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Discussion Starter · #1 ·
TL;DR:
The fuel pump on my celica isn't getting power and I'm completely out of ideas as to why.. pls help XD

The story so far:
I picked up this 1990 Celica SX a few months back that had been sitting on a farm for almost a decade in the hopes that I'd get it on the road soon.. That hasn't happened. Min problem being the fuel pump/tank.
The car would sometimes crank, but never start. I traced that issue to the fuel pump, which was absolutely covered in fuel varnish and not savable. After sourcing a new pump assembly and getting my tank properly cleaned, putting it all back together, it was finally time to start the thing.

No cigar.

The fuel pump still wasn't getting power, (I have confirmed that the pump is functional, there's just no power getting back there). My mechanic friend noticed there is an aftermarket alarm system on the car, specifically the mongoose mx40 mk2, which has the ability to cut power to the fuel pump. This was also the source of the issue where the car would only crank sometimes. The alarm was going off and stopping the ignition.

Great I thought, all I have to do is disable it and then the car will start! So I disabled the alarm with the pin, which thankfully was set to the factory default, turned the key, and....

No cigar.

The problem:
The fuel pump is not getting power and I have no idea why. I thought I'd post all this here in the hopes that someone will have an idea as to why there's no power getting down there before I have an auto electrician look at it.

I'm kind of leaning towards the thought that mice may have chewed up some cables but I'm hoping that's not the issue.

The way I'm testing the pump is through turning the key so the engine is cranking, and having the fuel lines disconnected from the pump so I can see if fuel is coming out of it.


Any help or ideas would be greatly appreciated,
Thanks!
 

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OEM wiring has power coming from the EFI fuse / relay to the fuel pump relay. The control signal for the relay gets it's power from the primary wire and it's ground is competed through the ecu. Ecu grounds the circuit, allowing fuel, when it senses proper conditions (ie signal from the distributor).

You can bypass the ecu and EFI circuit at the test port. Do not run this test for long periods as the wiring (and your jumper) may overheat. You can at least verify that the wiring from the engine bay back to the fp is operational. If the fp doesn't come on with the test port, then you have "mouse" problem (or fraying etc)

If the test port test works, then you are looking at control wire. You'll need a test meter to confirm different legs of different circuits.
  • first, you'll need to determine where the security system is installed in the circuit. Could be primary power, load side of the relay (to the fuel pump), or the control ground wire to the ecu. Ideally, remove it.
  • confirm power is at the relay. If not, then something wrong with wire harness from efi to the relay
  • confirm complete wire between relay and ecu for the ground circuit
 

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Contrary to popular belief a "storage" car is a PIA. Like Sefiro said you might have a mousie problem or corrosion. A voltage drop might indicate that. On my project under this relay panel the black/white wire was completely corroded apart where it was chewed. Before you crawl too far down a rabbit hole check the easy things first. There should be a factory jumper where the fuel pump relay is located. It was there on my '91 5SFE. If it's there then check wires under the hood.
31970
31971
 

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The diagnostic port jumper will power the fp without the relay. It's located driver side near the hinge.
 

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Discussion Starter · #5 ·
Thanks for the responses guys..

@Sea-J I've noticed something interesting:
Where your "Fuel Pump" relay is located, on my car that is labelled "Sub fan", and also interestingly, that relay is actually missing from the box...

Perhaps there's a difference between the Aussie/American versions of the car, or perhaps the difference is in the year model (1990/1991)... But I wonder what the chances are of that relay being what I need?

31974
31975
 

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Jump it in the diagnostic port and then try starting? That would answer a few questions.
 

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On some versions, it's called the curcuit opening relay, mounted on the frame that holds the ecu.
 

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Discussion Starter · #8 ·
On some versions, it's called the curcuit opening relay, mounted on the frame that holds the ecu.
I've done a bit of research, turns out that the fuel pump relay/sub fan relay is different depending on the engine:
31976

What engine does your car have @Sea-J? Maybe the 3s engines just have the relay in a different spot.

The circuit opening relay seems to be what I'm looking for though after some quick googling, do you know where I might be able to locate that @sefiro? I don't have a manual :(
 

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I'm running a 5sfe in a 91 GT USA.

Your topic title said 5S-FE. But your last post was 3S on SX - Australia?

If so, then circuit opening relay is the control point. I don't have a wiring diagram for Japan/Other/SX models.
 

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Discussion Starter · #12 ·
Your topic title said 5S-FE. But your last post was 3S on SX - Australia?
My car is definitely a 5S-FE, I thought Sea-Js may have been a 3s based on the difference in fuse box, my mistake.

Thanks for the info, I'll try to find a diagram of some sort today.
 

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Things are quite different depending what country the car was manufactured for. JDM (Japan Domestic Market) is strictly manufactured for Japan for sale in Japan only. Others that are manufactured for export were/are subject to different regulations and restrictions. A USDM might have stricter (or looser) emission regulations. Maybe one manufactured for sale in Australia has a slightly different wiring set. Getting off subject here, sorry. A 5S exported for US could be different than a 5S for your country. Either way, still gotta get that fuel pump going. Tempory hot wire and set it up like a racing car with a separate toggle switch to turn it on or off(y) If it was mine I would take a side cutter and do some surgery on the anti theft. Maybe you might find something here.

1990-1993 (Gen 5) Toyota Celica Electrical Wiring Diagram- Celicatech.com
 

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Discussion Starter · #14 ·
I ended up jumping FP/+B at the diagnostic port like you suggested @Sea-J.. Still nothing!

Must mean it's not an ECU/relay related issue, I'm thinking about just getting an auto electrician in to look at it at this point, I just want it to start
 

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How about all your ground points. Any possibility a ground point could be rusted? Does it fire for a brief time if you spray starting fluid in the intake? Even if the pump isn't getting power it should fart a few times with spray.
Here's a link to Scanner Danner, an auto electrician that might help.
Fuel Pump Electrical Circuits Description and Operation - YouTube
I have confidence that you WILL get it going. Think of the education you are getting :rolleyes:
 

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Discussion Starter · #16 ·
I haven't tried spraying starting fluid into the intake, it definitely cranks and the engine seems to be in order, what will spraying the intake tell me?
 

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