1982 C3 Fuel pump inop.

[jeanie2002]

I posted this problem under general instead of technical by mistake, but here is my fuel pump problem. I have checked for power with no success at the tank and oil pressure switch, I replaced the relay behind ECM, no luck, I jumped both outside terminals not the one in middle turned opposite direction of the oil pres. switch plug. I have a very dim light on my test light at one wire at the tank and oil pres. switch, is this normal? what is it? I can't figure out how something went this wrong from just sitting???? the fuel pump fuse is good. I added a extra ground wire from tank to frame. Fuel gauge is pegged, but I think it was like that long before this problem. I know someone out there has probably had same problem, can anyone help? I hope it is not the ECM, does anyone know of a diagnostic test for that? Thanks

 

[wishuwerehere82]

I'll get back to you when I get home from work 9 Hrs from now.
Don't worry, we'll get it figured out.

 

[wishuwerehere82]

Believe it or not, I typed in a full 1-1/2 Hr. qustion- by- question response earlier and lost all of it when my server connection went down in a thunderstorm. I don't have enough time left to do it all over right now. Sorry!

So this will be the shortened version.

It is my belief that your pump is either seized and that is why you see a dim light at the fuel pump connection, or you have a poor connection at the pump fuse. One will drop the Voltage to the pump and the other will not allow enough current to power the pump.

You really need a good meter to test the voltages at the different points from the ECM to the fuel pump, so get a cheap oner at Wal-Mart or Radio Shack. I don't like the idea of troubleshooting ECM o
utputs with a test light. They draw too much current and can blow the transistors on the ECM.

Test the ECM starting pulse at pin C of the pump relay. It should come to +12V when the key is turned on. This will activate the relay, and close the E and A pins on the relay. This completes the connection from +12V to the pump fuse.
There should be +12V on pin A at this point.
The relay is connected to the pump fuse by a Tan/White wire, and goes from the fuse block to the pump on a blue wire to the pump connector. Once past the connector it is a Tan/White wire again.
You should have +12V at the pump connector with respect to ground. If not, try unplugging the connector and then measure it. If it is _12V without the pump plugged in, then the pump is probably seized up and still drawing power, but not enough to blow the fuse.

The pump is also turned on by the Oil Pressure sensor.
The +12V source is the Orange wire and the circuit to the pump fuse is the Tan/White wire. You can try jumpering these 2 wires on the connector at the Oil Pressure Sensor if you unplug it from the sensor.
If the pump still does not come on, then it pretty certain there is a problem with either the fuse connection, or the pump itself.

Keep in mind these voltages will only be on when the key it in the on position, so get someone to help you with the key on - key off stuff.

Let us know the outcome of these tests please.

P.S. see this post for how the pump circuit works and where to get wiring diagrams that trace every signal tp the pump.
http://www.corvetteactioncenter.com/forums/thread122321.html

 

[jeanie2002]

Thanks Pete, I probably won't have time to work on it until weekend. Something I should add the Battery has been going dead just sitting and when I took it out and charged it, when I put it back in cables arched so I know there is a draw somewhere but did not think about the pump being seized on. Could I run a hot wire direct to pump plug to see if it pumps? But also I unplugged pump at top of tank and tried everything to see if I was getting power to pump and was not. only very dim light. I talked to guy I bought car from and he said battery always ran down unless you drove it every few days, so may not have anything to do with Fuel pump. Thanks

 

[wishuwerehere82]

Sorry. I can't reply from home. my cable guy will be here Sat. to fix it.

 

[wishuwerehere82]

Thanks Pete, I probably won't have time to work on it until weekend. Something I should add the Battery has been going dead just sitting and when I took it out and charged it, when I put it back in cables arched so I know there is a draw somewhere but did not think about the pump being seized on. Could I run a hot wire direct to pump plug to see if it pumps? But also I unplugged pump at top of tank and tried everything to see if I was getting power to pump and was not. only very dim light. I talked to guy I bought car from and he said battery always ran down unless you drove it every few days, so may not have anything to do with Fuel pump. Thanks

Do not run a hard wire directly to the pump. Put a 10 Amp fuse in line with it if you run a hot wire from the battery so it will have some overcurrent protection.
Remember that the pump is INSIDE the fuel tank!
That's the one place you DON'T want to have a SPARK!
If you want to try hard wiring the pump, I would remove it from the tank and try it out of the car. After it evaporates all of the fuel off.
It's not too much trouble to remove the filler neck and take the pump out. Then you can check all the connections to the pump and the guage while its out.

And I get about 3 weeks of sitting with a freshly charged battery before it goes dead enough not to crank.
There's a lot of stuff still active in the car even though it's not running.

