So after rebuilding my engine after a split crank shaft, i have run into a series of electrical issues. I have replaced multiple sensors and many connections in the wire harness. The vette kept throwing VATS code and would randomly shut off and show security light. My friend found a second anti theft system on the vette which i didnt know about (i bought it used). After trashing that and finding more horrible connections, the vette has a new problem. During idle, the vette loses voltage, then AFTER losing voltage, the car runs super rich and has no power. I have spent so much money on this damn car and any help would be MUCH appreciated. thanks!!

 

Stupid Question #1: Do you have a Helm Factory Service Manual?

Without that, you are pissing in the wind, brother....

 

well i dont know that much about this car. i just basically followed a build guide to build a stroker engine for the car. My experienced friend guided me. But other then the engine, i dont know what im doing. I sent the car to a performance shop and its in their hands. they said its not an engine problem. They've been working on it for quite some time, even they dont really know whats the problem. i was hoping someone on here had a similar issue

 

Probably a weak alternator.

 

thank you! im reading that alternator testing is unreliable. Should i test it or just buy a new one?

 

With a properly charged battery it should run for a while like 20 min at least without problem. I would trickle charge the battery and get it totally full. If the car is fine for a while it is a charging problem obviously. Get your alternator tested by a person who rebuilds them. Look around they are around. The test auto zone does is unreliable. Guys who can spin them hard to about 15k rpm to see if they are really in good shape. I've had them test fine from advanced but my guy here in town found them no good putting it on his motor spinning it hard.

I've also had voltage problems (still having them) with the sense wire that operates the regulator. Think it is the blue one.

I've piddled with the stock systems on these things for about 8 years now. It isn't worth it. Either slap a carb on it or get an aftermarket Holley efi unit or fast or something. Think about how much money even paying this shop to tinker on it and they might not even find anything. For less than $1000 buy a used unit and wire harness. No more vats, easy to tune and make changes or even get a self tune unit, never have phantom sensor glitches, it either works or it doesn't. So easy. All new wire harness will solve a ton or grimlins. If I knew what I know now all my vehicles would have started with aftermarket efi stuff. No questions asked first sign of any grimlins rip it all out.

 

Thank you for the info! So you still have voltage problems even though the alternator is fixed? And are you saying to convert my fuel injection car into a carburetor?? Can I do that with all of the modifications that are done?I have the engine bored 30 over, stroked 396, 39lb injectors, 255LPH fuel pump, pace setter headers. Edlebrock aluminum ported performance heads shaved 15 thousands of an inch, LT4 edlebrock intake, 1.6 roller rockers, 80mm mass air. All that can run off a carb? Please excuse my lack of knowledge about cars haha.

 

weak alternator? What gives you that idea?

Alternators only come into play once the engine is actually RUNNING.

So... First off, get a copy of the Helm Factory Service Manual. It will help you troubleshoot these types of problems.

I am betting money that the aftermarket security system has done some damage to the OEM harness.

Check grounds... there are two that count the most here, both in the kick panels under the dash. These grounds are where all dashboard wiring ground to. If something is crossed up or not grounded, all bets are off.

Also, make sure all grounds are present at the transmission. If something is missing there, you will have issues. There is also the main ground from the battery to the block. If that is lose or not right, more bets are off.

Go after the simple stuff first.

 

Moving to a carb takes all the complexity out of the engine. Conversion really just requires a different regulator, manifold and the actual carb. There might be few other tiny things but that is the basic idea. Clearance is the biggest issue.

For you really look into an aftermarket efi unit. I know C409 has a Holley commander 950 up for sale. If your engine runs fine now (excluding the voltage problem and you know it isn't the battery) for $550 you would have everything to just wire that sucker in. Really with the harness that comes with it it is more about removing the stock wire harness. It is such and easy conversion and the manual takes you step by step tuning. There is a bit of a curve but man it is so easy after the install and getting the base tune. Holley has good tech support too (takes a while to get through but they are good and knowledgeable. Guys name is woody who handles all the c950 stuff). Idle was hardest for me, took me about 30 min to figure it out. I got a base tune that I thought was same as factory tune in about 3 hours of driving around with a friend. Then it was just tweaking every so often but really it was good enough after 3 hours with the wideband o2 sensor compensating.

It made my life sooo much easier. No more check engine lights that don't mean anything. No more vats! No more emission egr crap. Just so much easier.

But sorry back to original problem yes I had a problem (unrelated to c950) because the voltage sense wire was reading wrong. Still worked but after hour of driving voltage dropped to about 12v running. Alt wasn't charging enough. You could always swap the bat and alt and if it works great if not, its a wire problem. I've had batteries crank and run fine but then out of nowhere have ignition problems and the battery is at fault. Batteries have to be working perfectly with fi motors for it all to work. Carbs will run till battery dies completely. Fi is a finniky animal.