Need help or advice on a C6Z Cranking Fuel problem
 

Ok here is my situation - Car is a 2006 Z06. Purchased Less than a year ago from Chevrolet dealer. It is under warranty. It is my primary source of transportation and now has 13xxx miles on it. I am having what I believe to be a fuel problem - its doesn't happen every day, prob 2x a week. The problem is (when it happens) is when I go to crank the car the car will try to turn over, sometimes it will either choke itself out (ie. it will crank but no rpms, no response when i push the throttle) and it will die. Other times it will try to crank but it will never actually start the engine. Im pretty sure its a fuel problem, as in it isn't getting any. Usually what will get the car to eventually crank is either pull the fuel pump fuse and/or relay under the hood and wiggle the fuse block and sometimes after doing that it will fire right up. Other times I have to disconnect the battery and let it sit for a few minutes (to reset the computer) as well as the relay/fuse thing then it will fire up. I have had to have it towed as well as nothing worked in one instance.

I have taken the car in to chevrolet prob 5x over the last month and a half. The first time they said it wasn't getting any fuel pressure, so the work they did was change the fuel pump. About 2 weeks later it started doing it again. Took it in, they kept the car for 3-4 days, said that they ran all sorts of tests on all of the systems in the car and everything looked good but they did tighten the fuse block down and that fixed it. 2 days later started doing it again. Went and bought a new fuel pump relay as per reading posts on here, still didn't fix it. Took it in a 3rd time - they said that my positive terminal on my battery was loose and since i had installed an stereo amp in the car it made the connection loose and that was the problem so it wouldn't be covered under warranty and I needed to change my positive battery terminal. I disconnected the amp, changed the terminal, not 2 days later it did it again. Took it in. They called and said that my battery (which is less than 6 months old, optima red top) is discharging too low when it cranks the car and they cant do any work on it until I go and change out the battery (which ive never had any dead battery problem, the car always tries to crank and the voltage stays usually 14.2v on the dash).

For one I do NOT believe for one second that the battery OR the terminal is an issue - the stereo, amp, battery has ALL been in the car for 6-7months (well before the problem started), they have had the car numerous times and these items were all in the car before when they ran these extensive "tests" they say that they ran. I think they are trying to cop out of doing warranty work because these are the ONLY aftermarket parts on the car (stereo system and battery).

At this point I BELIEVE something in the fuel system is causing the problem, and since they supposedly changed the fuel pump I'm leaning towards something being wrong with the fuse box. Any idea of what it could be?

I would get a fuse pressure gauge , to check it out.

First, do you mean to say this: "crank the car the car will try to turn over, sometimes it will either choke itself out (ie. it will crank but no rpms, no response when i push the throttle) and it will die. "

Cranking means the engine is turning over. No such thing as cranking at zero rpms.

Do you mean you can hear the starter solenoid clicking or the starter trying to turn the engine over or do you mean the engine is turning very slowly and the starter sounds like it is straining to do that?

Those symptoms are pretty much standard for an electrical problem. Just because you have 6 month old battery doesn't mean there are issues with it. You need to load check the battery, also check battery connections at the battery, at frame ground and at the starter. All it takes is a little corrosion or a loose connection to add enough resistance to the circuit that the car will not start reliably.

Poor electrical connections could keep the car from getting fuel pressure and your ability to get it started by pulling fuses, wiggling relays, etc seems to back that up.

Second; The throttle doesn't control fuel flow or the throttle blade. They are controled by the ECM. The throttle pedal only sends electrical signals to the ECM. When in start mode the only thing you can do is to push the throttle wide open which puts the system into clear flood mode by turning the fuel injectors off.

Have you had the codes checked using a scanner that can read all the codes and not just OBDII stuff?

There can be a lot of things that can cause this kind of problem. I pulled two diagnostic charts from the Service Manual so you could get an idea where to look if you want to do so yourself. Again, having a good scanner that can read all of the codes is required. Most scanners less than $400 can't read them all.

Bill

Thanks for the response Bill - To answer what I can:

"First, do you mean to say this: "crank the car the car will try to turn over, sometimes it will either choke itself out (ie. it will crank but no rpms, no response when i push the throttle) and it will die. "

Do you mean you can hear the starter solenoid clicking or the starter trying to turn the engine over or do you mean the engine is turning very slowly and the starter sounds like it is straining to do that?"


SOMETIMES it will "crank" and the engine is running very slowly for a few moments then will die. Other times it is trying to start when I push the engine start button and you hear the starter doing its thing but the car never actually fires.

"Have you had the codes checked using a scanner that can read all the codes and not just OBDII stuff?"

I PERSONALLY havn't checked any codes - I don't have a scanner and honestly don't know anything about it. I HAVE asked them when I have taken it into Chevrolet and they say that the car isn't throwing any codes.

