Saela

iTrader: (1)

Hey guys, I've been having a really weird issue recently and was wondering if this was a common issue. Normally, whenever I turn my key to the on position, the fuel pump starts up, and you can hear that little hum in the back. Then you turn the key, the car fires up, and you're on your way. Now, however, I've had this weird issue where when you turn the key to on, the fuel pump doesn't turn on. The other lights on the dash do, just not the fuel pump. Then if you twist the key slightly, before the car actually tries to start up, the fuel pump turns on. So if I twist the key, I can turn on the car, but to keep the car on I need to keep the key slightly turned.

Anybody have any idea of what causes this? I can only imagine it as a problem with my actual key cylinder, which I highly doubt I could fix. Is my only option rewiring the fuel pump to an external switch?

GSLSEforme

Electrical section of ignition switch likely culprit. Think of it as an early warning sign of failure. You can pull column shrouds and test switch with test light. Things like this wear out with age,replacing should resolve your issue.

Saela

iTrader: (1)

Oh thanks! Is this the right part? It's labeled as the ignition starter switch on rockauto. https://www.rockauto.com/en/moreinfo...=1192227&jsn=8

7aull

iTrader: (2)

yep, that should be the Bit you need.
Nice Sparky SA!

Stu Aull
80GS
AZ

Saela

iTrader: (1)

About to resurrect this thread because unfortunately the ignition switch does not seem to be the issue here.

I replaced it and had the same issue, I had to turn the key partially into the "start" position in order for the fuel pump to turn on again, so when I let go of the key the car just turns off. I looked at the key lock itself to see if it was actually rotating the little plastic rectangle that goes in the electric part of the ignition switch, and it seemed to be working fine.

Now what I'm confused by is where could the problem possibly be at this point. It seems kinda unlikely that the new part I just ordered from rockauto is doa with the same problem as my old one but I'll try and see if I can get a replacement. Other than that though, is there anything about turning the key half way that might give the pump more voltage or something? I just don't see how the problem could possibly be anywhere but the ignition switch.

DreamInRotary

iTrader: (49)

The failure most definitely could be in the lock cylinder of the ignition switch instead of the electrical switch itself which you replaced. Potentially the lock cylinder isn't rotating properly anymore and the key position is no longer accurate to where it's rotating the ignition switch. If the sequence goes from Acc - Off - On - Start, potentially between the On - Start positions the key lock cylinder isn't rotating properly between On - Start and returning to the On position. It should pull that black key-hole back to the On position in order to retain power to all parts of the car except the starter.

Easy test, try to pull the key lock cylinder out, or just pull the ignition switch off the cylinder again, and use a screwdriver to rotate that black keyhole to On and listen for the fuel pump. Try to start the car by continuing to rotate the black keyhole to Start and see if it returns to the On position correctly and keeps the fuel pump running. If you find that this test still doesn't solve the issue, we will have to continue diagnosing further by looking for bad leads or things of that nature.

Saela

iTrader: (1)

Well I just took a look at it today and it turns out that even with the screwdriver, I still have to turn it partially into the "start" position. So it's not even a return of the switch not returning to the right position, it's just that the "on" position doesn't connect to the fuel pump at all. This is a new problem, up until this problem came up the fuel pump would turn on if the key was in the on position for the 2 years I would daily the car.

One of the bigger concerns I have about finding a fix for this is the fact that this pump was installed by a previous owner, and I'm not too sure how exactly they wired it up. The only thing I can imagine doing now is somehow rewiring the fuel pump line to another point on the ignition switch that only has power on the "on" position. I'm just worried that the wire that provides power to the fuel pump also provides power to other areas of the car that I may not want on 24/7 (like the starter). Any ideas on potential fixes?

Gotta say, I love this community and all the support you give, even to less technically inclined guys like me!

Saela

iTrader: (1)

Quick update: I checked for voltage on the connector to the fuel pump behind the backseat. When the key is set to "off", it gets 0v as expected. When I turn it to "on" however, interestingly enough the voltage goes up to about 2v. Then, when I twist the key half way so just the fuel pump is on, I get the expected 12v. At this point, I'm guessing the issue might be a relay? Not sure what else could modulate voltage. Anybody know where the relay is on a 79 SA/ how I should bypass it?

Saela

iTrader: (1)

Well guys, my problem is fixed, and this might be the dumbest thing I've experienced in ages.

So I was going through the wiring diagrams, and the only thing I could see between the ignition switch and the pump was the fuse box. Well, I had already replaced my fuse first thing when I had problems, so it can't be that, right? Well I decided to look at the fuse box anyways and pulled out the fuse one more time to look over it anyways- but then I accidentally broke my fuse while pulling out, and so I had to replace it anyways. After that I decided to just go for it and see if it fixed my problem. It did. This entire time, it was literally just the fuse messing up.

So here's my lesson: if replacing the fuse doesn't fix your problem, replace your fuse again!

I'm glad it wasn't anything too serious in the end though haha

mazdaverx713b

iTrader: (91)

I wonder if the fuse wasnt seated properly to begin with and was having trouble deliver the necessary voltage to the circuit. Glad you were able to figure that out!