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Fuel pump won't turn on unless you bypass the efi relay

11K views 11 replies 5 participants last post by  95MITSECLIPSE 
#1 ·
Ok so I bought my car 93 2.0 nt and was told that the fuel pump was bad. So I replaced the pump and it still wouldn't kick on. So I bypassed the efi control relay with a jumper wire and it kicked on. I have spark but only thing is my battery is completely dead so I have been using jumper cables and my other cars battery. I bought a new efi relay and the pump still won't turn on. So I bypassed it again and tried to start it while the fuel pump was running but nothing, I do have spark I don't know if its because my battery is dead and the battery I am jumping it with is rated lower than my laser's or what the deal is. PLEASE HELP IT'S DRIVING ME CRAZY!!!!!!!!
 
#3 ·
I think so cause I tested the connector that goes into the relay and I had voltage. I checked terminal 10 like the manual said to. I am thinkin it is a problem after the relay before the pump. But I am noot sure if there are any fusable links or anything between the relay and the pump.
 
#5 ·
Hey when you bypassed the relay on your 95 did you try to start it? Cause originally sfter I put in the new relay and the pump still didn't kick on I was just going to perminantly bypass the relay and mount a switch in the dash for the pump. It won't work for me but it might for you I dunno, today I am going to tear into it cause I have the whole weekend off. So I will let you know if I figure it out. If anyone else has any ideas it would help narrow my search.
 
#6 ·
Start by thinking about what the heck you're looking at.

Start with the fuel pump relay outputs, pull the harness and check for the main 12v input from the battery. Once you verify that you have that, check for the 12v to the coil. Once you verify that you have that, have someone try to crank the car over and verify that you are getting a ground output from the ECU to the other side of the relay coil. If you have that then the possibilities are that the relay is bad, or that there is a discontinuity from the output of the relay to the actual fuel pump through the main 12v line to the pump.
 
#7 ·
I attempted to start the 95 after bypassing the relay but the battery was too low and I had to put it on the charger. I have not attempted to start it since then but plan on trying it out this Sunday when I get back in town. I thought about having a switch in the dash for the pump but I don't want to have anything that is not stock looking in the car.

To the comment for 16g-95gsx, I have checked all the connections and the relay and they are all giving the correct voltage.
What is in the same circuit that the computer reads in order to activate the fuel pump? Is it just the relay and the computer? What would cause the computer to not activate the pump? (I.E. on my dad's Blazer, if the computer did not see the oil pressure sensor, it would shut off the fuel pump).
 
#8 ·
I believe, and forgive me if I am wrong as I have been running AEM for a number of years, but the stock ecu primes the fuel pump when first turned on, and then it will turn the pump on whenever it measures an RPM signal.
 
#9 ·
Do you know if the ground wire from the fuel pump needs to still be hooked up in order to have the relay connected when doing the rewire? I did the rewire and just cut the wire that went from the stock harness and didn't connect it back up for the ground wire. I followed a write up on the FAQ to do it so other than that, I don't know what the problem could be.
 
#10 ·
Does anyone know where to get a electrical diagram of the fuel system other than a shop manual. Like maybe a link or something. Also what fuses under the hood are tied into the fuel system if any cause everyone keeps tellin me to check my fuses but not sure which ones they are tellin me to check. Like I said I am still a little green to the dsm world.
 
#11 ·
Had this happen to my 1g awhile back. Ended up being the ecu not sending the signal to turn on the fuel pump. I wired my fuel pump to turn on with the key for awhile til I got my eprom.
 
#12 ·
I was thinking it was the actual fuel pump but then I replaced it. Then I figured it was the ECU so I replaced it also. Still not pump unless I bypass the relay. If anyone has the diagram that mulishafan85 is wanting to get that may help out me also. If anyone knows where to get it for the 1g and the 2g that would be awesome.
 
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