1991 vette wont run 79k miles any help ?

[clewzy]

Here is a short history car has been sitting for 3 years with old gas and moisture in the interior after cleaning her up removing sending unit replacing fuel pump and in line filter fresh gas. when i try to start it turns over no problem but will not run . i hear nothing in the fuel tank that would tell me fuel pump is cycling i pinned the 4 prong plug and get no sign of power anywhere turning key on and off ,i am pretty sure i should be able to hear the pump run for a few seconds yes ?..i am trying to figure out why i have no power to fuel pump and wondering if security system or ecu maybe a fuel relay ( not sure where to find relay ) .i have read some threads talking about ohm testing and a few other checks i could use a little schooling on this any help would be appreciated a place to start would be good thanks :confused

 

[93Rubie]

The pump should run for a couple seconds on key on. If it does not, start with the basics-fuses. If you do not have a Field Service Manual now is the time. Wiring diagrams, diagnostic trees, etc, etc...

Is the security light or system light flashing or On???

 

[blmann]

Distributor

I wouldn't get to excited about fuel pump, once the system is up to pressure, no pump action. You mentioned moisture it the cab, I've got 2 1993 coups, moisture kills the distribtor, it will crank and will not even begin to fire, I've tried a hair dryer a few times, not a good remedy; however a good leaf blowed aimed below or in the water pump area for about 5 minutes has worked many times, live in Florida, winter is the worst. Good luck..

 

[clewzy]

hey rubie i have checked the fuses located on the passenger side dash,and with key in

The pump should run for a couple seconds on key on. If it does not, start with the basics-fuses. If you do not have a Field Service Manual now is the time. Wiring diagrams, diagnostic trees, etc, etc...

Is the security light or system light flashing or On???

Hey Rubie, thanks for the help i have checked the fuses located on the passenger side,are there some more located somewhere else and with the key in the ignition and in the off position my security light flashes on the lower left of my gauges it goes off as soon as i turn the key in the on position... the only other flashing light is (infl rest) which flashes 3 times when i turn the key to the on position.i have no idea what this light is .a little note i can get this thing to fire with starting fluid. and there are no signs of life with my fuel pump ..i will pick up a service book today any suggestions.i appreciate your time Chris.

 

[clewzy]

bmann

I wouldn't get to excited about fuel pump, once the system is up to pressure, no pump action. You mentioned moisture it the cab, I've got 2 1993 coups, moisture kills the distribtor, it will crank and will not even begin to fire, I've tried a hair dryer a few times, not a good remedy; however a good leaf blowed aimed below or in the water pump area for about 5 minutes has worked many times, live in Florida, winter is the worst. Good luck..

Hey Bman ,i can get the car to fire with starting fluid .i just replaced fuel pump and inline filter yesterday i had emptied fuel tank and cleaned spotless .put in 5 gallons of fresh.turned the key expecting to hear fuel pump engage to prime the empty fuel lines and nothing .oil pressure gauge (mechanical) starts to move after a few seconds of cranking.i am reading there needs to be 4 psi of oil pressure in order for fuel system to be enabled.i am wondering where the fuel relay is located for my 1991 so i can check it .thanks for your response i will try to pick up a service book today for this car

 

[93Rubie]

Hey Rubie, thanks for the help i have checked the fuses located on the passenger side,are there some more located somewhere else and with the key in the ignition and in the off position my security light flashes on the lower left of my gauges it goes off as soon as i turn the key in the on position... the only other flashing light is (infl rest) which flashes 3 times when i turn the key to the on position.i have no idea what this light is .a little note i can get this thing to fire with starting fluid. and there are no signs of life with my fuel pump ..i will pick up a service book today any suggestions.i appreciate your time Chris.

It sounds like the security light is acting normal, if you can fire it on starting fluid it is definitely a pump not running issue. Which light are you referring too, the system light? It is in the DIC, if you don't see it, don't worry about it. 3 flashes of the Air Bad (Infl. Rest) light is good, and normal.

I'm not sure on the 91 if it is exactly like a 93 but here go...it might be similar.

There are additional fuses under the hood near the battery. Two boxes one in front and one behind. I believe the fuel pump fuse is located there. My 93 manual shows an additional one in the pass. side fuse box. There is also a fuel pump relay in my 93 it is on the Pass. side behind the lower knee bolster, the carpeted area of the lower dash on the passenger side. You will have to take this down to access the relay. For diagnostic purposes you are going to need a Digital Multi Meter or DVOM for short.

If the fuses check ok, and you have power across them, I would go to the relay next. Take it out and verify power to the relay. I usually jump the relay at this point and see the pump runs. If it does not you will have to continue to trace the circuit back to the pump.

Also, I know from experience having a good known ground when testing electrical for your DVOM is critical. I have a homemade long like 30 foot jumper just for this, I run my negative lead right to the negative terminal on the battery.

 

[clewzy]

going a little deeper

It sounds like the security light is acting normal, if you can fire it on starting fluid it is definitely a pump not running issue. Which light are you referring too, the system light? It is in the DIC, if you don't see it, don't worry about it. 3 flashes of the Air Bad (Infl. Rest) light is good, and normal.

I'm not sure on the 91 if it is exactly like a 93 but here go...it might be similar.

There are additional fuses under the hood near the battery. Two boxes one in front and one behind. I believe the fuel pump fuse is located there. My 93 manual shows an additional one in the pass. side fuse box. There is also a fuel pump relay in my 93 it is on the Pass. side behind the lower knee bolster, the carpeted area of the lower dash on the passenger side. You will have to take this down to access the relay. For diagnostic purposes you are going to need a Digital Multi Meter or DVOM for short.

