problems with dual relay combo...

[81spidr]

81 spider 2000, my relay combo doesnt make a connection for fuel pump or injectors. I have bought a new one and it was tested on 3 other fiats and it worked fine. I put the old one back in because i had taken it apart and just reach under the dash and make the connection myself, once started there is never a problem till i shut it back off. Great security feature....lol. Anyone have a suggestion??????

[So Cal Mark]

what connection are you making by hand?

[81spidr]

The relay when taken apart has two plates that move together to make the connection.

[81spidr]

Mark dont you do the superbowl strut vids??? i love them.. great cars and group of guys..

[zachmac]

81 spider 2000, my relay combo doesnt make a connection for fuel pump or injectors. I have bought a new one and it was tested on 3 other fiats and it worked fine. I put the old one back in because i had taken it apart and just reach under the dash and make the connection myself, once started there is never a problem till i shut it back off. Great security feature....lol. Anyone have a suggestion??????

I recently went through a very similar situation on my 80.

The relay is fed from two different sources depending on the key position. When you first turn the car on you should energize the relay coils that closes the contacts that feed the injectors. This ALSO provides a path to energize the fuel pump coil in the relay BUT that path will still have an open in the circuit at the AFM.

Then, when you go to the crank position, a DIFFERENT current path is sent to the relay coil that closes contacts to power the fuel pump and the the heater for the Aux. Air Valve.

When the engine starts to crank it draws in air which opens the flap in the AFM which completes the OTHER path for current to the fuel pump coil in the relay which, as long as the injector coil stays powered and air keeps flowing into the engine, will stay powered when you release the key to run.

It sounds like you either don't have SUFFICIENT voltage to the first coil OR you don't have a good connection to the FIRST (key in cranking position) current path for the second coil.

Here's how you trouble shoot it:

1) With you or a friend helping, watch the relay as you turn the key to "on". The contacts that feed the FI should close. The contacts feeding the FP should still be open. If this is the case move on to step 2. If not then you aren't getting enough voltage at the first coil to make a large enough magnetic field to pull it closed. (BTW, the reason it still works if you manually close them is that you may have a low voltage there and once the contacts are closed the weak magnetic field from the coil will hold them closed but it isn't strong enough to initally draw them together). If this coil isn't closing on its own, start looking for a loose or corroded connection between the idnition switch and combination relay.

2) if in step one the FI coil picks up then most likely the problem is in the wire (red from 30 on the switch) that makes up the other coil circuit when you go to "cranking" on the switch. This position powers the relay fuel pump coil WITHOUT goign through the AFM. While cranking does the second coil contact set close? If not then start looking for an open in the wiring from the switch to the relay on the red wire.

The fact that the car will run when you close them by hand emost linely means the #2 step path isn't working. The pump starts to run when you go to "cranking" and will only keep running in "run" once the AFM flap opens. So if the power to the FIRST (cranking) current path to the raly is bad the car won't ever get fuel to begin with and won't fire.

3) IF the car fires while cranking but THEN dies, the current path to the second feed for the relay coil for the FP contacts ia getting voltage but again not enough!

Finally, this could also be due to a weak ground connection. Again, if the voltage to the realy is weak than there might be enough in the coil circuits to keep them closed but not enough to generate a magnetic field that will intially close them.

If I have been clear as mud here either PM me or contact me at bjzachmac@gforcecable.com. I can also send you a short excel spreadsheet I did that lists every input and output from the combination relay and what it does. Just PM me an off forum email to send it to you. Good hunting!

[Newell33]

Excellent info Zachmac

I have a similar question on my '76 carbureted model. Would you have info on how the fuel pump relay is supposed to work with the factory electric fuel pump installed? I've disassembled the car now, but when I got it the fuel pump would run contiuously when the key was on. Shouldn't the system run for a few seconds and then stop, unless the car is started?

Thanks for the info!
Josh

[zachmac]

Josh,

I can't say off the top of my head as I only currently own the 80 FI car and haven't looked at the prints for the earlier carbed / electric fuel pump cars. If you give me a day or two I'll be happy to look at the wiring diagrams and give you my $0.02 on how it should work but it might be better if some one with a 76 electric fuel pump car chimes in.

