jay7199

Ok im at a loss here, I have a 89 Formula with a 5.3 and a custom built harness with a 98 computer.

When the car is running and placed into reverse, The A7 Pin starts too smoke then the fuse pops.. The 3 wires that run into the pin are MAF/Transmission pin E/Fuel pump

With the key on but engine not runnin, I can put it into reverse with no problems.. Only when the car is running does it do this..

All other gears are fine..

What gives?

cprmn14

iTrader: (3)

Sounds like its grounding out. Check all the wires for exposure, or wires touching etc. Id also double check the pin make sure its not a ground in a power pin, vise versa

Pocket

iTrader: (24)

What connector is A7? What part of the fuel pump relay are you pulling from the IGN pin? Only 12v points on the FP relay are 12v in which should have its own 20A fuse, and the PCM commands 12v when it should activate

jay7199

A7 on the c100, the fuel pump is powered by switched ignition on this setup..'the car was previously LSx swapped and this is how they had it. I plan to add the relay in but I don't think it's the source of this problem.

Prokilllsx

it sounds like something simple. Follow pocket's advice.

Pocket

iTrader: (24)

I do, but lets find out instead of going on a hunch
Easy test is to snip the fuel pump wire from this and flick the IGN on. Does it still get hot or pop the fuse with the other two still on it? If it does, Id say theres a short somewhere between the fuseblock and that pin

Either way you slice it, the FP relay needs to be fed directly from the battery, preferably fused. It should not be ran from a simple IGN source

The old trick for turning on the fuel pump when converting to carb was to take the ECM wire from the relay and connect it to 12v IGN. This worked because it took the place of the ECM signal. Yours does not sound like it is wired this way, instead you say it has direct power from the emissions fused wire directly to the pump via 18ga wire... AND it has additional circuits also pulling power from the same point. Stock the emissions fuse point uses a 10A fuse. Stock the FP relay is on a 20A fuse and is known to blow it on occasion. No wonder it pops the fuse when all of that is on it

Prokilllsx

I say again, follow Pocket's advice.

jay7199

It does not get hot and blow the fuse with the key on, only with the motor running and the transmission in reverse. Drive and all the other gears are fine.

I will go ahead and make the fuel pump relay.. See what happens from there, just worried it's got to do with the transmission power wiring but I guess we will see what it does after the fuel pump relay is made.

jay7199

Im getting these check engine lights.

P0740 Torque Converter Lockup Malfunction
P0785 Malfunction Shift/Timing Solenoid
P1860
P1635

cprmn14

iTrader: (3)

i know its not completely the same, but my friends 2000 Grand Prix would pop the fuel pump fuse about once or twice a week, but not all the time. Took apart the dash and it was a few exposed wires grounding out.

jay7199

@Pocket, I am following your diagram here..

But I remember reading another 89 swap thread that you said the 89 is unique because the fuel pump is somehow tied into the C100, can you enlighten me?

Pocket

iTrader: (24)

http://www.austinthirdgen.org/mkport..._1989_C100.gif

Pin G4 for 89's

jay7199

G4 instead of into the computer R9?

86White_T/A305

dumb question but have you looked to see if maybe you are pinching wires at the trans when the car is running and in reverse and the trans is preloading?

Aside from Pockets advice on the fp relay which I agree to have seperated on its own circuit and fused.Sounds like it would be in your best interest to give the car a thorough glance over the wiring and routing.I think you may have some more gremlins lurking on that swap.This is the only problem when buying a car from someone who already did the swap..you are in the dark of knowing what problems they had before it traded hands.Hopefully its a small issue and no permanent damage is done to trans or ecu.

jay7199

Well I made the harness and put the motor together so luckily I know where most everything is, I am thinking the trans isn't getting power and that's why I have all those codes.. Or am I wrong?

There is not a ground on the 4l60e connector right?

cam-

If its only happening when you put the thing in reverse id say you have a short to ground on the reverse circuit. The "smoking gun" with wiring doesnt always reveal in the obvious places. It probably doesnt smoke when the car is not running because theres not enough ooomf in the bat to do so, but leave it in reverse overnight with the key on and id bet your car goes up in flames before morning.

jay7199

Any hints as to where those grounds for the reverse circuit are?

cam-

Pull the shifter cover and look in there first, It grounds right on the tunnel but the short will be on the +side of the circuit right? hence short to ground. So look at all the hot wires that goes into the shifter. Use a test light to verify which ones are hot with the key on/off and toggle the light probe around while in park, then in reverse, and you can track routing without diagrams pretty quickly. Then follow each one of those wires routing and look for pinches or possible wrong connections etc. When you have wires smoking you are either feeding power to ground thinking its a power circuit, Or you have a power circuit pinched or accidental sliced that is touching ground. Thats it there is no other way to make them smoke ( unless you voltage reg is gone and you have the worlds strongest alternator but your lights would be SUPER bright and likely burn bulbs out before melting anything )

If you dont find anything in the reverse circuit that is wrong, continue with the test light at the smoking wire area and use a similar process until you find the culprit.

My guess is you have a hot circuit accidentally wired to ground thats triggered by the reverse circuit when you put the shifter in reverse but guesstimating over the boards on electrical gremlins is no easy task....

I had a cigarette lighter short to ground once. The tabs that heat the element were bent ever so slightly an would touch ground and BOOM fuse pop and out goes my radio... which was intense I had amps and all sorts of speakers I just installed so naturally I dug in to the install... took me ALLLLL freakin summer to discover the lighter as the culprit. Of course none of the chiltons or haynes manuals I had even mentioned the lighter was on the radio circuit and this was long before the net so to say that was frustrating? Is an understatement. Brake lights would go out too btw so mega danger on that one.

Good luck, Test lights are your best friend with auto wiring because you can test power, and ground simply by putting the clip on the positive or negative side and touch anything you want without harm.

jay7199

I'll start digging around when I get home, i a hunch now, I had to desire my taillights to fit the gta tails, I wonder if something is grounding there.

Im now thinking the reverse lights and the trans check engine lights are different problems

cam-

Id start RIGHT there. Good luck

jay7199

Think I got it! like a dummy I had pin N and pin E switched (both pink) on the 4L60E connector, So I guess that wire was grounding out in reverse and causing the problems.. and also the lack of power to the transmission was the check engine lights.

Seems to be in working order, its lunging in drive with my foot on the break but im not sure what tuning I have for the converter.

86White_T/A305

glad you found it.its usually something stupid that can cause such big headaches lol.now get that thing tuned and running hard