 

[jeanie2002]

Thanks Pete,

Today I had time to mess with this, I checked F Pump connector {unplugged from pump}-NO power, I checked fuse-no power, I checked Oil switch connector- no power. I checked all of these and then went back and checked again with jumper on oil sw. connector still nothing, I checked F pump relay and had 12v at orange wire until I turn key, then no power for anywhere from 1 to 30 minutes after turn off key, nothing on tan/white wire at relay. Was not sure how to check ECM, all test were done with key on, but gave 5 minutes between to reset. I still don't think it is pump because I can't get any power to pump. all testing today was with pump unplugged. Any ideas???? Thanks

 

[wishuwerehere82]

Thanks Pete,

Today I had time to mess with this, I checked F Pump connector {unplugged from pump}-NO power, I checked fuse-no power, I checked Oil switch connector- no power. I checked all of these and then went back and checked again with jumper on oil sw. connector still nothing, I checked F pump relay and had 12v at orange wire until I turn key, then no power for anywhere from 1 to 30 minutes after turn off key, nothing on tan/white wire at relay. Was not sure how to check ECM, all test were done with key on, but gave 5 minutes between to reset. I still don't think it is pump because I can't get any power to pump. all testing today was with pump unplugged. Any ideas???? Thanks

Next to the battery is a fuseblock for the ECM in the rear outside corner of the battery compartment. You will also see a stud that has a red wire that runs from the battery terminal to the stud, and one that runs from the stud to the ECM fuse. There is a 3rd large wire that runs from the stud out of the battery box. Check and clean all the ring lugs on that stud first to make sure there are good connections to the wires.

Make sure to get those wiring diagrams from the earlier post to help troubleshoot where the voltage comes from.
There is a point where all of the orange wires from the ECM, Oil pressure sensor, Fuel pump relay join together and then run to the stud on the junction block in the battery box. I have never seen the point where the wires are tied together, but if you don't have power coming off that stud in the battery box, there will be NO voltage on any of the other wires. Start there first.

 

[jeanie2002]

Thanks Pete,

I cleaned junction block connection, but did not help so I started in and cleaned all connectors even ECM, and got pump working now. But car will not start unless I use starting fluid. I ran a tube down tank neck and shows 3" of gas but it stinks, I took air cleaner off to watch injectors and cannot see any fuel squirt out. When cranking I could faintly smell old fuel so I wonder if some is squirting out? A friend told me his sat for a year and they had to replace injectors due to varnish. I was thinking about pumping old fuel out of tank and replace with fresh but now I am worried about injectors, any suggestions?? Thanks I appreciate your help.

 

[wishuwerehere82]

Thanks Pete,

I cleaned junction block connection, but did not help so I started in and cleaned all connectors even ECM, and got pump working now. But car will not start unless I use starting fluid. I ran a tube down tank neck and shows 3" of gas but it stinks, I took air cleaner off to watch injectors and cannot see any fuel squirt out. When cranking I could faintly smell old fuel so I wonder if some is squirting out? A friend told me his sat for a year and they had to replace injectors due to varnish. I was thinking about pumping old fuel out of tank and replace with fresh but now I am worried about injectors, any suggestions?? Thanks I appreciate your help.

Well, you got the pump running. That's great!
So now you need to pump something good into the injectors.
OLD GAS NO GOOD. You probably should disconnect the fuel filter under the passenger side door sill, and drain the gas from the tank.
Siphon as much as you can out of the tank, and then let the rest drain out the filter line. Be careful, and do it outside. Flammable!

The filter is probably clogged up pretty good with the old gas, and will need to be replaced. Remember this is a recirculating fuel system the pumps gas from the pump, to the filter, to the front throttle body, to the rear throttle body, to the fuel pressure regulator, then back to the tank.
So whatever you have in the tank is going to be in the whole system. Fuel, Varnish, rust, you name it!
It would be worth your time to take the pump out and check the condition of the filter sock on the intake of the pump. They can get pretty cruddy over time, especially with bad gas. There is a short rubber hose between the fuel pump and the fuel line output that has a tendancy to crack, resulting in no fuel pressure to the injectors.
It's worth checking before you go too much further.
The other thing to check is your injector fuses. You can test to see if the injectors are getting firing pulses with your trouble light.
The terminals are right on top of the injectors. The red and white wires are are 12V from each fuse and the blue and green wires are to the ECM . The blue wire fires one injector, the green wire fires the other. If you put your test light on the green or blue wires referenced to ground, you should see the light flash 3 times fast when you turn the key on. That is the priming pulse for the injectors. Even if you don't have good fuel, you should still see the injectors firing.
Good luck!

