pbagley Posted November 24, 2013 Share Posted November 24, 2013 First, thanks in advance for any assistance with this fuel pump problem. Short problem description - I have power to the fuel pump plug briefly at key on and when the engine is cranking. The pump does not run. The pump and the fuel pump relay have been replaced. The new fuel pump is a turbine unit from Napa. The is continuity from the connector through the pump motor, reads near a dead short. Do does the old fuel pump. The only thing I can think of that would be a problem is the electrical connector at the tank (fuel pump and sending unit. I found a small brass near the plug just before I took the pump back out ofthe tank again, so I suspect the plug may (car side, not the tank side) be the problem. With the pump out of the tank I confirmed that the fuel lines were completely dry when O popped them off and that the pump was not running at key on or while the car was cranking. It seems odd that the old pump (220K miles) and the new pump both would not work. Are there any other ideas? Is there any possibility there is 12v at the plug, enough to read on a DMM but not enough to run the pump motor? Thanks! Quote Link to comment Share on other sites More sharing options...
naru Posted November 25, 2013 Share Posted November 25, 2013 (edited) 12 volts is 12 volts,as long as you checked while the pump was plugged in. How is the ground? Edited November 25, 2013 by naru Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted November 25, 2013 Share Posted November 25, 2013 If current was insufficient to run the pump the voltage at the pump would drop when the key is on. Did you check the connector inside the tank where the pump wire harness connects to the bottom of the top plate? (the plate that the hoses and wires to through) Sometimes the wire connector there gets loose and burns which causes the pump to get no power. You will need to unplug the connector to see if there is damage. You can also check for voltage on the ground side of the pump while it has power. If there is voltage more than 1vdc on the ground that would indicate a bad ground connection. Quote Link to comment Share on other sites More sharing options...
pbagley Posted November 25, 2013 Author Share Posted November 25, 2013 Thanks for the quick replies. I did check the ground, and the DMM read 0 ohms from the ground pin for the pump and the body (bare metal of a speaker frame). I found it problematic to check the voltages when the plug was connected to the fuel pump. I will double check the connector inside the fuel tank again, but I read 0 ohms across the two fuel pump pins. The one thing I did nto check was that there was 12v at the pump connector. The replacement fuel pump uses a two pin spade plug, not like the stock Subaru part. There is a '95 Impreza in a local u-pull boneyard. If the fuel pump is still there I think that will be what we try next. Quote Link to comment Share on other sites More sharing options...
naru Posted November 25, 2013 Share Posted November 25, 2013 (edited) 0 Ohms? Really?? If the fuel pump was really 0 ohms,fuse would blow instantly. Should be somewhere above 2 ohms, You have the range scale of your meter set too high. I don`t get 0 ohms even if I short my meter leads together.(on low range) Makes me question your 0 ohm ground reading. Ohmmeter readings are not really great for this.Circuit might be low resistance for the miniscule meter current but higher for any real current. Check ground pin voltage instead. I would test the pump by hot wiring it before buying another. Edited November 25, 2013 by naru Quote Link to comment Share on other sites More sharing options...
Cougar Posted November 25, 2013 Share Posted November 25, 2013 Naru, I think the OP was saying the ground lead for the pump had no resistance to it, which is a good thing. Like Naru stated, to see if the pump works okay just run power directly to it. Quote Link to comment Share on other sites More sharing options...
naru Posted November 25, 2013 Share Posted November 25, 2013 Naru, I think the OP was saying the ground lead for the pump had no resistance to it, which is a good thing. Like Naru stated, to see if the pump works okay just run power directly to it. Same meter said pump had impossibly low resistance. Not a good thing. If one measuremement is wrong,the other is questionible. Voltage measurement on a loaded circuit is much more informative. Quote Link to comment Share on other sites More sharing options...
Cougar Posted November 25, 2013 Share Posted November 25, 2013 First, thanks in advance for any assistance with this fuel pump problem. Is there any possibility there is 12v at the plug, enough to read on a DMM but not enough to run the pump motor? Thanks! As long as the circuit is closed and the load (pump motor) is making good connection to power and ground there should be 12 volts supplied to the motor windings and also to the meter. Now if the ground lead for the pump was open and you placed the meter reference probe on a good chassis ground point then the motor would not work since it has no connection to the ground return but your meter would show good voltage. If you placed the reference probe on the same open ground connection going to the motor the meter would not read any voltage. Quote Link to comment Share on other sites More sharing options...
pbagley Posted November 25, 2013 Author Share Posted November 25, 2013 Yes, I had the range on the DMM set too high. Heading to the U-Pull yard to get (hopefully) a used unit and car side plug (they usually toss that in for free). Only $9 for the part so not a big investment. Quote Link to comment Share on other sites More sharing options...
pbagley Posted November 25, 2013 Author Share Posted November 25, 2013 Back from the bone yard. DMM says the pulled pump reads 3.3 ohm at the wires on the other side of the plug. It also reads 3.3 ohm at the pump connection. Total cost was $15.94 - $2 to get into the yard, $13 for the part, and tax. I tried the pump via jumper cables (to get further away from my car just in case there was a spark) and it ran for the brief second I applied power. Did not want to run it dry and overheat it. We'll see if this fixes the car of if I'm wrong about the root cause here. Sadly it will be days or a week until I get back to my daughters to install it. Quote Link to comment Share on other sites More sharing options...
pbagley Posted December 7, 2013 Author Share Posted December 7, 2013 Update: The used fuel pump and plug are installed. Now there is no power on the blue/yellow wire to the fuel pump, the ground seems good. As a temporary measure I ran a wire from the battery to the fuel pump wire. the pump runs and the car starts. I drove it this way about 10 miles (daughter's moving day). Any ideas what to check for no power to the fuel pump? The fuel pump relay is new. The fuses are good. I'm running out of ideas. Thanks! Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 8, 2013 Share Posted December 8, 2013 Check for power at the relay. Make sure the relay clicks when the key is turned On. Check for 12V coming into the relay, and 12v coming out to the pump. (Will only be there for 3-4 seconds when the keynis turned On) If you have 12v on both sides there is a wire problem or loose connector between the relay and pump. Quote Link to comment Share on other sites More sharing options...
pbagley Posted December 8, 2013 Author Share Posted December 8, 2013 Thank you. That will be the next step when I get back to the car. Quote Link to comment Share on other sites More sharing options...
pbagley Posted March 2, 2017 Author Share Posted March 2, 2017 A very late reply. Apologies to those who may have suffered the same issue in the mean time. After changing relays and pump we still had no power at the pump. I used the same jumper wire to drive the car to a local Subaru specialist. The problem was a corroded connector under the back seat. A connector I had no idea existed. The fix was cheap, diagnosis was expensive. The car still runs fine more than 3 years later. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 2, 2017 Share Posted March 2, 2017 Seen that many times. As a Subaru specialist I would have found that in 20 minutes or less. GD Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.