4.8 lsx swap ecu problems
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
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How did you connect the fuel line to the rail? Should be able to disconnect it there.
I would fill it up and try it first, that would be easier, if that don't work we can go further. Right now I am leaning towards either sucking air somewhere or a restriction in the line.
Still would like to confirm actual fuel pressure with key on engine not running and running.
I would fill it up and try it first, that would be easier, if that don't work we can go further. Right now I am leaning towards either sucking air somewhere or a restriction in the line.
Still would like to confirm actual fuel pressure with key on engine not running and running.
And the lines were custom made by my father, and they went over where the fuel rails are and then he like crimped them or did something and I don't wanna try and take them off because knowing me, I would break them.
Aggghhhhh! If i was better at this i wouldn't have this problem. Im so mechanicly disabled.
ok will do that when I get up tomorrow morning, need to find the gauge.
And the lines were custom made by my father, and they went over where the fuel rails are and then he like crimped them or did something and I don't wanna try and take them off because knowing me, I would break them.
Aggghhhhh! If i was better at this i wouldn't have this problem. Im so mechanicly disabled.
And the lines were custom made by my father, and they went over where the fuel rails are and then he like crimped them or did something and I don't wanna try and take them off because knowing me, I would break them.
Aggghhhhh! If i was better at this i wouldn't have this problem. Im so mechanicly disabled.
Be patient, you will get it figured out.
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
There should be a push in connection coming into the fuel rail about 3/4 the way back on the drivers side, you will need a tool to disconnect it. If you dad built it he should have the tool and be able to show you how to take it apart.
Be patient, you will get it figured out.
Be patient, you will get it figured out.
I would get him to help but he is extremely busy and for atleast a good while, cannot help out so im kinda stuck on my own.
Oh, also trying to convince a friend of mine to get me like 3/4 of a tank so I can see if it still does it with a lot of fuel in the tank.
Im guessing if it doesn't then the electrical stuff is fine and that the pick up or baffle or (I have no idea how these fuel pumps and what knot work) and I have to drop the tank and fix it. And if it still does than it IS electrical?
TECH Enthusiast
Joined: Dec 2007
Posts: 566
Likes: 1
As a reference, it might be a good idea to post pictures of what kind of fuel connections were used at the engine and throughout the car. I have seen several fires related to improper fuel injection hose/clamps, etc. There were even fires when Russel fittings were used that mate the GM fuel rate to AN fittings. They have since revised that design though. We can help determine if they are correct.
Doug
Doug
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
As a reference, it might be a good idea to post pictures of what kind of fuel connections were used at the engine and throughout the car. I have seen several fires related to improper fuel injection hose/clamps, etc. There were even fires when Russel fittings were used that mate the GM fuel rate to AN fittings. They have since revised that design though. We can help determine if they are correct.
Doug
Doug
Will take a picture of it when I get home.
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
So fantastic news and bad news.
Good news is that with 3/4 of a tank, it doesn't do it. at all.
Bad ness is that doesn't mean its fixed and When driving I can feel the computer doing funky things like retarding timming and torque managment. So It definitly needs to be reprogrammed.
Also in over drive, below a certian RPM range, there is a violent missfire but as soon as I get past that speed, it goes away and purrs like a kitty car.
Im pretty sure its the computer so that is the next thing.
So I guess the pump pick up or somthing in the tank isn't fitted right because it was sucking air when it only had 1/4 tank of gas.
Any thoughts?
Also bought an air filter (lol its so dinky) and no longer running it without one.
(I will post some pictures here in a little while)
Had so much fun last night with a friend because it rained and it spins like you wouldn't believe!
Good news is that with 3/4 of a tank, it doesn't do it. at all.
Bad ness is that doesn't mean its fixed and When driving I can feel the computer doing funky things like retarding timming and torque managment. So It definitly needs to be reprogrammed.
Also in over drive, below a certian RPM range, there is a violent missfire but as soon as I get past that speed, it goes away and purrs like a kitty car.
Im pretty sure its the computer so that is the next thing.
So I guess the pump pick up or somthing in the tank isn't fitted right because it was sucking air when it only had 1/4 tank of gas.
Any thoughts?
Also bought an air filter (lol its so dinky) and no longer running it without one.
(I will post some pictures here in a little while)
Had so much fun last night with a friend because it rained and it spins like you wouldn't believe!
Last edited by agentruley; Apr 20, 2013 at 09:48 AM.
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See, now you have it narrowed down, the problem is in the tank, will need to get back in there and have a look. Sock on the pump should be level and basically at the bottom of the tank. You mentioned that it feels like the computer is doing strange things. If it is the stock tune for that engine then it should be fine and your issues are more likely cause by external issues.
Went back to first post and seen this.
Where are you located?
