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Car struggles to make fuel pressure

If your basket holds pressure, than it can only be a couple things causing pressure to drop: 1: filter clogged 2: fuel pump output too low (out of steam, defective)

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Old 04-07-2016, 03:03 PM   #61 (permalink)
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If your basket holds pressure, than it can only be a couple things causing pressure to drop:

1: filter clogged
2: fuel pump output too low (out of steam, defective) or wiring for it is not keeping up.
3: regulator bad
4: out-running the feed plumbing on the car, pressure dropping at high demand

I always ran a static pressure of 52-53psi in my car, no vacuum/boost reference.
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Old 04-07-2016, 03:25 PM   #62 (permalink)
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Quote:
Originally Posted by phunk View Post
If your basket holds pressure, than it can only be a couple things causing pressure to drop:

1: filter clogged
2: fuel pump output too low (out of steam, defective) or wiring for it is not keeping up.
3: regulator bad
4: out-running the feed plumbing on the car, pressure dropping at high demand

I always ran a static pressure of 52-53psi in my car, no vacuum/boost reference.
1. Filter could be clogged, but this would not explain why drop only occurs after repeated pulls.

2. Wiring does make sense, maybe repeated pulls heatsoak the wiring and as such the current and heat spiral out of of control (more heat, causes more current, which in turn causes more heat).

3. Doesn't explain why at the start of the pulls its perfect, 0 issues. Unless it is sensitive to engine bay heat, but I called automotive and they said they chances of it being the regulator are slim to none.

4. Also doesnt explain why its perfect when the pulls are starting. Ill get 2-5 pulls then she will start to really suffer.


My wife was looking through some R35 forums and one guy had a weak battery cause these issues, well mine is still the stock battery, so I think I will change that out as well as put more effort into tracing and diagnosing the wiring. Maybe I should go back to a static pressure in efforts of relieving the stress on the fuel pump wiring.
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Old 04-07-2016, 03:54 PM   #63 (permalink)
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Call me, its my fuel issues ALL over again
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Old 04-07-2016, 03:58 PM   #64 (permalink)
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Call me, its my fuel issues ALL over again
PM me your number I didnt save it anywhere.

Thanks Lloyd.
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Old 04-07-2016, 04:42 PM   #65 (permalink)
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Call me, its my fuel issues ALL over again
What was the fix?
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Old 04-07-2016, 04:45 PM   #66 (permalink)
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BTW, you are still running the factory EVAP system right? If you are getting a vacuum in the tank, that can cause a big fuel pressure problem once the car has been running for a little while and builds up a big vacuum in the tank.
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Old 04-07-2016, 05:16 PM   #67 (permalink)
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BTW, you are still running the factory EVAP system right? If you are getting a vacuum in the tank, that can cause a big fuel pressure problem once the car has been running for a little while and builds up a big vacuum in the tank.
I thought about that last night, so I shut everything off and listened for a suction when I opened the tank and there was none. I could try doing a few pulls with the lid off to see what happens tho, ill add that to the list of things to try.
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Old 04-07-2016, 10:04 PM   #68 (permalink)
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My car is doing something similar but when it seat overnight. When i turn the car cold it struggles for 4-5 seconds on the 1st try. Ones the car heat up no matter how many times i start the car during the day it fires right up. I upgraded the walbro 255 to a aeromotive 340 and 1000cc injectors. Before that i never had any problem before the upgrades.
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Old 04-08-2016, 11:34 PM   #69 (permalink)
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I took off the boost ref line today, set my regulator to 55psi and its been working perfect. I think the added pressure was causing to much of a current draw and heating up my wiring. Ill know for sure when I finalize the tuning tomorrow hopefully. But even down to a 1/4 tank she would only drop to about 52psi under wot.


