Electrical starting system shutdown-could be nuclear meltdown

[tomtom72]

I just had a BFO.....yea, I'm very senile. One of the things that the CCM does is house the VATS system. The VATS system is just an electronic switch or relay for the fuel pumps. That's what keeps the bad guys from hot wiring our cars. No key pellet ; no fuel. You hear the pumps right? Just humor me as an old guy who's senile.......Hook up a fuel pump pressure gauge to the rail. Drain off the built up pressure thru the dump, and then go put the key back in and turn it to run and observe the gauge. Sort of like the start of the fuel pump diagnostics KOEO test flow chart in section 6E. If you got F-pressure, the VATS & key & possibly key cylinder wire are all okay. I think that diagnostic thought train is valid.


Tom

[Dave2]

Further data:

Old trickle charger dead-no output though charge indicator is green

Purchase new trickle charger

Data from vehicle:

fuse keyoff key on* *new trickle charger connected
LCD 13.1v 12.6v
ECM 0v 12.7v
CCM 0v 12.5v

Data matches normal power side of CCM (service manual section 8A-50.8)
Looks like next step is get into the dash to check ground side resistance thru harness to ground. I contacted http://gmautocomputers.com/ who rebuilds the CCM and ECM's for their experience. I described my symptoms to the gentleman and he indicated it fit a CCM failure, and these units are susceptible to power spikes (16v+). (Avoid jumping vehicle with a battery booster). Possible power spike from old charger that failed took CCM with it since CCM is always powered up. Rebuilt cost $280, current 10 day turn around time. I'm still hoping for a ground side issue (get out of jail free card- though it's feeling more and more like a Hail Mary pass).

[tomtom72]

Okay Dave. I'm obviously a bit less advanced than you at this CCM stuff. So do I have this straight?
Charger was N/G, so you cooked that battery @ 40 amps for at least an hour to get it back up, right? You still have the same symptoms, no crank, but lights & everything else is okay?

I going to say unequivocally that I've seen more times than not an LT5 will not crank if it is powered by a less than 95% battery. I'm going to apologize again for asking that you're sure that this battery would/did pass a load test? It's not just about voltage for our system, the "system" light will flash if the battery voltage drops below 12v(?). I'm not sure about the exact number. I also know that an LT5 will not crank well or at all with a battery @ 12v and either a shorted cell or low amps due to bad electrolyte. I know I sound like a broken record here, sorry. I just don't want to see a brother tear out a CCM only to find that was not the cause.




Personally I hate trickle chargers as they just boil the electrolyte and make it useless. If I had power in my garage space I'd be tempted to get on of those C-Teck chargers, maybe.


Tom

[scottfab]

Originally Posted by tomtom72

....snip....
I also know that an LT5 will not crank well or at all with a battery @ 12v and either a shorted cell or low amps due to bad electrolyte. I know I sound like a broken record here, sorry. I just don't want to see a brother tear out a CCM only to find that was not the cause.

I'll second that. Unless you know that perhaps a charger may have been applied with no battery to hold the V down to 12V or maybe the battery electrically opened internally such that the V went north of 14V (as has been mentioned) I'd hate to see the $ go to e CCM you don't need.

Originally Posted by tomtom72

Personally I hate trickle chargers as they just boil the electrolyte and make it useless. If I had power in my garage space I'd be tempted to get on of those C-Teck chargers, maybe.


Tom

In my experience (and that of many others on here) a float charger of ~200ma will not damage a battery but only offset the car's draw plus battery internal current leakage.

[Dave2]

Thank you for your concern- I'm still hoping for an easy out.
Results of the battery test are:13.08v 751 CCA @66'F on a ESP800 tester. Though the DS engine and body grounds connections look clean, I'll disassemble clean and deox coat. Could be a cold connection.
Fuel pump test results- yes there is pressure at the manifold after turning the key on (Bled the PS schrader fitting down and then retried the ign. key-system repressurized). I'll need to fabricate an adapter to get an exact fuel pressure with my gauges.
I need to see if VATS circuit diagrams affect fuel pump power or injector firing power.
I'm probably going to start some of the disassembly toward the CCM tomorrow to test wiring from CCM toward vehicle. Is there any other steps or warnings missing from the prior posts related to dissassembly to reach the CCM?

