80 Carb Fuel Pump?

CandBMotorworks

CandBMotorworks

C&BMotorworks
I've done a bunch of reading tonight, but having not really seen direct answers to my questions, I am starting a thread. If I'm going over old material, please be gentle and kindly link me to the appropriate thread. :)

A while back I bought an 80 carb car. I suspect that, since 80 was the last year for carbs, this was a transition year and that there will be bits that are different from other carbed cars. Am I right?

I've seen two engines from two 80s (mine and another) that have the mechanical pump location covered by a plate. When I got my car much of it was dissembled to address an issue with the transmission. It hadn't been run in some time. The important part to this discussion is that it has an electric fuel pump. BUT, I can't figure where the darn thing was wired (i.e., it was in a box when I got it and not on the car). The pump works fine and when connected via jumper pumps fuel to the carb and the motor runs.

So my questions:

1. Did all of the MY 80 cars have electric fuel pumps? If not, was it common to convert and if so from where was the blanking plate acquired?

2. How is the electric fuel pump properly wired? I've seen discussions where people have talked about it being connected to the oil pressure sender circuit, but has anyone done this on a carb car, and if so, do you have pics showing how you wired it?

3. As to the latter, am I right in thinking that the sender is "closed" until there is oil pressure and then opens once the oil pressure comes up, thereby shutting off the light on the dash? Because if that is the case it would seem that you need some relay in the system so that the fuel pump comes "on" when the sender opens.

4. If the fuel pump is wired off of the oil pressure sender, what do you do to get it to pump when starting the car (since the sender will be registering no pressure at that point)?

Thanks in advance for your help in answering these questions. I have one more:

My car has a couple of short leads that come out from the firewall near the driver's side "frame rail", down low below where the carb cooling fan sits. These have banana type connectors. One set is a large and small wire that both appear green. The other appears yellow. I haven't found anything (yet) in the wiring diagram that idenfies these. When testing (with the motor off and ignition on), neither seems to have positive power. Anyone have a clue what these are?

Again, thanks.
 
Electric Fuel Pump

In all the years I have worked on these cars and owned a 79, still have it and an 80 which I took apart for parts, none have ever had an electricl fuel pump.

The carb engines had heat problems, I know I owned a few. The issue was vapour lock or for better terms fuel snuffing. The engine when hot would not only heat the carb, but the fuel pump and fuel lines. The mechanical fuel pump has 2 check valves made from brass for the seats and a phenolic disk and a spring for the check valve. Here is what would happen. Take the car for a good run on a hot day, get stuck in traffic and watch the temperature guage go up, finally stop somewhere for lunch or what ever. Come back to the car it starts but as soon as you put your foot down on the gas the hot fuel from the fuel pump and lines vapourizes and snuffs the engine out. You are stranded. The other thing that I saw happen was this. Hot run, hot day you park the car and the next day no fuel is getting into the carb. What happens is that the fuel in the lines gets hot and starts to expand. The fuel has no where to go and it hydralicly pushes the brass seat out of the fuel pump. The pump only has 1 valve and will not pump. Stranded in a city far from home I removed the vent line from the fuel tank and blew into it to pressurize the tank, this allowed the one valve to work and pump fuel. I drove 60 miles like this home, blowing into the vent line from the drivers seat and folding it over until the engine started to miss again.

Okay, nuts to this. I removed the mechanical fuel pump and purchased an electric pump. I just connected a switch on the dash to the pump, Anti Thieft, car would never start without the fuel pump running.

Your statement about the oil switch. You are correct you need a relay so that the pump would quit should you have an acident or a roll over. Also you need a by pass as if the car has no oil pressure you also don't have an electric fuel pump pumping fuel.

A switch on the dash in the centre consol worked for me, supplied after the ignition switch. If you look at my car you will notice that I have 2 hazard switches, one for the Hazard lights and another for the electric fuel pump. The X dash had cut outs for a spare switch.

The blanking plates were common and around from different Fiat cars I have a few laying around. The Electric fuel pump was not stock.

As for the mystry wires, on some cars there was a exhaust temp switch that lit up a light on the dash " SLOW DOWN" it was supose to be so you didn't over heat the Catalitic Converter, but I have never seen a car with it. The light and lens is in the dash if you take it apart.


TonyK.

Grimsby Ontario Canada.
 
You could try something like this:


DSCN0359.jpg



Connect the positive side of the pump to an ignition switched source, like the positive side of the coil ballast resistor. The negative side of the pump will get ground from two alternate sources: While the starter is engaged, the coil of the left relay is energized from the starter solenoid, and the relay completes the circuit to ground. During normal operation when you have oil pressure, the right relay is not energized, and terminal 87a and terminal 30 are connected together and complete the ground circuit. As soon as oil pressure goes low, the oil pressure sender grounds the coil of the right relay, breaking the ground connection to the pump. The right relay is a regular 5-pin Bosch type relay. The left relay is also a standard Bosh type relay, and can be either the 4 pin or the 5 pin variety.
 
Could be simpler?

I'm not sure, but will check my manuals for examples of this circuit. I was thinking that it only takes a moment of cranking the engine to build enough pressure to put out the low oil pressure light. If this is true, the relay could be very simple, power from a switched source to the relay, and from the relay to the pump, with the ground side of the relay switch to the low oil pressure sender.
 
