71 510 Fuel delivery problem

[jbcottrell]

My 71 510 doesn't start. I can pour gas in the carb, see the float rise, and it runs for a few seconds until it's empty.

 

Checked fuel pump, OK. Fuel is shooting out of the line that goes to the carb.

 

I've heard about a tiny filter in the carb that causes all sorts of problems. Could that be it??

 

It's a stock Hitachi.

[shacks510]

Float needle may be clogged or stuck. The float just opens and closes the needle to allow or stop fuel flow.

[datzenmike]

The brass screen would have to be totally plugged, unlikely, but possible. It's located at the banjo fitting of the fuel inlet to the carb.

 

While the banjo fitting is off, check that gas is getting to the carb by bumping the engine over with the starter. Use caution as this is gas under pressure.

 

Next, use a suitable socket (not pliers) to loosen the needle assembly and lift it off the carb. In the lower end is a small needle valve that is lifted up by the float to shut off the gas from the pump. It's likely stuck.

[banzai510(hainz)]

wack the banjo fitting gently while car is turing over and then see if gas enters the carb. Needle valve dirty.

 

this is a simple fix

 

best to buy a weber DGV 5a when you get a chance as these are getting 40yrs old(hitachi)

 

i recently bought a DGV for my 521 and up the idle jet to 70 and I dindt know how bad my old 25yr old weber DGV was untill i got a new one. Its alot smoother and not the weber bog as it used to have.

[Rays74]

My 71 510 doesn't start. I can pour gas in the carb, see the float rise, and it runs for a few seconds until it's empty.

 

Checked fuel pump, OK. Fuel is shooting out of the line that goes to the carb.

 

I've heard about a tiny filter in the carb that causes all sorts of problems. Could that be it??

 

It's a stock Hitachi.

Interesting that you can manually fill the float bowl fine (you are watching the float rise as you fill, correct?).....the pump is shooting fuel so we can assume it has enough pressure and fuel is getting to it fine. Could it be the line from the pump TO the carb is clogged shut? From what you're saying the float valve and screen assy is flowing fine (if gravity can fill the bowl..:D).

There's something simple in play here.

--Ray

[datzenmike]

I think he's filling through the bowl vent on top. This is what I have done.

[Rays74]

Ahhh, yep Mike I didn't figure that........so a blocked fuel inlet IS entirely possible :)

[Stoffregen Motorsports]

You may have a dirty tank which can be dumping debris into your carb. I thorough tank cleaning is probably required, but you can buy some time by clearing out the lines and in tank pick-up.

 

Disconnect the fuel hose from the pump and blow compressed air back through the feed line. You have to be careful when doing this as sometimes you can pressurize the tank and when you remove the air blower from the fuel line it can spit fuel back out into your face.

 

These old fuel systems are not complex and if it were in my shop, I would take the time to clear all hard lines and replace all soft lines and filters. Should only take an hour or two.

[datzenmike]

 

Checked fuel pump, OK. Fuel is shooting out of the line that goes to the carb.

 

 

 

 

Line from tank to pump appears to be clear if gas being pumped. Debris can't get to carb if you have the proper fuel filter on the line before the pump.

 

Take the line off right at the carb and crank engine over with the starter and see if gas getting that fat...

 

No...... line is plugged between pump and carb.

Yes.... fuel is being delivered to carb

 

Carb seems to be the problem. Maybe the brass screen at the banjo fitting is plugged, maybe the needle valve at the inlet is stuck closed.