Everyone,

Need some advice. I have a 2005 corvette that I did a heads and cam on. When the car is cold it will start all the time. When the car gets hot, sometimes you will go to start the car and it will just crank and not turn over.
I have checked the tune and replaced the injectors thinking that they were the culprit. Neither was the issue.
One thing that did happen was the cam sensor went bad when I initially put the car back together. I have since changed the cam sensor twice to eliminate that issue.
I have checked the fuel pressure, and the car is getting fuel.
I hope someone has come across this issue.

 

Well I was going to say cam sensor, but you took care of that. Here is a for ya

 

I know you said you have pressure, but if you prime fuel pump a couple times, will it start up right away? do you have an aftermarket fuel system?

 

Andy,

It is a h/C car. I put LS3 injectors, so all the injector data is from a stock ls3. Stock fuel pump and system otherwise.

someone said it could be the double roller timing chain. Really stumped.

Thanks,

Adam

 

One (or more) of your airflow tables is incorrect, either the Base Running table and/or the Startup Airflow table. Cars with heads and/or a cam typically need a lot more air compared to stock and it's something that people overlook quite frequently.

In addition to this there is an ECT (engine coolant temp) modifier table for your Base Running airflow table that will add more air using a multiplier based on the engine temperature. How this works is the first table controls the amount of airflow that the engine will see based on what gear you're in an engine RPM and then a multiplier is applied based on how hot the engine is.

To oversimplify this, let's say the Base Running airflow table in your tune dictates 12.0 g/sec while the car is just sitting there idling in Park (or neutral if it's a stick). The multiplier table might be 1.0 for a cold engine and then progressively increase to say 1.5 for when the car is closer to 200 degrees.

Using these numbers, your car would see an airflow value of 12 (12.0x1) when the car is cold and 18.0 (12.0x1.5) when the car is around 200 degrees. While the multiplier values might work well for a stock engine they probably won't be enough for a cammed car.

If your car starts fine when it's cold then you probably have the Base Running airflow table correct and by playing with the modifier table you should be able to also have it start properly when warm.

If you have access to your tune send it over and I can take a look at it tonight for you, as well as show you my stock tune compared to my current tune so you can see just how much I had to modify mine.

Christopher
syclone98@hotmail.com

 

Chris,

Thanks for the input. I tuned the car already and those tables are already modified for the larger cam. it is not a hard start issue. when the car starts it starts and runs fine.

the issue is... the car will sometimes just sit and crank. It will crank and not fire. It is getting fuel and no spark. I get no codes. I am going to replace the crank and cam sensor and see if that works.

thanks for the tuning advice, but this is not a tune issue. when the car starts hot or cold it starts fine and runs great.

 

I had a very similar problem, took me days to figure it out. I had just installed a new timing chain and cam sprocket. The problem was that the sprocket had four reluctors on it instead of just one, or vice versa. If you replaced your cam sprocket, it's a good bet it does not have the correct number of reluctors on it. Hope this helps. Good luck.

 

I had a similar problem last week, with a similar engine, I was intermitant with starter, DBS, thought sometimes it would rotate and not start, similar to the OP, changed battery and I haven't had a problem in two days.

 

I think that was it. I changed the battery and haven't seen the issue for the last day.

Thanks for the info.

 

Good news. It's interesting how many problems are solved with a new or charged battery.

 

New battery and disabled VATS 1 and 2.

Car Still has the cranking issue, so it isn't the battery or the vats

It will crank and not fire. You can push the pedal all the way to the floor and no difference. The car just sits and cranks.

It is getting fuel and no spark.

Thanks,

ADam

 

I think your problem is in your tune. I hope it works out for you. There's a lot of good people on this forum willing to help it seems.

Jeff

 

Jeff,

I have no ego to damage here. It is deff not the tune. When the car goes into a cranking condition, it gets no spark.

It is not a hard start and could happen once in 50 times hot or cold.

I am going to get a tech 2 and see if I can identify it.

Thanks for the feedback tho.

Adam

 

I continue to have a similar issue with my 89. Cold, starts up no problem, once hot barely a second start and forget a third, it cranks until the battery dies. I did a new battery as well. We also thought that maybe the heat from the engine was killing the starter. I put a heat shield on it and still the same issue. One of my headers was leaking and I thought it was boiling the starter, but I am back to square one. It is very frustrating.

 

I only just noticed that it's a 2005 so I agree with what Austin-vette said earlier about possibly having the wrong cam sprocket installed. Do you have any way of verifying whether it was the correct one for a 2005?

 

If You Hold the Gas Pedal to the floor when cranking the engine will not
start. I do this sometimes when car has not started in a long period of time. Use it so that oil pressure gets to bearings etc. before engine fires.
Not sure if this is your issue but do not hold pedal to floor while cranking, it won't start until you let up pedal.