4l60e torque converter wiring/ ls swap bugs

[cr92]

hey all,

got an 87 chev r10 was originally a 4.3tbi/ th350. it now has a 4.8 vortec and 4l60e in it i swapped over the winter. had it out this week trying to work out some of the bugs, wondering if anyone got any ideas...

1st of all, my fuel pressure with key ahead is like 30psi then drops down to about 5psi after 30 seconds or so. with the truck started its at 47-49psi... why is it so low? its a return style setup with brand new ep 381 pump, i hear they are supposed to be 55-60 at all times... fuel regulator doesn't leak any gas with cap off.. only thing stopping it is the fuel filter that was on it when it had a 4.3 tbi.. could that cause a restriction i wonder? i don't think its the injectors unless its all of them, not getting any misfire codes, plugs all look equal in color?

2nd of all, my tranny feels like its slipping.. doesn't wanna go over 3000rpm, over drive doesn't really lock up on it just feels like its slipping and sputtering when i tries to get into OD.. i know the torque converter needed to be wired to the brake switch, i wired it to the grey wire last year can't rememeber where i got that idea or diagram from now.. would the torque converter wired incorrectly cause any of those problems? or would it not even attempt to go into OD? anyone gotta diagram or info on how it is supposed to be wired to this truck?

and lastly, my long term fuel trims at idle are a constant +25%.. this seems high to me, does that sound right for an ls engine? the short term fuel trims are +/-5% at idle which does sound normal to me, o2's are brand new and fluctuating in the 200-800mv range which also seems normal to me, and while driving the truck the long term fuel trims go down around the +5% range which also seems normal, its only the idle trim seems a bit high, any help greatly appreciated!

[kdh454]

#1: You should have 55-62psi after cycling the key a few times. It should hold for quite some time. To find the leak, pinch the line coming from the pump after it builds pressure. If it holds, the problem is probably in the tank (pump or connection). If not, do the same with the return to eliminate the regulator. If it still bleeds down, I suppose you could have a stuck injector. I have had a bad regulator that did not leak, so that would be my guess.

#2: Not sure. I honestly do not remember how mine is wired.

#3: You need to fix your fuel pressure first. Positive LTFT would be a symptom of low fuel pressure. After that is sorted, drive the truck for some time (1hr+) and check them again. They should be +/- 5%.

[cr92]

thanks for the tip KDH i will check that out. i wonder what the voltage at the pump should be? something else to check too

[cr92]

i just ran out and tested the fuel pressure again, 47psi running with fuel pressure regulator hooked up. 56psi with the regulator unplugged! so i guess that is part of my problems.

the key ahead psi looks to be 52 psi while the pump is priming. as soon as it stops priming it drops down to 30 instantaneously then slowly descends downward. i think you may be right in saying the small rubber hose between sending unit and fuel pump is leaking? theres no way the injectors could be letting that much gas into the motor that quick

[cr92]

Originally Posted by kdh454

#1: You should have 55-62psi after cycling the key a few times. It should hold for quite some time. To find the leak, pinch the line coming from the pump after it builds pressure. If it holds, the problem is probably in the tank (pump or connection). If not, do the same with the return to eliminate the regulator. If it still bleeds down, I suppose you could have a stuck injector. I have had a bad regulator that did not leak, so that would be my guess.

#2: Not sure. I honestly do not remember how mine is wired.

#3: You need to fix your fuel pressure first. Positive LTFT would be a symptom of low fuel pressure. After that is sorted, drive the truck for some time (1hr+) and check them again. They should be +/- 5%.

see above post. auto parts shop is closed until tuesday. can i block off the vacuum line and run it without the regulator until then?

[cr92]

well today i went and bought a new fuel pressure regulator. that did not really make a difference. it sits at 50 psi while idling. 58-59psi when i unplug it.

i also dropped the tank and tried putting a new hose and clamps between the pump and sending unit. this helped my key ahead psi, while pump is priming its at 58-59psi, when the pump stops priming it holds at 52 now.

truck is still down on power but those things i did today did help. i don't think the transmission is slipping anymore i think this is the engine misfiring/stumbling under load.

truck is now showing code po300 random multiple cylinder misfire.

really would like to see the truck at 55-60psi for fuel pressure... not sure what else to do? if i unplug the regulator and it jumps up to 59 then it couldn't be a clogged filter could it? pump is way quieter now that i replaced that hose on the fuel pump.. must of been leaking a lot