What is up with my fuel system?
08-26-2012, 05:05 PM
#1
What is up with my fuel system? So suspected the stock pump was dieing a year or so ago and it progressively got worse and worse, and harder and harder to start the car.
About a month or so ago I got a racetronix hotwire kit, installed per instructions and like others have on here and seemed to get worse. Ran a scan and the car suddenly went lean on the top side, usually commanding and holding a 12.8 afr to running a 14.0 afr higher the revs went. Chalked this up to the pump most likely being on it's last leg and ordered a Walbro 255.
Installed the pump with the hotwire kit and car ran 100%. INJ duty dropped from 82% down to 68%. Threw the car on the dyno and power went from 435 to 457 and called it good, did some little tweaks with the tune just to correct for the over fueling with a good pump and ran like a top.
About a week later driving the car jumped on the throttle and it felt flat, lots of noise but no sink you in your seat feeling. Hooked up the WB and scanner and sure enough, just like before car was leaning out on the top end. Thought maybe the ground on the racetronix kit was bad and just disconnected it today to see if there was any difference and made none.
So now it leaves me totally stumped. Almost leaning towards the Walbro 255 is bad that I got from Sho-me-speed but with it barely being three weeks old I really doubt this is it.
Car hasn't been ran below 1/4 tank with the new pump, changed gas stations, changed fuel filters, updated my SD tune (now using 105% INJ duty just to barely hold a 13.5 afr WOT). Injectors should be plenty big enough for the car, running some 3.8 SC injectors on the car, so doubt I am having issues there.
Before I go and pull the tank for the 5th time or whatever it is now, just checking to see if there is anything obvious I should check out top side. Unfortunately I don't have a fuel pressure gauge but with it still firing up with a single crank mid pump prime I doubt that I'm loosing pressure, but without a gauge can't rule it out 100%.
Dad did suggest that the FPR could be bad, but thought at one point I read that failures of those are few and far between. Anyone have any quick easy checks before I go through this again?
So tempted to cut a quick access hole for the tank, but know my wife will flip when she sees me cutting up the inside of her car. 
About a month or so ago I got a racetronix hotwire kit, installed per instructions and like others have on here and seemed to get worse. Ran a scan and the car suddenly went lean on the top side, usually commanding and holding a 12.8 afr to running a 14.0 afr higher the revs went. Chalked this up to the pump most likely being on it's last leg and ordered a Walbro 255.
Installed the pump with the hotwire kit and car ran 100%. INJ duty dropped from 82% down to 68%. Threw the car on the dyno and power went from 435 to 457 and called it good, did some little tweaks with the tune just to correct for the over fueling with a good pump and ran like a top.
About a week later driving the car jumped on the throttle and it felt flat, lots of noise but no sink you in your seat feeling. Hooked up the WB and scanner and sure enough, just like before car was leaning out on the top end. Thought maybe the ground on the racetronix kit was bad and just disconnected it today to see if there was any difference and made none.
So now it leaves me totally stumped. Almost leaning towards the Walbro 255 is bad that I got from Sho-me-speed but with it barely being three weeks old I really doubt this is it.
Car hasn't been ran below 1/4 tank with the new pump, changed gas stations, changed fuel filters, updated my SD tune (now using 105% INJ duty just to barely hold a 13.5 afr WOT). Injectors should be plenty big enough for the car, running some 3.8 SC injectors on the car, so doubt I am having issues there.
Before I go and pull the tank for the 5th time or whatever it is now, just checking to see if there is anything obvious I should check out top side. Unfortunately I don't have a fuel pressure gauge but with it still firing up with a single crank mid pump prime I doubt that I'm loosing pressure, but without a gauge can't rule it out 100%.
Dad did suggest that the FPR could be bad, but thought at one point I read that failures of those are few and far between. Anyone have any quick easy checks before I go through this again?
So tempted to cut a quick access hole for the tank, but know my wife will flip when she sees me cutting up the inside of her car. 
08-27-2012, 08:36 AM
#2
" Unfortunately I don't have a fuel pressure gauge but with it still firing up with a single crank mid pump prime I doubt that I'm loosing pressure, but without a gauge can't rule it out 100%."
With low psi, it'll still start....
Guessing is worthless. Buy a fuel psi gauge.
With low psi, it'll still start....
Guessing is worthless. Buy a fuel psi gauge.
08-27-2012, 11:11 AM
#3
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buy fuel pressure gauge as suggested, and hook it up to the point on the rails, watch it during priming and see if it holds, then drive the car around and go WOT and see if pressure holds
what car is this on? is it a returned or return-less system? does it have a pressure regulator on it? that could be bad.... but you need a gauge...
what car is this on? is it a returned or return-less system? does it have a pressure regulator on it? that could be bad.... but you need a gauge...
08-27-2012, 03:21 PM
#6
Well on a gut instinct decided to pull the tank just to see if my fuel line came off on the feed and was barely feeding, and I was part right. Around the clamp the hose has blown apart. Looking inside the hose has swelled also and it was beginning to tear apart at the clamp also.
Doing a quick search found someone else that had this problem but with no resolution posted (http://m.modernhemi.com/forums/showthread.php?t=934046) and am fearful of just getting a different type of hose and having the same issue, but to a point where it would leave the car undrivable.
What fuel pump hose is recommended? Looking for something preferably at a local auto parts store but if I have to order something guess I have to order something.
ZL1 - Fuel injectors are from a 98 Grand Prix GTP. At the LS1 fuel pressure they are rated for approx 36#. Had these all flow tested and cleaned before I threw them on the car too and they were all within approx 2% flow from each other. Not bad for $24 at the local pick and pull.
Doing a quick search found someone else that had this problem but with no resolution posted (http://m.modernhemi.com/forums/showthread.php?t=934046) and am fearful of just getting a different type of hose and having the same issue, but to a point where it would leave the car undrivable.
What fuel pump hose is recommended? Looking for something preferably at a local auto parts store but if I have to order something guess I have to order something.
ZL1 - Fuel injectors are from a 98 Grand Prix GTP. At the LS1 fuel pressure they are rated for approx 36#. Had these all flow tested and cleaned before I threw them on the car too and they were all within approx 2% flow from each other. Not bad for $24 at the local pick and pull.
08-28-2012, 06:13 AM
#7
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08-28-2012, 03:57 PM
#8
This is the only type of in tank hose to use.
http://www.racetronix.biz/items.asp?...atus=0&Tp=&Bc=
http://www.racetronix.biz/items.asp?...atus=0&Tp=&Bc=