If the fuses check ok, and you have power across them, I would go to the relay next. Take it out and verify power to the relay. I usually jump the relay at this point and see the pump runs. If it does not you will have to continue to trace the circuit back to the pump.

Also, I know from experience having a good known ground when testing electrical for your DVOM is critical. I have a homemade long like 30 foot jumper just for this, I run my negative lead right to the negative terminal on the battery.

Hey Rubie, i am not finding another fuse box next to the battery it looks like right behind the battery is a main hub for a bunch of fusable links for grounds . one of the problems we are having is there was a fair amount of moisture inside this car causing all my fuses to have a light dusting of white powder.. i have removed and cleaned every one.. my concern is if the fuel relay which is located as you have said under the glove box behind the carpet knee pad passenger side .is propably of the same condition.couple of other notes the radio is not in this car and i am not sure if this affects security .i had a buddy over tonight he owns a 1990 formula 350 had some of the same problems he had a bad key after looking at mine a little closer it looks like this one is new next to nothing for wear on key ( i have only one )his fuel pump relay was located on his firewall next to master cylinder ,we spent 3 hrs or so chasing wires and checking all connections unfortunatly we are doing this in the driveway til my garage opens up a slot for this project in a week or so. we called it a night at dark if the fuel pump relay is located under the glove box knee area we will have this apart tomorrow and jump out the fuel pump .and last we are all a little confused by this we checked power to the coil and it was good but while checking spark we could get none we did not try spraying starting fluid only because once was enough and thought spark must have been present in order for motor to fire .i will continue writing this thread until i find the problem and publish my findings with the hope this will help others really appreciate all your imput.to be continued.thanks chris

 

[Hib Halverson]

What is posted here about how the fuel pump works is not correct.

When you key-up, the pump runs for a few seconds to build pressure. If the ECM sees no oil pressure, the pump relay shuts the pump off. Once the pump is off, pressure may or may not hold. It depends on the condition of the fuel system. If you've got leaky injectors, a faulty regulator or a bad ball check in the pump, pressure will drop off and in come cases it will do that quickly. In fact, one of the tests in the Service Manual for the fuel system is how quickly pressure drops after the pump shuts off.

If you don't hear that pump run for a couple of seconds after you key-up, either the pump, the pump wiring or the pump relay is bad.

Information on how to diagnose the fuel supply system is in the Factory Service Manual.

DO NOT use "starting fluid" on a Corvette engine. "Starting fluid" is primarily ether. While ether ignites easily, it is very, very low octane and causes instant detonation which can damage th engine.

If the starter cranks the engine then what the security light does is, obviously, not affecting the starter interlock.

 

[clewzy]

hey hib

What is posted here about how the fuel pump works is not correct.

When you key-up, the pump runs for a few seconds to build pressure. If the ECM sees no oil pressure, the pump relay shuts the pump off. Once the pump is off, pressure may or may not hold. It depends on the condition of the fuel system. If you've got leaky injectors, a faulty regulator or a bad ball check in the pump, pressure will drop off and in come cases it will do that quickly. In fact, one of the tests in the Service Manual for the fuel system is how quickly pressure drops after the pump shuts off.

If you don't hear that pump run for a couple of seconds after you key-up, either the pump, the pump wiring or the pump relay is bad.

Information on how to diagnose the fuel supply system is in the Factory Service Manual.

DO NOT use "starting fluid" on a Corvette engine. "Starting fluid" is primarily ether. While ether ignites easily, it is very, very low octane and causes instant detonation which can damage th engine.

If the starter cranks the engine then what the security light does is, obviously, not affecting the starter interlock.

thanks for the info we did give one shot of starting fluid car did not run for more then 3 seconds and we have not done it again .i will check the fuel relay which i am told is under the passenger side bolster, is that also where the auxilary fuses are located and where would i find the fuel pump fuse is it fp2 in auxilary fuse box

 

[John Robinson]

In the fuse block next to the battery there is a 20 amp fuel pump fuse. In the fuse panel in the passenger compartment there are 2 10 amp fuel pump fuses. according to the owners manual.
View attachment 4704

In the fuse block inside the car they are marked F.P.1 and F.P.2


If all the fuses are good then the next step is to clean all the grounds

I am putting my money on a bad fuse or dirty ground. Remember the ECM cannot do it's job if it is not getting any input from the fuel pump and it gets that from the ground not the hot wire.

 

[clewzy]

is it a fuse ?

In the fuse block next to the battery there is a 20 amp fuel pump fuse. In the fuse panel in the passenger compartment there are 2 10 amp fuel pump fuses. according to the owners manual.
View attachment 4704

In the fuse block inside the car they are marked F.P.1 and F.P.2


If all the fuses are good then the next step is to clean all the grounds

I am putting my money on a bad fuse or dirty ground. Remember the ECM cannot do it's job if it is not getting any input from the fuel pump and it gets that from the ground not the hot wire.

Hey John ,i did some research last night and the difference between your 93 vette and my 91 seems to be the location of the auxilary fuse box yours is next to your battery and mine so i am told is under the bolster on the passenger side i have located the fp1 fuse in the main f/b on passenger side dash my next move is to find aux f/b 1 and 2 and locate my fp2 fuse and fuel pump relay.in a diagram of the fuse box it shows a 10 amp fuse in the fp2 slot(aux fuse block #1 ) which i will try to find today.thanks for the info