 

[jeanie2002]

I have a little 12v portable pump I used to siphon out the gas, then put 5 gal. fresh in,tried to start no luck.The pump only runs for one second, then cuts off so I had to jump the oil press.switch plug to keep pump running. I can hear it running buzzing right along but no fuel, will only start if I prime it. I pulled the main fuel line from front T/Body and tried to pump fuel out into a can, no luck nothing. but pump was running. I need to pull pump, will it come through hole in body or do I have to drop tank? I think I will have like you said a dirty sock, split hose or weak pump. Also after I tried a time or two to start it normally the pump would not come back on for a 3rd time,even after 15 minutes, so I would have to jump the oil switch again. Thanks for your help. Will check injectors tommorow.

 

[wishuwerehere82]

I have a little 12v portable pump I used to siphon out the gas, then put 5 gal. fresh in,tried to start no luck.The pump only runs for one second, then cuts off so I had to jump the oil press.switch plug to keep pump running. I can hear it running buzzing right along but no fuel, will only start if I prime it. I pulled the main fuel line from front T/Body and tried to pump fuel out into a can, no luck nothing. but pump was running. I need to pull pump, will it come through hole in body or do I have to drop tank? I think I will have like you said a dirty sock, split hose or weak pump. Also after I tried a time or two to start it normally the pump would not come back on for a 3rd time,even after 15 minutes, so I would have to jump the oil switch again. Thanks for your help. Will check injectors tommorow.

The pump comes out with the filler neck. No need to drop the tank.
Take off the filler lid, rubber boot. Then you will see the screws that hold the filler neck to the tank. The whole assembly comes out if you rotate it just right.

I think you need to check the rubber hose on the pump. You will see it when you get the pump out. Your fuel filter might be completely clogged too.

 

[jeanie2002]

Pete,

Man that is a pain working that filler neck out of the hole in the body, but you hit the nail on the head. The rubber line connecting the pump to the steel line had dissolved, it had turned into a mushy black putty so pump was not even hooked to line anymore, sock was nasty but also the steel parts were all so rusted and 2 wires into tank were corroded like it has been in the ocean {terrible connection}. I am wondering if this is why my fuel gauge is inop. I cleaned parts, but wonder if I should coat with por-15 or chemical safe sealer. Do you know if anyone makes a service kit? I need the gasket or cushion on the bottom of the pump that supports it as well. I guess you must have worked on a few of these to know so much and I really appreciate your help. I ended up having soooo many problems with so many corroded connections to a pump that wasn't attached to the line anymore, and all this happened while it was just sitting in storage. Thanks so much, you've been awesome.

 

[wishuwerehere82]

I credit all those who have helped me in the past.
This wasn't the first time something like this has happened.
Thanks to The Corvette Action Center, I was able to get the answers to solve my problems in the past as you are doing now.
Look at my post count! Most of the originals were requests for help fixing MY 82.
I would like to recognise a few others that have helped me with my problems, and in doing so have enabled me to share a wealth of knowledge that for some reason, I can still remember.:L
Thank GMJunkie for the rubber fuel line hose connected to the pump.
Thank Geek-in-a-Vette for the how-to troubleshooting info.
Thank MoeJr. for fuel pump info. (I'll get to this in a minute)
And above all, thank Rob for providing this excellent venue for all of us to share our experiences.

Now comes the hard part. It's time to figure the options about how to get everything you need to get this back together and not having to take it apart again for a long time.
Get ready, this is going to hurt!
The proper rebuild for the pump stuff is to buy a new pump and install it with all of the parts it comes with. A 1985 Pump! It has more flow and pressure and will fit right in the same place as the old one.
Mid-America and Ekclers and probably a lot of places including your neighborhood auto parts store has them. Get the Strainer Sock and Fuel Filter too.
If your filler neck and wiring are shot, then the best course of action would be to replace them too. The filler neck assembly will come with all of the stuff except the pump, which shoul take care of your fuel gauge problem too. And it is made to fit the 82 fuel tank. Available a Mid-America and Ecklers also.
OK, so now you're up to about $300.00 plus S&H, does it hurt yet?

As far as the tank, I can't say what I would do.
I probably would get a new tank if it's really rusted, or drain it and see how it goes if not too bad.
Personally, I don't spend money unless I have to. But once I start, it's hard to say when enough is enough.
I would shudder to think how much this would cost if you were paying a garage or dealership to do this for you.
DIY and CAC go hand in hand!

 

[jeanie2002]

Thanks Pete,

By the time I read your reply I already have her back together and running, a buddy with a shop had a spare nitrile seat for the pump, stuck a piece of reg. fuel line on, replaced sock and filter, cleaned all rust and corrosion off with a brass toothbrush. I had fresh fuel in tank and drained all lines so she started on the first try. Fuel gauge is now working. You have been a huge help, thanks to you and your friends.

 

[wishuwerehere82]