• Please be sure to read the rules and adhere to them. Some banned members have complained that they are not spammers. But they spammed us. Some even tried to redirect our members to other forums. Duh. Be smart. Read the rules and adhere to them and we will all get along just fine. Cheers. :beer: Link to the rules: https://www.forumsforums.com/threads/forum-rules-info.2974/

Electric fuel pump - primer swtich

zspryte

Member
Site Supporter
I redid my fuel system a few years back and upgraded to an electric fuel pump. Since then after my Spryte sits for a week or more, the starter has to run 10 seconds or longer before the engine fires up. I figured out the carburetor drys out after about that long and it takes at least 10 seconds for the electric fuel pump to push fuel to the carb. Rather than have to run the starter for 10 seconds, I want to add a switch to run the fuel pump a bit before I try to start the engine.

I did a test run of this idea this weekend. The cat had not run in over a week. I hot wired the fuel pump for a bit and then tried to start the engine. It fired right as if it had just been turned off.

So, I installed a momentary push switch in dash. I ran a wire from the ignition switch (this wire is only live when the ignition is on) to the new push switch and then from the push switch to the wire that supplies power to the fuel pump. Turn key on, push the button, and power goes to the fuel pump. Great! Well almost - one problem, there is another power line that goes to the fuel pump form the oil pressure kill switch. When there is no oil pressure, this switch connects the wire on the starter switch to the fuel pump so the pump runs during starting. (It also supplies power to the pump when there is oil pressure.) Now when I push the primer button power also goes to the starter switch and the starter cranks. I need to keep power from going down the oil pressure kill switch to the starter. I thought about putting a diode in the wire between the starter and oil pressure switch. This should keep the starter from firing when I use the prime button. Has anybody done anything like this? Does anybody have a better idea?
 

IMP

Member
Site Supporter
Couldn't you just run a separate hot wire from the key switch to a non momentary fuel pump switch and eliminate all other wires to the fuel pump? The fuel pump has power at all times when the engine runs and is self regulating based on pressure in the line. At least that's how I wired mine.
 

JimVT

Bronze Member
GOLD Site Supporter
wire it so it turn on with the accessory switch prior to starting. i have it that way in my Studebaker. i just give it a few seconds in accessory prior to starting.
jim
 
I put an electric pump on my Spryte as well and it only had two wires, hot and ground. I wired the hot to the ignition switch so it always ran when the key was on. Worked great for the many years I had that Cat.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
your diode is the quick easy answer you could also get creative with relays but why change the wiring harness
 

jo5

Member
Tried to post earlier and didn't work
I put my electric pumps on a separate switch and only use them when the cats sit for a long time or it's really cold or it's hot and trying to vapor lock
Good luck
 

Cidertom

Chionophile
GOLD Site Supporter
On my trac is a SPDT on-off-<on> where the common goes to the pump, the on goes to the ign switch and the spring return <on> goes to a fused hot. push down <on> for prime. I can hear the change when the prime is done, then up for automatic.

And since it is an unlabeled switch...
 

zspryte

Member
Site Supporter
thanks for the replies. Glad I'm on this forum. I am sure one of these ways is going work.
 

mla2ofus

Well-known member
GOLD Site Supporter
I don't think you'd fry the ignition to just turn the ign switch to "run" long enough to fill the carb, then start cranking.
Mike
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
ive thought about this some I would run it through the ignition circuit and a op switch that way its not pumping with the engine off if you need to prime the carb than a momentary on switch added to the cold side of the op switch should work
 

redsqwrl

Bronze Member
GOLD Site Supporter
If I understand the question:
the oil pressure cut out was back feeding the starter solenoid. when he applied power to the pump the engine cranked.

I am thinking the HOT to the fuel pump could be moved to the other side of the (Open when not running) oil pressure switch.

Did I miss anything?
diode will do it as well.
the solution with the DPDT switch would enable the oil cut out still be in effect.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
tough to say with out seeing a schematic as the hot side could be going to a solenoid, or off the s terminal of the ign switch that would be the wire I would add the primer switch to as once the carb bowl is full it will run long enough to build op and keep the electric fuel pump running
 

zspryte

Member
Site Supporter
After leaving my lights on one too many times, I rewired things so the lights can only be on when the ignition is turned on. The nice thing about this setup is I can turn on the ignition and lights without the fuel pump or engine running. Also, whenever the engine stops so does the fuel pump - nice safety feature.

With no oil pressure, the oil pressure switch connects the yellow and blue lines attached to it. So I think adding the diode as shown should keep power from feeding back to the starter relay when I push the primer switch.
 

Attachments

  • Primer Wiring.pdf
    149.6 KB · Views: 185

redsqwrl

Bronze Member
GOLD Site Supporter
If the oil pressure is absent (motor off). the OPS will be open.

the yellow wire should remain dead while the primer button is pressed

either Im having a spell or something is not as it appears...

given:
the Switched controlled power is your coil/ignition.

Ive had/having a long week..... so be nice if captain obvious missed something
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
the schematic doesn't look right to me if using the primer switch why not get rid of the yellow wire the way I see it is the fuel pump only works when the engine is cranking. the only reason for an op switch should be to shut the pump off if the key is on and the engine isn't running the way that is drawn it appears the op switch only runs the pump when op is low and the engine is cranking. am I right Mike?
 

Two Track Mind

New member
Check continuity between yellow /green on oil p. switch in both directions while disconnected from main harness. since op has 3 separate wires it should have a diode built in. If you have cont. in one direction and not the other just switch where green hooks with yellow. If cont. in both directions install diode where you marked it. I think it is hooked up backwards because starter doesn't run when engine is running now and it should be if there isn't an internal diode. Hope this makes sense to you.
 

zspryte

Member
Site Supporter
The OPS is just a single-pole, double-throw switch activated by the oil pressure. No oil pressure, the yellow line is switched/connected to the blue fuel line. With oil pressure, the green line is connected/switched to the blue fuel line. When the momentary primer switch is pushed, the green line is connected to the tan line. This sends power down the tan line to the blue fuel pump line and the fuel pump runs. Since the tan line is connected to the blue line from the OPS, power also goes down the blue line, into the OPS, and comes out the yellow line to the starter relay. This causes the starter relay to energize the starter. The diode will prevent power from going from the OPS to the starter relay but allow power to go form the starter relay to the OPS.

The diode arrived today. I installed it and now every thing works as intended. The starter is not energized when the primer is push. Now if we can just get some snow ... Anybody know how to install a snow primer switch?
 
Top