I bought this 40th annv earlier this year knowing that it had a parasitic draw. Thought I had it fixed but appears not. Over the course of the last four months
i've replaced after testing the battery (was bad) , the alternator (reg bad), the injectors (one was plugged) and the spark plug wires. and the fuel pressure regulator (not holding pressure)

The same problem occurs; start the car runs fine. Revs fine sounds awesome but as soon as you put it in gear it starts to miss.

Two things we noticed; Key on good fuel pressure, key off pressure drops to 3psi. Neg cable when removed still has a spark and the rear hatch popped when neg cable removed.

when I disconnected the neg battery terminal the rear hatch popped and now seems like the door switches are activating on/off. Now the power antenna doesn't go all the way down.

My buddy whose a pretty good Corvette mechanic thinks I have a ground problem.

Previous owner never found the parasitic draw but replaced ECM (Summit Racing), Opti, Water Pump and plug wires.

I replaced the wires because the insulation was cut on one wire from being routed too close to pulley. I replaced the battery with a Diehard and in one month the drain ruined the battery had to get a new one.
For reference I did a parasitic draw test after waiting for the car to go asleep. I put the amp meter between neg cable and neg post and watched reading pulling one fuse after another and found no issues? Nothing changed.

I am suspecting maybe the hatch relay could be faulty because it opened when I pulled the negative terminal.

The car has had the VATS bypassed because I saw a resistor wired in.Don't know why or what the problem with the VATS was?

Has anyone had experience with a ground issue and can tell me what to look for?

Have FSM and been following the prescribed repair routes but am getting close to getting rid of the car. I have not once this year taken the car for a ride unless it was to my different buddies shops. I've had five vettes never run into such a maze

 

wow! what a nightmare.......parasitic draws are evidently common on the forum.....what was the draw?...you do know that when you put the meter in series with the neg cable, it's like opening the door again...there will be a extra draw until the "timer" shuts off....the courtesy circuit, a major circuit which includes the rear hatch, is a big offender for draws....mirror lights, spare lites, etc.....assuming you've went out there when in totally dark to see if anything is on.....I would get a circuit tester and try it .....sound like you've got a short somewhere....also there are several ground locations which you can see from the fsm.....wouldn't hurt to clean them for better ground....couldn't hurt.....good luck......

 

Have you probed the Voltage at the pump?

I am curious about your FPR change and what Opti is on your car.

From your previous post you had stated 38PSI at idle. What led to the FPR being changed? Was it leaking into the manifold? I ask because while it sounds like you have an electrical issue, it may not (or may) be affecting the engine running. If your FPR was leakign into the manifold and running rich you could have 02 or spark plug issues.

I question the opti because most aftermarket units are known to be crap.

 

an update

i have 38 psi with engine running and when moving car

As soon as car warms up a little the car starts to miss. Prev owner changed opti, water pump and ecm.
I changed wires, plugs, fpr and fuel injectors

whatever the parastic draw it is compounding finding why car misses when warmed up

my buddy who works on alot of corvette feels its a ground issue. Another pretty good mechanic says check TPS

I don't have any cel's

I asked my buddy to put some grounds on the car, engine , frame etc and let me know. I have my doubts

I think it's in the ECM that came from Summit. I'm beginning to realize that the PO had same problems and chased many to no avail.

any help is def appreciated

 

key on 38 psi
key off pressure drops to 5 psi
replaced FPR

now holds pressure

 

Holding pressure after key off isn't a big issue unless both supply and return are crimped to trap the pressurized fuel in the rail. This helps check for leaking or open injectors. Some newer pumps don't have check valves. It still makes me wonder what was up with the FPR, where was the fuel going, and has it caused any issues with your O2 or plugs.

Check your TPS, its easy. Probe it, at closed throttle you should be near .55V and WOT near 5V and a nice smooth sweep.

Also, is your CTS providing appropriate readings?

No harm is confirming the grounds. If nothing else you eliminate it being an issue and you can move on to the next potential issue.

Unfortunately I can't look past an aftermarket Opti and ECM being potential issues. No CEL may be part of a bad ECM.

 

thanks will check the tps and cts out

 

TPS is 3 wires: Ground, 5V Ref, and then the output varying voltage.

 

may have been inaccurate when I said no CEL. One occassionally comes on with ASW. When I put my Bosch Code scanner in (reads I and II) there are no codes. Previous owner bought in Feb 2017 Opti and ECM from Summit.

Car sat before last owner before me bought the car cheap. He replaced a ton of stuff in the chassis as well as the Opti and ECM. There has been a persistent parasitic draw issue so bad that PO gave me his jumper cables because it would drain the battery so often.

