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So over the last month or two I've been cleaning up my fuel system, or so I thought. I sent my injectors to be cleaned replaced all the rubbers to the fuel rail and injectors and added a fuel pressure gauge. Now that I've put everything back together I get no fuel pressure with key turned to ON or START. If I bridge F/P to GND in the diag port I get fuel pressure and power to the pump and fuel flows and gauge sees pressure, otherwise there is no power to the pump. Is it possible something could be disconnected which is telling the computer to not send power? I've tested my EGI fuse and EGI relay. Both are working. I'm currently looking in the service manual for a solution but was hoping someone might have some insight.
I also disconnected the airbag, disconnected the airbag computer on the drivers side next to the gas pedal, but I wouldn't think that would be related. I removed it because it was constantly screaming at me when I was driving.
I tested the fuel pump resistor below the brake booster for continuity. Seems good. Tested the fuel pump relay and the circuit opening relay, both are good. I tested them with power and they click and allow power to flow through. I'm trying to understand the electrical diagram right now to see how I can trace the wire to see where my power is stopping.
To my understanding, looking at these pages from the FSM. It looks like bridging F/P to GND on the Diagnostic connector just grounds the circuit opening relays coil which activates it. Normally the ECU would ground it out so the ecu isn't activating the circuit opening relay because it does not meet the requirements to do so or the ECU is faulty. So I'm still stuck but this means if you bridge F/P to GND and your fuel pump runs you know your circuit relay is good, which is nice to know because that thing sucks to pull out, the plastic housing on mine cracked trying to pull mine out to test it.
Have you checked the voltage at the pump with a multimeter? To make sure it is really a voltage issue... Unplug the connector to the pump hanger and verify voltage between white/red and black pins (while someone cranks the car)
Have you checked the voltage at the pump with a multimeter? To make sure it is really a voltage issue... Unplug the connector to the pump hanger and verify voltage between white/red and black pins (while someone cranks the car)
I didn’t go it with the car cranking in start but I did it with the car as it turned to ON. No voltage. But when F/P is bridged to GND I get voltage.
Also after you jump the pump from diagnostics, does it keep pressure afterwards (for a few minutes at least)?
No voltage to the pump connector at the top of the hanger. The same pins on the pump connector that had power when I bridge diagnostics, don’t have power when I turn the key to on. The pressure starts to go down pretty fast when I unbridge, I installed a aeromotive fpr apparently they’re known to not hold pressure when the pump stops.
Investigate how the resistor works with the F/P relay. I think power flows through the resistor to a certain level, then the relay switches on (or something like that). Perhaps borrow a resistor from a friend and try that. It is fairly accessable.
I recently bought a new resistor off Buyee for a reasonable price. I had it swapped in, although there was no sign my resistor was bad. But It had 170k km on it and was 25 years old.
The wire to the resistor takes a long route through the front harness. Is your front harness getting rubbed in the front wheel well? If yes all hell might be ready to break out all along your front harness.
No voltage to the pump connector at the top of the hanger. The same pins on the pump connector that had power when I bridge diagnostics, don’t have power when I turn the key to on. The pressure starts to go down pretty fast when I unbridge, I installed a aeromotive fpr apparently they’re known to not hold pressure when the pump stops.
Well, that leaves us with one option that ECU does not trigger (or that wire somehow shorted) ?? (at least that's what I see in the diagram)
Both diagnostics and ecu wire connect to B1-03 connector (Blue/Black wire) which is the fuel pump relay. Maybe it's worth double checking the voltage on that wire with key in ON position.
Investigate how the resistor works with the F/P relay. I think power flows through the resistor to a certain level, then the relay switches on (or something like that). Perhaps borrow a resistor from a friend and try that. It is fairly accessable.
I recently bought a new resistor off Buyee for a reasonable price. I had it swapped in, although there was no sign my resistor was bad. But It had 170k km on it and was 25 years old.
Maybe try a new relay.
Between my basic knowledge of electrical and what I’ve learned about the FD here. The fuel pump runs at two different voltages. One is the lower voltage, which is just the resistor. Next is the ecu tells the fuel relay to kick on which is the higher voltage. I tested that relay it opens when powered and allows power to pass through with no resistance. However I may try to bridge that relay to check.
Edit: Don’t quote me on this, but I’m pretty sure thats how it works lol Also I realized I pretty much said exactly what you just said.
Last edited by LegoMontego; May 30, 2024 at 04:47 PM.
are you rhd or lhd, and, regardless which version are you?
1993 lhd base model, stock ecu, I was running the car before I decided to clean the injectors and replace the fpr with a aeromotive. I also removed the airbag computer, removed the airbag fuse, and unplugged the air bag.
Last edited by LegoMontego; May 30, 2024 at 04:50 PM.
If you have replaced the stock FPR (and its controlling solenoid), the ECU might be ;looking for that solenoid, and sensing it is not there, turns off the pump?
On RHD, the ecu may put the car in limp mode if the FPR solenoid is coding out (or missing). But you would still be getting some fuel through.
If you have replaced the stock FPR (and its controlling solenoid), the ECU might be ;looking for that solenoid, and sensing it is not there, turns off the pump?
On RHD, the ecu may put the car in limp mode if the FPR solenoid is coding out (or missing). But you would still be getting some fuel through.
So to me it definitely looks like the ecu is not telling the cycle relay to open. Because the F/P diag port opens that relay. So I’m pretty sure something is preventing the ecu from opening the cycle relay. Maybe I left something unplugged or something is loose. I’ll have to take the UIM off when I get home and check.
If you have replaced the stock FPR (and its controlling solenoid), the ECU might be ;looking for that solenoid, and sensing it is not there, turns off the pump?
On RHD, the ecu may put the car in limp mode if the FPR solenoid is coding out (or missing). But you would still be getting some fuel through.
also I forgot to mention, I left the solenoid for the FPR installed
So little update, I’d decided to test the power at the fuel pump harness again. Now I’m getting power to the pump harness, but now the pump wont run. The sun is setting so I’ll open the fuel tank in the morning and test the bulk head fitting and my walbro pump.
Put power directly to the bulk head at the topside of the pump hanger. Fuel pump runs. Turn key to on with F/P bridged to GND. I see power at the harness that plugs into the top of the fuel hanger. I plug them together and the pump doesn’t run. I cleaned the contacts still no power transfer the plugs look fine on both sides don’t look dirty at all or damaged but they must be. I’ll try to bend the harness end to make it tighter.
So I decided to check my codes. I have a lot of solenoid codes but they're all solenoid codes. I'm not sure which of these are normal from emission deleting. My thoughts is maybe one of these solenoids "not showing up" to the ecu could be the reason the ecu doesn't tell the pump to run unless I use the diag port. I have a few solenoids in the rats nest that are plugged in but have no hoses run to them, I assume to trick the ecu.
My codes are:
30 Split Air Bypass
33 Port Air Bypass
38 Accelerated Warm Up and Air Supply
39 Relief 2
40 Purge Control
50 Double Throttle Control
Edit: 30, 33, and 39 in the FSM show as part of the ACV which has never existed in the car since I bought it. Code 38 Accelerated warm up is deleted as well.
Last edited by LegoMontego; Jun 2, 2024 at 05:20 PM.
