fuel pressure problems????

Krimzen · 01-22-2007, 10:21 AM

I got an mk1 4agze and I put an aftermarket Fuel pressure regulator (FPR) on it. My pressure is reading 75 psi, I know that stock is supposed to be something like 36 to 38 psi. I have a venom pump and injectors installed giving it an advertized ten percent boost in psi from stock. I also have no water in the system yet. The other odd thing is that I do not have an O2 sensor wire on the harness. I believe I have the JDM setup throughout the long block, including the wiring harness. Now if I am reading 75 psi and the car still idles (roughly), Is this wrong????

thank you.

Jerry.

Enthalpy · 01-22-2007, 10:40 AM

75 psi is WAY TOO MUCH for the majority of injectors. You can't reliably open the injector at all, especially at low pulsewidths.

Bumping from 38 to 75 gives you a 40% increase in fuel delivery. So, assuming your injectors can open against such a crippling fuel pressure, then you are WAY over-fueling your engine, and it's likely rich misfiring.

Drop the fuel pressure down below at least 60. I never run over 50 psi myself.

Why do you think you need so much fuel?

Krimzen · 01-22-2007, 07:12 PM

For some reason the adjuster is not effecting the psi pressure. It was at seventy five psi when I installed the FPR as a default. Its a dial gauge mounted in my engine, perhaps I am not getting a good reading but it its lowest wobble I am hitting 60 psi. The Venom injectors and fuel pump advertised only a ten percent increase. I guess I will keep on messing with it until it will drop. I actually still idle, somewhat but it does that reverberating with the throttle. Kind of like when the coolant has air bubbles in it.

I appreciate your advise.

Jerry

Krimzen · 01-22-2007, 09:32 PM

I just unscrewed the vacuum port all the way on the after market FPR and I am now reading fifty psi. So basically, I have to be adjusted all the way out for me to start being within the range. What do you think my fuel pressure should be running 264, 8.1 lift cams, underdrive pulley, aluminum flywheel? Will fifty PSI make the car run too rich? I allready noticed a huge difference when it dropped to fifty. It Idled way smoother!

PETC · 01-22-2007, 09:48 PM

If you're motor is stock aside from the fuel modifications you can probably pump the FP down closer to stock levels and it'll run even better!

Enthalpy · 01-22-2007, 11:59 PM

If you can't adjust pressure down to minimum regulator spec, then you have something choking the flow in the return system or in the regulator itself. This could become a huge problem as the injector put more fuel in the engine and relieve the restriction. As this happens, your fuel pressure will plummet and you will be underfueled.

If you intend to run like this, don't do any open throttle testing without monitoring fuel pressure!

Krimzen · 01-23-2007, 07:42 AM

thanks for all the help, I managed to get it down to 50psi at about 1800 rpm, idling cold. I have yet to warm the car up and put water in it. I sounds so much better than when I had it at 75. I think my regulator is ranged to hight. The regulator advertises immediate fuel pressure increase. My engine itself is not modified with the exception of the block being rebored and rebuilt. I have 264, 8.1 cams, hks valve springs, and adj. cams. I have a gigantic header on it, and I am running a super coil and premium plugs. So far I think fifty might work unless you think that is still too high. What are you running in yours???? I might end up having to go back to a stock FPR, or buy another one that is more adjustable on a lower range.

thanks alot guys.

Enthalpy · 01-23-2007, 10:58 AM

Oh, I see. The minimum adjustment on the regulator is still above stock.

This will deliver more fuel. However, you don't have any way to control the extra fueling. This rich operation will sludge up your oil faster and crap on your mileage.

If your engine won't behave with stock everything combined with those cams, then it might be time to think about something different electronically.

Krimzen · 01-23-2007, 03:44 PM

I was hoping that I wouldnt have to go that route. Is it wishful thinking that the stock ecu would be enough???? At this point it might have been better to remain with the stock pump and injectors. Even still, with the injectors and pump being at a 10 percent increase, shouldnt I be pushing only say 40 psi. I guess its the regulator then. The company I bought it from (auto square), said it was a 1 to 1 ratio regulator. My question is, will it damage me to run it at fifty PSI? Also, what options do I have for the electronics?Standalone is worth a pretty penny.