When disconnecting negative battery cable theres always a spark even when system times out. Last time I disconnected the hatch opened which made me think bad ground or bad hatch relay. Buddy thinks its a ground issue because car starts and revs fine when cold but as soon as warmed up starts missing.

IDK its been a real pita. I have not driven the car for pleasure once just to various buddies shops for repair.

The draw issue may be coming from radio relay but it's so bad and intermittent that it killed a new diehard battery in a month. I say intermittent because sometimes car can sit for weeks and start battery fine which makes me think a relay somewhere is taking draw. I Amp checked all fuses and nothing that I pulled made any difference on the meter.

We are going to put car in air and check all grounds for a start. Power antenna now not going down all the way which makes me wonder about the radio relay end of things. Also now when disconnecting the neg battery cable the door locks cycle? VATS has been bypassed with a resistor wired in.

WE'll get to unplugging the opti and testing that. Both Opti and ECM came from Summit. I read somewhere that you could tap on ecm while car is missing to see if that affects it in some manner?

 

You are describing two totally different problems.. the engine miss and a power draw. I would like to know is the battery holding charge after a few days sitting and what the voltage is with a DVM with the engine running ..both at idle and 2k rpm. If your battery is maintaining a charge for a few days you can put that on the back burner. Now to address the idle, start from scratch with the FSM trouble tree for a miss - and I do mean start from scratch, forget everything you have done with the electrical at this point. Find the cause of the miss and fix that, you may find everything clears up after that. Did you test and change ignition coils ( again follow the FSM) , also have you light sprayed the engine with mist from a water bottle and check it in the dark for wire arcing?

 

ok after weeks of looking and asking on the forum I think I found the problem but not sure what to do about it

I followed the FSM and in the end found that when I pulled the fuse for CCM #2 the amps sat still at .45a
with the fuse plugged in it jumped to .77-.84a

Central Control Module for interior lights , security and hood lamps among other things.

The PO said the car wouldn't run and shop wired in resistor to bypass VATS. Everything points to CCM being a problem from the amp draw present with fuse intact and half the draw without fuse in place.. This could account for the car starting fine and maybe a minute or two it acts like its missing. If it affects the security system it could affect the fuel delivery.

Anyways does anyone know anything about the CCM? I've hardly heard of these going bad and if they go bad is what I'm seeing the symptoms?

HELP

 

The CCM rarely goes bad and is the #1 most replaced part that turns out not to be the problem....plus its a real pain to replace, program, only second to heater core.

 

voltage 14.23 when running
after sitting a day 11.6 v but sometimes its a lot less which started me thinking a relay is energized or something?
changed ignition coil (LT1)
installed new 8.2 mm spark plug wires

po installed new summit ecm and summit opti in 2017

 

what would cause the amp draw

under hood is 20amp maxi fuse
i/p is 5 amp ccm 2 fuse

big amp draw until I pull th maxi or the 5amp

do you think it has something to do with vats/security system??
5/01/18 service records show that the pcm was bad and sent out for repair

That is not the same as the ECM which was replaced with a unit from Summit

so maybe it is PCM/CCM same thng?

 

As I mentioned, you complained of a running/idle issue. The is likely not a CCM problem. I would trouble shoot that before even starting on an electric drain.

 

when I remove the fuse for CCM 2 the draw goes from ,8 amps to .45 amps well within the spec.

Don't you think high amp draw at the ccm 2 fuse identifies a problem withe the ccm?

One other item that I forgot to mention. My dash flips its display from kilomoeters to miles per hour back and forth. I replaced DIC and same result.
Does the CCM control the dash reading?

wanted to mention the dash flips erratically when key turned on. Reading flips from kilometers to MPH, other rradings on the display change as well. I replaced the DIC and it changed nothing. Does this tie into CCM?

 

was hoping that someone would chime in on dash flipping from mph to km back to mph does it all the time.

Going to call Battee today see what they say

 

Zip Corvette tested my ccm and it was not bad. I'm really bummed. I am reading the DIC interface with ccm and will start testing as manual advises.

I feel like I'm not going to solve this

 

wow what an education I have been getting on this car. CCM was good but the C68 head was defective.

Amp draw is 4 amps! So I disconnected the hot wire and the plug on the alternator and amp draw still 4.0 which is huge.

I don't know why I did this but I think i've found it..
I had a test light put alligator clip on negative terminal and put probe on alternator case and guess what had a glow on the bub!!! Put the probe on the intake and same glow. I've got a hot wire shorted! Gonna pull battery and fender well on divers side and xplore that area I bet I find a shorted wire. Fingers crossed.

After month or more dabding at it I'm more than proficient at reading the FSM and have plenty of black n blues from fighting this car. Fingers crossed

will report working on it Sunday.