Gentleman...this is my first post and I am in desperate need of advice on a no-crank situation that occured (like most) out of nowhere. After wintering in the garage and my normal bi-monthly starting and pulling out of the garage, checking fluids and the like, warm weather gave me the bug to drive her to our place in Branson, about 200 miles south of Kansas City. The trip was uneventful and she purred like a kitten...but the next morning I went to start her up...nothing! Not a sound...no courtesy lights...no security light...no door ajar...nothing! Thinking it was possibly the battery cables (although I maintain them on a regular basis...after all, this IS my baby!)...pulled them loose and cleaned an already clean post and cable, decided to check battery voltage and my DMM read a decent 12.8 volts. Okay....starting to become concerned...I had heard many times about VATS problems with C4's and it so happens the last time I was in the dealership I purchased a brand new key, only used once, the day I purchased it...inserted key...nothing! Headlights work, fuel pump energizes, heater blower works, but...I tried jumping the ALDL, nothing. There appears to be no power to the ALDL! The starter is about 1 year old, so I don't think it is at fault. But why can't I pull any codes? I do not presently have a FSM (I have one on order), BTW, I have checked ALL fuses for continuity and all are fine. Any help would be greatly appreciated, as I really don't want to have to flatbed her 200 miles! Thank you in advance!

 

Since you seem to have normal voltage and the non-engine bus energises normaly I would have to assume a VATS problem. I haven't encountered one yet so I don't know much about the system. Try exploring a search on VATS bypass.

You said you have a new key have you checked the resistance of the "chip" and compared both to make shure they are the same?

 

If the security light isn't on, it shouldn't be a VATS fault. Look elsewhere.

If '95 is wired the same as my '94, the fault could be in the ignition switch, starter enable relay, starter solenoid, CCM, clutch safety switch (manual trans), neutral safety switch (auto trans), crank P/N clutch fuse, or any of the associated wiring and connections. This is, presuming of course, that your battery voltage remains at or near the 12.8 volts you measured while you're trying to crank the engine.

Here's a hand-drawn sketch of the crank circuit for my '94:



The source of the 12v for this circuit is the ignition switch (again, presuming that you have a solid 12v getting to the switch from the battery). The switch then feeds that 12v to both the start enable relay's contacts and to the start enable relay's windings via the crank P/N clutch fuse and clutch/neutral safety switch. The far side of the start enable relay's windings is switched to ground by the VATS section of the CCM. If the start enable relay kicks and feeds current to the solenoid, and the solenoid still won't kick, the solenoid (or the connection to it) is faulty.

If you can safely get under the car, measure the voltage across the solenoid's start post and chassis ground while somebody tries to crank the engine (make sure they know to stomp the clutch to the floor or put the car in neutral/park). If you get 12v at the start post, but the solenoid still won't kick, you need a new solenoid. Easy fix. If you're not getting 12v to the solenoid, you need to chase the fault back to the source.

If you need to get the car started once to avoid a 200 mile rollback ride, push start it if it's a manual trans. If it's an automatic, and you can get under the car safely, you can jumper 12v to the start post of the solenoid (make DAMNED sure the car is not in gear if you try this!!!).

Best of luck with it.

Be well,

SJW

 

Thank you for your suggestions...needless to say I had to leave the car where it sits until this weekend when I can return and investigate further. As far as the key resistance, I have not physically checked both keys to compare, however I know the new key worked when I tried it at the dealership. Again your input is greatly appreciated!

 

Yes, if you have the key inserted in the ignition and turned to the "ON" position, jumping the solenoid with 12V can start the engine. BUT AS SJW SAID MAKE DAMNED SURE THE TRANS IS NOT IN GEAR!!!!

The only other thing I can think of is the neutral safety switch.

Years ago I had an occasion where the engine wouldn't crank with the gear shift selector in PARK but it WOULD start with it in neutral.

Hope this helps.

Jake

 

If the security light isn't on, forget about a VATS fault. Your key isn't the problem.

Be well,

SJW

 

I can't find the link right now, but there is a Corvette site that lists recalls and Technical Service Bulletins that has a Bulletin for the '95 Corvette only.
That TSB indicates the CCM was a problem on some '95 Corvettes and would prevent starting.
The solution was to replace the CCM.

Here's the description:
------------------------------------------------------
Make: CHEVROLET
Model: CORVETTE
Year: 1995

Service Bulletin Number: 01053
NHTSA Item Number: 39336
Summary Description:
INTERMITTENT OPEN GROUND ON VATS CIRCUIT OF THE CCM CAUSING VEHICLES TO EXPERIENCE A NO CRANK CONDITION. *TW
-------------------------------------------------------

Here's the link:
http://www.corvetteactioncenter.com/....php?qstId=151

Tom Piper

 

Thank you Tom Piper and SJW for your input, I appreciate your interest in my situation. The TSB indicates a solenoid click, and a re-start possible when cold, but mine does neither.

 

If I read you correctly you went out to start it and everything electrical was dead. Then after cleaning the battery cables you got some electrical items back to working? Is this correct? Did you also charge the battery?

