Fuel cut and Fuel Pump relation

[Prodigyman]

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I finally fixed up my car and no more check engine light and it's driving very nice and fast but the problem I get, on cold days in any gear @ WOT @ ~5800 RPM I always hit fuel cut, on worm days it never happens. Since I have 32" FMIC I checked the logger air which gets in my engine is just 2 degrees C higher then outside temp so ECU sees tons of air coming in and not enough fuel. Since I am not ready to get MAFT Gen 2, 190 LP and 550cc yet I heard then rewiring fuel pump with higher gage wires (for less resistance and better FP work) will eliminate fuel cut because all it is, is ECU cutting power to it.

Correct me if I am wrong on this or am I approaching this problem from the wrong angle? Also I tired searching in tech articles full guide with pictures how to re wire it with GEN2 but I couldn't find anything and I remember seeing one like a year ago (on 99 spyder). If anyone still has a link I'd appreciate that.

 

[Quasimondo]

Fuel cut has nothing to do with rewiring your fuel pump. Fuel cut is triggered when the MAS sees too much air, sending an irregular signal that confuses the ECU. The confused ecu doesn't know what to do so it shuts down the injectors.

First thing to do is test your intake for leaks. That's the most common cause behind fuel cut.
How much boost are you running with your new turbo? Do you have an AFC or other tuning device installed?

 

[hairybeanbag]

Check my profile for full mod list

I finally fixed up my car and no more check engine light and its driving very nice and fast but the problem I get, on cold days in any gear @ WOT @ ~5800 RPM I always hit fuel cut, on worm days it never happens. Since I have 32 FMIC I checked the logger air which gets in my engine is just 2 degrees C higher then outside temp so ECU sees tons of air coming in and not enough fuel. Since I am not ready to get MAFT Gen 2, 190 LP and 550cc yet I heard then rewiring fuel pump with higher gage wires (for less resistance and better FP work) will eliminate fuel cut because all it is, is ECU cutting power to it.

Correct me if I am wrong on this or am I approaching this problem from the wrong angle? Also I tired searching in tech articles full guide with pictures how to re wire it with GEN2 but I couldnt find anything and I remember seeing one like a year ago (on 99 spyder). If anyone still has a link Id appreciate that.

Air is more dense on colder days, I had the same problem before ditching all piggybacks for a AEM EMS.

I'm not sure about the FP rewire? but you can get a voltage clamp style Fuel cut defenser for not alot of money, or a EPROM ECU with a chip to remove fuel cut properly.

Let us know if the rewire helps!!

 

[Prodigyman]

Fuel cut has nothing to do with rewiring your fuel pump. Fuel cut is triggered when the MAS sees too much air, sending an irregular signal that confuses the ECU. The confused ECU doesn't know what to do so it shuts down the injectors.

First thing to do is test your intake for leaks. That's the most common cause behind fuel cut.
How much boost are you running with your new turbo? Do you have an AFC or other tuning device installed?

My intake system has no leaks at all. I just tested it 2 month ago. I installed my HID lights so igniter is on the way of intake filter so I had to take out longer Injen intake pipe and put stock one for now but still no leaks. I have no tuning devices yet just bolt ons. I heard stock PSI is 11-12 but at WOT most of the time I run @ solid 14 PSI @ 2800 all the way till redline and it pulls very good though I am 100% sure I don't have manual BC. I have Greddy Profec BII inbox but I think it rather useless ATM.

Air is more dense on colder days, I had the same problem before ditching all piggybacks for a AEM EMS.

I'm not sure about the FP rewire? but you can get a voltage clamp style Fuel cut defenser for not alot of money, or a EPROM ECU with a chip to remove fuel cut properly.

Let us know if the rewire helps!!

Yeah I'll be doing the rewire this weekend with my buddy in his garage while he rewires his 240SX fuel pump at the same time. I really hope it helps and I thought ECU cuts the power to the fuel pump and not the injectors. So if I could rewire pump to ignition wiring I would have constant power to it while the car is on.

 

[hairybeanbag]

Yeah I'll be doing the rewire this weekend with my buddy in his garage while he rewires his 240SX fuel pump at the same time. I really hope it helps and I thought ECU cuts the power to the fuel pump and no the injectors so if I could rewire pump to ignition wiring I would have constant power to it while the car is on.

Save your self the hassle and buy a Fuel Cut defencer for $100 bucks, The ecu cuts the injectors not the pump. If the ecu cut the pump you would still have pressure for a few secounds as the fuel pressure would still run through the rail and injectors into the engine. when the injectors cut it's instant no more fuel, that's why you feel like you hit a wall. Don't burn your car down with some crazy wiring job trying to eliminate your problem.

 

[oldman]

I'm not sure about the FP rewire? but you can get a voltage clamp style Fuel cut defenser for not alot of money, or a eprom ecu with a chip to remove fuel cut properly.

Bad ideas, both are nothing but cover up for other problems. Mondo is right on, this is an air flow issue. Either there are boost leaks, a defective maf sending wrong signals to ECU or you need to turn your boost down. Without realizing the cause, blindly altering air flow signals to the ECU via FCD or removing fuel cut function through an EPROM can be extremely dangerous.

Prodigyman,

1. How do you know for sure you have no leaks? Describe your boost leak test process/results in detail.

2. Is your MAS hacked?

3. What PSI? MBC? Is the MBC tapping off your "VENTED" BOV line?

 

[Prodigyman]

Bad ideas, both are nothing but cover up for other problems. Mondo is right on, this is an air flow issue. Either there are boost leaks, a defective maf sending wrong signals to ECU or you need to turn your boost down. Without realizing the cause, blindly altering air flow signals to the ECU via FCD or removing fuel cut function through an eprom can be extremely dangerous.