Krimzen · 01-23-2007, 03:46 PM

Also, Enthalpy. What do you mean exacty by controlling the extra fuel? I am a little unfamiliar with ECU setup and the process.

I appreciate it..

Jerry

Enthalpy · 01-23-2007, 05:19 PM

If you are using the stock supercharger at stock boost, then there's probably no need to update your fuel system unless you are running the highest flow intake and exhaust manifolds in the world and you use cams.

If you really want to put in a fueling system with bigger injectors or a higher base pressure, then the stock ECU will have difficulty controlling that and delivering stock-like drivability and performance.

Without an oxygen sensor, your ECU probably won't be happy. You need to fix this issue.

So:
-Fix the O2 sensor wiring.
-If you have the stock super @ stock boost, put the stock fuel system back in, regulator and all.

Krimzen · 01-23-2007, 06:30 PM

Hey, I appreciate it. I bought the boost junky kit from a shop in NC, its the same size as the cusco pulley. I did a ecu diagnostic test and it read a code 5, which translates to the AC circuit, and the idle valve, and the TPS. I removed my AC all together, I have the wires dangling. Do I need to by some kind of cap to plug into the AC plug? I will double check for the O2 sensor as well, that could be my whole problem.

One more question. How many turns from the bottom should the air flow meter adjuster screw be? Mine is three turns from the bottom.

Thanks alot.

Jerry.

Enthalpy · 01-23-2007, 07:46 PM

I'm not intimately familiar with the 4A-GZE ECU. If you have issues with your idle air valve and TPS, that has the potential to cause big drivability issues.

You should fix these issues before going about modifying the engine in any way for more power. Before asking the engine for more power, it needs to be in very good running condition or you are asking for problems!

AFM adjuster screws are usually factory set and shouldn't be messed with. I'm not actually sure what to set it to, but if you want, you can find a buddy with an identical car and see how far his is set.

When it does come time to bump the boost, you need to have the stock fueling in place and do dyno tests to see if you are running lean. If so, the most ghetto way I can think of to correct it would be bump the fuel pressure.

I'm just being honest here.

01-22-2007, 10:21 AM	#1 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	fuel pressure problems???? I got an mk1 4agze and I put an aftermarket Fuel pressure regulator (FPR) on it. My pressure is reading 75 psi, I know that stock is supposed to be something like 36 to 38 psi. I have a venom pump and injectors installed giving it an advertized ten percent boost in psi from stock. I also have no water in the system yet. The other odd thing is that I do not have an O2 sensor wire on the harness. I believe I have the JDM setup throughout the long block, including the wiring harness. Now if I am reading 75 psi and the car still idles (roughly), Is this wrong???? thank you. Jerry.

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01-22-2007, 10:40 AM	#2 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	75 psi is WAY TOO MUCH for the majority of injectors. You can't reliably open the injector at all, especially at low pulsewidths. Bumping from 38 to 75 gives you a 40% increase in fuel delivery. So, assuming your injectors can open against such a crippling fuel pressure, then you are WAY over-fueling your engine, and it's likely rich misfiring. Drop the fuel pressure down below at least 60. I never run over 50 psi myself. Why do you think you need so much fuel?

01-22-2007, 07:12 PM	#3 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	For some reason the adjuster is not effecting the psi pressure. It was at seventy five psi when I installed the FPR as a default. Its a dial gauge mounted in my engine, perhaps I am not getting a good reading but it its lowest wobble I am hitting 60 psi. The Venom injectors and fuel pump advertised only a ten percent increase. I guess I will keep on messing with it until it will drop. I actually still idle, somewhat but it does that reverberating with the throttle. Kind of like when the coolant has air bubbles in it. I appreciate your advise. Jerry

01-22-2007, 09:32 PM	#4 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	I just unscrewed the vacuum port all the way on the after market FPR and I am now reading fifty psi. So basically, I have to be adjusted all the way out for me to start being within the range. What do you think my fuel pressure should be running 264, 8.1 lift cams, underdrive pulley, aluminum flywheel? Will fifty PSI make the car run too rich? I allready noticed a huge difference when it dropped to fifty. It Idled way smoother!

