I have only bypassed the resistor. Should I remove the 2 speed relay also?
Which connections would I bridge?
Fuel pump not priming - car slow to start - why?
- Thread starter eddyvr4
- Start date
Which connections would I bridge?
You can eliminate the speed relay entirely by connecting the output of the main fuel pump relay in the cabin to the fuel pump power wire that fucks off down the side of the car.
Ive had the speed relay fail before. The car ran fine with 12v to the pump when idling (relay in low speed position) but the relay had a rusty contact so when the engine saw load and the ecu switched the relay to bypass the resistor the pump got no voltage. This was a real head scratcher to diagnose.
And As above if you just connect the main FP relay directly to the pump itself you can pull that big ugly relay and resistor out entirely.
I have a loom opened up on the bench at home. So ill take a photo of what relay it is and what to connect when i get home
- Location
- SA
- First Name
- Bill
- Drive
- 2000 Galant Type-V
1997 MK Triton GLS [6G74 conversion]
2019 i30 N-Line
Here's a wiring diagram of the relay/resistor block and fuel pump. If you want to test, take the relay out and bridge pin 5 + 2, the pump will run at 12v all the time.
Connector that plugs into main fuel pump relay (C-63) is located near the ECU.
B-11 is the connector for the hi/low speed relay, located on the firewall with the resistor block (connector B-14)
The transition between low and high also causes a blip in fuel pressure, which corelates to blip in AFR, hence why it's better to delete (or if you want to bridge, not just bridge B-14 to eliminate the resistor block)
There's a couple of other parameters, but ECU switches over between low and high is at 80% load. (Essentially start of boost if you wanna look at it that way.)
Best to hardwire as @6A13TT TYPE S has mentioned. Get some firewall real estate back!
Connector that plugs into main fuel pump relay (C-63) is located near the ECU.
B-11 is the connector for the hi/low speed relay, located on the firewall with the resistor block (connector B-14)
The transition between low and high also causes a blip in fuel pressure, which corelates to blip in AFR, hence why it's better to delete (or if you want to bridge, not just bridge B-14 to eliminate the resistor block)
There's a couple of other parameters, but ECU switches over between low and high is at 80% load. (Essentially start of boost if you wanna look at it that way.)
Best to hardwire as @6A13TT TYPE S has mentioned. Get some firewall real estate back!
And while your at it delete the fuel pressure reg vaccum signal solenoid. As from my understanding that cuts vaccum signal to the stock FPR to comensate for the lower fuel pressure being delivered during the pump running through the resistor.
Behind the head unit is 2 relays. Left is your fuel pump relay. Right is the ignition relays.
Front left wire is the output of the relay which goes off to supply power to the resistor relay.
Black w' blue stripe
This 4 pin connector connects the engine loom to the body loom. Again Black w' blue stripe is the power that goes to the fuel pump itself.
Normally the main fuel pump relay output goes through the firewall up to the FP speed relay whicb either switches between the resistor or no resistor then it goes back through the firewall back to that 4 pin plug. I assume they did this purely as mounting the resistor under the dash is a fire hazzard.
But you can just connect the 2 together.
Front left wire is the output of the relay which goes off to supply power to the resistor relay.
Black w' blue stripe
This 4 pin connector connects the engine loom to the body loom. Again Black w' blue stripe is the power that goes to the fuel pump itself.
Normally the main fuel pump relay output goes through the firewall up to the FP speed relay whicb either switches between the resistor or no resistor then it goes back through the firewall back to that 4 pin plug. I assume they did this purely as mounting the resistor under the dash is a fire hazzard.
But you can just connect the 2 together.
Hey guys, thanks a bunch! I'll clean this all up tomorrow and get back to you
Many thanks!
Many thanks!
Thanks for going to the trouble of taking photo's, it's really appreciated! Looking forward to losing the relay and resistor!
Not sure how easy it is to pull the wires out of the loom in situ. As ive cut this loom apart to rewire it for 6 coil and a link ecu but even just not needing that relay there gives you some space and can just tuck the wires out of the way
Ok have access to the two relays just behind the head unit, anyone have a rough idea where the 3 way plug is hiding for the fuel pump relay?
It heads toward the steering column way toward the right side of the cabin.
Right, found it was looking at the wrong side with diff colour's!
Worked a treat removed the resistor and 3 connectors from the firewall.
Thanks guys!!