[tomtom72]

Hi Dave, Okay & understand: battery appears to be 100%. Did you run thru the diagnostics for the starter circuit? I'm talking about the "No Start" wirte ups we have over at the NetRegistry site in the Maintenance section? There could be some very useful stuff there. The clutch safety switch & starter relay come to mind and then the connection at the starter solenoid and finally the copper contact disk inside the starter solenoid.

Okay, my understanding of the VATS function is that the resistance of our pellet completes a circuit. Having the correct pellet matching the ohms programed into your CCM then completes a circuit that energizes the fuel pump enable relay. That's all our VATS system does, it's a fancy fuel shut off. Again, that is my squash's understanding of a C4 VATS system....in it's simplest form. Do you have a scanner? Or maybe Gordon's jumper kit? I was thinking to hook up the battery and do a KOEO test of the CCM.

Oh, on the starter. There is a write by Marc Haibeck about how you can give the starter a wack while trying to crank & if it responds then you've narrowed the issue....maybe. You can just snake a long 3/8" extension down thru two of the plenum runners and get it against the starter so you can wack it. I just never had to do it so I'm thin on details. Also, there is a way to do a KOEO simple test on the clutch safety switch, over at Haibeck's also. I think with the key in the "Start" position you work the clutch and watch the volt gauge, if it moves it's good. Scott knows better than I on this subject.

On the CCM R&R....shift knob 1st, then console 2nd, A/C register 3rd, actual center bezel: four 10mm screws I think plus two lower edge locating pins(?) and then those clips left & right. Everything in the center stack comes out: the same 10mm or 7mm screws are obvious except for the radio head unit. There are some at the right edge that I had to pry the dashpad to the right to get on them. I used painter's tape on the dashpad so the mounting ears for the radio didn't scratch it on the way out...yea mine was that tight anyway. Now I'm out of steps because I never have been any deeper into the back of the dash. Sorry. I will look up this in my FSM set and report back. Or I can give you my digits or as you're in CT I could make a field trip. Or, if you don't have a FSM set I can ship you mine. Your choice man, I'm just trying to help a Brother out.


Tom
P.S. I'm just some back yard hack....no ASE Tech here, so my knowledge base is a bit shallow.

[tomtom72]

now I'm really On the electrical system's ground integrity .... this seems to be an issue for every gen vette. Plastic cars have issues. When I first got mine She was 14 yrs old. Since it was winter in NY I had all winter to take apart every connector and ground I could reach & find easily. I cleaned all the connectors' pins with contact cleaner & pencil erasers and then coated with dielectric grease. I paid special attention to the rubber ribbed gaskets on the connectors. I massaged them with the dielectric grease. Taking care of the grounds is easy...you know that drill, star washers are your best friend. Took me about two months a bit at a time. I guess what I'm saying is that I ( knock on wood ) have not had much of an opportunity to chase electrical issues due to poor or / and oxidized connections. To this day every two yrs I go thru it again just to be sure. It don't take that long as the stuff stays clean mostly and I'm mostly just shooting more dielectric in the connectors & on the rubber gaskets. Oh, and this seems very important or to me it is. The electrical standards for automotive wiring insulation changed with the 92's (?) and the older stuff is crack prone and chafe prone. I found that over at the NetRegistry site in the TSB section I think. So I eyed up all the runs and took action ( mostly using rubber vacuum hose & heater hose & zip ties. Yea it ain't pretty! ) to insure against chafe & vibration. I did the same drill when I got to change my OE injectors...man what a cluster F___ under the plenum! At least it made it easy to get to the back of the block! Watch now I just brought electrical nightmares down on me by saying this!!!

I guess what I'm trying to say is that I know I stink at electrical diagnostics so this seemed prudent for me to do. Also, by extension....I'm fairly ignorant and proly should keep my trap shut as I'm not much help in the electrical department...just ask my Z-Brother Lou from Norwalk!!!


Tom

[Dynomite]

Originally Posted by Dave2

still had no interior lights, dash LED, no security indicator, or door chime. Headlight are nice and bright. Where should I start on diagnosing this?

Ground Connections as tomtom72 suggests.
There are two engine block ground connections (multiple grounds each) located just above the Bell Housing (rear of engine block) one on each side of the engine. There are several ground connections on the chassis near the battery frame rail and other ground connections near chassis components. There is also an engine to chassis ground strap from drivers side of engine block (on side rear of engine block) to drivers side frame rail. The main Battery negative cable attaches to the side of the engine block just in front of the Bell Housing (primarily for the starter ground).

