Strange fuel pump issue

[Nimbus]

In the process of building my second FJ (1992) into a naked Café/track bike. I purchased an Equus 8080 tach, as I have removed the stock gauges. So I took the original grey wire tach signal and fed it to the new unit and set it to a 2 cylinder setting and tach worked great. Took it for a ride but only got a few blocks and it stumbled and died, felt like when you run out of gas. To make a long story short the fuel pump operates when you first turn the key as it should for 5 seconds. Once the bike starts I should get power back to the fuel pump, but I do not. Looking at the schematic I see the same grey tach wire also goes to the fuel pump relay. So I figured the new tach is interrupting that signal. I disconnected the grey wire at the tach but no change, still no fuel pump power after startup. Did I screw up the 'igniter unit', the tach still works and am at a loss to explain. Can I not just run power (brown wire) directly to the fuel pump. Alternately I am looking at a new igniter unit and then get my tach signal from the optional inductive pickup. Any input appreciated.

[Nimbus]

Forgot to add that I did try another relay with no change.

[FJ111200]

Dump the pump.

[Nimbus]

Seriously.... so just gravity feed, and I guess a petcock?

[Zwartie]

Seriously.... so just gravity feed, and I guess a petcock?

Follow this thread for some good information from the group on the fuel pump. My replacement fuel pump has been working just fine for over 15,000 km now.
http://www.fjowners.com/index.php?topic=9724.0

You can run a gravity feed system but you may find that the carbs are being starved of fuel when the tank is less than 1/2 full and you running hard under load.

Good luck!

Zwartie

[FJmonkey]

Seriously.... so just gravity feed, and I guess a petcock?

GF OEM style - Petcock, needle seats (GF has larger holes), 10MM tees (2 pcs) between carbs 1 &2 and 3 & 4 (with O-rings) , short pipe piece with O-rings between carb 2 & 3 (or cap off existing 6 MM tee), 10 MM Y shapped tee for fuel line, 10 MM fuel line, 5 more hose clamps. Reset your float heights. Did I miss anything?

Or you could attempt to go GF with a 6 MM hose from petcock to carb, ditch your filter if you do. May not get your full Kookaloo below 1/2 tank.

[movenon]

My opinion. Don't even think about gravity. Just fix your fuel system. Stay with the pump. Just a question. After the pump pressurizes it will shut off, (as it should) I assume you continued to run it and it fuel starved ? I don't think you will  see voltage until you use up some of the fuel.  I guess I need to go look at the wiring diagram..  
George

[Nimbus]

Yes it does pressurize and shuts off. When you turn ignition on the igniter gives 5 seconds of power and shuts off as it should until a signal from the coils (tach wire grey) saying the bike is running then you should get your battery voltage all the time. That is my problem I have lost that running voltage. The relay that the grey wire goes too is good as is the pump.

[racerrad8]

The fuel pump relay shuts down after the 5 second window if it does not see a tach signal from the engine indicating it is running. For some reason the tach you have mounted has changed that circuit or caused another issue that will not allow the relay to see that tach signal from the CDI box. It does not shut off because it is pressurized, only because it does not see the tach signal and the engine running.

You can run a switched power source to the fuel pump as a direct wire and eliminate the relay. There are only two issues with that...

1) If the switch gets left on for some reason the pump never shuts off and it can burn up the pump or cause the carbs to flood over from the consistent pulsing of the fuel pump.

2) In the event of a crash, the pump will continue to run even if the engine dies. If the bike is on its side the fuel can continually be pumped through the carbs onto the ground and cause a fire hazard.

Randy - RPM

[RichBaker]

Did you somehow disconnect the relay from the circuit when you swapped tachs? How exactly did you make the switch?

[Nimbus]

I just disconnected the gauges and found the stock wire (grey) going to the original tach and used that wire as well ground and the brown positive....
Appreciate all the replies, I will not go GF and will go over the wiring with a fine tooth comb this weekend and hope for an Eureka.

[movenon]

I just disconnected the gauges and found the stock wire (grey) going to the original tach and used that wire as well ground and the brown positive....
Appreciate all the replies, I will not go GF and will go over the wiring with a fine tooth comb this weekend and hope for an Eureka.

You might temporally hook the stock tach back up and see if it go's back to normal operation ?
George

[FJ_Hooligan]

I just disconnected the gauges and found the stock wire (grey) going to the original tach and used that wire as well ground and the brown positive....

Is this an incomplete sentence?  I read it as you used the grey (coil) wire as a ground?  That doesn't make sense.  Is this what you have currently wired?

[RichBaker]

Seems to me, the gray wire is a signal lead, not a ground..... IOW, it carries the signal to the tach and the relay, but I don't have the wiring diagram handy, so I'm not sure. But, I don't think you want that wire grounded....

[Nimbus]

No I did not use the grey as ground, correct it is for tach signal, the new tach works great, the black and brown are used for tach power. I am thinking the igniter has a transistor or diode switch that is now open due to the new tach taking more current. Hope to have some time to troubleshoot this weekend.
Cheers,
Henning