5.3 fuel pressure issues - S-10 Forum
 
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post #1 of 22 Old 04-18-2017, 07:13 PM Thread Starter
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5.3 fuel pressure issues

I finally got a pedal to work, I haven't mounted it yet but thats no big deal. I wonder if you can help with my new problem though. I got the motor in and running. It will start up and idle like a champ as long as you want it to. If you touch the throttle petal though, it will rev slightly then fall on its face. You can smell it running very rich. I first thought the problem was the 02 sensors were too close to the end of the open headers (I'm running the Racing Innovation shorties). I put 18" of flex pipe on the end of the collectors. Still have the same problem. I hooked up the fuel pressure gauge today. When you turn the key on, it goes to 70psi, which I think is way too high, then bleeds off when the pump shuts off. It also holds the 70psi while its running. I have a Walbro 255 in my tank going through stock fuel lines to the stock Sonoma fuel filter then to a Corvette style filter/regulator. I am wondering now if I have a leaking injector since the pressure leaks down so fast. But why is the psi running at 70? Any ideas are very much appreciated.

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post #2 of 22 Old 04-18-2017, 10:21 PM
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Re: 5.3 fuel pressure issues

70 psi does seem high. Perhaps it is a cheap filter/regulator, and not a good name brand one, and it's just off? If this is a fresh build, and the ecm is not tuned for this setup, running rich is not abnormal out of the gate. Make sure you have the 02's on the correct side and not crossed. Lots of fuels systems bleed down pretty quick, I wouldn't worry too much about that yet. The falling on it's face off idle is more than likely the tune. What is the specifics of the build?

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post #3 of 22 Old 04-18-2017, 11:04 PM Thread Starter
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5.3 fuel pressure issues

The ecm was tuned by Texas Speed because it has their cam in it. The injectors are the same ones that cam in it, flex fuel injectors. The filter/reg is part of a Ls swap kit that I got on eBay that included all of the fittings and line needed. I am thinking that is a good place to start is get a new wix 33737 on there. The o2 sensors are brand new and on the right sides. I am using a cpw harness and it is labeled so I know it's correct. I am just guessing that too much psi could cause it to run rich? If it does take any throttle it does puff smoke.


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post #4 of 22 Old 04-18-2017, 11:04 PM Thread Starter
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Re: 5.3 fuel pressure issues

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The ecm was tuned by Texas Speed because it has their cam in it. The injectors are the same ones that cam in it, flex fuel injectors. The filter/reg is part of a Ls swap kit that I got on eBay that included all of the fittings and line needed. I am thinking that is a good place to start is get a new wix 33737 on there. The o2 sensors are brand new and on the right sides. I am using a cpw harness and it is labeled so I know it's correct. I am just guessing that too much psi could cause it to run rich? If it does take any throttle it does puff smoke.


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post #5 of 22 Old 04-19-2017, 08:11 PM
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Re: 5.3 fuel pressure issues

I get ya. I will just say this, CPW has made mistakes. They are only human, and I love CPW, but I think I would start with the filter. I have heard of issues with the cheaper brands.

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post #6 of 22 Old 04-19-2017, 08:53 PM Thread Starter
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Re: 5.3 fuel pressure issues

Well I put a new vette filter/regulator on it today but I still get 65psi. Maybe the gauge is bad but it never has been before. I don't know what the answer is but I can't keep throwing parts at it.


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post #7 of 22 Old 04-20-2017, 12:45 PM
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Re: 5.3 fuel pressure issues

flex fuel injectors as in from an L59?
those flow 33lbs at 50psi, and should be up to 37lbs at 65psi don't really think that will cause a huge problem...

Sounds kinda similar how my truck ran when I messed up some wiring and fried an o2 sensor along with blowing the fuse that ran my maf, map, tps, and a few other sensors.... I would double check to make sure all the sensors are getting power and going to the correct pin at the pcm.


Also, how much pressure bleeds off when the truck isn't running?

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post #8 of 22 Old 04-20-2017, 01:57 PM Thread Starter
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Re: 5.3 fuel pressure issues

All of the pressure bleeds off when the pump isn't running. I may have a problem with a check valve in the pump or something. As far as I know no fuses are blown. I know the throttle body is still working anyway.


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post #9 of 22 Old 04-21-2017, 08:10 PM
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Re: 5.3 fuel pressure issues

It could be that, it could be a bleeding injector. It's nothing I would really worry about, unless you have a issue with the way it runs, or the mpg's. Most of the aftermarket pumps I have used, have had this issue.

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post #10 of 22 Old 04-21-2017, 08:23 PM
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Re: 5.3 fuel pressure issues

Quote:
Originally Posted by Iroc-10 View Post
It could be that, it could be a bleeding injector. It's nothing I would really worry about, unless you have a issue with the way it runs, or the mpg's. Most of the aftermarket pumps I have used, have had this issue.

