Fuel pump blowing fuses

[Gunwriter]

Was trying to get one of my Deuces started today and had a rough time. Spun over but no love. I finally got it started with a shot of starting fluid (hate the stuff but I used it) and it ran fine for about 3-4 minutes, got rough a couple times and then died. No luck starting it again. Noticed I could not hear the fuel pump. Pulled the fuse and it wouldn't power the pump in my running truck. Stuck a different fuse in the non-running truck and it blew when I turned the power on.

What's going on? Bad pump? What do you guys recommend next?

Also will I have to bleed the fuel system now?

 

[Gunwriter]

Just threw another fuse in it. Truck started normally and ran fine for
about 30 seconds and died. Another blown fuse.

 

[doghead]

What are using as a replacement fuse? I needs to be a "slow-blow" fuse, 3-5 amps(depends where you read).

 

[AceHigh]

Once the pump does start pumping it will purge air automatically. I had the same problem and just put a 24volt in line pump on.

 

[gimpyrobb]

I use a 5A slow blow fuse. I use that because I run WMO. I believe stock is 3A. If you find something is wrong with your intank pump and want a stock replacement, I have them cheaper than you can get from the manufacturer.

 

[Gunwriter]

Thanks email sent, after 3 fuses (2 USGI 1 15 AMP) I think its the pump.
I pulled it and it was hot to the touch...

 

[Gunwriter]

gimpyrobb came to the rescue!

Want to thank everyone for the replies and gimpyrobb for going over and above to help me out.

I need this truck running for an industry event this weekend and he took care of me no questions asked.

THANKS!!

 

[micmccon]

I would like to see a pic of a "slow blow fuse". I am familiar with most all automotive fuses but I kinda need to see it to correctly identify the fuse. I've got a temporary fuse in there, but a 20a fuse for a 12v system isn't the same as a 24v fuse I imagine. Any help?

 

[doghead]

I would like to see a pic of a "slow blow fuse". I am familiar with most all automotive fuses but I kinda need to see it to correctly identify the fuse. I've got a temporary fuse in there, but a 20a fuse for a 12v system isn't the same as a 24v fuse I imagine. Any help?

4.0-Amp 250V 1¼x¼" Slow-Blow Fuse (4-Pack) - RadioShack.com


oh, found that with a google search!

 

[Gunwriter]

google 3 amp slow blow fuse

 

[micmccon]

Thanks guys. I did Google it! All I saw was a standard glass type 250v 3a fuse. Didn't ever call them "slow blow" fuses. I guess it's a difference in terminology. I can barely believe a 3a fuse is gonna hold up in a fuel pump circuit. I didn't do the math yet to figure the difference in current, etc at 24v. In 12v cars and trucks a 20a fuse is somewhat common. I figured it would be rated higher, I guess. I was envisioning something like a "Pacific Fuse Element" but they weren't around in 1971 now were they?

 

[micmccon]

Did I mention that the correct fuse had been replaced (by a member of the military) with a 20a mini fuse, acouple crimp-on female blade style connectors and a crimp-on ring eye? There was nothing there to compare it to. I just remade the same arrangement with a new 20a fuse and it works.........for now.

 

[doghead]

those look like the fuses in a VW fron the 60s-70s

 

[doghead]

You very well may have a bad in-tank pump motor.

Oh, the amp draw difference between 24v or 12v, is half. 24v takes half the amps of 12 for the same load.

 

[micmccon]

So a fuse rated at 20a @12v would be equivalent to 10a? If so, a 10a fuse would be "more correct" than a 20a fuse. I will try to see what the current draw is with it running to see what I've got going on. I just wanted to get the pump running and see if it fired up like it should. It did do that, but I think that I have to assume there is a reason the fuse blew in the first place. The wiring was smooshed (before the fuse) between the cover and the tank so a short there would not have blown the fuse. I'll post up the current reading when I get the result.

 

[Bill W]

You very well may have a bad in-tank pump motor.

Oh, the amp draw difference between 24v or 12v, is half. 24v takes half the amps of 12 for the same load.

Then what would be the (24v) amp rating of the 250v fuse you posted a link to at Radio shack??? or is it a ac/dc amp thing

 

[doghead]

No, a 10 amp rated fuse, is simply rated at 10 amps, no matter what the voltage rating is(within a range, typically 0-250 volts).

So, 10 amp fuse is good for 10 amps at 12v, 24v, 120v, 240v, etc...

ac or dc , does not matter...

 

[micmccon]

I took a moment tonight to check the actual current measured at the fuel pump power feed. I measured it to be 1.75a . I didn't run it long enough to get hot so I still wonder if it would be best to hook up a meter and watch the reading while driving. I used an inductive meter so I can't very well watch that while driving but I guess I'll come up with a way with a little research. Anybody take a reading of a good pump while running? Don't mean to beat it to death but knowing I'm in the good range would ease my mind a little bit.

 

[micmccon]

It looks like ckt#654 splits off from the starter button, so after starting I should be able to put the inductive meter inside the cab where I might be able to see it and measure the current there. I'll post if it works....

 

[gimpyrobb]

The stock fuse is a 3amp fuse. Many of us use the 5amp slow blow because of running WMO. 1.75 sounds like you are good.