Strider

OK, concerned with the poor starting of my car in the mornings, I figured that it is partly caused by there not being adequate fuel delivery to the carb during startup after sitting all night. I think that some of the gas in the bowls drains via gravity back to the tank (more on that later.)

So here is what I did:

I purchased a 3 position toggle switch, Double Pole, Double Throw (DPDT), and wired it into the fuel pump wiring. The fuel pump wires are under the driver's side storage compartment. If you pull that out you see a set of two wires with a quick disconnect that goes out the floor of the car through a rubber grommet in about the middle of the compartment area, right where the fuel pump is located underneith. One of the wires is blue and white, and the other is black.

I soldiered wires to the switch on its three tabs(six total actually, DPDT switch and all, I actually used six wires total, with two wires per switch position. I did this just so that I wouldn't create any extra resistance in the circuit), black wire in the center, white wire for one side, and red for the other.

I cut the blue and white wire (the pump power wire, black is the ground) in the middle. The black (center, common) wire on the switch I soldiered and nutted to the end of the blue wire going to the pump, and the white wire on the switch I connected to the other end of the blue wire, (the end of the wire connected to its power source). I then used my voltmeter and found a power supply wire that is on when the key is on in the wire loom that has a very large quick disconnect to the loom running to the rear of the car. (It was red, and larger than the others in the loom, or else I may have run a new wire from the fuse panel under the dash back to there.) I then spliced the red wire from my switch into that +12V keyed wire. All wire splices were carefully done and soldiered, nutted, protected with electrical tape and spiral loom wrap.

The result is that I can now select if I want my fuel pump to turn on with the key, or select for it to act like it always had, only on when the motor was running. I can also select for the fuel pump to be turned off with the center position of the switch. The switch is hidden, so this can be used to act as a measure of theft prevention, as the bastards won't go anywhere without any fuel supply to the carb.

Remember, my car is an 85 GS, and the fuel pump only runs when the motor is running. This morning I set the switch to come on with the key, turned the key on, and let it run for a few moments. I could hear the fuel tank gurgle a bit, which told me that gas was being pumped to the carb. During startup, the motor only died on me once, compared to how it normally died four or five times on cold morning startups before this mod. (15 degrees F this morning.)

I'm thinking that I should switch to a less viscous oil. Currently I have 20W-50 in the crankcase (Castrol GTX mineral oil) I was thinking that for this cold weather I should switch to 10W-40.....or??????

Suparslinc

sweet. already done that though

Strider

Yeah, well, great minds think alike and all that....

alien_rx7

Hmm, guess the '85 GS was wired different for the fuel pump than the '82? On my '82 I can hear the fuel pump just humming away if I just leave the key in the on position before starting.

Hyper4mance2k

iTrader: (40)

me 2 in muh 83

Strider

That's right...I think it was in 84 when Mazda added this "feature".

diabolical1

iTrader: (3)

yeah ... i believe they put some relay in the circuit starting in 84, and when it goes south, it makes it look like the pump is dead.

FD Racer

yeah on my 83 'key on, FP on.

I am however gonna put in a switch to turn it off as an anti theft device.

RotorMotorDriver

iTrader: (1)

Yeah, my 83 also...If the keys on, the pumps on. It starts better than my 85...I wonder if this has anything to do with it? Cause if they are both sitting at my house, same weather and everything, the 83: key on, pull choke, wait second, hit key. the engine fires to life before you even hear it turn over practically. The 85: key on, pull choke, turn key (no sense in waiting for anything really), over and over and over (about one complete engine revoloution). Suddely it roars to life...Hmmm...

~T.J.

Manntis

I just put the key in, twist, and she starts... Oh, wait. EGI.

Wankelguy

10W-40 or 10W-30 is more appropriate for Winter use than the 20W-50 you're currently using. Makes for easier starting in the cold temperatures.

NanaimoRx-7

I'm going to do this for a little extra security, no one really cares about alarms anymore. I have an '80, what kind of switch would be best for it? I was just going to intterupt the ground with a normal switch, but is there a performance of safety issue with this? What way should I go about it? Thanks.

damon

got this already... damn I need some new toys!!

peace

adam c

iTrader: (2)

I did this in my 82 GSL years ago. Too cheap to buy an alarm. I put it in the passenger storage compartment. It kind of sucks when you forget to turn it back on.

diabolical1

iTrader: (3)

i'm assuming you got rid of the '82 you speak of, right? wasn't this supposed to be confidential info?

Strider

I should think you want to use a slide type switch, one capable of 10amps or so (better safe than sorry, the motor probably draws a only a few amps.)

Just find a discrete location for it, and yeah, for that purpose you could simply use a ground interupt. (assuming there is no short between the motor and your interupt switch, or else it won't work as intended, but not to worry, that is unlikely I think.)

So how far do you suppose someone could drive without the fuel pump on the gas in the carb?

Strider

Bastage!

FD Racer

Yeah my FD does that too.....Oh, wait. 350, EGI smoking, horsepower!

alien_rx7

Yes, there is a safety issue. Good electrical practice is never break a ground with a switch. Always break the positive wire with the switch as it is too easy for a short to happen on the ground side of things when positive is always applied.

NanaimoRx-7

Thank you alien_rx7, the only reason I thought of a ground wire interupt is because that's the way you disconnect the battery.

I'd think it would idle for about 30 seconds before it drained the bowls and the lines. Or would it even drain the lines, hmm. I'm not sure.

jr69187

ok on 84-85 they made a switch in the wiring. It turns out they hooked the fuel pump up to the trailing ignition so a dead give away that your trailing ignition went out is that there was no fuel. This a common reason that if you let an 84-85 set and try to start it it appears the fuel pump went out. I just bought an 85 the guy said he let it set for about 6 months and would not start anymore. i went out pulled the driver side storage bin jumped the wire from the stock amp to the positive on the fuel pump and walla i have good running 85 with 122k on it.

jr

Alien You still loking for a body? Drop me an email i got a whole car right now. jr69187@hotmail.com