As for the battery, I know I'm not a mechanic and Im trying to do everything they (the Chevrolet dealership) says to do, which now they are saying I need to take that battery back to where I got it from (advanced auto parts) and get a new one under warranty (the date is on top of the battery). My only concerns about this situation is that the car has been in numerous times and they are just now saying oh that aftermarket battery that you installed is bad. And this is after they supposedly did system checks on everything before they released the car to me a previous time.

UPDATE: they tested battery at service, said it was bad - swapped it out with new optima red top (under warranty), car had no issues for roughly 3 weeks, now here we go again - Car is back in service dept, been there for a week - had it towed in when the problem started again so that way they could diagnose it while it was down/not cranking correctly. Just went up there today, they said of course that it cranked right up, they took the fuse block out and put it in a freezer to simulate cold crank, still cranked right up for them. He said there is something grounding out somewhere but they have no clue where. Anyone ever had a similar problem? This is extremely frustrating.

Check the electrical
 

In may case: after I replaced the fuel pump which I think was def fried, I had started having the same problem again a few months later. After MUCH investigation, it turned out to be a bad fuse box (the one inside the hood).

Just adding my case to the mix so that you may have another point to check:
(both of these thread end up with the correct result)
http://forums.corvetteforum.com/c6-t...not-start.html

http://forums.corvetteforum.com/c6-t...n-3-weeks.html

For me, it boiled down to the connection between the fuse block after relay #55 and a the harness after a bulk head under the hood being bad. I'm not sure if your harness will be in the same position (on my base model car it was behind the battery), but I'm sure the connection still exists.

Best of luck to you.

Thank you for the responses - I printed out the threads off here (and a few others)and gave them to the guys at the service dept today - hopefully they can get some ideas of where to look from some of the info I gave them.

btw Sevinn the tech at chevrolet said you are the man due to you changing out your fuel pump in your driveway on a C6! :cheers:

haha, thank you very much. I wouldn't have attempted it if it weren't for a few others (namely Motorhead-47) explaining every part about it.

I don't know if you've seen this thread, but it is amazing:
http://forums.corvetteforum.com/c6-t...fuel-pump.html

I had the same issue yesterday, where the car would turn over, but wouldn't start. I have a 2006 C6 Z06, with 46k kms on it, and never had an issue. I finally figured out that the fuel relay was burnt/bad, swapped it with another one, and it worked fine. I then bought a new relay, and put the new one for the fuel pump. So it is working fine now, but from reading this and other posts, it looks like it may be an electrical wiring issue, and this may happen again... In any case, I have an extra relay ready to go, and hope it doesn't happen again. If so, I'll likely want to get deeper in to the re-wiring solution...

Any tips/recommendations would be appreciated...

It sounds like a loose ground wire.

Here what my problem was - after MONTHS of dealing with it, it turned out the FUSE BLOCK ITSELF had an issue - the wiring under where the relay goes had gotten hot and the wire was just barely hanging on literally by a thread. Im assuming the relay didn't trip or whatnot one time and it allowed the plastic fuse block to get too hot - Once they pulled it out, it was clearly visible (brown burn spot) on the underside where the wiring plugs in to the block itself - $17 part. Basically the plastic had heated up to the point that it warped and the wire didn't fit in there snug anymore so when I would push the relay it would find connection but once the car bounced (driving down the road) it would fall out of place. If I can figure out how to post a picture i took a pic of the part im talking about.

Good luck :cheers:

Thanks for making these symptoms/solutions known on this forum !

I got my car fixed today, and it was a loose pin/connection inside the fuse box, underneath where the fuel pump relay is. They replace the pin/connection, and it is working great ! (several starts / stops / trips over the last few days to confirm no issues). Thanks to www.championmotors.ca for a great job, finding the issue quickly, and charging just the reasonable labor for the job...

While the car was in the shop, I decided to give this stock car a tune, and got a 6% improvement in hp (now 451 whp, 531 at the crank) and 419 wtq.

Yup thats the same one. Glad everythings back in order :cheers:

Why it takes so long to find a common GM fuse block problem is unreal.

The current 'W' body Impala has a very common, but similar problem with the underhood fuse block that controls the cooling fans. Complete disassembly of the fuse block, 2 piece, is required to see the problem. On the surface everything looks fine, then check the harness connector and see the discolored wires , hint, hint.

Every fuse block that I have seen will have a damaged harness as the result of overheat caused be excessive draw of the component. The block itself will usually have the pins blackened from the heat as well and maybe have the plastic around the relay melted.

Yesterday I went to my GM dealer with a picture of the terminal I needed but the guy said I need the part number because they have hundreds of different terminals. By chance do you have the part number of the terminal (pin) Champion Motors has change for you?

Sorry, no I don't have the part number. They had the parts in stock and never made a note of it.
If you want, you could call Champion motors, they might know

Ok.