fuel pump wiring issues ta22

[celbelle]

Hey all,

Having some issues running a fuel pump and being a total rookie I have no idea what to do next.
The car is a '73 Celica Ta22 with a 2tgeu. Previous owner installed a swirl pot in the boot to accommodate the efi system.
System includes two pumps. One low pressure between fuel tank and swirl, and one high pressure between swirl and rail.
Problem is the high pressure pump that goes to the rail won't run, and the low pressure pump doesn't have enough guts to get the fuel to the rail.
Tested the pump - it's fine.
The confusing part is that both pumps are wired to the coil. Low pressure pump that works - wired to the positive side of the coil. High pressure pump that doesn't work - wired to the negative side of the coil. (how anything could run off the negative side of the coil is too much for my little brain - but that's how the car was purchased and ran for years)
Now, when I attach the high pressure pump to the positive side of the coil - it runs. But if I try to run both pumps off the positive side - nothing.

Does anyone have an idea what the deal is? and what would be the best way to get it running? (this was supposed to be the easy first step of the rebuild ha ha ha)

[masterofsinanju]

I really don't now much but it seems to me that running your pump direct from the coil is not a good idea.

I would expect some sort of relay which also allows the hi pressure pump to start pumping before you even start the engine. All that aside, maybe you have a short somewhere?

[celbelle]

Cheers masterofsinanju, although there's a relay and fuse in line I still wasn't sure it should be wired to the coil at all.. Let alone the negative side.. Have been testing everything with multimeter and test lights and nothing is screaming 'I'm the problem' so I will keep testing and tinkering until I find something I guess!

[ToyTA22]

Hey all,

Having some issues running a fuel pump and being a total rookie I have no idea what to do next.
The car is a '73 Celica Ta22 with a 2tgeu. Previous owner installed a swirl pot in the boot to accommodate the efi system.
System includes two pumps. One low pressure between fuel tank and swirl, and one high pressure between swirl and rail.
Problem is the high pressure pump that goes to the rail won't run, and the low pressure pump doesn't have enough guts to get the fuel to the rail.
Tested the pump - it's fine.
The confusing part is that both pumps are wired to the coil. Low pressure pump that works - wired to the positive side of the coil. High pressure pump that doesn't work - wired to the negative side of the coil. (how anything could run off the negative side of the coil is too much for my little brain - but that's how the car was purchased and ran for years)
Now, when I attach the high pressure pump to the positive side of the coil - it runs. But if I try to run both pumps off the positive side - nothing.

Does anyone have an idea what the deal is? and what would be the best way to get it running? (this was supposed to be the easy first step of the rebuild ha ha ha)

Check where wiring is going. I could be wrong as not being there to see, but it could be using a signal from negative side of coil via the ecu to start the HP pump only while engine is cranking or running, which for safety reasons they should only do. This sounds possible to me since it has been running before this time okay.
Forgot to ask, is it original ecu or after market?

[celbelle]

Check where wiring is going. I could be wrong as not being there to see, but it could be using a signal from negative side of coil via the ecu to start the HP pump only while engine is cranking or running, which for safety reasons they should only do. This sounds possible to me since it has been running before this time okay.
Forgot to ask, is it original ecu or after market?

Just did a check and looks like it is wired through the computer. (Whoever did the wiring was a maniac and it's a pretty big mess) It's an original 2t computer also.

No idea where to go from here.

[masterofsinanju]

http://khi-santh.canberracelica.org/files/2tgeu.pdf

Take a look at this and compare to what yours looks like.

I'm still learning to read these things but it does look like a -ve connection from the coil to the ECU and that your fuel pumps should be hooked up through relays

[celbelle]

http://khi-santh.canberracelica.org/files/2tgeu.pdf

Take a look at this and compare to what yours looks like.

I'm still learning to read these things but it does look like a -ve connection from the coil to the ECU and that your fuel pumps should be hooked up through relays

Looks pretty spot on from what I can see so far. I'll have to pull apart their makeshift looms to trace things properly before I'm certain, but before I do that...

The car turns over, but won't fire. Assumed it was the fuel pump because you can hear the other one running.
Have since worked out that the other one is run direct to the coil.
Checked the coil, checked the pump itself, checked the relay, checked the fuse, haven't yet checked the ecu(read some people had issues with capacitors leaking and causing havoc)
I'm almost certain it's not, because the pump in question doesn't prime, but what's the possibility of the problem being something else? If it's the injectors for example, would the ecu not start the pump because it detects a fault?

[ToyTA22]

Have you tried checking voltage with multimeter at fuel pump whilst cranking engine, to make sure signal from ecu is turning pump relay on. If not try checking for voltage at relay terminal where ecu connects to pump relay coil. also if those tests don't help. Just check your fuse with multimeter, glass fuses can look good but be faulty, not usually the blade type but you never know.

[masterofsinanju]

I don't think these old ECU's do any error checking. Purely for engine running.

Now to get all empirical; Have you tried another high pressure pump? I know you've said that the existing one worked when +ve wired but since the normal running mode is -ve polarity it seems like a good place to start.

It's just possible that its cooked itself in some way, being outside of the tank it doesn't get uber cooling of fuel submersion.

[celbelle]

Have you tried checking voltage with multimeter at fuel pump whilst cranking engine, to make sure signal from ecu is turning pump relay on. If not try checking for voltage at relay terminal where ecu connects to pump relay coil. also if those tests don't help. Just check your fuse with multimeter, glass fuses can look good but be faulty, not usually the blade type but you never know.

Fuel pump gets no voltage whilst cranking.
Relay is only getting 1.4 volts on accessories and no change when cranking. Replace relay???

[Camos]

What are the wires on the relay connected to?
Should have pos, neg, signal and load switch. Will be labeled 30,86, 87 and maybe an 87a.
Next check you have voltage between 30 and 85 when key is off. And nothing between 85-86 and 85-87.
Turn the key on and should be voltage between 85-86 and 85-87.

If it has an 87a connection it will be a bit different, will be the reverse of above.
87 is a normally open switch and closes when triggered and the 87a is normally closed and opens when triggered.

This might help to know where to look next

[celbelle]

So we decided to clean the battery terminals and all of a sudden we've got 12volts at the relay, and around about 4 at the pump when cranking. Pump is audibly pumping, but engine still isn't firing.

[Camos]

Pull the wire off the relay and run a new wire to the fuel pump temporarily and check the voltage again.
Also is the relay wired directly to battery or tapped into another 12v circuit/system? Try supplying power to the relay directly from battery with another temp wire.
Depending on results I would then pull the horn or light relay (or any other not used for startup) and see if it's a faulty relay. Unlikely but would check all the same.

[Camos]

You have 4v at the pump when cranking, do you have 12 or 4 at the relay when cranking?
all readings should be 12v

[celbelle]

You have 4v at the pump when cranking, do you have 12 or 4 at the relay when cranking?
all readings should be 12v

There's 12v at the relay whilst cranking. So both pumps should be reading 12v?
The lift pump is wired directly off the coil and has the same reading of around 4v when cranking as well.
Whilst cranking we noticed the relay was clicking constantly, opposed to just once on startup.