87 starts sometimes
Thread Starter
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 1
87 starts sometimes
ok I am back with my 87 not starting. changed plugs, cap, rotor, ignition module, fuel filter. cranks great- will not start. Used to be able to pull a connector to an injector and it would start- no more. Starting fluid gets it going, but it obviously dies after a few seconds. Thinking now fuel pump- turn the key and hear click up front- oh yeah also replaced the pump relay. I get 10 volts of power at the pump connector in the rear- is this right? When it starts occasionally it runs great. Just can not get it to start most of the time. I have fuel at the rails. Desperate for help- should I just change the pump- I hear it is an easy job on the c4.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You clearly have no fuel pressure, and you should have measured it at the shrader valve on the end of the fuel rail, you would have found out right away the pump isn't working . Is your battery run down from cranking? Measure the battery voltage, you should have 12v on the fuel pump connector, not 10 volts! Charge your battery up if it is under 12.0 volts! You can jump 12v to the fuel pump motor and see if you can hear the pump motor run, and if it does, then try to start the car with the pump still jumped. If no start, then unplug an injector and put a noid light (available at parts store) or a low power 12v lamp like a side marker lamp on the injector socket and crank, the lamp should pulse during cranking. Let us know what you find.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
You clearly have no fuel pressure, and you should have measured it at the shrader valve on the end of the fuel rail, you would have found out right away the pump isn't working . Is your battery run down from cranking? Measure the battery voltage, you should have 12v on the fuel pump connector, not 10 volts! Charge your battery up if it is under 12.0 volts! You can jump 12v to the fuel pump motor and see if you can hear the pump motor run, and if it does, then try to start the car with the pump still jumped. If no start, then unplug an injector and put a noid light (available at parts store) or a low power 12v lamp like a side marker lamp on the injector socket and crank, the lamp should pulse during cranking. Let us know what you find.
you need to attach a fuel pressure guage to see what pressure you have. If you have fuel pressure in the mid thirtys or around fourty psi, then I would check the injectors pulses. The ten volts you got at the fuel pump connector was probably correct and due to a low battery voltage. The connector volts will equal the battery volts.
Thread Starter
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 1
87 Vette
Its is a new battery and it cranks well- car dash reads 12.1 volts when I first turn the key. I ran a 12v wire from the battery to the g pin and the car still does not start. I asked advanced auto parts about a noid light and they looked at me like I had 2 heads !! so much for hiring people with automotive knowledge. I am going to swap out the pump saturday morning and see what happens. If the pump was bad- would it work sometimes? when it ran, it ran great. Also sometimes when I disconnected one fuel injector wire it would start. Warm weekend coming and the start of the marcus dairy car meets- I need to get the beast out of the garage !!
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Thought you might be coming back. Have you bought a fuel pressure guage yet? About 35-40 at autozone......checking the pressure with a guage is a must, seems like I remember you saying you didn't have a guage.The guage will help you diagnos fuel pump, fuel pump regualator and injectors...cheap tool, beats throwing parts at it. I suspect your fuel pump is bad, but it's about $100. your choice.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Disconnecting one injector allowing your engine to start could be a shorted injector coil, but that would have blown one of the two injector fuses, BTW, check the continuity of both injector fuses with an ohmeter.
Fuel pump motors can be intermittent!
Fuel pump motors can be intermittent!
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Thread Starter
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 1
87 Vette
FUEL PUMP !! FUEL PUMP !! First part I bought and last one I changed- Real easy job- new one in and car started right up - took it out- gased it up and restarts and runs great !! Thanks everyone for the help- hope this really was it as the car meets start this weekend !!