No power to fuel pump

980 Views 51 Replies 8 Participants Last post by GDII, 5 d ago

JohnnyJohnny

Discussion Starter · 1 mo ago

Hi, I have a 1991 MR2 turbo with a 4th gen 3sgte. Engine is fully rebuilt and engine harness from Doug (wiregap). Prior to getting the engine harness I was getting no power to the fuel. I was hoping the new harness might fix it so I can rule that out. The only problem I do have with this harness is that the obd scanner won’t turn on with it. My previous harness I was able to get codes. I replaced the efi relay and the COR still no power to the fuel pump. I only get 1v instead of the 12. I tested the starter relay and the ign relay all passed the testing procedure. I also checked all the fuses up front and replaced the 120a one. The starter is also new as well as the alternator. When I connected the fuel pump straight to the battery it would start right up without shutting off. So my car only starts with starter fluid or if I wire the fuel pump straight to battery. The only thing I changed prior to it not starting was the pipe that goes from the turbo to the side Intercooler. The connector that’s behind the driver seat is also plugged in, battery is also new. All the grounds are connected too, I sanded down the paint just Incase too. Anything else I should look for that could prevent power going to the fuel pump?
Thanks

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GDII

· #41 · 14 d ago

JohnnyJohnny said:
Yeah I’m gonna have to trace it, it’s pin 4? I can test the continuity by putting the lead on pin 4 and the power on the F/P connector? Also can the ignition main relay be the problem? That’s the only relay I haven’t replaced.

The main ignition relay should power the injectors and coils. Not the fuel pump.

How to check continuity to the fuel pump. Place either lead of the multimeter in pin 1 of the C/OPN Relay socket (take the relay out) then onto the blue with black wire that the fuel pump inside the car. You might need to run another wire to make the multimeter cables longer to do this.

Let me list some tests.

Are you getting power to the EFI fuse when the key is ON
Are you getting power to the C/OPN Relay pin 2 when the key is ON
Are you getting continuity from the C/OPN Relay to the pump

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JohnnyJohnny

Discussion Starter · #42 · 7 d ago

GDII said:
The main ignition relay should power the injectors and coils. Not the fuel pump.

How to check continuity to the fuel pump. Place either lead of the multimeter in pin 1 of the C/OPN Relay socket (take the relay out) then onto the blue with black wire that the fuel pump inside the car. You might need to run another wire to make the multimeter cables longer to do this.

Let me list some tests.

Are you getting power to the EFI fuse when the key is ON

Are you getting power to the C/OPN Relay pin 2 when the key is ON

Are you getting continuity from the C/OPN Relay to the pump

Yes to 1 and 2 and on step 3 I was getting OL. I traced the blue/black wire with a wire tracer and couldn’t find a break in the body harness. I’m assuming maybe it’s the fuse link. Some of the wires were off on it Im Gonna try to get it fixed this week. I’ll get back to you if that did anything or not

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GDII

· #43 · 7 d ago (Edited)

JohnnyJohnny said:
Yes to 1 and 2 and on step 3 I was getting OL. I traced the blue/black wire with a wire tracer and couldn’t find a break in the body harness. I’m assuming maybe it’s the fuse link. Some of the wires were off on it Im Gonna try to get it fixed this week. I’ll get back to you if that did anything or not
View attachment 87584

Good to know.
Which wires are the fuel pump? I see a blue wire on the far right or is it blue wires and the red ones to that plug?
I think I see the fuel pump wire split into 2 wires at the top of the photo?

To me that white plug on the T-Top cover should be plugged in as it is this one. The blue and orange plug in the diagram below.

Map Infrastructure Slope Urban design Font

If this isn't plugged in then the pump won't run.

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JohnnyJohnny

Discussion Starter · #44 · 7 d ago

GDII said:
Good to know.
Which wires are the fuel pump? I see a blue wire on the far right or is it blue wires and the red ones to that plug?
I think I see the fuel pump wire split into 2 wires at the top of the photo?

To me that white plug on the T-Top cover should be plugged in as it is this one. The blue and orange plug in the diagram below.
View attachment 87585
View attachment 87586

If this isn't plugged in then the pump won't run.

View attachment 87587

Yeah that blue wire that’s split in 2 and next to the red one by the plug is for the fuel pump, it’s the blue/black wire. That’s not suppose to be split? That white plug was connected I just disconnected it to try to find a break

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Also the connector by the ecu is the pin that has the blue/black wire suppose to be connected to something? The connector with the purple wire only came with those 3 wires. I’m assuming it doesn’t affect it because even with my previous harness it wouldn’t start but I just wanted to ask

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GDII

· #45 · 7 d ago

JohnnyJohnny said:
Yeah that blue wire that’s split in 2 and next to the red one by the plug is for the fuel pump, it’s the blue/black wire. That’s not suppose to be split? That white plug was connected I just disconnected it to try to find a break
View attachment 87588
Also the connector by the ecu is the pin that has the blue/black wire suppose to be connected to something? The connector with the purple wire only came with those 3 wires. I’m assuming it doesn’t affect it because even with my previous harness it wouldn’t start but I just wanted to ask View attachment 87589

Oh ok.

The last photo, that green with red wire in the socket with the foam on it is the FC pin. This is CRITICAL to making the fuel pump stay on. Note the light green wire in the plug you are holding. It must be plugged in. It keeps the C/OPN relay closed.

