mitsu-guy

Hello, guy's, here's a quick background to give you an idea of what series of events went down and some general information. Firstmost my name is Jordon and I just graduated with an Associates in Automotive/Motorsports/Diesel Truck Technology. I'd say on average I'm a Tech B mechanic but I've had some bad luck here and there and well this is one of them. I have a 2008 Z51 Base 3LT MZ6 with roughly 45k on the odometer.

Around October of last year, I had maybe three hard starts with the Corvette. Where it would experience long cranking and hesitation to turn over. I would let it sit over night and then it would turn over as if there was no preexisting problem.


The last time it would not turn over I happened to be parked outside the garage at the college I was attending. Me and one of the master techs (previously worked at a GM dealership for 20+ years) did a really short and quick diagnosis of the fuel pump. I turned the ignition on and didn't hear the pump kick on so we jumped the fuel pump relay and still didn't hear the fuel pump kick on.


So he suggested there was a good chance it was the pump which I agreed. I figured the fuel pump had to come down anyway so I mine as well replace it while I was there because the car is 8 years old and has close to 45k on it. I ended up ordering a Denso fuel pump off of RockAuto. When The pump came in we managed to secure a scissor lift in one of the bays and I would have between my off time that I wasn't at work and in between classes to get this fuel pump done. I wanna say because of a lack of time and a couple set backs it was on the lift for about a week with only being able to work on it maybe 45-60 mins every other day.


I managed to get the tank down without lowering the transmission which was nice. The only real difficult part was the convoluted crossover tube. Anyways I took the old pump out and used the new one to pump the remaining gas out of the tank and into my daily driver; to make it easier to install the tank with less gas in it (it was 3/4 full at the time). Afterwards, I buttoned everything up and got ready to start it. As soon as I went to start it I had a random thought pop in my head "Did I reconnect the wiring harness to the fuel pump ?"
. I go to start it and nothing happens. arrrgghhhh, I drop the fuel tank again and this time I reconnect the wiring harness and bolt everything back up. I go to start it now and it just cranks away refusing to turn over.

Now I'm thinking, battery voltage check, reconnected all the lines and connectors check, jump the relay check. Hmm maybe do something irrational like check for power and ground going to the pump. This is now the third time I am taking this pump down so I can get at this connector. I get an old headlamp and run a wire from my positive battery and attach it to the headlamp and use a jumper wire to jump the ground wire to the headlamp and tadah the lamp lights up. I disconnect the wires and now I'm connecting the negative lead from the battery from a jumper wire to the headlamp negative. I go to connect a jumper from the battery voltage to the fuel pump to the headlamp and it does not illuminate. Bingo found the "true" problem.


I follow the wiring harness from the pump till about 2 feet in length and come across a melted connector that is the wire that sends power to the pump. I got on the one end and confirmed that is the problem with a test light. So I cut out each wire individually and butt connect them with these high grade butt connectors (run about 3 bucks a pop {Also recommended wire repair by GM}). I go and button everything back up. Put the tank back up again and go to turn it over and it still won't turn over


So power and ground are good the pump is turning on what could be the problem ? I put a fuel gauge on the rail and go to crank it and I'm getting like 15 PSI out of the recommended 50-60. Im a little bewildered because I primed this new pump quite a bit by jumping the relay before starting. So I talk to a couple master techs and we decide we should try to see if it gets to pressure right when it leaves the tank. So now I drop the tank for the 4th time and rig a fuel pressure connector right to the fuel rail supply line from the tank. turn the key on and the gauge instantly hits 65 PSI. Hmm.... Maybe it needs more then the five gallons in the tank to start up ? So I Put the tank back up and button everything back up and go get some more fuel. I add five more gallons of gasoline


Now the moment of anticipation. I go to start her and she fires right up. I'm pumped up , finally got this nightmare over with. I go to back out off the lift and I get a low fuel indicator pop up on the dash along with a service fuel message. Hmm.... I shut her off install a fuel pressure gauge and turn it over and I got 55 PSI. Soo...thats good. I think to myself "What if you got the fuel level sender somehow stuck on the bottom". Well yep, I don't have the best luck at this moment why not that could definitely be the problem. Well at this rate its November and winter is coming and so is the inspection and I'm low on money to buy tires to pass inspection. So I'll put her in storage and bring her out late spring.


Late spring comes and I get some new Nitto Invos and Continental Extremecontactsports put on and get the inspection done. I however now notice If I hammer down on the throttle she just bogs down . If I go over 3k RPM she just falls flat on her face. So I talk to a few buddies and they ask if I tested the fuel pressure under load. It didn't occur to me because I had the right fuel pressure at idle and it's a name brand Denso pump on a returnless style fuel system so the pump will maintain the pressure. At this point I'm willing to try any suggestion. I put the fuel gauge on close the hood and have my buddy hold and read the gauge while I give it some quick spirited runs in an empty parking lot. What we found was at idle the fuel pressure remained at 55 PSI. However when a load was placed on it the fuel pressure would start dropping after 2k RPM. At one point about 3.5-4K RPM the fuel pressure fell as low as 15 PSI.


Afterwards I hooked up a Snapon Veras scanner and pulled some codes and read some data. I pulled up two codes a P0461 and a P0463. To sum up the P0461 it states that if the computer detects there is 7.5 gallons of gas in the driver side tank and less than 1.5 gallons in the passenger tank it will drop the fuel level gauge to zero and display low fuel (Both Symptoms I have). And to sum up P0463 is basically a short to power ( maybe the sender somehow got connected to the wrong connector in the tank ?). The data that I did read on the scanner points to there being little to no fuel in the passenger tank compared to the driver side tank.


And right now I will have the lift open this Tuesday 6/7/16 to drop the tank and do some diagnosis on this fuel system and was wondering if you guys had any ideas where to look at first for the fuel level sender problem and the not maintaining fuel pressure under load.

Kinda curious if anyone has had these symptoms before. In my gut I feel the fuel pressure problem is due to the jet fuel lines in the convoluted cross over tube. The reason I believe this is because

1. That *ucking stupid damn cross over tube is the only difficult thing to deal with. Took me at first 2/3 hours to disconnect/reconnect it.

2. While the tank was down I found the holder of the jet fuel lines laying in the tank. I put it back in the opening so it was snug. But seriously with that tube there how the hell do I know that it stayed in place ? How do I really know those lines are together when you are doing it in the blind and you cannot see if they are connected. You have barely any room to move your hands and you have this damn piece of *hit stainless steel cross over tubing that refuses to budge more then 1/4 an inch. I went so far to use painters mark to line up the notches but it still took over 45 mins to reconnect that god damn cross over tube.


Is there any tips or tricks you guys would be able to give me ? I appreciate all the help and reading this, Thank you guys

schpenxel

In all the time you've spent messing with you could have lowered the rear cradle and then had clear access. Sounds like an internal leak with the crossover stuff to me, but it's tough to say.

(hmmm)

I wonder whether the underlining cause is something mechanical or electrical.
Knowing the fuel pressure at the pump under load would be very telling. And while you have the tank down again (sorry), monitor the fuel pump leads to see if the voltage changes in sync with the lower pressures when under a load.
A good number of years ago, this problem most likely would have been a partially clogged fuel filter, but now times have changed! GL