ready to throw in the towel

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ready to throw in the towel

jimyz jimyz
I watched Corvette Summer | Posts: 7 | Joined: 03/07
Posted: 11/12/12
02:49 PM

I have 94 vert w/56k, garage kept, has lived a good life. Sat. I took the car about 7 miles down the road and it quit running. Had to be towed, ruined the beautiful day. This is the second time this car has stranded me. I am fairly mechanical, Ive had no other cars do this to me. I could always limp home and figure it out. New opti 2 years ago/fuel filter/wires/etc, 56k. I pay more to have this car sit than be used. Kind of like a fireman waiting on the next call knowing the maintenance has been done and hope that everything works. When the car runs dependably, good perf., good economy/ergos. I think Ill buy a weekend warrior that gets 8-15 mpg that I know how to diagnose and get home. Sorry, just venting.-Soon to be ex-vette owner  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/12/12
09:30 PM


i hope you get this...

there is an adaptor harness from the side of the optispark to the computer harness..

you can build one out of components from the parts store.. or you can buy a complete one from one of the supplier.. i think they were around 40 buck... gm wanted several hundred..

if you can get the engine running...    reach over and UNPLUG the fuel pump relay.. the engine should CONTINUE to run.. if it dies.. change the 3 wire oil pressure switch...

you will also want to invest the UNDER 20 bucks and replace the IGNITION SWITCH..

look inside at the contacts...


any of the 3 could cause the car to stall.. just like you describe...

if you replace the oil pressure switch.. change the fuel pump relay also...  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/12/12
10:05 PM

why am i telling you to get in and change these parts... they are really CHEEP compared to the EXPENSIVE labor intensive components...

the OPTISPARK harness adaptor has been FOUND to be filled with GREEEN corrosion and failing..

it transmits tiny signals to the Computer..   if the signals get scrambled. the computer looses count and the engine dies...  sorry. i did not design it.. i only fix them...

the oil pressure switches fail... but they don't fail to display oil pressure.. there are 3 wires to it...

there is an ORANGE wire to one side of the oil pressure switch connector is HOT battery positive.. with usually a FUSIBLE LINK.. not a fuse...  a grey wire on the other side goes to the fuel pump..  usually through a fuse... between the oil pressure switch and the pump...

but.. the oil pressure switch and the fuel pump relay are wired in parallel..  so the same orange and probably grey wire exist on the fuel pump relay..  

the reason to replace the fuel pump relay is the contacts burn and fail to make good connection..

when the oil pressure switch/fuel pump contacts don't make good contact.. all the current for the fuel pump goes through the relay.. it was never designed to handle ALL THE CURRENT.. only for short amounts of time..  some relays have tiny terminal pins that overheat and cause opens..

please.. DO NOT PROBE with a TEST LIGHT the GREEN and white stripe wire into the fuel pump relay SOCKET... this can cause the socket terminals to Expand and loose good grip on the relay terminals.. causing the engine to die...

why do the ignition switch... first.. THEY FAIL a LOT... even the C5 switches have issues and need cleaning or replacing.. since they are about 200 bucks.. the C4 switch is about 20 bucks..
a lot of other corvette owners have spent thousands of bucks only to finally replace the 20 buck ignition switch..  

jimyz jimyz
I watched Corvette Summer | Posts: 7 | Joined: 03/07
Posted: 11/13/12
06:49 AM

where are all these relay switches located? where is the ignition switch? If these are the culprit, wouldnt i get some reponse in trying to start the car? I get nothing  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/13/12
08:36 AM

fuel pump relay is #3 in a square outline in this component locator..


the ignition switch is on top of the steering column.... under the dash board..  shown as item 80 on this image..


if you get NOTHING when you attempt to crank the engine...

i would start with cleaning the battery cable ends..    take the terminals off the battery side.. remove the bolts from the rubber battery cable boots..  they wiggle and unscrew out..

examine the inside .. you can pour hot water over it to soften the boot and use a small screw driver to pull the loop of the boot over the ring terminal end to get in and wire brush the ring terminals...  clean the bottom side of the battery bolts also.. along with the face of the battery post...

let me look up some more stuff for you...

