1985 C4 questions
Thread Starter
Heel & Toe
Joined: Sep 2007
Posts: 15
Likes: 0
1985 C4 questions
I am an old timer in muscle cars of the 60s and 70s but new to the Corvette world. I bought an 1985 Corvette as a cheap project. Previous owner said it ran but idled roughly. I have been unable to get it started. It has 35 lbs of pressure at the fuel rail. I tested each injector with a noid light and they are firing. I pulled a plug and grounded it and the plugs are also firing upon cranking. It cranks very well and builds 10 lbs of oil pressure while cranking. The security light flashes on the instrument panel but I think in 1985 the only security was to blow the horn if disturbed.
Questions:
1) Can you "prime" a TPI engine with starting fluid?
2) Any ideas why it won't start?
Thanks for any help!
Questions:
1) Can you "prime" a TPI engine with starting fluid?
2) Any ideas why it won't start?
Thanks for any help!
Last edited by Rick84Vette; Sep 28, 2007 at 09:25 PM.
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
security?
Since you have mentioned it has fuel pressure and spark with a flashing security light I would have to guess that something may have activated the ingition lock feature of the security system. Since you mentioned the horns are not honking, try this test, activate the horns manually at the steering wheel and see if they work. My 85's security system would not honk the horns many years ago because part of the manual horn honker under the steering wheel cap had broken. Saw the problem when I removed the cap. Fixed it and the horn honked manually and with the security system. Without getting out my owners manual or service manual, I am pretty sure the car becomes a no starter when the security system is activated. Try locking and unlocking the drivers door to get cancel the blinking security light. One thing I have learned to do with my 85 to give me instant starts either hot or cold engine is to turn on the ignition, listen to the fuel pump relay click to verify that the fuel pump in the tank just put fuel pressure in the system and then start the car. Giving the system about 15 seconds to be ready, my 85 just starts when I turn the key to the start position, saves wear and tear on the starter for sure.
Last edited by 70ZZ3 96LT4; Sep 28, 2007 at 11:18 PM.
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
Welcome to the world of fuel injection, it sucks. Security light? Are you sure its not the check engine light? Yes you can shoot some starter fluid into the intake to see if it'll start that way. Be careful though cause unlike a carbed engine it may backfire with a fireball out of the intake if you spray too much, ask me how i know 
The first thing i'd do is check for codes. You can do this using a paper clip or just a short length of wire. Locate the ALDL connector under the driver side dash. Put one end of the wire into the top right pin and the other end in the one right next to it. Then turn the key to on, but dont crank it. The check engine light will flash, Once, then 2 flashes, thats a code 12 and it will repeat 3 times. What your looking for is anything other than code 12. Alright well theres a lot more to it than just the fuel system and spark. You should also check the MAF sensor, mine was broken and flooding the engine so bad it would barely start.
The first thing i'd do is check for codes. You can do this using a paper clip or just a short length of wire. Locate the ALDL connector under the driver side dash. Put one end of the wire into the top right pin and the other end in the one right next to it. Then turn the key to on, but dont crank it. The check engine light will flash, Once, then 2 flashes, thats a code 12 and it will repeat 3 times. What your looking for is anything other than code 12. Alright well theres a lot more to it than just the fuel system and spark. You should also check the MAF sensor, mine was broken and flooding the engine so bad it would barely start.
Last edited by Demonic85; Sep 28, 2007 at 11:41 PM.
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
On an '85 the flashing security light is normal when the doors are not locked. When you lock them the light will come on steady until you shut the doors.
As far as the no-run situation, since you have fuel pressure and spark I would check compression. Has the car sat a long time? Is there a possibility of collapsed lifters? Also check for codes as 4Ever21 stated. Pull the pass side valve cover, (the drivers side is a beach) and check rocker movement. Do these things then let us know what you find.
As far as the no-run situation, since you have fuel pressure and spark I would check compression. Has the car sat a long time? Is there a possibility of collapsed lifters? Also check for codes as 4Ever21 stated. Pull the pass side valve cover, (the drivers side is a beach) and check rocker movement. Do these things then let us know what you find.
Thread Starter
Heel & Toe
Joined: Sep 2007
Posts: 15
Likes: 0
Here is what I have tried so far with no luck:
- Diagnostic computer codes flash 12 then 12 (this indicates ECU is
functional and has no stored error codes)
- Fuel gauge placed on fuel rail jumps to 35 lbs once ignition key is
on (within specs)
- Noid lights placed on fuel injectors all flash indicating computer
is firing injectors
- Coil is 12V hot once ignition is on
- Pulled plugs are clean and non corroded, lightly moist with fuel
- Spark plugs pulled and grounded fire upon cranking (indicating
working coil and distributor)
- Battery is strong and has great cranking speed
- Mass Air Flow sensor indicates correct voltage
- I have tried unhooking MAF which forces ECU to use a default
reading. No luck.
- I have tried a shot of starting fluid into the airstream. No luck.
The search continues. Next step is to start running diagnostic jumper
tests on the ECU and various sub components. I will run compression tests.
- It just makes no sense to me that it does not fire at all. I have
learned more about fuel injection in that last two weeks than ever.
- Diagnostic computer codes flash 12 then 12 (this indicates ECU is
functional and has no stored error codes)
- Fuel gauge placed on fuel rail jumps to 35 lbs once ignition key is
on (within specs)
- Noid lights placed on fuel injectors all flash indicating computer
is firing injectors
- Coil is 12V hot once ignition is on
- Pulled plugs are clean and non corroded, lightly moist with fuel
- Spark plugs pulled and grounded fire upon cranking (indicating
working coil and distributor)
- Battery is strong and has great cranking speed
- Mass Air Flow sensor indicates correct voltage
- I have tried unhooking MAF which forces ECU to use a default
reading. No luck.
- I have tried a shot of starting fluid into the airstream. No luck.
The search continues. Next step is to start running diagnostic jumper
tests on the ECU and various sub components. I will run compression tests.
- It just makes no sense to me that it does not fire at all. I have
learned more about fuel injection in that last two weeks than ever.
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Team Owner
Joined: Jan 2003
Posts: 20,315
Likes: 245
From: Summerland B.C. Canada
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
No start
Rick you have checked out a lot on the car. Another option is to call Gordon Killebrew and spend a few dollars on his trouble shooting expertise service. He also runs a school for tech information on working on our C4's. I hope to take my 85 to Gordon's School one day, it is in Cross Plains, TN. He was at Mid America's Funfest in Effingham,IL last month and had free tech sessions with questions from the audience. Hope he is there next year. His phone is 615-654-2864/ 800-F-Y-VETTE.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
I ran into something like this last year. I had screwed up timing so bad car wouldn't fire. Check the timing, all components to include rotor position vs TDC.
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
You said the previous owner claimed it ran but idled rough, did you ever hear it run or did you buy it without hearing it run? I'm asking this because I'm leaning towards the timing too, it's about all that's left. Maybe the guy messed with it trying to make it better and got it all out of whack. Get the mark on the balancer lined up with the "zero" on the timing tab, then pop the distributor cap. The rotor should be pointing to either number one terminal or number six terminal. If it's any place else at all then you need to verify true tdc and set the distributor in properly and make sure the wires are all in their proper position.