Strange Electrical Problem

[RattleTrap]

I have a 1980 FI Spider that I brought back from the dead. It was in storage for a long time. After changing injectors, cleaning out the fuel system, and replacing the fuel pump, I have it running. And when it runs, it runs well!

I'm having an intermittent electrical problem that I'm hoping the forum can help me out with. I turn the car on every once in a while (usually when I need to rely on it) and it will die when I:
-Turn on the headlights
-Put it into reverse, because it turns the back-up lights on
-Press the brakes
Regardless of RPMs, it will kill the engine.

I can handle simple electrical troubleshooting but can't figure this one out. One other clue: when I press the brake pedal, the front turn signals activate along with the brake lights in the back. At least the people ahead of me can tell when I'm slowing down!

Thanks for the help in advance.
Pete

[divace73]

first thing is to check all the earth point on the car, they may need a good clean and diaelectric grease...
It is a strange problem, you may have to check on a wiring diagram if there a common link... I have an 80 as well and I had issues with my ignition barrell, over time and as all the power runs through it, they build up a resistance dropping volage across it when it shouldn't. I'd reccomend cleaning it out (there is a good doc on the mirafiore website somewhere) and then adding relays to power sapping items, like headlights etc..
While you are checking the ground, check the connection in you fuse box as well..
hope this helps??

[rlux4]

It could be something as simple as a ground. Look in the trunk by the rear of the wheel well on the driver's side, you'll see two ground wires bolted together. Make sure this ground is good. I seem to recall that these two grounds are rear lights and fuel pump. If it's an inadequate ground the fuel pump may stop running when those lights go on.
Ron

[bradartigue]

Oh it's a ground. As the other guys said, it's a ground. The trunk ground, both engine grounds, the "star" grounds under the dash and in the engine compartment all need to be checked. Also did you change the light bulbs recently? Putting in the wrong lightbulb (for example, a single filament in a dual filament slot) will do all kinds of nutty things. Finally simply unplug and plug back in the circuit boards in the trunk (the white connectors on top of the light housings), this will re-cut the copper connection point. You can also spray the connector (which is aluminum inside) with electrical contact cleaner.

FIATs have a tendency to try and use whatever ground they can find, and in many cases that ends up being the speedometer cable. So another way to tell if you have a lot of bad grounds is if you break speedo cables with regularity!

[GeorgeT]

FIATs have a tendency to try and use whatever ground they can find, and in many cases that ends up being the speedometer cable. So another way to tell if you have a lot of bad grounds is if you break speedo cables with regularity!

More so the clutch cable. It is an excellant ground cable.

[Zippy]

More so the clutch cable. It is an excellant ground cable.

Many clutch cables have been fried because the engine ground didn't get hooked back up after the engine was removed from the car. I have also heard it is connected to one of the starter bolts but haven't seen that myself.

[bradartigue]

More so the clutch cable. It is an excellant ground cable.

Many clutch cables have been fried because the engine ground didn't get hooked back up after the engine was removed from the car. I have also heard it is connected to one of the starter bolts but haven't seen that myself.

I've found factory grounds connected:

1) From the exhaust cambox rear shield lower bolt to the firewall
2) From the starter lower bolt to the sidewall
3) From the transmission bellhousing bolt (passenger side) to the sidewall
4) From the engine mount bolt to the sidewall

#1 I've only seen on FI cars.

[RRoller123]

hmmmm.. So on an FI car, where "should" the ground be? I would like to check this out and make sure it is secured properly.

[RattleTrap]

Thanks for all the helpful info. I know the taillight ground for the fuel pump is tight on there, but I'll try and clean that one up tomorrow, along with all the other grounds. I'll keep you posted!

[rlux4]

One way to check that ground would be touch the terminal and another spot with bare metal somewhere with the two probes of a continuity tester, it'll tell you if you're making good ground.
Ron

[giuliot60]

I hate electrical issues. I had a loose connection on an aftermarket amp meter gauge that would prevent the car from starting. It drove me nuts until I discovered it. But it did get me to clean all my grounds and grease them with dielectric grease. Need to check my trunk grounds after reading this post. Preventive maintenance.

Let us know when you get this resolved, because you will.

[RattleTrap]

Here's an update:
So the fuel pump is losing its power when the lights go on, but it only has 5V when the engine is running, and running normally. Shouldn't it have 12? I cleaned up the LH rear ground and there's no resistance between the pump and there. That didn't change any of the symptoms.

I've yet to clean up all the engine grounds, maybe that's all it needs.

[rlux4]

What's your battery voltage with the engine off and then running?
Ron

[RattleTrap]

Problem solved!!
I only thought that the ground in the back was clean. It turns out that it wasn't really grounding there, it must've found another way I guess. It was 5V because 12V were going into the positive side and 7V were coming back through the headlight/taillight circuits that grounded back there with the fuel pump. I put a wire from the ground nut to the negative side of the battery, and it ran perfectly! I used a dremel tool to sand off the paint (which the italians should've done in the first place) there at the ground to permanently fix it. Thank you all for all the input!

[giuliot60]

See I told you you'd get it resolved. Doesn't it feel good?

Post a picture of exactly what you did.