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1983 Celica Supra P Type Manual 80k original
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Discussion Starter · #1 · (Edited)
I decided to write this up based on help I'd received from others on the forum (thank you all very much!) I searched but didn't find a detailed write up on this simple but handy trick.

THE WHY

For various reasons you may have a need to "prime" your fuel pump from time to time. Obvious reasons include having removed the gas tank, replaced the fuel pump, or done other work where you drained the fuel line. In addition, many of us with these cars experience a situation where after they sit for awhile (weeks or more,) it takes them a number of cranks to get fuel flowing again and for the engine to start. I believe this is due to not (no longer) having a fully sealed system, or is the result of aftermarket fuel pumps. I do not think this situation is indicative of a serious issue at all (rather, something to be dealt with on a 40 year old car that has likely had some work done on the fuel delivery system throughout its lifetime), but it is annoying and not good to crank an engine over cold too long after it's been sitting for a long time and lacking oil in the top end.

Also, because in our early EFI cars, (as best I can figure,) they were still learning how to synchronize the fuel pump, air flow meter, etc, the Toyota engineers built our cars so that the fuel pump only runs when the engine is cranking. It does not run or "prime" when you turn the key on alone.

THE HOW

To bypass this, happily, Toyota added a test plug that that is wired in parallel to the switch on the air flow meter so you can "jump" this and run the fuel pump without having to run or crank the engine!

*I believe this applies to all models whether you have an in-tank or external fuel pump. Mine is an '84 with an external and this works perfectly.

Before you start the car,

1 - Cut a paperclip into a "U" to use as your jumper. (or a small piece of wire of some sort etc.)


Automotive tire Automotive exterior Bumper Finger Automotive lighting


2 - Locate your plug on the left side of the engine bay (with you facing the front windshield). It is located on the same wiring loom that goes to the air flow meter just down to the left of the power steering pump.

Motor vehicle Automotive tire Hood Gas Automotive exterior


3 - Remove the cap and insert the U shaped wire / paperclip. Push it in between the contacts firmly so it stays in place.

Motor vehicle Automotive tire Plant Automotive exterior Bumper


4 - Now, leave the hood up and go back and turn your key on. You will now hear the fuel pump running. Allow it to run for 20-30 seconds to "prime" your fuel system. Once you do that, go back and remove the jumper / clip. Now press your gas pedal once and then crank and it should start pretty quick. NOTE: You can start the car with the jumper still in but sometimes this will cause issues depending on how long you have let it prime so in my view it's best to remove it before you attempt to start / crank the car.

I have been keeping my "jumper paperclip" in a small bag in my center console so I always have it near when I need it (for me, after the car has been sitting for a week or two and I'm going to start it.)
 

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I searched but didn't find a detailed write up on this simple but handy trick.
I couldn't find the previous write-ups either so it's good to have a fresh write-up.
THE WHY
in our early EFI cars, (as best I can figure,) they were still learning how to synchronize the fuel pump, air flow meter, etc, the Toyota engineers built our cars so that the fuel pump only runs when the engine is cranking. It does not run or "prime" when you turn the key on alone.
During normal operation, the fuel pump runs only while the engine is running or cranking over (AFM flapper door open and ignition is in On or Start position) for safety reasons. Say you're in an accident, your car comes to a stop, your engine quits but the ignition key is still On. You wouldn't want your fuel pump still pumping fuel.
Here's a link to a discussion that goes into a bit more detail about the subject.
 

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1983 Celica Supra P Type Manual 80k original
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Discussion Starter · #3 ·
I couldn't find the previous write-ups either so it's good to have a fresh write-up.

During normal operation, the fuel pump runs only while the engine is running or cranking over (AFM flapper door open and ignition is in On or Start position) for safety reasons. Say you're in an accident, your car comes to a stop, your engine quits but the ignition key is still On. You wouldn't want your fuel pump still pumping fuel.
Here's a link to a discussion that goes into a bit more detail about the subject.
Good info and makes sense. I guess the only other experiences I’ve had with external electric fuel pumps were on “pusher” pumps we have added to some of our old classic cars and these just run off the key or even a switch. But yes that makes sense and most modern cars do not run with just the key although I have seen some that will run initially to prime and then turn off once that’s done.
 

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I was having a look at this connector and found that the 1982/3 connectors are as you show, but my wife's 1984 uses a different connector. It looks like the same function though.

Automotive tire Tire Synthetic rubber Automotive lighting Tread

1982/3 as per your article.

Motor vehicle Sleeve Hood Gesture Bumper

1984 style connector.

I've never noticed the difference before your great write up.

Dale
 

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1983 Celica Supra P Type Manual 80k original
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Discussion Starter · #5 ·
I was having a look at this connector and found that the 1982/3 connectors are as you show, but my wife's 1984 uses a different connector. It looks like the same function though.

View attachment 21467
1982/3 as per your article.

View attachment 21468
1984 style connector.

I've never noticed the difference before your great write up.

Dale
Ah good to know and good clarification. Great to have someone who has multiple cars of different years to compare!
 
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