fuel pressure
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From: Howell & Fenton MI
Need your guys opinion on one other thing here... when I was driving the car today the fuel pressure started dropping at low speed, but would jump quick...then drop again...so on so on! The car started bucking and wanting to stall when at a stop. Does this still sound like a fuel pump issue here? Could a bad pump (or weak pump) cause this surging? Or does that sound more like a fuel pressure regulator maybe? It had not done this ever before, but the only difference was that it was hotter outside today...not sure if that matters or not. Give me your thoughts here guys. I could really use them at this point lol! I don't want to keep on buying the wrong parts only to realize that it was something else, and wasting my money in the meantime lol! Right now i'm thinking to buy a new fuel pump, new fuel pressure regulator, and a new sock for the pump
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From: Howell & Fenton MI
Thank you, and yes the bucket was modified a little since it is an actual Walbro pump that I have. That's why i'm looking for a 255 (and hoping it has the same dementions) since it's perfect for my application
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From: Howell & Fenton MI
Okay guys, I went ahead and purchased a new bucket (since mine was hacked up, and could've been part of my surging issue) and a Racetronix pump and hot wire kit from Lonnies Performance. For $400 this better do the damn trick lol!
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From: Howell & Fenton MI
damn! I feel ya man.
I just did my racetronix/hotwire this weekend. I didnt do the trap door I dropped the tank but i read you cant do that.
just an fyi,,,,here is how i ran my relay and ground.
I just did my racetronix/hotwire this weekend. I didnt do the trap door I dropped the tank but i read you cant do that.
just an fyi,,,,here is how i ran my relay and ground.
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From: Howell & Fenton MI
Thanks! That's looks pretty good! Where exactly is that mounted? Drivers side above the rear axle maybe? BTW, regardless of what they say, cutting a access hole from the top was super easy, and makes it easier if you ever need to get back into the tank.
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Verdad Gallardo yeah man...its right above the rear axle drivers side. It where your connections should be also.
and here is where I mounted the other end of the harness after routing it with the fuel lines and behind the heat shields to stay off the headers... so i could wire it to the alternator.
and here is where I mounted the other end of the harness after routing it with the fuel lines and behind the heat shields to stay off the headers... so i could wire it to the alternator.
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From: Howell & Fenton MI
Gotcha! Thanks for the pics! Yeah, I have some homemade hotwire kit on there now in that spot (from the previous owner and looks like crap lol) but this Racetronix one looks so much better.
let us know how it all turns out.
my fuel gauge is mounted to my rail so i dont have the comforts of viewing it while in the car but i rev'ed it almost all the way full throttle at the linkage and about hit the bumpstop and the fuel pressure never dropped below 58psi.
my fuel gauge is mounted to my rail so i dont have the comforts of viewing it while in the car but i rev'ed it almost all the way full throttle at the linkage and about hit the bumpstop and the fuel pressure never dropped below 58psi.
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From: Howell & Fenton MI
Yeah mine is mounted in the a-pillar along with the nitrous gauge. That's good to know that it won't drop below 58 psi. That gives me a reference point. Thanks! I'll keep everyone posted for sure. BTW, how's it all going with your ride? Are you all set and out whippin some *** with the juice yet? 
so did you get everything changed out? when are you scheduled to go to the dyno?
as far as i can tell im good to go. Just gotta change the plugs out and get the bottle filled and then hope i got it all wired right....LOL~~
as far as i can tell im good to go. Just gotta change the plugs out and get the bottle filled and then hope i got it all wired right....LOL~~
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From: Howell & Fenton MI
Awesome! Well I still need to install the Ractronix kit, do the plugs, and schedule a dyno date since I had to cancel my last one due to this damn fuel issue lol 
I'm actually in the process of looking at an entire re-tune from a very reputable LS tuner in the area right now, but he has not got back with me yet
I'm actually in the process of looking at an entire re-tune from a very reputable LS tuner in the area right now, but he has not got back with me yet Thread Starter
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From: Howell & Fenton MI
Update: Installed the Racetronix fuel pump assembly (pump with new hat and full assembly) and am currently using the old hotwire kit that was on the car, but bought one from Racetronix just in case. Okay here is the deal...My electrical Autometer fuel pressure gauge used to read 50 psi at idle and light throttle, but would read close to 30 psi at WOT at redline. So during that time I went and rented a good manual fuel pressure gauge from Autozone, and it said I had 58 psi at idle, and about 38 psi at WOT. So basically may gauge appeared to be off but I still had the same 20 psi drop with either gauge. So now with the new fuel pump and hat assembly (but still the old hotwire kit) my gauge now reads 58 psi instead of 50 psi at idle but will still drop to about 50 psi at WOT. I haven't checked it with the Autozone gauge, but have to wonder if my Autometer gauge now reads correctly since I have a whole new pump and assembly in the tank. So my question is, do you think a 8 psi drop under WOT is acceptable, AND will it likely stay the same on a 100 shot? Is the regulator kicking in or something to prevent any loss below 50 psi? What do you all think? Thanks
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From: Howell & Fenton MI
I just hooked up the manual gauge to the fuel rail, and got 64 psi at idle. So I guess that means i'm at 56-58 psi at WOT at redline. Now the question becomes what will it be on the 100 shot lol! I talked to Lonnies Performance and he said anything lower than a "true" 50 psi reading on the 100 shot would not be advisable. So I guess it will boil down to weather or not the 100 shot will bring me down more than another 8 psi or not. I also need to do a voltage test again to see if i'm getting any voltage drop this time as well. With the old pump and assembly I got a solid 13.5-13.7 across the board, so if it drops with the new pump and assembly it will be time to wire up the Racetronix hot wire kit and see if that fixes it. If I get no voltage drop running this old hotwire kit then i'm not sure why I would still see a 6-8 psi drop anyways
You should not see any pressure drop if your pump is doing its job. Period.
I have an electric autometer fuel pressure gauge as well and it reads about 8-10psi lower than an analog gauge I have on the same tee off my fuel pressure regulator. I trust the analog gauge more.
I have an electric autometer fuel pressure gauge as well and it reads about 8-10psi lower than an analog gauge I have on the same tee off my fuel pressure regulator. I trust the analog gauge more.
The might be typical of a stock setup, but all that means is the fuel pump is too small for the injectors. In a properly set up and sized fuel system, the pressure should never decrease under load. Only the rail pressure will decrease is if there is a boost reference regulator and the engine is under vacuum, and then the injector still sees the same pressure difference because of the regulator.
With that said, 5psi is probably manageable, but there shouldnt be any if you can help it. When the pressure decreases it lowers the injector flow rate.
To go back to a question early in the thread about having it tuned now with the pressure drop issue and then upgrading/fixing the pumps later asking if that will be fine. The answer is no. Assuming he tunes for fueling and your injectors are large enough, when you fix the fuel pump problem you will have a very rich condition.
With that said, 5psi is probably manageable, but there shouldnt be any if you can help it. When the pressure decreases it lowers the injector flow rate.
To go back to a question early in the thread about having it tuned now with the pressure drop issue and then upgrading/fixing the pumps later asking if that will be fine. The answer is no. Assuming he tunes for fueling and your injectors are large enough, when you fix the fuel pump problem you will have a very rich condition.