded when he did the timing. There is no mension of this step in any service manual ive read, what it does say is that the EST connector must be unpluged before you do the checking and adjustment. Its a single wire on the left hand side of the engine somewhere. It could be anywhere if the car is converted to right hand drive, and im not certain but i believe the colour is tan with a black stripe on it.
Im in QLD, youre abit too far away to drive over there, so i cant loan you my service manual!!
Do you have a service manual for this vehicle?? If not you probably should get one even if its only a Haynes.
I say this because of your willingness to bet he didnt have the ALDL terminals grounded when he did the timing. There is no mension of this step in any service manual ive read, what it does say is that the EST connector must be unpluged before you do the checking and adjustment. Its a single wire on the left hand side of the engine somewhere. It could be anywhere if the car is converted to right hand drive, and im not certain but i believe the colour is tan with a black stripe on it.
Im in QLD, youre abit too far away to drive over there, so i cant loan you my service manual!!
Thread Starter
5th Gear
Joined: Oct 2006
Posts: 5
Likes: 0
From: Victoria
Thanks mate,
I've just read this after having it on the dyno and had forgotten the different procedure for checking base timing. I have the moates emulator and it has a switch on it that you can select either normal mode, aldl dump mode or self diagnostic/backup mode. Setting to backup mode shorts pin A and B which bought timing back to around 0 - 2 deg so I wound it up to 8deg. That made a fair difference.
I went to run it up on the dyno and it leaned right out 17:1 plus, so wound up the fuel pressure back to 42-44psi. Idle was rich so leaned that out on the chip and then run it up on dyno mid to high 13:1's down low and into 11's up high so am in the ball park. Spent 1/2 hour on it and got it running better.
Will check it next time, maybe friday and compare the two timing check procedures and get back on here. This is job for a mate thing so it might take a few weeks of after hours work to fully sort.
BTW the early commodores (VN-VS) run the same computer basically and the pin A-B short is the procedure and wind dissy back to 10 deg.
Thanks for your help.
I've just read this after having it on the dyno and had forgotten the different procedure for checking base timing. I have the moates emulator and it has a switch on it that you can select either normal mode, aldl dump mode or self diagnostic/backup mode. Setting to backup mode shorts pin A and B which bought timing back to around 0 - 2 deg so I wound it up to 8deg. That made a fair difference.
I went to run it up on the dyno and it leaned right out 17:1 plus, so wound up the fuel pressure back to 42-44psi. Idle was rich so leaned that out on the chip and then run it up on dyno mid to high 13:1's down low and into 11's up high so am in the ball park. Spent 1/2 hour on it and got it running better.
Will check it next time, maybe friday and compare the two timing check procedures and get back on here. This is job for a mate thing so it might take a few weeks of after hours work to fully sort.
BTW the early commodores (VN-VS) run the same computer basically and the pin A-B short is the procedure and wind dissy back to 10 deg.
Thanks for your help.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
If the timing and fuel pressure were out by that much who knows what else could be set wrong, so if i were you and you want this car to run right, id follow the correct procedure in the service manual to set the throttle stop screw, and then set the throttle posistion sensor correctly according to the manual as well. You probably know the fact that the throttle stop screw IS NOT for setting the idle speed, its for setting the minimum air flow or minimum throttle plate angle. The IAC will always try to make the idle speed conform with the settings in the chip. (as i say im sure youd know that, but the last person that tampered with the car probably didnt.)
Thread Starter
5th Gear
Joined: Oct 2006
Posts: 5
Likes: 0
From: Victoria
Well, had it back on the dyno yesterday arvo (afternoon) and rechecked the timing. Was still at 8deg in diag mode, so unhooked the est wire and it dropped down to 2 atdc, nearly stalling. This was a good thing cause it meant i could wind it up more.
Set that to 8 and restarted, ran a bit smoother too.
Ran it up on the dyno again, pulled 156 kw (200hp)at wheels, up 10kw (13hp) from last run. Thats with the std timing curve from ABTT Bin. The first run last week barely made 120kw (156hp) at wheels.
It now pulls in O/D. so am now getting somewhere.
Next play is next week sometime.
Cheers
Set that to 8 and restarted, ran a bit smoother too.
Ran it up on the dyno again, pulled 156 kw (200hp)at wheels, up 10kw (13hp) from last run. Thats with the std timing curve from ABTT Bin. The first run last week barely made 120kw (156hp) at wheels.
It now pulls in O/D. so am now getting somewhere.
Next play is next week sometime.
Cheers
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Yep, field service diagnostic mode is not when you set the timing, you need to disconnect the EST wire.
I think i remember you saying something about this car before in terms of a modded Edelbrock intake on it, i cant remember if it was the same car or not, or if that was all it had or more. I reckon you should be able to get about another 10 or 15 horses at least. (asuming its got a good exhaust on it)
Good that youve got it running better!!
I think i remember you saying something about this car before in terms of a modded Edelbrock intake on it, i cant remember if it was the same car or not, or if that was all it had or more. I reckon you should be able to get about another 10 or 15 horses at least. (asuming its got a good exhaust on it)
Good that youve got it running better!!
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