The split in the blue and black wire was just a description to lead you to where I was looking. That's normal.

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JohnnyJohnny

Discussion Starter · #46 · 7 d ago

GDII said:
Oh ok.

The last photo, that green with red wire in the socket with the foam on it is the FC pin. This is CRITICAL to making the fuel pump stay on. Note the light green wire in the plug you are holding. It must be plugged in. It keeps the C/OPN relay closed.

The split in the blue and black wire was just a description to lead you to where I was looking. That's normal.

Ok, I just had it disconnected to take that picture. Also how can I test the fuse link to see if it’s good or not? That’s the last thing I haven’t tested, visually I know it wasn’t perfect so I know I need to make it connect better. But I’m just asking to be 100% sure that I’m testing it right. When I used the wire tracer to see if it would beep, it made no noise. I assumed since it’s the first thing the battery has to pass through to get the fuel pump on it would make a tone but nothing. I already replaced the 120a fuse as well, I believe I mentioned it in my earlier posts.

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GDII

· #47 · 6 d ago

JohnnyJohnny said:
Ok, I just had it disconnected to take that picture. Also how can I test the fuse link to see if it’s good or not? That’s the last thing I haven’t tested, visually I know it wasn’t perfect so I know I need to make it connect better. But I’m just asking to be 100% sure that I’m testing it right. When I used the wire tracer to see if it would beep, it made no noise. I assumed since it’s the first thing the battery has to pass through to get the fuel pump on it would make a tone but nothing. I already replaced the 120a fuse as well, I believe I mentioned it in my earlier posts.

Ok understood.

Which fuse link are you meaning? There is only one fuseable link in the car and it's at the battery.

Let me get some photos of under the fuse box in the engine bay and get you to test from there to the plug behind the seat then there to the fuel pump. It seems this is where the break is although visually you've not found it.

So testing from pin 1 on the C/OPN relay (with it disconnected) to pin 6 on AE5(blue with black) behind the seat gives you OL? Or no beep. And testing between pin 6 AE5 and the fuel pump give OL too?

The power path to the fuel pump goes as follows.

Battery
Fuseable link
40A AM2 fuse in the frunk
15A EFI fuse in the engine bay
EFI main relay
Circuit Opening Relay
Then back towards AE5 behind the seat.
Then to be fuel pump
Then grounds to the chassis under the radio and ash tray area.

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JohnnyJohnny

Discussion Starter · #48 · 6 d ago

GDII said:
Ok understood.

Which fuse link are you meaning? There is only one fuseable link in the car and it's at the battery.

Let me get some photos of under the fuse box in the engine bay and get you to test from there to the plug behind the seat then there to the fuel pump. It seems this is where the break is although visually you've not found it.

So testing from pin 1 on the C/OPN relay (with it disconnected) to pin 6 on AE5(blue with black) behind the seat gives you OL? Or no beep. And testing between pin 6 AE5 and the fuel pump give OL too?

The power path to the fuel pump goes as follows.

Battery
Fuseable link
40A AM2 fuse in the frunk
15A EFI fuse in the engine bay
EFI main relay
Circuit Opening Relay
Then back towards AE5 behind the seat.
Then to be fuel pump
Then grounds to the chassis under the radio and ash tray area.

Sorry I meant fusible link

From AE5 pin 6 to fuel pump I get continuity so no break in that line. But from pin 1 C/OPN I get OL, so I’m gonna try to look for a break there.

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dustinkhen

· #49 · 6 d ago

JohnnyJohnny said:
Yeah that blue wire that’s split in 2 and next to the red one by the plug is for the fuel pump, it’s the blue/black wire. That’s not suppose to be split? That white plug was connected I just disconnected it to try to find a break
View attachment 87588
Also the connector by the ecu is the pin that has the blue/black wire suppose to be connected to something? The connector with the purple wire only came with those 3 wires. I’m assuming it doesn’t affect it because even with my previous harness it wouldn’t start but I just wanted to ask View attachment 87589

On the last pic, your two grey plugs are STILL plugged in the wrong way to each other.
Yes they both are male plugs, yes the original has female pins, yes the one in your actual hand is a male plug and pin.
Please fix this. I've sent a picture about this in page two.

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JohnnyJohnny

Discussion Starter · #50 · 6 d ago

dustinkhen said:
On the last pic, your two grey plugs are STILL plugged in the wrong way to each other.
Yes they both are male plugs, yes the original has female pins, yes the one in your actual hand is a male plug and pin.
Please fix this. I've sent a picture about this in page two.

I apologize I see what you’re referring to now. I pulled out the body harness but when I install it back in I’ll connect it that way.

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JohnnyJohnny

Discussion Starter · #51 · 6 d ago

This is what I found following the blue/black wire, green corrosion. The only thing holding it together was electrically tape. I’ll get back to you guys once I get that fixed.

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GDII

· #52 · 5 d ago (Edited)

JohnnyJohnny said:
This is what I found following the blue/black wire, green corrosion. The only thing holding it together was electrically tape. I’ll get back to you guys once I get that fixed.
View attachment 87592

Well done finding that! That's not a great connection. I do hope that makes it work.

I know it's taken a while, especially with time zones being different but I think we got there in the end.
Finding electrical faults can be difficult as proved here but when you look back at how you've tested each part and isolated the bit that doesn't test out as expected, you get to the bottom of the issue.

What part of the harness is this photo located?

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