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My car is doing something similar but when it seat overnight. When i turn the car cold it struggles for 4-5 seconds on the 1st try. Ones the car heat up no matter how many times i start the car during the day it fires right up. I upgraded the walbro 255 to a aeromotive 340 and 1000cc injectors. Before that i never had any problem before the upgrades.
I think you might have one of the issues I was having. Do you have a way to watch fuel pressure? If you do, turn the key on let the system pressure up then kill the fuel pump and watch the pressure, it should slowly bleed. If it dumps all at once then you know you have a internal leak inside the basket. That said if you have a return type system a good practice is to turn the key on, wait 2-3 seconds for the pump to build up pressure then crank. If you go straight to cranking you have to wait for the pump to work up the pressure. Alternatively it could be tuning, in ECUtek there is fuel tables for cranking that may have to be adjusted. That said if your tuner dialed in the injectors correctly they they shouldnt have to touch them, I didnt but I am only at 750s.
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Old 04-09-2016, 12:29 AM   #70 (permalink)
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Originally Posted by Mitco39 View Post
I took off the boost ref line today, set my regulator to 55psi and its been working perfect. I think the added pressure was causing to much of a current draw and heating up my wiring. Ill know for sure when I finalize the tuning tomorrow hopefully. But even down to a 1/4 tank she would only drop to about 52psi under wot.




I think you might have one of the issues I was having. Do you have a way to watch fuel pressure? If you do, turn the key on let the system pressure up then kill the fuel pump and watch the pressure, it should slowly bleed. If it dumps all at once then you know you have a internal leak inside the basket. That said if you have a return type system a good practice is to turn the key on, wait 2-3 seconds for the pump to build up pressure then crank. If you go straight to cranking you have to wait for the pump to work up the pressure. Alternatively it could be tuning, in ECUtek there is fuel tables for cranking that may have to be adjusted. That said if your tuner dialed in the injectors correctly they they shouldnt have to touch them, I didnt but I am only at 750s.

Thanks for the tip man. I do have CJM Return Fuel System. When i got the car back from the upgrades and tune the car work perfectly for 3 days after that it started acting up when cold and it was really bad. The car struggle after trying to crank 7-8 times then it would fire up. My tuner adjusted the fuel tables but still it does it but now is just after the 1st cranking that the car has difficulty to start. Plus now the damn car is throwing p2101 which is the throttle body on the passenger side which is just great I'll be taking the car back to the shop to have it look at and do what you said. Thanks
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Old 04-09-2016, 01:13 PM   #71 (permalink)
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What was the fix?
The black gunk plugging the pre filter is the fuel hose breaking down. For some reason if the clamps are tightened too tight and the hose is cut, it decomposes.
Once I replaced the fuel hose, the black gunk never appeared again.
GTM kit btw.

Once that happens the black gunk plugs the basket fill orifice's and it wont run right again. Fuel pressure goes low at high fuel demand. That is as far as I got. Returned the car to stock and replaced the fuel pump with a stock one.

That's my educated guess based on my experience.
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Old 04-09-2016, 11:58 PM   #72 (permalink)
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Originally Posted by Zat_Zuma View Post
The black gunk plugging the pre filter is the fuel hose breaking down. For some reason if the clamps are tightened too tight and the hose is cut, it decomposes.
Once I replaced the fuel hose, the black gunk never appeared again.
GTM kit btw.

Once that happens the black gunk plugs the basket fill orifice's and it wont run right again. Fuel pressure goes low at high fuel demand. That is as far as I got. Returned the car to stock and replaced the fuel pump with a stock one.

That's my educated guess based on my experience.
That could all make sense. What fuel hose did you replace? All the hose in the tank is the hard plastic type. Everytime I do pull apart that basket there is that gunk in the bottom, I assumed it was a result of the orings.

Also I ran into a low pressure condition again, just when I think its all good I get a nice shot of 30psi during a wot pull, its downright dangerous, thank god for ecuteks good knock strategy protection.
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Old 04-10-2016, 11:05 AM   #73 (permalink)
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Hoses from the fuel pump that came with the hose clamps
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Old 04-10-2016, 12:40 PM   #74 (permalink)
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Hoses from the fuel pump that came with the hose clamps
The two short pieces that make up the U that feeds the intank filter?
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Old 04-10-2016, 02:01 PM   #75 (permalink)
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Yup replaced them and viola ..... no more black gunk chunks
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