check your messages above..  just to the left of where you log out at..

please. DESCRIBE the complete issues and what works and what does not.. also check the messages and use the number i posted..  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/13/12
09:17 AM

oh.... also..  DO ME A HUGE FAVOR..

stick the ignition key in...   if the car does NOT start... look over at the Security system light on the dash board... if its ON or Flashing.. that could be the WHOLE issue that would leave you stranded..

what happens is after a decade or two of use..  the VATS ignition system components in the ignition switch can break or fail...

how it works is there is a resistor pellet in your key..  when you slide the key in.. contacts inside the ignition lock cylinder contact and complete the circuit ... this tells the computer that the proper ignition key is the Correct one to start the car..

there is a 4 minute TIME out if the system gets the WRONG key or the resistance is wrong through the circuit..

lets look at a slightly earlier vats ignition lock cylinder...


the white wires actually are attached and flex inside the lock cylinder.. so they can fatigue and break..  the contacts can also get pushed out and fail... sometimes just a short blast of WD40 and working the key in and out a few times will restore the contact surfaces..

i have CHEEP ways and they are easy ways to BYPASS this if you have a radio shack nearby.. this bypass only works if you have the proper ignition key and a OHM meter to measure the resistance of the pellet and the 10 turn trimmer pot from RS to adjust it prior to installation.

so... is the security system light flashing when it fails to start????

or when it died...

if you have a SCAN tool.. or a code reader...  for the 4 minutes until the lockout expires..

it will have a CODE 46 in the memory...

if you don't have a scan tool.. i put up a thread on which scan tools for C4 corvettes a while back.. its not buried too deep in the active posts.. its probably in the C4 forum section...  

pepsi1 pepsi1
Duntov Incarnate | Posts: 88 | Joined: 01/12
Posted: 11/16/12
08:39 PM

Great metaphor! I was a fireman and sometime that's what happened. The equipment had to be ready.

  It was something that blew out or failed, by that I mean your car is OBD1. If it wasn't a major problem it does have a limp home mode.
  When it died did you smell fuel?

Does the engine crank?
  If it cranks its either spark or fuel. When you turn the key to the start position, can you hear the fuel pump come on. It will only come on for 3 to 5 secs. So be some where you can hear it.
I'm sure you have been thru the fuse box. You may want to use a tester to probe those fuses. I've seen them half blow. They look good, but blown.
  Then see if for have fuel in the fuel rail. Check the fuel pressure regulator. Remove the vacuum line and see if there is fuel in it. If there is fuel in the vacuum line the regulator is leaking. That could flood the engine out and make it die.
  Then check it for spark. Does that have the Opti Spark or a regular coil?
The opti spark and coil controlled spark you can test the same way just crank the engine with a spark plug wire off, and jump it to ground. BEING CAREFUL you don't want to get Zapped by those bad boys, they hurt...LOL...Been there done that!!!
  If all that checks out, I would start looking at the ECM. If you can get the engine running just with an open hand slap the ECM a few times. If the engine dies that's your problem. If that is the problem. I would go to the dealer for your Vette. They have all the Updated ECM's. I'm sure NAPA and Advantage will have them.Good Luck let us know what you find.


pepsi1 pepsi1
Duntov Incarnate | Posts: 88 | Joined: 01/12
Posted: 11/22/12
02:48 AM


I thought of something you can check. Down on the starter wires are there any fusable links. Thats where the ECM gets the Voltage to run. If there is fusable links sometime they will turn green in color near the connector, that means they are Chitty.
  A friend of mine has had a small repair shop in NJ as longer then I've known him 38 years. He had a Vette that would start when it was cold. As soon as the engine got hot it would shut off. The owner told him keep it until he finds it.
  It drove him crazy! He had me look at some of his wierd and sometime unusual problems.I found this purely by accident. I did what GM calls the wiggle and tug test,etc. I grabbed the starter wires and they came apart in my hand. I think a good part of that problem was the salt roads in the winter. I replaced all the wires without any fusable links. I started the engine and put blankets over the hood to do what is called a hot soak, and it never failed. The owner was chasing a vapor lock problem that never existed.