Check for ground continuity of any suspect component using an ohm meter. With one probe on the negative battery terminal and the other probe on the negative terminal of the suspect component you should get zero ohms with ignition key off as most components are not grounded through any switch.

Loosening those two engine block connections will not be easy as I mistakenly left the HVAC fan ground disconnected when installing the engine last time from the passenger side engine ground connection. I tried to get at the passenger side block ground connection from underneath (It could be very difficult) and I have Headers which makes the underneath approach considerably different. Cleaning Engine Block Ground Connections

I decided to connect that HVAC fan ground to the rear most Plenum bolt instead which works perfectly as it helps keep that passenger side wire harness in place.

Disconnect ground wires, clean surfaces, clean grounding bolts or screws, use star washers if applicable.

As an aside.....and I am prolly the only one on this Forum......I do NOT use trickle chargers but rather disconnect negative battery connection if ZR-1, Toyota Truck, JD Tractor sits for a period of time without starting. When I reconnect the negative battery connection (even when sitting disconnected over winter) the ZR-1, Toyota Truck, JD Tractor fires right up. I do not have power leaking through all the ground connections or trickle chargers powered up with wires strung all over. Disconnecting a trickle charger takes longer than just reconnecting the negative battery connection.

In one of the photos below there is a Green Ground Wire to Chassis.
that Green Wire is the New Starter Relay Ground Wire Starter Relay, Wiring Harness, Battery, and Plugs Tricks

Ground Strap Connection to Engine.............................Ground Connection from Bat and Engine to Chassis
.................................................. ...................................(green wire is NEW starter Relay ground)



Ground Connections Bolt to Engine Pass Side....................Ground Connections Bolt to Engine Drivers Side


Torx #30 to remove Drivers side Batt Panel....................5/16 inch Flex Ratchet to remove Negative Batt Terminal
SS Allen Head Bat Hold Down bolt shown..........................I remove if ZR-1 left sitting for more than two days


Electrical Ground Connections and Clutch Start Switch Linkage

[scottfab]

Dave,
It would seem to me now that you've verified a good battery source that the next move is obvious. Rather than guess and do a hit-or miss approach why not just measure on one of the known faulty systems?

The courtesy lamps would seem a good choice. They are right there easy to get at. The goal is to determine if you missing ground or 12V at the lamp. From there you continue you hunt for the cause of one or the other, ground or 12v missing.

Steps:
1. take cover off one of the courtesy lamps.
2. remove bulb
3. place the black probe (important) right on the Neg post of the battery.
4. Measure inside the lamp socket on both contact points.
Either contact have 12V? If No then next step is to find out why so you can stop here. Next steps (not listed) would be 12V supply line troubleshooting.
5. If you have 12V on stop 4 then remove the probe on the Neg post of the battery and place the red probe directly on the Pos post of the battery.
6. Now probe the two lamp socket contacts with the black probe. Do you get 12V on one of the contacts? At this point if you get no 12V your missing the ground at the socket. Next step is ground fault isolation.

Since the courtesy lamp does not come on when you open the door you have to be missing ground or 12V (unless all bulbs are popped)
Let us know which one.........

[Dave2]

Ladies and Gentlemen- we have the answer........................

CCM failure. The failed unit that was in the car had a factory rebuilt sticker on it-
The DERM (SIR system) also had a factory rebuilt sticker
Sent my CCM unit to K&B Special Products Alpharetta Ga. (GM authorized rebuilder) 770-777-1034 and $280. The tech's there indicated #1 cause of failure is high voltage- either a spike or voltage regulator drift 15V+. But they reiterated several times that these units had a limited life, and have seen units just croak.
I reinstalled the rebuilt CCM in the car (remember the story of the proctologist who did a valve job on his car engine via the exhaust pipe,) the CCM is buried against the firewall so it's either a choice of pulling the whole dash or forcing it out the center console area and risk collateral damage. I voted for the former though it resulted in a lengthy delay due to my lack of free time.
Turned the key and everything worked!!!
Now I just need to figure out what to disconnect/bepass for the Low tire Pressure Warning system indicator- I'm not running the sensors in my street tires and rims.

See you at Carlisle!