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
See, now you have it narrowed down, the problem is in the tank, will need to get back in there and have a look. Sock on the pump should be level and basically at the bottom of the tank. You mentioned that it feels like the computer is doing strange things. If it is the stock tune for that engine then it should be fine and your issues are more likely cause by external issues.
Went back to first post and seen this.
Need to determine the cause of both and fix them before wasting time trying to tune it out. Does it still idle high? have you cleared the codes and tried again?
Where are you located?
Knock sensor thing was fixed. And it didn't idle high, the ECU just didn't see the vehicle moving. The tune is for an 5.3 automatic, so I guess thats why its going insane.
But when I get a proper stock 4.8 tune, atleast I can start from there. I also think this ECU needs to do the Crank relearn procedure. If only I knew people who could help me with that lolol.
You near nc?
anybody in nc?
NC BOII!!!
Knock sensor thing was fixed. And it didn't idle high, the ECU just didn't see the vehicle moving. The tune is for an 5.3 automatic, so I guess thats why its going insane.
But when I get a proper stock 4.8 tune, atleast I can start from there. I also think this ECU needs to do the Crank relearn procedure. If only I knew people who could help me with that lolol.
You near nc?
anybody in nc?
Knock sensor thing was fixed. And it didn't idle high, the ECU just didn't see the vehicle moving. The tune is for an 5.3 automatic, so I guess thats why its going insane.
But when I get a proper stock 4.8 tune, atleast I can start from there. I also think this ECU needs to do the Crank relearn procedure. If only I knew people who could help me with that lolol.
You near nc?
anybody in nc?
I wouldn't worry about the Crank relearn, it is only used for monitoring misfires, nothing else.
I'm near KC, never been to NC other than in airports.
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
So got a actual 4.8 tune and computer 'ordered' and I suppose early next week is when I or my father will get it.
Also found out that the pump most likely WAS sucking air because of the way the baffles are made inside the tank (i think?) and the gas tanks were changed in 1996 when they went with type 'R' engines so it looks like I might has to to swap tanks. But for now its all good.
Took a few pictures and here is the one with the fuel connections.
Should I make like a progress build thread? Troll
, I think its already to close to being done. Oh well 
Also found out that the pump most likely WAS sucking air because of the way the baffles are made inside the tank (i think?) and the gas tanks were changed in 1996 when they went with type 'R' engines so it looks like I might has to to swap tanks. But for now its all good.
Took a few pictures and here is the one with the fuel connections.
Should I make like a progress build thread? Troll
, I think its already to close to being done. Oh well TECH Enthusiast
Joined: Dec 2007
Posts: 566
Likes: 1
It looks like the fuel line is double clamped with the correct clamps (not worm style). I would think this should be acceptable. Definitely keep an eye out for dried lines as you get some mileage on the vehicle.
Doug
Doug
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
FIXED IT!
You wont believe what the problem was!
Finally dropped the pump and the pump looked fine, the same with baffles in a smaller tank. (from like 32 to 24 gallons)
So I swapped pumps and to a smaller tank.
But when I replaced the fuel pump screen sock thingy, I noticed that it felt weird.
And I will be damned if the little piece of plastic broke inside the sock and was RIGHT infront of the inlet.
So with a smaller tank, a smaller fuel sock screen, and a new pump.
Everything runs fine.
No miss fire at cruising and no fuel pressure drop, even with 'low' fuel.
Yay for poor teenager engineering!!!!
You wont believe what the problem was!
Finally dropped the pump and the pump looked fine, the same with baffles in a smaller tank. (from like 32 to 24 gallons)
So I swapped pumps and to a smaller tank.
But when I replaced the fuel pump screen sock thingy, I noticed that it felt weird.
And I will be damned if the little piece of plastic broke inside the sock and was RIGHT infront of the inlet.
So with a smaller tank, a smaller fuel sock screen, and a new pump.
Everything runs fine.
No miss fire at cruising and no fuel pressure drop, even with 'low' fuel.
Yay for poor teenager engineering!!!!
Thread Starter
Staging Lane
Joined: Apr 2013
Posts: 82
Likes: 0
Not yet! haha this 3.20 10bolt open rear end is killing me.
So I am going to pick up one of those ratchet locking things (they are like $300 bucks) and put that in and hold me off until I do a t56 swap.
When I do the t56 swap, some 4.56's are going in that thing. I mean, the latter t56's had .5 over drive. I will have all the pick up in the world and get some massive highway mileage. OOHHHH!!!!!
BTW, Robert, I love you. You are awesome....
So I am going to pick up one of those ratchet locking things (they are like $300 bucks) and put that in and hold me off until I do a t56 swap.
When I do the t56 swap, some 4.56's are going in that thing. I mean, the latter t56's had .5 over drive. I will have all the pick up in the world and get some massive highway mileage. OOHHHH!!!!!
BTW, Robert, I love you. You are awesome....
