Fuel Pressure for an IROC 305??
03-17-2002, 08:59 PM
#1
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Fuel Pressure for an IROC 305??
According to my scan tool, my car is running lean. I tested the fuel pressure with all the vacuum hoses hooked up and here is what I got.
Static reading--44
Idling--38
Here is my car info and mods...
1987 IROC-Z TPI 305, manual tranny
Mods...
K & N Air Filters
Eastern Manufacturing Hi-Flow Cat
Flowmaster American Thunder Cat-Back
Hypertech Thermomaster Chip
SLP 1 5/8 Stainless Headers
Art Houser Rear: 3:73's with an Auburn 3-Series Posi & Moser Axles, Upgraded to a 28 Spline
High Density Drive Shaft
8mm High Performance Wires
MAF Screens Removed
Hypertech Airfoil
I have a BBK AFPR that I want to install this week along with underdrive pulleys. I wanted to get a reading to see where I was at being that my scan tool showed a lean condition.
1. What should the stock pressure be set at?
2. With my mods, what should I adjust the fuel pressure to? It seems kind of high to me though....Thanks.
Static reading--44
Idling--38
Here is my car info and mods...
1987 IROC-Z TPI 305, manual tranny
Mods...
K & N Air Filters
Eastern Manufacturing Hi-Flow Cat
Flowmaster American Thunder Cat-Back
Hypertech Thermomaster Chip
SLP 1 5/8 Stainless Headers
Art Houser Rear: 3:73's with an Auburn 3-Series Posi & Moser Axles, Upgraded to a 28 Spline
High Density Drive Shaft
8mm High Performance Wires
MAF Screens Removed
Hypertech Airfoil
I have a BBK AFPR that I want to install this week along with underdrive pulleys. I wanted to get a reading to see where I was at being that my scan tool showed a lean condition.
1. What should the stock pressure be set at?
2. With my mods, what should I adjust the fuel pressure to? It seems kind of high to me though....Thanks.
Last edited by Hurst; 03-17-2002 at 09:12 PM.
03-17-2002, 10:52 PM
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If your scanner shows Intergrator and Block Learn you can set
the pressure by watching the Block Learn.
Get your AFPR in and turn the pump on. Turn the ignition on
without starting the engine to pressurize the rail and note the
fuel pressure. Bump the pressure up a bit at a time while cycling
the ignition switch each time until it is at 38lbs. Start the car and
let it warm up while watching the Block Learn. It wants to be at
128, if your reading is higher than this you are running lean and
need to bump the pressure a bit. If it is lower than 128 it is rich
so drop your pressure a bit.
Once you have it at 128 at a warm idle, take her out for a drive
and take your tools with you. Watch the Block Learn while doing
some average driving. The Integrator will be all over the place
so don't worry about that one just watch the Block Learn. You
want it at 128 cruising with a light throttle at an even speed.
Stop and play with it till you get it set. Now in park at an idle it
should be at 128 and the Integrator should be close to 128 also.
With the mods you have you will be probably wind up at about
42-45lbs idling.
the pressure by watching the Block Learn.
Get your AFPR in and turn the pump on. Turn the ignition on
without starting the engine to pressurize the rail and note the
fuel pressure. Bump the pressure up a bit at a time while cycling
the ignition switch each time until it is at 38lbs. Start the car and
let it warm up while watching the Block Learn. It wants to be at
128, if your reading is higher than this you are running lean and
need to bump the pressure a bit. If it is lower than 128 it is rich
so drop your pressure a bit.
Once you have it at 128 at a warm idle, take her out for a drive
and take your tools with you. Watch the Block Learn while doing
some average driving. The Integrator will be all over the place
so don't worry about that one just watch the Block Learn. You
want it at 128 cruising with a light throttle at an even speed.
Stop and play with it till you get it set. Now in park at an idle it
should be at 128 and the Integrator should be close to 128 also.
With the mods you have you will be probably wind up at about
42-45lbs idling.
03-18-2002, 08:31 AM
#5
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One important procedure that was missed....you must check the fuel pressure with the vacuum line OFF and plugged, not on.
If you check your pressure with the vacuum line on (engine running), your pressure will be artificially low because engine vacuum is lowering the fuel pressure.
Checking the pressure by turning the ignition on and off is not the preferred method and will give inconsistent results.
If you check your pressure with the vacuum line on (engine running), your pressure will be artificially low because engine vacuum is lowering the fuel pressure.
Checking the pressure by turning the ignition on and off is not the preferred method and will give inconsistent results.
03-18-2002, 08:53 AM
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I am just trying to get him in the ballpark setting the new AFPR
before starting the car, then he can dial it in to get ready for the
road test.
before starting the car, then he can dial it in to get ready for the
road test.
Last edited by Swapmaster; 03-18-2002 at 08:56 AM.
03-18-2002, 12:46 PM
#7
A quick, easy way with fuel press guage is to unhook the vacuum line and set idle pressure to around 55psi...that's not very scientific but I had excellent results there with similar mods on the same 305/T5.
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03-18-2002, 07:23 PM
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55lbs will be too much for the 305.
55lbs would feed a 350 with the 305 injectors.
Follow my steps and it will set the pressure at
an optimum level without throwing any codes.
Setting the pressure at 38-40 lbs with the engine
off will set the pressure just about at the factory
specs at idle.
Once at spec you can begin fiddling, you already
have the tools to do it properly.
55lbs would feed a 350 with the 305 injectors.
Follow my steps and it will set the pressure at
an optimum level without throwing any codes.
Setting the pressure at 38-40 lbs with the engine
off will set the pressure just about at the factory
specs at idle.
Once at spec you can begin fiddling, you already
have the tools to do it properly.
03-19-2002, 12:18 PM
#11
Actually now that I think about it I ended up bringing my pressure down to 50-52psi...the 55 was a little rich. I'm not saying this is the better way, it's just what worked for me so you can use it as a guideline.
03-21-2002, 07:08 AM
#12
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AFPR
Thanks. Now I have a good reference point.
By the way, I set mine at 44 with all the vacuum lines intact. I remember checking the block learn and it was at 128. I'll have to re-check it under light throttle and steady driving.
By the way, I set mine at 44 with all the vacuum lines intact. I remember checking the block learn and it was at 128. I'll have to re-check it under light throttle and steady driving.
Last edited by Hurst; 03-29-2002 at 09:34 PM.
03-30-2002, 02:17 AM
#14
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Car: 1990 Iroc/Z
Engine: LB9 305 TPI
Transmission: Borg Warner 5 speed
yes, unhook the one from the AFPR. Unhook it from the manifold of course, and just plug it with something. I use a screwdriver.
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