FPR and BOV
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
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From: Athens OH
FPR and BOV
My car seems to be running pretty rich sice I installed the h/c/i+Procharger and realted mods. I have been racking my brain trying to figure out whwat i may have done wrong to cause it to run rich and I just remembered blowing through the vaccum port on the BOV and it seemed to flow through freely.
1. Is that normal?
2. I have the BOV tee'd to my FPR. If there is a vaccum leak there, will it cause the car to run rich?
3. Should I put the BOV hose to another source?
thanks....again
1. Is that normal?
2. I have the BOV tee'd to my FPR. If there is a vaccum leak there, will it cause the car to run rich?
3. Should I put the BOV hose to another source?
thanks....again
Intermediate
Joined: Nov 2006
Posts: 49
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From: Slidell La
If I'm decoding this right the FPR (fuel pressure regulator) is hooked to the BOV (Blow off valve)? I believe that the BOV should be hooked to a vacuum source not a fuel source. Unless the FRP is boost referenced. Maybe some one else can chime in on this, but I believe most people hook up the BOV to the intake manifold or brake booster vacuum.
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
Likes: 0
From: Athens OH
If I'm decoding this right the FPR (fuel pressure regulator) is hooked to the BOV (Blow off valve)? I believe that the BOV should be hooked to a vacuum source not a fuel source. Unless the FRP is boost referenced. Maybe some one else can chime in on this, but I believe most people hook up the BOV to the intake manifold or brake booster vacuum.
I guess what I am asking is how the FPR works. If it has a vaccum leak, would it cause the engine to run higher fuelpressure, lower fuel pressure or neither?
Last edited by AMRAAM; Apr 29, 2008 at 07:02 PM.
Melting Slicks
Joined: Jul 2004
Posts: 2,844
Likes: 144
From: Northern Ireland
Its better to use a dedicated vacuum/boost line to each item where possible.
A leak in the BOV signal line, could cause it to open when it shouldnt. Which if the BOV is placed after the MAF, then the MAF will think there is a lot more air going thru the engine, than there actually is. Which could cause it to go rich.
On the other hand, that same leak applied to the FPR signal line, would mean FP wont rise in accordance with boost, so could potentially cause a lean condition...
Fix the leaks.
A leak in the BOV signal line, could cause it to open when it shouldnt. Which if the BOV is placed after the MAF, then the MAF will think there is a lot more air going thru the engine, than there actually is. Which could cause it to go rich.
On the other hand, that same leak applied to the FPR signal line, would mean FP wont rise in accordance with boost, so could potentially cause a lean condition...
Fix the leaks.
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Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
Likes: 0
From: Athens OH
I don't have any way of logging yet, so i don't know.
I think this quote tells me what I need to know. this is how I assumed things worked, but wasn't sure.
If there is a vaccum leak, or the hose isn't connected, it would be the same as having a low vaccum signal so the fuel pressure would be higher, thus running a bit rich.
I should be able to get it hooked up correctly tonight.
What is the best way to do a pressure check? I have a plate that goes into my intake piping for my 3000gt to presusre check, but I'm not sure if it will fit in the C5 piping.
I think this quote tells me what I need to know. this is how I assumed things worked, but wasn't sure.
Inside the FPR is a diaphragm with a valve. At idle when engine vacuum is high, it opens the valve lowering fuel pressure. At higher RPM's when engine vacuum is low, the valve closes increasing fuel pressure.
I should be able to get it hooked up correctly tonight.
What is the best way to do a pressure check? I have a plate that goes into my intake piping for my 3000gt to presusre check, but I'm not sure if it will fit in the C5 piping.
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
I think a boost leak test would be your best bet. you could have your BOV adjusted wrong allowing too much/too little air in...
if you ahve a vac leak you should be sucking in additional air which would give you a lean condition @ idle... nothing to worry about really since there is no load on the motor.
I would check and see what your LTFT & STFT's are before you go crazy.
Also, maybe try disconnecting your battery for a few minutes with the KEY held in the ON position to discharge any capacitors there might be in the ECU. let the car re-learn its fuel trims again.
if you ahve a vac leak you should be sucking in additional air which would give you a lean condition @ idle... nothing to worry about really since there is no load on the motor.
I would check and see what your LTFT & STFT's are before you go crazy.
Also, maybe try disconnecting your battery for a few minutes with the KEY held in the ON position to discharge any capacitors there might be in the ECU. let the car re-learn its fuel trims again.
