Have trouble with fuel pump system, possibly the spark unit.

1987 VFR700F2. OK, I am having trouble getting my fuel pump to push fuel to the carbs. I have checked the fuel pump, the fuel pump itself is working, and I checked the fuel pump relay according to the chilton manual, it is working correctly, checked the wiring going to and from the the fuel pump and the relay, no breaks, I can only get the fuel pump to work by bypassing it using a jumper wire between the black and black/blue wires. I even tried jerry rigging it by splicing into those wires, and connecting them to the engine stop switch, weird results don't try this. My only theory is that it is the spark unit. I think I tried everything else. Does anyone know how to test the spark unit, or have any other ideas on how on what to check next?

 

How do you know the carbs are not getting any fuel?
Did you remove a drain plug from a float bowl to see if fuel comes out when the petcock is on?
And if a vent is clogged it won't get fuel. Remove the gas cap- then check again.
Just because the fuel pump will not work what makes you think it is the spark unit?
Do you have spark now? Take a plug wire off and plug in a spare spark plug.
Does it get spark when turning the engine over?

Your bike does not even need a fuel pump really.
But the tank would need a crossover tube.

You say you can get the fuel pump to work by connecting the blue and black wire
and "bypassing it" It what? What are you bypassing? See what I mean?
The fuel pump has to sense low pressure THEN pump to supply more fuel to the float bowls.
You can manually jump the fuel pump and get it to work so there must be a pressure switch that does not work.

Personally I run my Honda VF 1000R with no fuel pump and I have no problems at all.
I do not think most motorcycles with carbs need a fuel pump at all.

Also there is a switch that causes the fuel pump to turn off if the bike crashes.
That is WHY they put in a fuel pump so they can electrically shut off the pump with a MERCURY
switch. You need to see if you can find that switch.


On a Kawasaki 1500 I had, if you took the instruments off of the gas tank and turned them upside down
on a work bench, the mercury switch would get turned over and then the fuel pump would not work anymore.
The mercury switch was hidden with tape. A real hair puller.

I bought a electric fuel pump too once for my chopper and the relay and I had the same experience. I could jump it and make it work but it would not work as a complete system. There has to be a pressure switch or mercury switch hidden somewhere that is keeping the pump from turning on.

I just got rid of the whole mess and I have no more worries.
Np pump ,no hoses,no relays, no fuses, none of it.

 

I know it is not getting fuel because I removed the tank, hooked up a working tank that allows me to work it, and with everything connected properly it is not pumping fuel, when temp tank is on, and the engine is started. Funny thing, the spark unit is the Honda name for the ECU, on the bike. And I know it is a fuel problem because I tested to see if it is getting spark, the timing has not changed, and I pulled the air filter, so it is getting air. 4 things to make an engine run, really, timing, fuel, air, and spark, the only thing left is fuel. And you bypass the fuel relay by putting a jumper wire between the black and black/blue wire on the relay.

Thanks for the try, but it sounds like you don't know much about the mechanics of the 87 vfr.

 

when I by passed the fuel relay the fuel pump would work. I checked the fuel relay with the test procedures in the chilton manual, and the FSM that I have. relay is good.

 

actually, not a bad idea to just connect the carbs to a working tank to see if I can get it started. the float valve should control the fuel supply going to the carbs.

 

OK, just tried that, still will not get the engine to catch. I visually checked the spark. I don't understand. And I know the carbs are clean, cause I just cleaned them. and it has new gas.

 

I know, I know, but I pulled carbs off the bike, pulled them completely apart, and cleaned them myself. Man they sparkle. How is that for knowing?

 

Here's a couple of things to look at. I took a look at the 86 wiring diagram. It's not much different than my 83. Check your start sw button/kill sw. One leg of the fuel relay is tied there. Another leg goes to the #4 coil signal to fire the coil from the CDI box. The center wire from the relay supplies 12v to the pump when the coil fires. I doubt your getting the 12v from the fuel pump relay. If the coil fires the CDI box is good to the fuel relay unless you have a broken wire. There is a transistor/diode in the relay that switches on the 12v to the pump from the CDI/coil signal. If that's bad your relay is no good. Make sure you have the right connector to the fuel pump relay. Also check the #C fuse. It supplies 12v to one side of the relay.

Now here's something I did the other night when I was not in the frame of mind to be working on my bike. I inadvertently plugged the turn signal relay connector in to the fuel pump relay and visa versa. The connectors are the same size and shape, but a different color. My pump didn't work. I then put gravity feed on for the carbs and took it for a ride. The motor did NOT like gravity feed at all! I went to turn around and put my blinker on. No workie. Then I thought DAAAA I know what I did. So could it be that simple?

 

"when I by passed the fuel relay the fuel pump would work. I checked the fuel relay with the test procedures in the chilton manual, and the FSM that I have. relay is good"


Chilton is wrong. Factory manual is better in every way

If the pump only works when you bypass the relay with the jumper wire, it PROVES the relay is bad.

Install the jumper permanently, tape up the connection, and ride on, brotha.

 

I am quite sure that the fuel pump relay is the fuel pump relay. and the relay is good according to all tests, when I by pass the relay, it does get enough voltage. However this is an 87 vfr 700 f2, not the 86, the wiring is a bit different, the relay is connected on either end to the ECU (aka spark unit), then to fuel pump. the relay tests good. But good idea to check to see if the coil is sending a message to the ECU, or rather if it there is continuity between the spark unit and the coil packs.

no it does not prove the relay is bad, it could prove that the system controling the relay is bad, or that the messages to the spark units are messed up or missing.

 

So just what is the proper pump relay test proceedure ??


You're probably over-analyzing and reject practical advice from old-timers, so carry on bravely, Bunkie, and be careful where you randomly hook wires.

 

It is tested with a multimeter, I don't have the books in front of me at the moment. And any workable advice i am getting, I use dude, it may sound arrogent to you but really, dude, I have thought this out long and hard, and truth is I am dealing with a bucket with cascading problems. I have put many many hours into this bike. And I am not stupid.

 

Good try, Tink, but he already stated the relay is good......and dude's not stupid, he claims. (?)

Some blokes just won't listen.

 

I have had a good fuel pump that would pump gas and a known good relay.
Pump still would not pump when demand was low.

There has to be a pressure switch or mercury switch involved?

 

Yes that is what I thought too.. but no dice.
There has to be a switch that tells the pump that demand is needed.