No power to fuel pump only when connected

[redcivic92]

Now ive been beating my head with this problem. My car died and only cranks...I sprayed starter fluid and car fired up...noticed I don't have fuel pressure. I have a manual and followed all the flow charts. I have removed the relay and checked the relay per manual and determined relay is fine. I put a jumper wire on the 5 & 7 terminals and checked the plug at the pump and there is battery voltage. At the same time, with a different battery, I applied voltage to fuel pump and it turned on. NOW WHEN I PLUG IN THE CONNECTION THE VOLTAGE GOES TO 0v and there is no power to fuel pump. I did the checks the manual tells you to do...checking the relay harness and checking the the ECU terminals with a multimeter for voltage and continuity. Anyone have any idea why I would not have power at the fuel pump only when I plug into the fuel pump connector????

 

[redcivic92]

Ok according to the manual it says A7 is a + (hot wire) right...so you are saying to use a jumper wire and put it on A7 and touch the body of the car to ground it?

 

[redcivic92]

ok so I removed the connector on the ecu...turned the ignition to the II position, grounded the A7 pin and can only hear the relay clicking as I moved the jumper on/off the pin. pump did not turn on....have any idea what this means????

 

[redcivic92]

if I jump 1 to 7 pump doesn't turn on. if I jump 5 to 7 pump don't turn on. like I said in my post....I can disconnect the pump under the seat and jump 5 to 7 turn on to II position and there is battery voltage at the connector end. but when I connect to the pump and check the power it drops to 0v. That's what making me bang my head....its losing power only when connected to the pump..could it be a faulty ECU or some other relay/sensor stopping the power when connected.

 

[civteck]

Sounds like pump may be shorted, try unhooking the harness under the rear seat and check voltage there with key on and off etc report back voltages

Sent from my boujea ass phone

 

[redcivic92]

Removed rely and jumped the following and recorded voltages at disconnected fuel pump connector . Jumped pin 7 & 1, with ignition off got 12.8V with the ignition on 12.3v. Jumped 5 & 1, the dash icons (srs, bat, cel, etc...) lit up and there is 0v at the connector when ignition is on or off.

 

[redcivic92]

civtek I had changed the fuel pump....I followed the diagnose chart in the manual cause I found I had spark but no fuel. I jumped the 5 & 7 pins turned ignition to on position and found battery voltage....so according to the flow chart it said to replace fuel pump. I have a motorcycle battery and I used jumper from + to + and - to - on the fuel pump and I can hear the fuel pump turning....I even loosened the fuel filter to verify fuel pressure. Would the fuel pump still run if it was shorted?

 

[redcivic92]

unless the manual is wrong It says jump blk/yel 5 to yel/grn 7...maybe I got a bunk manual. do you know what the fuse is...15A, 20A or the ID of it...and if its fine any other idea. In advance thanks for all your help I really appreciate your knowledge.

 

[redcivic92]

no problem 1 & 7 is the same as above test...with the 5 & 7 pins jumped I get 0v with ignition off and 12.1v with the ignition on.

 

[redcivic92]

ok boss....I removed the ECU A connector and grounded A7 pin, turned on the ignition and got 12.1v at the pump connector. I left the Neg in the pump connector and touched the Neg batt post/cable and got a continuity tone. So I have power and when jumped and continuity on the ground to the battery....is this car cursed????

 

[redcivic92]

I read in a post, when I was searching my issue, that one person had a similar problem and he traced it back to a screw that fell loose in his distributor causing some kind of short. Does this sound possible...the distributor causing this issue. I feel like I'm beating a dead horse at this point.

 

[redcivic92]

I already changed the fuel pump...if I take my motorcycle battery and supply power to the pump, the pump runs fine, even my old pump works fine, I only changed the pump cause the flow chart led me to believe that it was faulty...when I remove the connector to the pump I have power at the connector...is it possible the housing of the pump (even though it runs fine when an external power supply is applied) is shorted in some way causing a safety in the ecu to cut the power to prevent a short when the power is connected to pump???

 

[redcivic92]

Ok I don't think its a short around pump housing...I connected the original pump I changed to the pump connector with jumpers and when I turned the key on the pump I was holding in my hand didn't turn on...I know the pump works cause I walked it over to my motorcycle battery and the pump came on....its obvious something isn't working when there is a load supplied to the circuit. The manual says if all the test were done to replace the ECU with a know working ECU and if the problem clears then its the ECU.

 

[redcivic92]

Yes I did the A7 ground test and nothing...but like I posted, I already changed out the pump before all this troubleshooting.

 

[Restotech]

This is what I would do, and involves backprobing the connector while it is connected.

Supply power power to your pump from the vehicles battery while the key is off. ( don't want to power the car from backfeeding)

If it doesn't run, you have a ground problem.
If it does run you have a power problem. Please report with your findings.
Do not use an external battery, use the vehicles battery. The goal here is to isolate the fuel pump ground. I have seen , not often, a relay supply voltage, but not carry current. Aka will not power something that pulls current, but will show voltage with no load.

P.s. You have proven that the pump will run with external power and ground.

 

[civteck]

Did you recently install an amplifier, remove the seats, remove carpet??? It sounds like you have a weak or shorted lead to the pump. Can you test voltage at the pump connector while doing said tests? I had a similar issue on my 93 hatch (pic attached) but then again i have 2 pumps in tank and individually relayed n such but just something to look for.

Sent from my boujea ass phone

 

[redcivic92]

Is there any kind of switch or relay connection to the transmission....cause the last thing I did before the car stopped running is I was idling in front of my house and in a fast motion slammed in park and shut off ignition at the same time...then I noticed that I was to far from curb and tried to start the car up and it only cranked....I'm just throwing it out there cause I followed the manual flow chart and advise to the T and did it several times to verify and I cant figure it out what the heck is going on. Maybe I need to clean the ground wire connection. I will supply power from car battery to pump and see what happens.

 

[redcivic92]

Restotech-I brought power from the car battery to the back of the pump connector while connected (backprobed)...I only had to touch the positive side of the connector with the probe and the pump turned on. So would that rule out bad grounds since it came on with just me backprobing the positive?

 

[redcivic92]

ok I going to try a test I'm going to run a wire from the back of the relay (Yel/Grn) to the back of the fuel pump while connected and see if it turns on.

 

[redcivic92]

Well here are the results of that running a wire from the relay to the pump....it came on, primed for 2 seconds then went off like it should. Now is that c415/c551 connector under the carpet...I have a feeling if it is it might be the victim of years of water/liquids dropping of the floor since ive had the car since 93???