Worked a treat removed the resistor and 3 connectors from the firewall.
Thanks guys!!
The 4 way was clipped onto another larger white connector directly below the head unit. Back of it had the right colours and positions as shown above. If nothing else it allow d me to piss of that 2 speed relay and crusty cables. Taking the passenger side trim centre console is a great help, easy to move those relays and plate around as one.
I'll wait for the car to cool down and see how it starts up, also bypassed the hot start/ vacuum solenoid to th FPR.
I'll wait for the car to cool down and see how it starts up, also bypassed the hot start/ vacuum solenoid to th FPR.
It wont start any easier as the ecu still doesnt prime on "key on" but its a redundant system completely removed so it cant cause any issues in future
Blackbandt
Hesitantly Boosting
Hi
I would also like to remove the resistor and speed relay. But I still have questions because I do not quite understand it yet
I would like to test this first. If I understand it correctly, I take out the relay on the firewall and bridge pin 5+2 right? Or do I have to remove the connector from the resistor and bridge pin 5+2 there so that the pump runs permanently with 12v ?
And if I want to remove the resistor and speed relay. Which cable do I have to connect to which? I do not quite understand
Thank you
I would also like to remove the resistor and speed relay. But I still have questions because I do not quite understand it yet
I would like to test this first. If I understand it correctly, I take out the relay on the firewall and bridge pin 5+2 right? Or do I have to remove the connector from the resistor and bridge pin 5+2 there so that the pump runs permanently with 12v ?
And if I want to remove the resistor and speed relay. Which cable do I have to connect to which? I do not quite understand
Thank you
Ok, the relay in the above image and white connector are sitting just below the head unit/stereo.
Remove the facia from the t/bar surround and the centre facia from the cigarette lighter up to the vents.
In addition to this, remove the centre console panel side (LHS) to gain better access to the 2 small relays behind and below the head set.
The connector is roughly in the middle further forward. Use the diagrams above to place a link wire from the 4 wire relay to the 3 wire connector.
When this is done you should be able to remove the speed relay in the firewall and the vehicle will start and run at 12 volts always.
Remove the facia from the t/bar surround and the centre facia from the cigarette lighter up to the vents.
In addition to this, remove the centre console panel side (LHS) to gain better access to the 2 small relays behind and below the head set.
The connector is roughly in the middle further forward. Use the diagrams above to place a link wire from the 4 wire relay to the 3 wire connector.
When this is done you should be able to remove the speed relay in the firewall and the vehicle will start and run at 12 volts always.
- Location
- Chicago
- First Name
- Mike
- Drive
- 1997 Mitsubishi Legnum VR4 COTY
2022 Subaru Outback Onyx XT
1999 Honda Civic EX
Going to try this, I am out of ideas.
While chasing a stumble and rough cold idle I decided to swap out the Tomei FPR to a turbosmart unit.
The Tomei holds no pressure after the pump is off, the turbosmart does. So, not all aftermarket fpr's hold pressure AND not all fuel pumps have a check valve built Into the output feed.
After a failed Walbro I switched back to a DW200 with a check valve, it wasn't working right so a few manual pushes on the pin and some throttle body body cleaner got it going.
On switch off I now have residual pressure though not long lasting.
It has totally sorted the hard starting issue even after falling to zero pressure.
I had noticed when installing new injectors that the fuel lines where practically dry 30 mins after starting up.
To add to this, not all fuel pumps are identical in length, feed height and end diameter.
This means I believe that we need to trial different O rings and spacers to maintain a proper seal to the fuel pump cradle.
I was using a 4 X 8 O ring previously and on swapping out fuel pumps found that it had distorted after a few months. The Internal diameter was no longer round when I removed the fuel pump.
Another issue is that the lower cushion or rubber supplied varies in height to accommodate different pumps. Mismatching these will effect the seating pressure at the output nozzle so care needs to be taken here too.
- Location
- Chicago
- First Name
- Mike
- Drive
- 1997 Mitsubishi Legnum VR4 COTY
2022 Subaru Outback Onyx XT
1999 Honda Civic EX
Did you use the white cap with the new gasket as well?
Yes. I always use new O ring between the pump and pump cradle. I used the existing white cap as it snapped on tight to the Denso pump.
I place the top hat spacer with the flat facing up to provided better support for the lower O ring.
I place the top hat spacer with the flat facing up to provided better support for the lower O ring.
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