Prodigyman,

1. How do you know for sure you have no leaks? Describe your boost leak test process/results in detail.

2. Is your mas hacked?

3. What psi? MBC? Is the mbc tapping off your "VENTED" BOV line?

Yeah I defiantly thought FCD is a BAD idea. I rather save up and get 550ccs and MAFT Gen 2 with 190 FP

1. Just made one myself as per guide on these forums with a compressor and connected it to the turbo (where intake pipe was) and checked for leaks. The thing is my FMIC pipes are custom and ALL welded xept the intake manifold part so there are no leaks there and I thoroughly checked everything else and it was fine.

2. No its not. Fully stock

3. I run @ 14 PSI 2800 to 7000 RPM soild and no MBC or anything to put it higher, and yes i am venting but thats whole other story (Btw BOV is NOT leaking i checked it few times)

 

[oldman]

How much did the boost gauge register during the boost leak test?

 

[Prodigyman]

How much did the boost gauge register during the boost leak test?

I brought it up to 30 PSI and no more, I didn't want to blow my turbo seals

Edit:

If this might help also, I've had this problem for a long time, when I am in driving in gear and WOT it RPM goes up but there is no power at all, its like driving with huge hole in intake pipes, turbo spools up but no power at all then I clutch it or down shift and it takes off. No one really knows what it is but I learned to live with it. My Emission control solenoid (the ones goes to FPR and pipe where i tap my Boost Gage) was dead and I recently replaced it and problems occurs a lot less but still exists.

 

[oldman]

30 psi is a lot, are you sure that is what was showing on the boost gauge in the cockpit (you do have a boost gauge right?) rather than the gauge on the air compressor regulator. Having access to a logger would be very helpful right about now. Also, are you sure you're hitting fuel cut?

 

[Prodigyman]

(you do have a boost gauge right?)

That thing with lights showing PSI reading inside my car?


"Also, are you sure you're hitting fuel cut?"


When my car accelerates @ WOT @ 5800 RPM making a HUGE bang sound out of exhaust and having feeling like I just hit a wall, and pushing me forward a bit ... I think that just about sums up fuel cut...

Reading was on my compressor; my Boost Gage was showing solid 18.


Last few boost leak tests I had air escaping around compressor housing of my turbo though but I was told that was fine.

 

[Quasimondo]

Reading was on my compressor; my Boost Gage was showing solid 18.

Last few boost leak tests I had air escaping around compressor housing of my turbo though but I was told that was fine.

That may be the problem. Air leaking out of the compressor housing is just as bad as any other leak. There's an o-ring that seals the compressor housing to the cartridge. It may have gone bad.

 

[bojanglesracing]

Now if all he has is bolt on and still running stock ECU setting, would that not be a problem. I mean he has opened up the intake for more air, and a big intercooler to cool it better. So if his ECU is still trying to run stock would that not cause a problem.

Someone help me understand maybe I got it all wrong. I though that that was a must when you change things like that.

 

[oldman]

Last few boost leak tests I had air escaping around compressor housing of my turbo though but I was told that was fine.

You seem pretty smart yourself, what do you think?

 

[NewB2dsm]

Why hasnt anyone told him to get an afc or some kind of piggy back to fix the problem?

Also seems like the leak you have is causing the problem since the PSI you are running not a whole lot. Get that fixed and if it still does it your only option is to get a eprom ecu with a chip for no fuel cut, or a piggy back to trick the ecu into thinking less air is going into the motor than actually is.

 

[oldman]

Why hasnt anyone told him to get an afc or some kind of piggy back to fix the problem?

Already covered in post #7.

 

[Prodigyman]

You seem pretty smart yourself, what do you think?

I see your point

I did boost leak test today and my throttle body was leaking a bit. I changed both gaskets and it was gone but there are A LOT of air escaping through turbo housing area. The inside boost gauge shows steady 8 PSI and dropping when I pump 40-60 PSI from the compressor, and today in Toronto was pretty cold so I hit fuel cut dead on 5800 RPM when I make most power @ WOT according to dyno test I did few month ago.

And it still has same struggle problem when I am in any gear sometimes, turbo spools up full boost (14 PSI) car is no go (making sound like if you are in 3,4,5 gear @ 1500 RPM), downshift or clutch it and it goes fine again. I am also going to recalculate my BOV as soon as I get Greedy RS recirculation kit until I can afford MAFT Gen 2 and GM MAF.

Replacing a new turbo is not an option for me nor rebuilding it due to money and getting MAFT Gen 2 and 550cc with 190 FP hopefully would fix this problem. But then it always could be something else.

 

[NewB2dsm]

I did boost leak test today and my throttle body was leaking a bit. I changed both gaskets and it was gone but there are A LOT of air escaping through turbo housing area. The inside boost gauge shows steady 8 PSI and dropping when I pump 40-60 PSI from the compressor, and today in Toronto was pretty cold so I hit fuel cut dead on 5800 RPM when I make most power @ WOT according to dyno test I did few month ago.

Before you spend anymore you need to get that leak fixed! nothing else is going to "fix" your problem because that leak is the problem. Understand?

Already covered in post #7.

Missed that part, last sentance

 

[Prodigyman]

Before you spend anymore you need to get that leak fixed! nothing else is going to "fix" your problem beacuse that leak is the problem. Understand?

Yeah that means I have to take out my turbo and take it apart, which I never done before. I installed everything myself but disassembling a turbo is whole other story


Anyone knows a place/person in GTA (Greater Toronto area) who fix a broken seal on new FPBig T28?