Jump to content
Ultimate Subaru Message Board

Fuel pump


Recommended Posts

My car was originally a carbie motor.Im 99.8% done with the EJ swap.The only things left are install FI fuel pump and assorted FI lines.The fuel pump is out of an 89 MPFI car.physically it bolts right in.the connector though is different.

Both connectors in question have two wires going in to each other.

 

are the wire positions the same in each connector?ie

carbie connector [ + - ] mpfi connector [ + - ]?

 

 

also is it required to connect the signal wire from the ej harness to the fuel pump?The pump as it is wired with the EA harness starts pumping when I turn the key.

Link to comment
Share on other sites

also is it required to connect the signal wire from the ej harness to the fuel pump?The pump as it is wired with the EA harness starts pumping when I turn the key.

I think the reason you power the pump from the EJ harness is because it only gives it power when the motor is turning over. Now the reegulator on the EJ engine opens when you have vacuum, so if your pump is on and the motor isn't turning over the pump is building up pressure and may pops some pipes or even die. I powered my pump off the EJ's pump relay. But on my first start it was just wired to the battery. So the engine will run even is the EJ harness has nothing to do with the pump.

Link to comment
Share on other sites

  • 2 weeks later...
I think the reason you power the pump from the EJ harness is because it only gives it power when the motor is turning over. Now the reegulator on the EJ engine opens when you have vacuum, so if your pump is on and the motor isn't turning over the pump is building up pressure and may pops some pipes or even die. I powered my pump off the EJ's pump relay. But on my first start it was just wired to the battery. So the engine will run even is the EJ harness has nothing to do with the pump.

Should I be concerned? after reading this thread I'm wondering if I should be

concerned about my fuel pump (they are spendy as I'm sure you know)

My pump cycles on/off as soon as the key is on, Before start! I thought this was normal. isn't there a pressure regulator with a relief to send excess fuel back to the tank? Thus preventing overpressure damage. The car had a bad fuel pump when I bought it. Now I wonder if it failed because I have a problem with the associated circuitry, I hope I misunderstood the thread!

Is My system NOT supposed to cycle before the engine is running? I'm sure the entire circuit is stock, But may have a problem if pump should not run with engine off. 91 loyale.

Link to comment
Share on other sites

  • 4 months later...
  • 4 weeks later...
Atleast on the SPFI EA82's the fuel pump should cycle for a second or so when you turn the key on. That's how I diagnosed mine when it went bad - silence from the rear when I turned the key on!

 

What problems were you having with your car when you found it was the fuel pump? Any running issues, or just silence from the rear?

Link to comment
Share on other sites

Atleast on the SPFI EA82's the fuel pump should cycle for a second or so when you turn the key on. That's how I diagnosed mine when it went bad - silence from the rear when I turned the key on!

not all of us-- some ECU's (mine included) only turn the fuel pump on when the key is in start or the engine is running.

Link to comment
Share on other sites

What problems were you having with your car when you found it was the fuel pump? Any running issues, or just silence from the rear?

 

My car sometimes simply wouldn't start. After I noticed there was no noise when I turned the switch on, I would go back and whop on the fuel pump a couple times with a BFH and the pump would cycle the next time I turned the key, then run fine for awhile, no loss of power or any other symptoms.

 

After a couple weeks of this, it started dying while I was driving down the road, just ran out of gas and quit. A few more whacks with the hammer (not fun at 5PM on I-10 in Phoenix!) and it would run maybe 30 minutes and die again, so I decided to replace it before it died altogether.

 

I replaced it with an F150 fuel pump from NAPA, a bit of a pain to get in and a little noisy, but it works fine.

Link to comment
Share on other sites

not all of us-- some ECU's (mine included) only turn the fuel pump on when the key is in start or the engine is running.

 

Yeah, I guess most of my replies have a disclaimer of "at least on my 91" because of the variations.

 

One question - I don't understand how yours knows whether the engine is running or not - do you know how that part works?

Link to comment
Share on other sites

Yeah, I guess most of my replies have a disclaimer of "at least on my 91" because of the variations.

 

One question - I don't understand how yours knows whether the engine is running or not - do you know how that part works?

 

I have been meaning to look into that; I know most vehicles with a flapper-type AFM incorporate a switch there that energizes the fuel pump relay (which is also energized by the key going into the "start" position) but since mine is a hotwire MAF type (as is all SPFI) it is almost definitely switched inside the ECU. My guess is that the ECU is signaled by the CAS? In any case, I am not entirely certain, nor does it matter (as long as I continue having no fuel pump issues, heh.)

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...