Jeff

[zachmac]

Josh,

I found some wiring diagrams for your car on the Miafiori pages: http://www.mirafiori.com/faq/content/Fi ... iagram.htm Based on a QUICK unqualified look here is how your car should work (again I only spent a minute or two on this just now so anyone who knows better jump in):

When you first turn on the key the pump should NOT run. You complete a power path through the ignition switch and fuse box to the fuel pump relay (128/3 located on the left side inner fender; one of six there) BUT there is still an open in the circuit based on the oil pressure switch not yet being closed.

When you go to the "cranking" position in addition to energizing the starter you contact an alternative power path (green / black stripe wire) to the fuel pump that bypasses the relay and the oil pressure switch and allows the pump to run and provide fuel for starting. IF the start builds oil pressure then a contact closes in the other circuit (green wire to the pump) such that the relay energizes and sends power to the pump when the switch is released to the run position.

In other words, the pump shouldn't start running until you crank the car and then, if you have oil pressure, should run continuously. BTW, this means that if you crank it enough to build pressure BUT the car doesn't start, the pump should continue running when you let go of the key UNTIL the oil pressure drops back down to a level that opens the pressure swirtch back up.

Anyone else confirm what I think the prints were telling me?

[Newell33]

Thanks Jeff

That makes sense. If I remember right I believe that my oil pressure guage didn't work (but the light did). I'm guessing the sending unit is bad causing the fuel pump relay to engage when it's not supposed to, thus causing the pump to run continuously when the key is on.

Thanks for the help!
Josh

[zachmac]

Thanks Jeff

That makes sense. If I remember right I believe that my oil pressure guage didn't work (but the light did). I'm guessing the sending unit is bad causing the fuel pump relay to engage when it's not supposed to, thus causing the pump to run continuously when the key is on.

Thanks for the help!
Josh

That would do it! You should fix it for three reasons:

1) the light tells you you've lost oil pressure
2) the switch having to close makes sure the car doesn't start if you don't build pressure cranking
3) the switch should open, shutting off the pump if the engine stops running with the ignition in the run position

The first two keep you from toasting you engine if you don't have oil pressure. The third shuts off the pump if you are in a wreck (engine not running) so that any possible fuel line breaks don't feed a fire that toasts you!

[rlux4]

The fuel pump gets the 12V through the green with black stripe wire out of the dual relay. This happens when the flap in the AFM opens as the engine takes in air on the intake stroke. The loss of oil pressure won't turn off the fuel pump. By turning off the engine you are stopping the oil pump also. If you had a loss of oil pressure, say from low, or no oil in the engine, the fuel pump would still operate until the engine froze up and stopped taking in air through the AFM. (On FI cars.)
Ron

[81spidr]

Thanks guys you all are a bunch of great help and I"m glad to be a newer member here (joined about a year ago).
i will be posting pics of myself and my car on here soon. As with all spider owners i'm a proud pa pa..lol
She's my baby and have done a lot of work on her the past year. Thanks again guys...

[BEEK]

fuel pump portion of the relay is controlled by the air door in the air flow meter. a leaky hose will stop the fuel pump from running, the big black hose is prone to breaking inside of the pleats. to test remove the hose from the air flow meter, turn ignition switch on. use a finger to move the door in the air flow meter. the relay should click and the fuel pump should run. if it does not run, and the relay clicks, check the ground on the drivers taillight. unless its been moved or you have a 83 or newer car.

[baltobernie]

Would you have info on how the fuel pump relay is supposed to work with the factory electric fuel pump installed?

On carburetor cars, the fuel pump runs continuously with the ignition ON. There is a return fuel line back to the tank.

[zachmac]

The fuel pump gets the 12V through the green with black stripe wire out of the dual relay. This happens when the flap in the AFM opens as the engine takes in air on the intake stroke. The loss of oil pressure won't turn off the fuel pump. By turning off the engine you are stopping the oil pump also. If you had a loss of oil pressure, say from low, or no oil in the engine, the fuel pump would still operate until the engine froze up and stopped taking in air through the AFM. (On FI cars.)
Ron

Ron,

I think you are confusing my answer to the question about the 76 in this thread with the FI car.