Intermittent Fuel Pressure, HELP
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Intermittent Fuel Pressure, HELP
TLDR:
Trying to track down why sometimes I am losing fuel pressure and it seems random. I have plenty of fuel to handle well above 200whp, but only pushing 140whp at best. Logs show pulling to 6k+ fine then later fuel pressure dropping doing a similar pull just 20 mins later after cruising.
Specs:
Car 1988 Mazda 323GTX
Engine: 1.6L
Turbo: Stock vj14(smaller then S13 T25)
Injector: KAInjection Gt500 injectors 630cc
Fuel Pump: New DW300
Adjustable Regulator, set to 45psi base pressure
DIYPNP with low dollar sensor
Fuel pump has a rewired, with a 30 amp relay, and a direct line with a 20 amp fuse.
So I have been trying to track down an issue with my "Miata". Start back in Oct after my first track day when once the car was hot, it would start misfiring on the track. After cooling down I was able to push it again before it started bucking again.
I then replaced the stock regulator with an SXracing Regulator(old stock from my old turbo Miata) to allow the use of a LowDollarMotorSports Fuel Pressure sensor. Where I was able to log the misfire and spotted my fuel pressure dropping. I have since replaced my old Walbro 255 with a new DW300 and replaced the fuel filter. The car drives great and pulls nice and strong, but once it starts losing pressure, it seems to be repeatable.
These current log files are with a fuel tank so no issues with low fuel levels.
low-pressure log has a pull around record ~1300 with no issues, and ~12000 is where the fuel pressure drops.
AfterCrusie is just me driving the car back afterward.
Small Sample Run is post-LowPressure where I did a few small pulls on the highway.
PLEASE HELP. Have another track day on May 15th.
Trying to track down why sometimes I am losing fuel pressure and it seems random. I have plenty of fuel to handle well above 200whp, but only pushing 140whp at best. Logs show pulling to 6k+ fine then later fuel pressure dropping doing a similar pull just 20 mins later after cruising.
Specs:
Car 1988 Mazda 323GTX
Engine: 1.6L
Turbo: Stock vj14(smaller then S13 T25)
Injector: KAInjection Gt500 injectors 630cc
Fuel Pump: New DW300
Adjustable Regulator, set to 45psi base pressure
DIYPNP with low dollar sensor
Fuel pump has a rewired, with a 30 amp relay, and a direct line with a 20 amp fuse.
So I have been trying to track down an issue with my "Miata". Start back in Oct after my first track day when once the car was hot, it would start misfiring on the track. After cooling down I was able to push it again before it started bucking again.
I then replaced the stock regulator with an SXracing Regulator(old stock from my old turbo Miata) to allow the use of a LowDollarMotorSports Fuel Pressure sensor. Where I was able to log the misfire and spotted my fuel pressure dropping. I have since replaced my old Walbro 255 with a new DW300 and replaced the fuel filter. The car drives great and pulls nice and strong, but once it starts losing pressure, it seems to be repeatable.
These current log files are with a fuel tank so no issues with low fuel levels.
low-pressure log has a pull around record ~1300 with no issues, and ~12000 is where the fuel pressure drops.
AfterCrusie is just me driving the car back afterward.
Small Sample Run is post-LowPressure where I did a few small pulls on the highway.
PLEASE HELP. Have another track day on May 15th.
Last edited by wildfire0310; 05-03-2022 at 04:05 AM.
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#5
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I did drain the tank recently and removed some rusty-sand like crap from the tank. Replace the fuel filter since the cleaning and the pump screen has been clean the last few times I have looked at it.
That logs are post cleaning. :(
That logs are post cleaning. :(
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Will try and see if I can get some clear roads to do some hard pulls while "cold", to get more data.
Btw thank you, everyone.
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So did some testing last night, and while it looks like my Alternator needs to be replaced, the voltage at the fuel pump didn't change during hiccups.
Also, I was able to get the issue to happen about 5ish mins after a cold start. I did notice what may be some correlation, when the issue happens it seems to be at the highest boost level(aka overboosting) I need to look at the logs and see if my theory is right. Cause last night it seem to happen when it was hitting 15psi but the next pull at 10psi no loss in pressure. So I am wondering if my AFR is losing references or if the pump is somehow getting in way of the pump.
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As for FPR, this issue happens on the stock FPR and Adjustable aftermarket one.
I am thinking of running a test tonight of kicking the pump on with the car not running and then using my air compressor to run "boost" into the FPR and walk the fuel pressure up.
#12
So I've been having a similar issue that I believe I have solved. I had a DW200 pump and installed it with a new fuel sock. Pretty much every event after about a lap it would start starving on fuel after any prolonged boost. What I finally figured out it wasn't how much boost, but how long. I switched the FPR, rewired, wired direct to the battery, fuel filter, all the hard lines, cleaned the injectors, and swapped to a DW300 pump. Same frigging issue. Finally on a whim I swapped to the fuel sock (to a denso sock) that came with the dw300 pump. All of the sudden only on tight left hand corners it starved. Everywhere else it was good. So I replaced the sock with a new OEM sock and issue disappeared. What it appears is the sock did not flow enough and was very restrictive. At low boost it flowed enough that it would run, but under any prolonged boost it would empty the sock and start the pump cavitating. Just something simple to try.
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So I've been having a similar issue that I believe I have solved. I had a DW200 pump and installed it with a new fuel sock. Pretty much every event after about a lap it would start starving on fuel after any prolonged boost. What I finally figured out it wasn't how much boost, but how long. I switched the FPR, rewired, wired direct to the battery, fuel filter, all the hard lines, cleaned the injectors, and swapped to a DW300 pump. Same frigging issue. Finally on a whim I swapped to the fuel sock (to a denso sock) that came with the dw300 pump. All of the sudden only on tight left hand corners it starved. Everywhere else it was good. So I replaced the sock with a new OEM sock and issue disappeared. What it appears is the sock did not flow enough and was very restrictive. At low boost it flowed enough that it would run, but under any prolonged boost it would empty the sock and start the pump cavitating. Just something simple to try.
I do think I may have resolved it. My current test drive didn't have that issue, but I made three changes and am not sure which one solved it but I think it was the first of my 3.
1) I raised the pump up in the tank, as the Miata-based filter was touching the bottom of the tank, in the gtx. Google said that too close to the floor could restrict flow(guessing suction to the tank floor, or dirt)
2) Swapped out to a Lotus filter which points it in a better direction in the tank and is flat.
3) I replaced the in-tank hose, the one on there seemed good but maybe(had a new one with my lotus install kit). I also replaced the clamps with higher-end ones that are used for air compressors and should hold at a high PSI. Granted 60 psi isn't that high but was under the hood.
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