01-22-2007, 09:48 PM	#5 (permalink)
PETC √(176400) Join Date: Nov 2005 Location: Bellingham, WA Posts: 2,690 Thanks: 43 Thanked 65 Times in 53 Posts My Google Map iTrader Rating: (4/100% )	If you're motor is stock aside from the fuel modifications you can probably pump the FP down closer to stock levels and it'll run even better!

01-22-2007, 11:59 PM	#6 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	If you can't adjust pressure down to minimum regulator spec, then you have something choking the flow in the return system or in the regulator itself. This could become a huge problem as the injector put more fuel in the engine and relieve the restriction. As this happens, your fuel pressure will plummet and you will be underfueled. If you intend to run like this, don't do any open throttle testing without monitoring fuel pressure!

01-23-2007, 07:42 AM	#7 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	thanks for all the help, I managed to get it down to 50psi at about 1800 rpm, idling cold. I have yet to warm the car up and put water in it. I sounds so much better than when I had it at 75. I think my regulator is ranged to hight. The regulator advertises immediate fuel pressure increase. My engine itself is not modified with the exception of the block being rebored and rebuilt. I have 264, 8.1 cams, hks valve springs, and adj. cams. I have a gigantic header on it, and I am running a super coil and premium plugs. So far I think fifty might work unless you think that is still too high. What are you running in yours???? I might end up having to go back to a stock FPR, or buy another one that is more adjustable on a lower range. thanks alot guys.

01-23-2007, 10:58 AM	#8 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	Oh, I see. The minimum adjustment on the regulator is still above stock. This will deliver more fuel. However, you don't have any way to control the extra fueling. This rich operation will sludge up your oil faster and crap on your mileage. If your engine won't behave with stock everything combined with those cams, then it might be time to think about something different electronically.

01-23-2007, 03:44 PM	#9 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	I was hoping that I wouldnt have to go that route. Is it wishful thinking that the stock ecu would be enough???? At this point it might have been better to remain with the stock pump and injectors. Even still, with the injectors and pump being at a 10 percent increase, shouldnt I be pushing only say 40 psi. I guess its the regulator then. The company I bought it from (auto square), said it was a 1 to 1 ratio regulator. My question is, will it damage me to run it at fifty PSI? Also, what options do I have for the electronics?Standalone is worth a pretty penny.

01-23-2007, 03:46 PM	#10 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Also, Enthalpy. What do you mean exacty by controlling the extra fuel? I am a little unfamiliar with ECU setup and the process. I appreciate it.. Jerry

01-23-2007, 05:19 PM	#11 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	If you are using the stock supercharger at stock boost, then there's probably no need to update your fuel system unless you are running the highest flow intake and exhaust manifolds in the world and you use cams. If you really want to put in a fueling system with bigger injectors or a higher base pressure, then the stock ECU will have difficulty controlling that and delivering stock-like drivability and performance. Without an oxygen sensor, your ECU probably won't be happy. You need to fix this issue. So: -Fix the O2 sensor wiring. -If you have the stock super @ stock boost, put the stock fuel system back in, regulator and all.

01-23-2007, 06:30 PM	#12 (permalink)
Krimzen No Skills Join Date: May 2005 Location: Marietta, GA Posts: 65 Thanks: 8 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Hey, I appreciate it. I bought the boost junky kit from a shop in NC, its the same size as the cusco pulley. I did a ecu diagnostic test and it read a code 5, which translates to the AC circuit, and the idle valve, and the TPS. I removed my AC all together, I have the wires dangling. Do I need to by some kind of cap to plug into the AC plug? I will double check for the O2 sensor as well, that could be my whole problem. One more question. How many turns from the bottom should the air flow meter adjuster screw be? Mine is three turns from the bottom. Thanks alot. Jerry.

01-23-2007, 07:46 PM	#13 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	I'm not intimately familiar with the 4A-GZE ECU. If you have issues with your idle air valve and TPS, that has the potential to cause big drivability issues. You should fix these issues before going about modifying the engine in any way for more power. Before asking the engine for more power, it needs to be in very good running condition or you are asking for problems! AFM adjuster screws are usually factory set and shouldn't be messed with. I'm not actually sure what to set it to, but if you want, you can find a buddy with an identical car and see how far his is set. When it does come time to bump the boost, you need to have the stock fueling in place and do dyno tests to see if you are running lean. If so, the most ghetto way I can think of to correct it would be bump the fuel pressure. I'm just being honest here.