86 corvette will not start when hot

  
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86 corvette will not start when hot

 
Cartero Cartero
I watched Corvette Summer | Posts: 14 | Joined: 09/09
Posted: 09/09/12
03:08 PM

My 86 Vette starts fine when cold and runs fine as long you don`t turn it off.Once i shut it down it may start or not,it is very erratic.I replaced the ignition module plus the coil and it improve it a little bit. While doing this,i get some voltage but not a spark at the ignition coil.A friend ran a scan and found no codes and i also running the fuel pump straight from the battery and can hear the fuel flowing. Can you help me? Confused  Confused  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 09/09/12
04:43 PM

1...  do you have a fuel pressure tester??? so you can monitor the fuel rail pressure .. not just see if there is pressure...
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2..  do you have a timing light.. so you can clamp it over any spark plug wire and tape or rubber band the trigger in the on position to use the flashing of the timing light to indicate if you are getting secondary high voltage spark.... while cranking????

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3...  do you have a circuit tester.. so you can pull the coil dust cover off.. shove the probe of the circuit tester into the red wire from the coil to the cap.. then ground the clip...   as you slowly turn the key from off to ON and then up through cranking the engine and back to run position.. you should NOT loose power to the coil primary...  if this ignition primary voltage from the ignition switch drops out at any time from on to crank and back to ON.. you have a bad ignition switch..

Heibigcap

why do i want you to do this 10 minute test.. 10 minutes is how long it takes to get the dust cap off the distributer cap ...  because i have found way to many burned out ignition switches...

ignition switches cost under 20 bucks at most stores.. take about an hour curled under your C4 dashboard after you take a several layers of panels off..  and sometimes drop the column slightly to get a good shot at it..  

this is the inside of the GM ignition switch that should be on your car.. note the depressed area in the brass contacts..  thats where the switch is in the RUN position.. and thats an intermittent contact ... they are cheep... they wear out..  C5 and C6 vettes even have ignition switch issues.. except those switches cost well over 200 bucks..  and will drive those owners crazy with random connections...

Ignitionswitchwornoutcontact  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 09/09/12
04:58 PM

if you get good power at the coil positive.. but still not putting out spark...

did you check the ignition rotor... that it did not burn through...  my tool mans truck died... he changed the cap.. coil .. module.. pick up coil... still no spark... had his tool truck towed to the dealer.. they replaced the 5 buck rotor and sent him on his way...

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how are the connections at the pick up coil????   i am hoping not green and covered with corrosion..

if you can get the cap off.. and unplug the pick up coil wiring from the module..

set the volt meter to 2K ohms..  ohm the pick up coil.. usually around 980 ohms..  somewhere between 500 and 1500 ohms is kinda expected...

before disconnecting..  flip the meter to 2 volts AC scale..    while you have the probes connected to the pick up coil.. either spin the distributer shaft if the distributer is out.. or have somebody crank the engine while you make sure nothing gets snagged..   you should have just over 1.0 volt AC.. if you don't pass the resistance test.  or you don't pass the AC voltage output test.. replace the pick up coil...  

pepsi1 pepsi1
Duntov Incarnate | Posts: 88 | Joined: 01/12
Posted: 09/14/12
05:44 PM

See if you have fuel up to the TBI when it's hot...

Bob  

pepsi1 pepsi1
Duntov Incarnate | Posts: 88 | Joined: 01/12
Posted: 09/15/12
08:09 PM

If it come down to you having to replace the fuel pump,check and see if there is a HiPerformance fuel pump for your application. I don't know if you purchased the Vette new. So you would not know if the fuel pump has been replaced.

Whatever the issue if you need to replace the pump replace all the filters with it. There is a filter on the pump in the tank. It's a sock fuel filter. Then of course the inline fuel filter. The pump may not pump fuel, but it may not be holding pressure also. The pump serves 2 purposes. 1 It pumps the fuel, and 2. It has a check valve in the pump. It should hold fuel pressure for a programmed amount of time. When the key is turned off.

Bob