Honda Shadow Forums banner

1986 vt700c fuel pump not pumping?

8K views 29 replies 3 participants last post by  swifty2014 
#1 ·
Here's the story. Bike had been running great after I cleaned carbs and tanks....bike had set for two years prior.

Got it running great for last two weeks, but charging system wasn't working. Put a stator in it two nights ago, charging good now.

This morning, before fire up, checked voltage on battery to make sure it was good. In process my one test lead sparked to the frame for a milli second.

Bike started up. Ran to end of street and died. Pushed home. Checked tonight. Have good spark and coils check out. Pull fue hose off that feeds carbs and no gas.

Take a wire and go from neg on battery to green wire on pump and positive of battery to black wire on pump and it does nothing.

This means my pump is bad right?

Sent from my SM-G920P using Tapatalk
 
#2 ·
If you power the pump with the hose off the carbs it should pump steady. Tap on the pump to see if the contacts are dirty and sticking.
 
#4 ·
It's normal for it to shut off once it's built pressure. (providing you had the fuel line connected) The pump is on demand and only runs as needed to maintain line pressure. Now if the line was disconnected and it did that, you may want to look into a possible fuel cut relay problem.
 
#6 ·
Not sure how your bike is configured. On the old magna, it was connected to the battery holder in a rubber retainer if I remember correctly. If you don't already have one, get yourself an oem service manual for your bike. It's the most important tool you can own and will have all the diagnostic procedures listed for testing your systems.
 
#9 ·
Try the pump test again. If you jump it then it should stay running longer. The specs are approx. 1 quart in a minute. So a pint should be in about 20 to 30 seconds. It should just keep pumping.
 
#11 ·
More testing tonight. I can jumper the black and bl/yl wires on fuel pump with hose disconnected. Pumps fuel. Hook hose back up. Jumper again and pump runs till pressure builds up then shuts off. Start the bike. It runs till gas in carb is burnt then dies. Jumper again to build up pressure and so on. Thoughts?

Sent from my SM-G920P using Tapatalk
 
#16 ·
Follow those wires you're jumping. Anyone here have a schematic they can send this guy? Go to the stickys at the top of the tech discussion and look for a downloadable freebie . There may be one there for your bike. It will help you out a lot.
 
#17 ·
Follow those wires you're jumping. Anyone here have a schematic they can send this guy? Go to the stickys at the top of the tech discussion and look for a downloadable feebie . There may be one there for your bike. It will help you out a lot.
Naw, I looked. Could the relay be built into the pump. I ask because 3 wire go in to pump and 4 wires come out of pump.

Sent from my SM-G920P using Tapatalk
 
#21 ·
Wires going into that red plug are black with brown stripe, white with yellow stripe, gray with black stripe and green.

Wires coming out of pump, blue, black, green and back with yellow stripe.

Wires going in to pump, black blue and green

Sent from my SM-G920P using Tapatalk
 
#22 ·
Wish I could help, but without a schematic, I'm only guessing. I'm operating on memory of going through the son's 83 Magna a few years back. Look for another relay similar to that one, I do believe there are two different relays if same as the magna.
 
#23 ·
Here is the wiring for your fuel pump and relay. The black wire is ignition power. The green is ground. The blue is from the front coil negative signal to show the engine is running . The blue goes to the relay to trigger the fuel pump circuit on. Safety system to cut the fuel if the ignition is still on but the engine stops.
 

Attachments

#25 ·
#27 ·
I am not sure about that because I have looked at the wiring before and on mine it shows a separate part but on yours it almost looks like it sitting on the pump or is a part of it- ???
Here is what I mean - my bike shows the relay around the air filter cover. Yours may be at the pump. My pump has only 2 wires yours shows 3 into 4 at the pump.
 

Attachments

#30 ·
It will work OK but you lose the safety function if the bike falls over and the engine dies the fuel keeps pumping.
Maybe see if there is a signal from the coil on the blue wire to the connector there and if not repair the wiring and it could work as designed again. A meter will show some type of pulsing voltage signal from the coil grounding. Compare the signal at the coil negative terminal directly.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top