Hello, all just wondering if its possible that the crank position sensor or cam position sensor would fail and not throw a code? My car doesn't want to start now and just trying to get some feedback. Ive changed the plugs, fuel filter and jumped the fuel pump relay and the fuel pump does run. My battery is good and connections are tight. The car has 174k btw.

My symptoms was the car would just act like you completely took your foot of the gas pedal then just kick you back like it was hit from the back. Its gotten to the point now where if its cold it will crank and run for 30 seconds then shut off. Now it will not fire at all. I jumped the fuel pump relay to see if the pump works removed the jumper then tried to start the car. It will fire but will quickly shut off.
I haven't checked the fuel pressure yet. The previous owner said he replaced the oem pump with a new pump in either 04 or 05. If my cats were clogged wouldn't the car still fire up and idle?

Mike

 

What procedure are you using to check codes?

Some people think when a problem happens that the code automatically pops up in the DIC but there is a procedure for retrieving fault codes, use this and see what your car is trying to tell you.

https://www.corvetteforum.com/techti...D=26&TopicID=1

 

I got the codes from the DIC. The only codes I have/had is the p0463.

This was for the fuel gauge and was like that since I bought the car 10/21/08. I did manage to run out of fuel once and was only able to put in like 8 or 9 gallons. Im aware of the transfer system problem. This still seems unrelated to my current problem. This evening I will get a chance to check the G107 location on the head. Do I have to remove the LH valve cover to get to it?

 

You need to put a gauge on the fuel rail to verify pressure. Alleviate this variable before chasing other options.

 

Is there a fitting that screws onto the schraider valve that i can use to a gauge? I really believe i have a fuel pump problem.

 

The schrader valve is inside the rail, no need to remove. A fuel pressure gauge only need be screwed on to the end of the fuel rail. They are pretty standard, and inexpensive. Available at your local auto parts store.

 

well, I'm getting 55-60psi at the fuel rail when cranking and running the pump with the car off, so i must have spark or a timing issue.

Still no codes. I checked the ground on the back of the head and its on tight with 2 small wires on it I believe if thats the right one. I could barely see it. Maybe some of my coils are bad. I will do some searching to find out how to test for sparks without electrocuting myself.

 

im getting spark now. Seems like it always starts right off after the car has sat over night. It still shuts of within a minute of running. It even ran decent with 1 plug wire disconnected that i used to test for spark. Should I replace the 4 year old msd wires and then try again? I only checked the left side to see spark. It ran fine when I cranked it up the first time for a few seconds. Still no codes. Again I swear I should be at least seeing a code if the crank sensor was bad?

I used a mirror and laid the spark plug on the end of the wire just underneath the alternator on the frame. I could see this while sitting in the driver seat!

 

175k miles on the car ? , try replacing the fuel filter .

Try to check fuel pressure when the car is running .

 

ahhh....post #7

 

car will start w/ a bad cam sensor

 

It will post pressure all day long with a bad filter and not running it but will falter and not run worth a dam when the car is started .

Let us know when you figure it out .

And a bad crank sensor .

 

I am getting spark. I changed the fuel filter before while chasing this down. Ive searched some old threads and someone said the crank position sensor can be bad without throwing a code. I already took it off last night and was about to go get a replacement.

I failed to mention I have a Optima Red Top Battery dated 5/05. when I had that checked it needed to be charged. It passed the load test they do at autozone after charging. When I turn on the ignition the DIC reads 11.4-11.5 volts with the car not running. Is this too low? Should I just reinstall my crank sensor and try a new battery? As far as the crank position sensor should there be a little bit of oil on the tip of it? I also doubt the chain is bad since it will run smooth for about 15 seconds when cold before shutting off. Someone also suggested the MAF bad. I also disconnected that once, but still noticed the same symptoms.

So far Ive checked:

fuel filter (replaced)
fuel pump (runs when jumped by the relay)
fuel pressure (55-60 psi at the rail)
spark plugs (replaced with NGK TR5's gapped at .050)
spark plug wires (replaced/checked with different wires)
ground wire on the back LH head
Battery turns the starter good.
NO codes on the DIC!

Yes, I'm getting acquainted with the car real fast! Nothing like my Honda's or Toyota's.

 

If the car starts and runs but dies shortly afterwards, then don't troubleshoot it when it's fresh, let it run until it dies.

And as far as fuel pressure goes that should be checked while running or even driving, I've seen a car idle at 55 psi and driving down the freeway it would show 55 psi but if you kept driving long enough it would drop down to mid 40's

 

Ill probably replace the crank pos. sensor and see what happens after that. Maybe today I will have better luck.

 

There is a procedure in your service manual to check the sensor before just changing the part.

 

dont have a service manual yet. I'll try to search online. I may get a scanner this eve and see if I can read something. For the DTC to set a code does the car have to be running for a certain period of time with the problem? If thats the case and my ckp sensor is intermittently working it wont show a code will it? Especially now since it won't run for even a minute.

 

It may not trip the light but it will show an H behind the code (history) if it has been a problem. And a C if it is happening currently when you use the DIC to scan codes..

 

I really appreciate everyones help. I hate to just buy parts and not have any reason to. Ive been searching on this forum and found a thread on the g105 ground under the block. This is a ground for the fuel pump relay. I will check it this evening!

 

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