1990 corvette problem
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Joined: Oct 2025
Posts: 57
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From: des moines
I had an issue with my L98 in our 1988 C4 with the engine not running and issues similar to yours. It was a fairly easy fix, once I identified what the problem was.
What voltage do you see at the fuses? I would measure the voltage of the battery, at the battery and then start measuring through the fuse block. I found less than 10 volts on some of the fuses coming into the panel. I checked the radio and it had low voltage as well. With this situation I noticed that my fuel pump was not working, likely to low power as well.
Using a Power Probe I then took battery power to the fuel pump harness near the pump and checked it with a full 12 volts and the pump ran fine. The voltage getting to the pump was the problem. I traced it back to the fuel pump relay and replaced it as well. The low voltage was the cause for the pump fault. With full power it worked great. After realizing that the fuses were not getting full voltage, I followed the power and it went to a small post on the drivers side compartment near the battery. This post has a large wire that went from the post to the battery positive terminal and supplied the post with full battery power. The post on my C4 was covered in corrosion and this was what caused my low voltage situation. After removing the 7 fusible links and their ring terminals I cleaned each one down to bare metal and then cleaned the post as well. This post essentially powers the entire car by feeding the power into the fuse blocks. The corrosion had created a huge resistance to the power flowing through this connection. After cleaning and re-assembling with Conductive BATTERY Grease and re-attaching to the post, the battery voltage was spot on inside the car and out. The fuel pump ran full speed and the car was working again.
What is the battery voltage of the car sitting? How about when running? Are the headlights as bright as they need to be? Low voltage can make them produce less light. Fuel pumps will not make pressure without the right voltage going into them...
Best regards,
Chris
What voltage do you see at the fuses? I would measure the voltage of the battery, at the battery and then start measuring through the fuse block. I found less than 10 volts on some of the fuses coming into the panel. I checked the radio and it had low voltage as well. With this situation I noticed that my fuel pump was not working, likely to low power as well.
Using a Power Probe I then took battery power to the fuel pump harness near the pump and checked it with a full 12 volts and the pump ran fine. The voltage getting to the pump was the problem. I traced it back to the fuel pump relay and replaced it as well. The low voltage was the cause for the pump fault. With full power it worked great. After realizing that the fuses were not getting full voltage, I followed the power and it went to a small post on the drivers side compartment near the battery. This post has a large wire that went from the post to the battery positive terminal and supplied the post with full battery power. The post on my C4 was covered in corrosion and this was what caused my low voltage situation. After removing the 7 fusible links and their ring terminals I cleaned each one down to bare metal and then cleaned the post as well. This post essentially powers the entire car by feeding the power into the fuse blocks. The corrosion had created a huge resistance to the power flowing through this connection. After cleaning and re-assembling with Conductive BATTERY Grease and re-attaching to the post, the battery voltage was spot on inside the car and out. The fuel pump ran full speed and the car was working again.
What is the battery voltage of the car sitting? How about when running? Are the headlights as bright as they need to be? Low voltage can make them produce less light. Fuel pumps will not make pressure without the right voltage going into them...
Best regards,
Chris
Melting Slicks
Joined: Feb 2003
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From: Saskatoon Sask.
Melting Slicks
Joined: Nov 2016
Posts: 2,217
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From: So Cal
2023 C4 of the Year Finalist - Unmodified
With the key in RUN, is the SECURITY light SOLID-ON? (Not "flashing" with the key off and a door open, which is normal.)
Jumper cavity A&B in the ALDL diagnostic connector and turn the key to RUN. Watch the Service Engine Soon light. Is Code 46 present?
Either of the above indicate a VATS fuel disable, and will result in "runs on starter fluid, but not on its own." Normally, VATS also inhibits the starter from cranking, but in a 35 year old car it is possible that a previous owner bypassed the starter relay. They may have also installed a resistor bypass, which is now malfunctioning.
F - E - D - C - B - A
G - H - J - K - L - M
Jumper cavity A&B in the ALDL diagnostic connector and turn the key to RUN. Watch the Service Engine Soon light. Is Code 46 present?
Either of the above indicate a VATS fuel disable, and will result in "runs on starter fluid, but not on its own." Normally, VATS also inhibits the starter from cranking, but in a 35 year old car it is possible that a previous owner bypassed the starter relay. They may have also installed a resistor bypass, which is now malfunctioning.
F - E - D - C - B - A
G - H - J - K - L - M