Most of the time you'd probably be fine without the left relay. There is fuel in the float bowl, oil pressure comes up pretty quickly etc. If it fails you could always jumper the relay. I'd rather use both relays and not have to worry about it.
 
On my 78

I had fuel issues and one of the trouble shooting tips Steve Ambrose and I came up with was to bypass the mechanical fuel pump and install a electric fuel pump. He told me to just find a key on hot wire in the engine compartment to tap off of and it worked just fine. So as long as you can find a hot wire with the key on, cold when off, you should be golden.
 
Only thing there is..

if you were in an accident, engine stalls, key is still on... pump will keep running.

Designs above are to have a pump cut off when the engine dies...
 
Diagram Question

Thanks for taking the time to draw this out. That's above and beyond in my book. I was hoping someone already had their car wired and could post pics to show it.

I'm in AZ, so it's very possible that this care was converted at some point to electric fuel pump to avoid the vaporization issue.

Anyway, looking at the diagram, it appears that the "right" relay is wired in parallel off the same source as the pump. Is that correct? So both draw positive power off the ignition and then the relay switches the ground. I had been thinking the relay would switch positive instead of negative, but either works. I agree with another comment that this seemed an elaborate system, but I think I understand your thought process behind it.

Guys, thanks much for the help.

Also, on the mystery wires, they are located about where the fuel injection cars have their fuel pump. I thought originally that they were the leads for the pump for this car, but again, neither ever seems live. So, I don't know.
 
looking at the diagram, it appears that the "right" relay is wired in parallel off the same source as the pump. Is that correct?
Click to expand...
Yes, that is what I intended.

I agree with another comment that this seemed an elaborate system
Click to expand...
It is a bit elaborate, but then again, so is the stock FI fuel pump relay circuit.

A slightly less complex alternative would be to use a diode instead of a relay to turn on the pump during starting:


DSCN0360.jpg


The diode needs to be able to handle the current draw of the pump. A car is a pretty harsh environment for electronics, so a reasonable reverse voltage rating is needed too. DigiKey part number 10A07-TDICT-ND has a 10 Amp forward current rating (plenty for a low-pressure fuel pump) and 1000V reverse voltage rating (way overkill).
 
Other wires...

Cars were often wired for A/C even when A/C wasn't fitted. That area sounds about right for the A/C pressure switch, and there was also an idle-up electrovalve on later cars at least.
 
Fuel Pump Wiring

O.K., let me give this some thought. I presume the relays are standard and can be picked up at Checker O'Reilly or Pep?

I might have to fab brackets to mount the relays, but think I could put them next to an existing relay in the spare tire well.

If I put this in place I'll try to put up photos of the finished job.
 
AC wiring

Thanks for the thoughts. It'd be nice to have it show in a wiring diagram. I can check the 80 wiring diagram on this site for the AC wiring to see if that jibes. If so, I presume these wires are dead simply because there is no fuse in place. Might be a good take-off point. I will say that these appear to be heavy duty wires, so something like an AC compressor or something that needs fairly heavy load requirements would make sense.
 
ng_randolph:

In your diagram, you are drawing power to the 85 post for the right relay from the coil and having it pass to the oil sender.

Apparently there are 2 oil senders for this car -- one near the top of the engine and one down closer to the dipstick entry point into the block.

I tested both of these. The high one has power when the ignition key is switched on and continues to have power when the engine is running.

The lower one has no power with the ignition on and DOES have power when the engine is running. I tapped into this wire and ran it to 85 on my right switch, and ran 86 to ground. However, there seems to be inadquate power through this wire to switch the coil on the relay, and so my fuel pump does not come on. Also, with things connected in this fashion the oil light on the dash dims, but does not go out.

If I run power from a point that is on with the ignition (i.e., from by the coil before the ballast), will I not over power the oil sender circuit?
 
senders...

The top one you describe, is it in the head vs. the block?

1300 senders:
in the head = water temperature
in the block by the dipstick = oil dummy light
large unit in the block by the oil filter = oil pressure gauge, if so equipped.
 
Tom: Mine appear to be the same, though this is a 1500, not a 1300. Also, by the wiring diagram and my testing, I get the impression that the oil pressure light is controlled off the lower one, and the upper one is the control for the oil pressure gauge, when installed.

Anyway, I hooked up the second relay control (coil circuit) as per ng_randolph's suggestion (see earlier diagram in this thread) and it worked. The only thing I did differently is that instead of hooking up the relays in parallel I hooked them up in series, using single pole double throw relays (i.e., the relays have 5 connectors, so that when the relay is not switched on, the power passes through the "off" switch pole, and when it is "on" it passes through the other). The relays I used have 30, 87, 87A, 85, and 86. 85 and 86 control the coil to switch on the relay. 30 is the input source, 87 is the output source when the relay is switched on, and 87A is an output source when the relay is switched off. When the starter is switched on, the relay connects the ground wire of the pump to ground, enabling it to work (the hot side of the pump is connected to a hot lead that is on when the ignition key is on). When the starter is off, the ground passes through it to the second relay's input side. When the oil pressure is low, the ground circuit for the pump is interrupted. When it is normal, the ground is completed and the pump operates.

It works well. Thanks to all who offered help in this thread.

Oh, for those who wondered about the 2 plus month gap between my initial inquiry and finishing it today, the answer is that it got hot out and I didn't feel like suffering in the 115F Arizona heat to work on the car. The temps this weekend dipped under 100, so I got back to work.

Cheers!
 
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