Fuel Delivery

[Williespeed]

I have an 82 720 that was running great after putting on a new Weber 32/36 I took it for a test drive this morning and 4 blocks in it died. I had replaced the fuel filter at the pump when I did the carb that was tuesday. I can hear the pump running there is fuel in the filter at the pump but it doesn't seem to be pulling fuel from the tank. Is there another filter I am missing? has anyone everr run into an issue with the fuel pick up. I just added another 5 gallons of gas and it reads over 3/4 full. anybody got a parts truck with a stock fuel cell for sale? I'm in Seattle.

[Zeusimo]

Is Your Pump Electric?

If So Check Your Connections... Unplug And Connect Again

My Pump Use To Do That On Cold Days When Moisture Would Get Into The Connection,

It Sounds Like Its Running But Doesn't Pump Anything

I Just Soldered Them Together And That Solved My Problem :cool:

[Logical1]

I'm no truck expert, but it sounds like you have an electric fuel pump. If so pull the fuel line off your carb, put into a jug/bucket and turn your key to 'on' but don't start it. If fuel pumps into your jug, it has to do with the carb. I just fixed a 32/36 with a similar problem, It was old debris in the float bowls that would clog the jets when the bowls got low under acceleration.

[izzo]

the 1980 720 has a manual pump, its an L20.

 

If there is gas in your filter, then likely it is pumping gas? Take the filter off, drain it. See if it fills back up. take the line off at the carb and pump and blow thru, see if its getting fuel.

 

Check for vacuum leaks, usually the cause. Take the top of the carb off and see if its got gas in there.

 

 

You could also take the line off at the carb, crank it a few times and see if gas comes out.... If so then its prob a carb issue

[banzai510(hainz)]

he has 82 720.

 

look inside the carb and cycle the linkage. If you see gas squirting in then you know you have gas in the carb. if no gas then carb is empty. either fuel pump or the needle valve/float issue

if you have gas then ck for leaks.

 

 

to me you ran out of gas.

[Williespeed]

It's a Z22 with electric pump I will pull the connections and check them out and then check the bowls.

[izzo]

Damnit lol... Thought it said 80, oh well. Either way you can remove the line off the carb and see if some fuel comes out. So you plugged everything off when you swapped it? Maybe one of the plugs or w/e came undone on the 423482390482390 vacuum lines. Good luck, this sounds like a pretty simple fix.

[Sealik]

Try unscrewing the base of the pump and cleaning the filter.

 

Edit.

 

Might not be the issue....but I'll bet there's a lot of crud in there.

[Williespeed]

I pulled the 12v connection replugged it pulled the line at the carb and turned the key on and the fuel just trickled out it should push at a fair rate insted of barely coming out. I think there is a fuel pump in my future. The manual said I would have to replace 1 transistor 2 diodes and 3 resistors so a new pump is probably the way to go. IF anybody has removed the pump filter and that is merely a suggestion let me know and i will check it. Thanks for the help thus far anybody got a drivers side tail light lens?

[Sealik]

I pulled the 12v connection replugged it pulled the line at the carb and turned the key on and the fuel just trickled out it should push at a fair rate insted of barely coming out. I think there is a fuel pump in my future. The manual said I would have to replace 1 transistor 2 diodes and 3 resistors so a new pump is probably the way to go. IF anybody has removed the pump filter and that is merely a suggestion let me know and i will check it. Thanks for the help thus far anybody got a drivers side tail light lens?

 

Ya...I have pulled the filter out of the pump, which remedied my problems

Grab some large channel locks and rotate the base.

Just watch how it comes a part...clean the filter out in gas.

 

Edit.....

 

Might be amazed how much crap is in there

Edited February 24, 2011 by Sealik

[Logical1]

I pulled the 12v connection replugged it pulled the line at the carb and turned the key on and the fuel just trickled out it should push at a fair rate insted of barely coming out. I think there is a fuel pump in my future. The manual said I would have to replace 1 transistor 2 diodes and 3 resistors so a new pump is probably the way to go. IF anybody has removed the pump filter and that is merely a suggestion let me know and i will check it. Thanks for the help thus far anybody got a drivers side tail light lens?

 

If the pump is running, fuel should be shooting out of there! Even with mechanical fuel pumps or electric carb pumps at 3psi it moves ALOT of fuel!

[Sealik]

If the pump is running, fuel should be shooting out of there! Even with mechanical fuel pumps or electric carb pumps at 3psi it moves ALOT of fuel!

 

Not really...pump will still (trickle out) run if it's partially plugged.

Also has a different pitch....if you listen closely :D

I just cleaned all of my lines, replaced the tank and still no fuel at carb.