12.8V is actually just above the defective battery borderline of 12.6V and normal charged battery should be 13.6V+- a .2. Next time check battery voltage before you even try to start it. Simply turn on the key and read the voltage on the gauge. To drain down to near zero that quickly would make the alternator a prime suspect, but bad cables and connections also need to be considered. Hope this helps.

 

When I FIST GOT MY 95 I HAD A SPARE KEY MADE IT HAD A OPEN IN IT
AND WOULD SOMETIME WORK. I RETURNED IT TO THE STORE WHERE A CHECK REVEALED IT WAS A OPEN RESISTOR. NEEDLESS TO SAY THE VATS DID NOT LIKE IT AT ALL CHECK YOUR KEY. GOOD LUCK

 

A few months back my 96 LT1 had an intrmittent NO-Crank condition. 75% of the time the engine would fire right up on the first turn of the key, the remainder of the time NOTHING. No solenoid click, nothing; however all the lights worked fine.

I replaced the starter and haven't had a single recurrence. I know you said your starter is only 1 year old, but still . . .

Just trying to help.

Jake

 

I don't want to be negative but I had the same occurance happen to my 1994. I took it to the local Corvette only repair center. After a thorough testing, they were able to make it start briefly by bypassing the body control module [also known as the ccm]. However after about 15 seconds it cut off due to the VATS override. The conclusion was a bad CCM. The car was taken to a local Chevy dealer whom confirmed this diagnosis. Unfortunately, this part as a new item will not be available until at least June 30th. I sure hope you don't suffer this situation.

 

I replaced the 1 year old OPTIMA battery...got 'er started to my surprise, however, when I returned home (safely in the garage) I immediately tried to start and SOS, nothing. Voltage reading is 14.6 volts on DVM....received my FSM finally, hopefully this helps....but at least it is home! Thanks to all for tips!

 

The '95 does not have an ALDC...it has the OBDII connector but only OBDI capability. You have to have a code reader/scanner to pull or reset codes.

And this sure sounds like a VATS problem; worn contacts in the igniton switch cylinder. The good thing is that the part is only around $45....the bad....takes awhile to replace.

I suggest measuring the key resistor pellet, finding out what the nominal value should be from a list of VATS key codes and then inserting a resistor across the connector from the ignition switch, under the dash. You will then have to get a new key without the resistor to see if the car starts everytime. All of this just to check if its the contacts in the cylinder are worn or not.

I do not recommend by-passing VATS other than a test.

 

With all due respect, I must disagree. If it were a VATS fault, the security light should be active, and the OP noted that it is not. The fact that the car also would not crank with a brand new, known good spare ignition key also suggests that it's unlikely to be a VATS fault.

Be well,

SJW

 

I have a similar story. I came home from vacation and started the car up with no problem. I drove down to the video store and parked it. When I came back out, nothing. Dead. Towed it to the dealer and they said I must have gone through a big puddle and got watter in the computer. I really think I would have remembered a puddle that big, but... Anyway they put a new computer in it and it started right up.

To pull codes on a 95 you need to jump pins 12 and 4 then turn the ignition on. If you can do that it's probably not your computer.

Good luck.

 

As I wrote previously, My 96 LT1 had a similar problem, occasionally NO CRANK AT ALL.

I first thought battery and since I was leaving Texas for Indiana in the heart of winter, I decided to up the CCAs, so I bought a new 720 CCA battery from AutoZone. Problem persisted.

I then ordered a new starter and after installing it I haven't had a single problem. I suspect it was the solenoid.

Jake

 

Be careful here, you are correct that the '95 has an OBDII connector with OBDI capability, but the codes CAN be cleared by disconnecting the negative battery cable for a few seconds, and you CAN retrieve the codes without a code reader/scanner by shorting ALDC pins #12 and #4 together, and reading the error codes off of the gas gauge display.

 

MikeC4,
Oh really.....so you can jumper pins and get the codes without a reader....well...I'll be....learned something new.

SJW,
I missed the fact that the security light did not come on. But anyways, if it was the contacts in the switch...a spare key would not make any difference...right? But if the spare key worked everytime, then would not the problem be the key or rather the resistor has either changed value and is now out of range or the contacts on the resistor are worn?
How tight a tolerance does the VATS allow on the resistor anyways?

Still learning about these cars.

 

A spare key might or might not make a difference if the contacts in the lock cylinder are worn. It would probably depend upon whether the original key's pellet contacts were also worn and/or contaminated.

Resistors don't often drift much in value due to age. I'd be very surprised to learn of a VATS resistor pellet that drifted enough to go out of range.

Here are the ranges for each VATS resistor value:

402 ohms (386-438)
523 ohms (502-564)
681 ohms (650-728)
887 ohms (850-942)
1130 ohms (1085-1195)
1470 ohms (1411-1549)
1870 ohms (1795-1965)
2370 ohms (2275-2485)
3010 ohms (2890-3150)
3740 ohms (3590-3910)
4750 ohms (4560-4960)
6040 ohms (5798-6302)
7500 ohms (7200-7820)
9530 ohms (9149-9931)
11800 ohms (11328-12292)

We all are, my friend. There isn't a soul out there who knows it all...

Be well,

SJW