SR20 Forum banner

1 - 16 of 16 Posts

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #1 ·
Hello all, I'm new here.

Figured this problem i've been having should be shared to the forums. So recently I upgraded my turbo from the APEXI AX53B70 to the newly designed MMP NS400 Turbo. (.86 exhaust and .63 AR T2 stock replacement turbo pretty much.) After changing the turbo, I obviously went to get it tuned. Found out that the fuel pressures were dropping, causing the AFR to go SUPER lean. Fuel pressure would rise up until 6100 RPM and fall drastically to base pressures (38 psi). We changed to DW200 (255lph) and changed fuel filter to Z32 filter. Problem was still there. Left the tuner, installed a Aeromotive FPR, upgrading from the what looked like Nismo FPR. Problem still existed. We decided to run a separate completely new line, above the car, it's own specific fuel filter to the feed. Although it held a little longer, fuel pressure still dropped almost similar. The new fuel pump was hard wired from the start, then hard wire with relay was done directly to the battery since it's in the back. I've ran out of ideas. If this situation has been on here, I apologize and ask that you direct me to that forum with a link.

Upgrades that have been done since but not taken back for tuning are:
AEM 340lph In tank fuel pump
FiveO 750cc side feed injectors.
PS: Turbo was at 18psi, with the 6000 rpm pull, the car made 366 WHP but for safety precautions further tuning was not done. Please guys help me out! Thank you in advance!
 

·
Registered
Joined
·
1 Posts
Like the fuel pressure goes up with the boost then off boost(under vacuum) it goes back to 38psi? If so it seems like it’s working as it should. If you want the FPR just to be a static let 60psi or whatever for your application then disconnect and vacuum/boost line to it and set it up like that
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #4 ·
It could be a fuel tank vent issue. If it is restricted, the fuel pump will pull a vacum in the tank and limit the fuel flow.
What exactly would cause the tank to have a vent issue? Only reason why I ask cause the issues started after I upgraded turbos.
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #5 ·
Like the fuel pressure goes up with the boost then off boost(under vacuum) it goes back to 38psi? If so it seems like it’s working as it should. If you want the FPR just to be a static let 60psi or whatever for your application then disconnect and vacuum/boost line to it and set it up like that
Goes up with boost and drops while still WOT.
 

·
Registered
Joined
·
13 Posts
I had a similar problem and it was the Power to pumps , to solve it I ran new thicker 12 gauge cable directly from the battery to the pumps through a fused relay . Pumps don’t flow efficiently if they don’t have enough power

Sent from my iPhone using Tapatalk
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #8 ·
Goes up with boost and drops while still WOT.
I had a similar problem and it was the Power to pumps , to solve it I ran new thicker 12 gauge cable directly from the battery to the pumps through a fused relay . Pumps don’t flow efficiently if they don’t have enough power


Sent from my iPhone using Tapatalk
Yeah we were quick to do that with the new pump and still. We thought the pump was faulty. Hence why I bought an aem 340.
 

·
Registered
Joined
·
13 Posts
Yeah we were quick to do that with the new pump and still. We thought the pump was faulty. Hence why I bought an aem 340.
Also I did have the problem another time and it was a blocked fuel filter

Are you running e85? If so you’re injectors are probably too small as it requires 30% more fuel than 98

I run two Bosch 044 pumps and 1000cc injectors

What size lines are you running in and return your return line could be restricting the flow

Sent from my iPhone using Tapatalk
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #10 ·
Also I did have the problem another time and it was a blocked fuel filter

Are you running e85? If so you’re injectors are probably too small as it requires 30% more fuel than 98

I run to Bosch 044 pumps and 1000cc injectors

What size lines are you running in and return your return line could be restricting the flow

Sent from my iPhone using Tapatalk
No, currently running 100 octane, specifically the 260 GT from sunoco.
Before I was on the DW 200 which is 255lph, and what I assumed were 550cc injectors.
Fuel line sizes are oem, oem hardlines under and regular ones to the feed and return.
You think the return line is dirty? I mean the car did sit for two years before being shipped here from Japan.
 

·
Registered
Joined
·
13 Posts
No, currently running 100 octane, specifically the 260 GT from sunoco.
Before I was on the DW 200 which is 255lph, and what I assumed were 550cc injectors.
Fuel line sizes are oem, oem hardlines under and regular ones to the feed and return.
You think the return line is dirty? I mean the car did sit for two years before being shipped here from Japan.
What fuel filter are you running between the pump and the injectors could be blocked due to the old dirty lines.. Quick test would be take a reading of your fuel pressure then remove the filter and take another Reading to see if it is the same if the reading goes up a lot without the filter the filter is blocked


Sent from my iPhone using Tapatalk
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #12 ·
What fuel filter are you running between the pump and the injectors could be blocked due to the old dirty lines.. Quick test would be take a reading of your fuel pressure then remove the filter and take another Reading to see if it is the same if the reading goes up a lot without the filter the filter is blocked


Sent from my iPhone using Tapatalk
Filter got changed out to a brand new Z32 filter. Other than that, we tested a separate line with brand new fuel lines and brand new fuel filter, pressures were a bit steady but still dropped.
 

·
Registered
Joined
·
13 Posts
Filter got changed out to a brand new Z32 filter. Other than that, we tested a separate line with brand new fuel lines and brand new fuel filter, pressures were a bit steady but still dropped.
What size wire did you use to the pump and how exactly is it wired ?

Suggest 12 gauge positive from battery through fused relay to pump . 12 gauge negative to battery or a good earth point

Use a multimeter and check the voltage at the pump while it is running to make sure your getting good voltage close to the same voltage as directly from battery


Sent from my iPhone using Tapatalk
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #14 ·
What size wire did you use to the pump and how exactly is it wired ?

Suggest 12 gauge positive from battery through fused relay to pump . 12 gauge negative to battery or a good earth point

Use a multimeter and check the voltage at the pump while it is running to make sure your getting good voltage close to the same voltage as directly from battery


Sent from my iPhone using Tapatalk
Both are 12 gauge wire through fused relay with a 30amp fuse directly to the battery. So both power and ground are directly on battery.
 

·
Registered
Joined
·
13 Posts
Both are 12 gauge wire through fused relay with a 30amp fuse directly to the battery. So both power and ground are directly on battery.
Is your alternator working properly I would still check the voltage at the pump and battery to compare when motor is running also check and compare at the alternator


Sent from my iPhone using Tapatalk
 

·
Registered
1994 Nissan 180sx
Joined
·
8 Posts
Discussion Starter · #16 ·
Is your alternator working properly I would still check the voltage at the pump and battery to compare when motor is running also check and compare at the alternator


Sent from my iPhone using Tapatalk
I haven't checked alternator, but I will.
 
1 - 16 of 16 Posts
Top