I chased a bleeding fuel pressure issue for almost 4 years.... several vacuum fpr's and a vette filter later, I thought the pump was the issue....
turns out the line between the pump and sending unit was loose.
which also caused a fuel starvation issue wat sustained high speeds

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post #11 of 22 Old 04-21-2017, 08:29 PM
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Re: 5.3 fuel pressure issues

Wow, thats kind of crazy.

Maybe Fall of '16 Turbonetics TC78
Currently Running:
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post #12 of 22 Old 04-21-2017, 08:53 PM Thread Starter
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Re: 5.3 fuel pressure issues


Here is a video of what it's doing. In this video I even changed back to the original throttle pedal. No change.


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post #13 of 22 Old 04-21-2017, 11:42 PM
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Re: 5.3 fuel pressure issues

Quote:
Originally Posted by Jbabb View Post
https://youtu.be/sxkGsZnf4Sk

Here is a video of what it's doing. In this video I even changed back to the original throttle pedal. No change.


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almostly like what mine did when I forgot to plug in the ECT sensor.

skip to 2:33


Other than a sensor not working right... Maybe it's in the tune.
Forgot the table, but it control the over/under speed idle and if it's not right it can lead to erratic idle hunting like that.
basically it adjusts itself too fast from under speed, goes over speed and starts a loop of overshooting the target idle.

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post #14 of 22 Old 04-22-2017, 08:20 PM Thread Starter
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Re: 5.3 fuel pressure issues

Well a friend of mine brought over his scan tool to borrow for awhile. What should I even be looking for?


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post #15 of 22 Old 04-22-2017, 08:57 PM
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Re: 5.3 fuel pressure issues

Your going to have to look at everything honestly, but I would start with what the air fuel ratio is. If you can check commanded and actual, that would be a good start. Also, check the fuel trims. You probably only have short term right now. If you can get some more exhaust on it, that will really help. At this point, with a base tune at best, and no exhaust, the O2 sensors are being washed out by oxygen, so it is adding fuel because it thinks it's lean.

Is the base tune in this, set for your specific injectors, and correct cubic inch? Has anything been done on the tune at all? I thought I remember you saying this has a tune by someone? Did they tweak VE for the cam?

Maybe Fall of '16 Turbonetics TC78
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post #16 of 22 Old 04-22-2017, 09:01 PM Thread Starter
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Re: 5.3 fuel pressure issues

Well we checked fuel trims last night, not really knowing what we were looking at. Both ST and LT numbers were really negative. Anywhere from -12 to -20. No positive at any time.
I did end up getting two pieces of flex exhaust pipe 18" long to put on the shorty headers, hoping to help out the o2 sensors.


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post #17 of 22 Old 04-22-2017, 09:08 PM
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Re: 5.3 fuel pressure issues

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Well a friend of mine brought over his scan tool to borrow for awhile. What should I even be looking for?


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You're going to be looking at the way negative fuel trims.

Was it tuned for the injectors you have?

Whatever fuel pressure it was tuned for is what you need to have.

I have a Wix filter regulator on the garage floor because it put out 65 psi, it's a lot easier to get the fuel pressure to match the tune than it is to get the tune to match the fuel pressure.
Tuning around fuel pressure is ass backwards.
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post #18 of 22 Old 04-22-2017, 09:10 PM
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Re: 5.3 fuel pressure issues

Quote:
Originally Posted by Jbabb View Post
Well we checked fuel trims last night, not really knowing what we were looking at. Both ST and LT numbers were really negative. Anywhere from -12 to -20. No positive at any time.
I did end up getting two pieces of flex exhaust pipe 18" long to put on the shorty headers, hoping to help out the o2 sensors.


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I was typing as you posted that. When I ditched the wix vette filter/regulator and got the fuel pressure set to what it was tuned for my fuel trims went from way negative to +/- 4.
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post #19 of 22 Old 04-22-2017, 09:11 PM Thread Starter
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5.3 fuel pressure issues

Yes it "should" be tuned for the L59 injectors. I have no idea what fuel pressure it was tuned for. I do get a steady 64-65 with the wix though. Maybe I should swap to a fuel rail with a return and regulator?


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post #20 of 22 Old 04-22-2017, 09:15 PM Thread Starter
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Re: 5.3 fuel pressure issues

So when you ditched the vette filter, what did you go to. Remember, the truck still has open headers to. Would that screw the trim numbers up?


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post #21 of 22 Old 04-22-2017, 09:18 PM Thread Starter
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Re: 5.3 fuel pressure issues

We also, just for shits and giggles, swapped the o2 plugs from driver to passenger side, even though they are labeled. One of the trim numbers, I can't remember which, went from negative to positive 7 or so. Maybe they were labeled wrong?


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post #22 of 22 Old 04-22-2017, 11:30 PM
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Re: 5.3 fuel pressure issues

Still to me sounds like a dead sensor to me.
negative the engine is running rich, so it's pulling fuel.
if it was the header it would see a false lean and be positive trim.

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