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
doing a boost leak test would be the same on the 3S as the vette except you only need to hookup a tester to ONE compressor inlet.
I'm going to be doing a how-to in the next couple of weeks because I've gotten so many questions about the process.
I'm going to be doing a how-to in the next couple of weeks because I've gotten so many questions about the process.
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
Likes: 0
From: Athens OH
I think a boost leak test would be your best bet. you could have your BOV adjusted wrong allowing too much/too little air in...
if you ahve a vac leak you should be sucking in additional air which would give you a lean condition @ idle... nothing to worry about really since there is no load on the motor.
I would check and see what your LTFT & STFT's are before you go crazy.
Also, maybe try disconnecting your battery for a few minutes with the KEY held in the ON position to discharge any capacitors there might be in the ECU. let the car re-learn its fuel trims again.
if you ahve a vac leak you should be sucking in additional air which would give you a lean condition @ idle... nothing to worry about really since there is no load on the motor.
I would check and see what your LTFT & STFT's are before you go crazy.
Also, maybe try disconnecting your battery for a few minutes with the KEY held in the ON position to discharge any capacitors there might be in the ECU. let the car re-learn its fuel trims again.
There's a possibility that the BOV may not be set correctly, too.
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
Likes: 0
From: Athens OH
Tried a boost leak test, sort of. I don't have a compressor at my garage, so i used a bike pump. I didn't get the pressure very high at all, but I could get enough that it was coming out of the oil fill. i pulled off the catch can hose and plugged it(even though it has a check valve) and it didn't help. I know that could be an indication of rings, but I don't think that is an issue. Is there anything that I should have disconnected or plugged?
I also ran it for a few minutes. The ful pressure seems to be be around 48 to 51. i have a video of it that I'll post tomorrow sometime.
I also ran it for a few minutes. The ful pressure seems to be be around 48 to 51. i have a video of it that I'll post tomorrow sometime.
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
its difficult to do w/o an air compressor. Back in the day when I didn't have one I used to drive to a close by gas station and use the air hose they had out for tires. 
you shouldn't have to disconnect anything except for the intake pipe on the blower inlet. Everything else should stay in place, same as your 3S. Until you can use an air compressor and build 10-15psi MAX of pressure in the system I wouldn't worry about the air coming out of the breather.
you shouldn't have to disconnect anything except for the intake pipe on the blower inlet. Everything else should stay in place, same as your 3S. Until you can use an air compressor and build 10-15psi MAX of pressure in the system I wouldn't worry about the air coming out of the breather.
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
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From: Athens OH
At the moment, I'm not sure I could get it to a gas station to use their hose. Besides, nowadays it cost $.75 for air
Apparently the gas stations aren't making enough money on the >3.60/gal of gas.
I knew I would need more pressure, but that was all I had at the time and I thought it would give me some idea if there was a major leak somewhere.
I pulled the coupler from the MAF to the throttlebody and put the test plate in the coupler. It actually fit fairly well.
Apparently the gas stations aren't making enough money on the >3.60/gal of gas.I knew I would need more pressure, but that was all I had at the time and I thought it would give me some idea if there was a major leak somewhere.
I pulled the coupler from the MAF to the throttlebody and put the test plate in the coupler. It actually fit fairly well.
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
At the moment, I'm not sure I could get it to a gas station to use their hose. Besides, nowadays it cost $.75 for air Apparently the gas stations aren't making enough money on the >3.60/gal of gas.
I knew I would need more pressure, but that was all I had at the time and I thought it would give me some idea if there was a major leak somewhere.
I pulled the coupler from the MAF to the throttlebody and put the test plate in the coupler. It actually fit fairly well.
Apparently the gas stations aren't making enough money on the >3.60/gal of gas.I knew I would need more pressure, but that was all I had at the time and I thought it would give me some idea if there was a major leak somewhere.
I pulled the coupler from the MAF to the throttlebody and put the test plate in the coupler. It actually fit fairly well.
you don't want to disconnect anything except for the inlet on the blower. that would defeat the whole purpose of doing a leak test in the first place.
Thread Starter
Melting Slicks
Joined: Jan 2007
Posts: 3,333
Likes: 0
From: Athens OH
I don't have everything completely set up yet on the IC and procharger. I was just checking the stuff on the engine after doing heads and cam(vaccum lines, intake..etc)