Before I replaced the pump, I checked then cleaned the filter....good to go.

[datzenmike]

It should pump just under 1.5 liters (47.5 US fluid oz. for you Yanks) per minute. With the end capped, pressure should be between 2.7 and 3.4 PSI.

 

Doug is correct, there is a filter in the base that collects the crap in the tank to keep it from going through the mechanical parts of the pump. The dealer replacement filter is 16404 28500 about $5.That's way cheaper than replacing.

 

Also keep in mind that webers, old webers specially, do not like fuel pressures much over 3 PSI.

[DanielC]

After 40 years it is common for some crud to get in the gas tank. With the recent change to E-10 gasoline, some of this crud may be worked loose again. This crud can also plug the fuel pickup pipe in the gas tank.

The quick fix is to blow air backwards from the engine compartment back to the tank, and many tines that will dislodge the crud on the fuel pickup. There is a really good chance the problem will return.

The long term fix is to pull the empty gas tank out of the vehicle, and clean it out.

 

These are the specifications for a L-16 mechanical pump.

The fuel pump should deliver about a quart of fuel in a minute, at 1000 RPM.

The fuel pump should have a pressure of 2.5 to 3.4 pounds per square inch.

[Sealik]

Here's a couple of aftermarket 720 pumps.....the internals look slightly different than the stock/OE pump... :blink: ..although I could of been drinking and or that day :lol: :lol:

But the same filter....these look pretty good.

The last one I pulled was caked in crud....pump was always under a load

Might not even be your pump..???....but it's a good idea anyways to check the filter out.

Eliminate the 'obvious'

 

[Williespeed]

The truck ran great yesterday under the same test drive 4 blocks up to the grade school a hot lap around the parking lot and home. I got into the secondaries a couple of times to make sure I had full throttle. I went up again this morning to check traction in the snow and test the 4 wheel drive and it died when I got to the school. I think it's gonna be the filter the truck sat for nearly two years with less than a quarter tank before I got it. I need to go to my buddies and get my other pair of channel locks so I can get the filter off the Pump. I also found a guy here in Seattle on Craigslist with 6 OEM NOS pumps for 8 bucks each I'm gonna get 2 from him when he returns home on Saturday. and replace it but I will check the filter first.

 

Tailight anyone yes I already looked in parts for sale.

[Sealik]

Tailight anyone yes I already looked in parts for sale.

 

Just missed the boat...sold my last ones to another member.

[ggzilla]

We been using E10 since the 1980s, at least I some gas stations here in Washington have. Most famously ARCO, but now they all doing it. Its never caused me a problem (never had a fuel problem since the mid-1980s).

[Zeusimo]

I Think There Was A Thread Around Here A While Ago That Said Old Gas That Is Contained Eventually Creates Rust :blink:

[deadmonkey]

I Think There Was A Thread Around Here A While Ago That Said Old Gas That Is Contained Eventually Creates Rust :blink:

I believe it was the jerry can thread saying the new gas rusted his can, when in reality old fuel absorbs water which can rust a tank if left over time...

 

at least I believe that's what the convo was about.

[banzai510(hainz)]

if the truck had a eleltric pump orginally. then its the correct pressure. just make sure the new pump is not like from a Z car with FI or soemthing then yes it wants a low pressure pump say of 3 pounds.

[SyN]

you didn't say anything about a pressure regulator but alot of guys with webers run those cheapo regulators, I've seen em fail an cut fuel off completely. better to not use one and just get a pump thats in specs for the carb.

[Williespeed]

http://hubpages.com/hub/The-Datsun-and-Nissan-Pickup-Fuel-Pump-Relay-What-the-Haynes-Automotive-Repair-Manual-Wont-Tell-You

 

I think Its my pump filter but I found this article interesting.

[Sealik]

http://hubpages.com/hub/The-Datsun-and-Nissan-Pickup-Fuel-Pump-Relay-What-the-Haynes-Automotive-Repair-Manual-Wont-Tell-You

 

I think Its my pump filter but I found this article interesting.

 

 

Ya....I read that a while back.

Changed the relay...still ended up being the pump.

Good to know though.

[Williespeed]

OK the big update pulled the filter from the pump and spent an hour at the parts store before giving the guy datzenmikes part # and Voila found the part ordered two @ 6.25 per put one in and about 1200 miles without a hickup I gotta re adjust the weber though it's not opening the secondaries any longer. but it runs great. Except for the exhaust note which is the equivalent of the mental brown noise at 70. So a header and full system are in the works, thanks for all your help I truly would not have been able to get it done without you guys.