i have a 2000 ls1 in my 79 1/2 ton. finally got it all running, and a few days ago, i was driving it around an industrial park close to the house. i drove it for about 30-45 mins., the longest i have driven it since it has been running. this was on the original 4 gallons of gas i bought when we first started it.

well, since it was running so good, i decided to drive to a buddies house, about 10 miles away. i filled up the 12 gallon fuel cell, and started over there. about 1 mile from his house, it started stumbling hard under acceleration, where it would almost die. let off the gas, and it would idle up, give it gas, and would crap out.

i thought it was the fuel filter. so i take off one of the fuel lines, and was looking at the fluid running down the driveway, and notice it is two different fluids. water in the gas tank. still unsure of how it got there, went back to the gas station and their gas was water free.

anyway, i drained all the gas, drained all the lines, and replaced the fuel filter. i am using a walbro inline pump with the wix corvette filter with the internal regulator and return. 12 gallon summit fuel cell, mounted in the rear of the bed.

replaced the filter and added 5 gallons of new gas, and almost half a bottle of sea foam.

started it, ran fine for 2-3 minutes, then started stumbling hard again when i give it gas. i pull over, put it in park, and hear the MAF start drawking air like crazy. turn it off, wait a minute, start it again. drives fine for about 5 blocks, then starts the same thing all over again.

it will hardly stay running even under light acceleration.

i thought it was just the fuel problem, but obvioulsly not.

could the computer have made adjustments when the water was in the fuel, and it hasnt adjusted back?

someone thought maybe the MAF has gone bad?

any thoughts??

and it seems like since the problems began, the fuel pump is a lot more noticeable, a lot higher pitched than i remember it being before the problems.

any help is greatly appreciated..

and it has been tuned, once, and like i said, was running fine up until i filled the gas tank. i am going to try to het hptuners on it again to see if it electronic related, unless someone can tell me something else is wrong.

thanks

 

I know next to nothing but you might try pulling the negative battery cable and letting it sit for ten minutes and then reconnect and see what happens.

Seems I've read this before somewhere else and it worked.

 

After you try resetting the computer, put a pressure guage on the fuel rail. Sounds to me like your fuel pump is failing.

 

Unplug the MAF and see if the problem vanishes.

Check the fuse the MAF is on.

 

ok fellas, thanks. will check all of this.

 

Check your basics fuel pressure 50 lbsmin , spark quality, and mil codes. Go from there and DO NOT just start throwing parts at it. Look at all of your o2 data fuel trim especially and see what it is doing and maybe try to load up a data log we can look at.

 

i do not have and tuning software, but have a buddy that does and will i am going to try to get it to him asap.

but, i did reset the PCM. drove it, same thing, stumbles under even light acceleration after about minute.

left it running, got out and unplugged the MAF, it started surging and wanted to die, but didnt. put it in drive, and wouldnt hardly move when i presses the gas pedal.

plugged the MAF back in, and same ol same ol.

if this is PCM related, that is fine, hopefully we can sort it out.

but the fuel pump being louder makes me winder if it pressure related???

thanks guys

 

when i bought the MAF, the guy said it has a resistor in it, would that have anything to do with these problems?

 

The resistor would cause issues with a factory tuned ECU. Since the MAF will give different voltages to the ECU which would cause the car to load up or lean way out.

 

I'm not 100%, but it sounds to me like a bad MAF, since it appears to only give you trouble in open loop (i.e. a few minutes after startup). Can you yank a MAF off a friend's car and try it out on yours? That would at least eliminate one factor if nothing else. HTH

 

You're stabbing in the dark until you get a scan tool on there to see what the PCM thinks is wrong. Save yourself a lot of headaches and park it until you have the right tool to diagnose it.

It's not an open vs closed loop issue if it runs ok for 2-3 minutes. If it runs worse with the MAF disconnected, it's probably not a MAF issue (unless you've replaced the cam and not tuned the SD tables).

I 2nd the recommendation to check your fuel pressure. If the pump is crapping out when it heats up, I'd expect symptoms like you're seeing.

Also, what'd you do with the EGR and EVAP systems?

 

Actually, the resistor is there to make it look more like the stock MAF did... and in any case it's a moot point considering the setup was tuned with that MAF.

I bet it's MAF/water related, though, your unplugging it and it running rough go against that notion unless your VE is untuned (except for the idle area).

 

obviously you guys can tell i am new to these engines, and i dont know what you are talking about with VE, SD tables, etc. but i am pretty sure the EGR and EVAP were deleted when the tune was done.

i dont have a fuel pressure gauge, but am trying to locate a friend with one so i can get that checked. i am hoping to have it him sunday, he also has the HPTuners, so we should be able to get it sorted out.

thanks

 

just put a FP gauge on it. the problem is slapping you in the face and you are ignoring it.

 

obviously you think the water damaged the fuel pump, huh?

 

UNplug the 02 sensors and see if it still tries to do this> If it stumbles at cruise blip the throttle straight to WOT and see if it clears out. That will take the 02 sensors out of the loop as well. If it does clear out, plug one and then the other back in until you find your problem coming back and change that sensor. Also make sure your MAP sensor and all those small sensors are still plugged in and theres no vacuum leaks.

Does the thing have a cam in it?

 

ok, i will try that tomorrow. i am going to check the fuel pressure too, some think it sounds like the water could have burned the fuel pump up.

before i found the water in the gas, i looked at the 02 wires, and the drivers side conduit had metled to the collector, but the wires looked to be ok, no burning or discoloration.

it has either the crane 216/224 551/551, or 224/224 551/551. i got the long block from a buddy that bought the car from another guy, and he couldnt remember which one he bought. also has LT's and my custom homemade air intake, courtesy of lowe's.

thanks

 

put the fuel pressure gauge on it...idled right at 60psi. would drop to almost 50psi then go right back to 60 under normal acceleration. but under hard acceleration, it would drop to about 30-40, then quickly get back to 60 when i let off.

then, after a few minutes of driving, even just driving around the neighborhood from stop sign to stop sign, the pressure would drop to under 20 while accelerating. even cruising at 30-40, the pressure would hover right around 20, then when i let off the gas, it would slowly build back up to 60.

the longer i drove it, the faster it would fall and longer it would take it to build back when i let off the gas.

thanks for the help, will be looking for a fuel pump tomorrow. i guess the water hinders the lubrication from the gas, and burned it up.