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2G Lean after new fuel filter

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LidnDom

Proven Member
34
0
Jan 13, 2014
Tampa, Florida
I just finished adding a new weldon fuel filter along with replacing all the fuel lines from the tank to the rail. When I start the car the AFRs dance around 10.0 - 14.7 before it leans out and stays at three dashed lines. I checked and fixed all the fuel leaks to no success. Not sure what is going on, any ideas?
 
I agree just recheck your work.... any wiring you may have disturbed during this work. Also I don't know about the weldon filter but some have plugs in them to keep trash out during packaging and shipping. I once looked right at the plug... didn't realize it was a stupid plug it, installed it car started and would idle wouldn't rev much. It was backfiring lean at idle I spent 3 days looking for the issue haha, I figured if it was a plug it wouldn't have started I was wrong. Call me dumb whatever stupid things have happened to the best of us.
 
I just finished adding a new weldon fuel filter along with replacing all the fuel lines from the tank to the rail. When I start the car the AFRs dance around 10.0 - 14.7 before it leans out and stays at three dashed lines. I checked and fixed all the fuel leaks to no success. Not sure what is going on, any ideas?
Could you have something in your tank that is partially plugging up the pickup? That might explain the fluctuation at first then the constant low fuel condition.
 
I agree just recheck your work.... any wiring you may have disturbed during this work. Also I don't know about the weldon filter but some have plugs in them to keep trash out during packaging and shipping. I once looked right at the plug... didn't realize it was a stupid plug it, installed it car started and would idle wouldn't rev much. It was backfiring lean at idle I spent 3 days looking for the issue haha, I figured if it was a plug it wouldn't have started I was wrong. Call me dumb whatever stupid things have happened to the best of us.
I did the same thing.
Double check your filter to make sure no plugs were left in it.
Also, recheck your base fuel pressure.
 
Hey guys, updating my situation. I checked to make sure there were no kinks in the new line and I also confirmed that my fuel pressure is at 43.5. I took the filter out to see if there were any plugs left inside but I couldn't find anything, I blew air through it with a compressor as well.

Potential useless information: The car is very hard to start and requires me to pedal the throttle to stop it from dying. The AFRs will initially read okay before leaning out all the way at 3 dashed lines after 30 seconds or so. Not entirely sure but I believe I smell something burning after the gauge leans?
 
You said it goes to 10.0 which is actually really rich on start up not lean. What does 3 dashed lines mean? Does that mean lean?

When you said you set the fuel at 43.5, did you disconnect the vacuum line on the AFPR before you set it at 43.5? I have done that a few times as well and it causes difficult starts. What happens is it goes very rich on startup which is why you have to feather the throttle until the ECU corrects with fuel trims.

Either way, I did a fuel upgrade from tank to rail and back to tank as well. When you change the fuel line and upgrade the pump it removes a lot of restriction from the fuel system. You must set the AFPR (with no vac line hooked up) much higher (still at 43.5 just more turns on the adjuster) than before. You also must drill out the siphon tube in the tank (assuming you have AWD) as well. The siphon tube allows the 2 sides of the awd fuel tank to drain from the DS to the PS of the tank where the fuel pump pick up is. Where the rear drive shaft goes "through" the tank there is a high spot that fuel cannot get over, so there is a siphon tube in theis to transfer fuel over via siphoning action. When you upgraded everything you are now moving much more fuel and the siphon cannot keep up. What happens is the DS of the tank fills up and the PS of the tank goes dry. This could be your problem or not, but you will likely have to do this as well as the fuel line upgrade from the tank will cause issues with the siphon.

To fix remove the siphon tube (little white plastic tube a few inches long) and drill the whole bigger. Don't remember what size drill bit but if you search there are a few threads on it.
 
Situation update: I took out my injectors and cleaned them, checked for 12v at the fuel pump, and I confirmed that the AFPR is at 43.5 psi with the vacuum line disconnected.
To clarify some information, the car is a GST and here is a video of what the AFR is doing:
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That video helps narrow it down quite a bit. AFPR is set properly so that's good. Your boost gauge shows constant vacuum at ~18-20 inhg so there is no vac leak after the throttle body so that is good too.

When it goes really lean there is no change in the RPM's nor a change in sound of the engine....if it really was that lean you would likely hear the engine stumble or the RPM's would move around a bit. It's likely means it's the gauge or the sensor....might even be the wiring.

Can you reacilbrate the gauge/sensor like you can with an LC-1?
 
I'm not sure about recalibrating but I took the sensor out and tested it by placing it into a soaked rag. In the rag it read full rich and in open air it read full lean so I'm thinking that the sensor is good. I'll try swapping in a friend's sensor and see if that does anything.
 
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