Datsun Roadster Forum-311s.org

So, on the pass. fender there is a small box shaped device which i assume is an electric fuel pump (sorry, very new to this car). The previous owner put in a inline fuel filter right after the pump. Its connected with rubber hose from the pump to the filter and from the filter to a hard line that is routed under the alternator, over the block, and finally to the carbs. There is a flare fitting on the hard line that isnt being used- the rubber fuel hose is hose-clamped onto it. This is clearly a "non factory" rig job, which MIGHT be OK if it weren't leaking. I want to fix this. What are my solutions? Build a new hard line and connect it to an line filter with fittings? what comes factory here?

Thanks,
-Neil

Pics would help. Do you still have the stock fuel pump? Just forward of the oil filter at the bottom of the motor. Sometimes those leak, and rather than rebuild or replace them people use cheap aftermarket electric pumps which are inferior to stock in my opinion.

If you have an early car ( pre 68) The hardline you describe would be correct.

Here are some photos- the small gold box is the fuel pump.


Here is where the hard-line connects to the rubber line. You can see the connector right under the alternator there.


and one more for good measure.


Also- it may be important to note that the chassis is a 2000 but somewhere along the line a previous owner dropped in a 1600. Not sure when the fuel pump was put in, but probably 5+ yrs ago.

Ok, The hard line going in between your valve cover and the water tower is original and correct, but seems to have been cut shorter it would have been connected right to the stock fuel pump which I am not seeing in this picture.

The braided line going to the fuel pump is not original. It would have had a hard line going all the way to the original fuel filter and 68 would have still had the glass filter.

So it appears to have had some cut and splice going on there. Stock routing is hard line from tank to fuel filter. Soft line from filter to fuel pump. hard line from fuel pump to carb junction point. soft line to individual carbs.

From the pics it would seem that someone installed an early non smog 1600 motor.

As to the leaks, I guess you just gotta trace it down. I bet a lot of your problem is that fake Pep boys areo covering stuff....you know, the slip on stuff that people buy to make it look like a 100k dragster.

anhizer wrote: There is a flare fitting on the hard line that isnt being used- the rubber fuel hose is hose-clamped onto it.
-Neil

If so, that flare fitting was most likely attached to the original fuel pump and they cut the nut off. That hard line screwed right into a fitting on the pump.

On my car a rubber line goes from the outlet of the stock mechanical pump to the hard line that crosses over to the other side. The transition point looks to be at about the same location as in the photo, above the alternator. Otherwise it is as Roman describes.

Edit; See next post with decent pics

Here are some better pics.





So, we have hardline to the filter and hardline to carbs. The filter and pump are connected by a soft line which I currently don't have hooked up.

It seems like you still have the nut on the hardline, that part wasn't cut at all.

I would get a stock fuel pump, make sure to get the spacer that goes with it, and ditch all that braided stuff. It is more reliable and safer too. Your electric pump will keep pumping as long as it has power.

Perhaps my hardline was cut and spliced with a rubber line at some point between the pump and the carbs. I have seen other cars plumbed this way at Solvang. I suspect that hardline can get bent or kinked when someone tries to take the water pump off.

Looking at the online drawings, they describe what Roman's photos indicate:
http://www.carpartsmanual.com/datsun311 ... ult.aspx#2

bikermike wrote:Perhaps my hardline was cut and spliced with a rubber line at some point between the pump and the carbs. I have seen other cars plumbed this way at Solvang. I suspect that hardline can get bent or kinked when someone tries to take the water pump off.

Looking at the online drawings, they describe what Roman's photos indicate:
http://www.carpartsmanual.com/datsun311 ... ult.aspx#2

Yeah, it probably was cut some time in the past. The motor I pictured is a low miles 67.5 motor that hadn't been monkeyed with. I have seen plenty cut myself as well. I would imagine a primary cause for many was the installation of an electric fuel pump. I've seen over the years a lot where the diaphragm would fail, and rather than replace or rebuild the pump, the owner would head off to Pep boys and get an electric pump for 20 bucks or less. Then the lines would get chopped. Later as people became more savvy and concerned with originality, they got converted back.

There, for what it's worth, that's my forensics theory on cut hard lines.

My 70 had an electric pump when I first bought it. It still had the mechanical pump, when I hooked it up, it leaked like a sieve. I just rebuilt it and it worked fine, but my lines were cut so I had to do the rubber hose.

If the leak is where the rubber hose connects to the hard line, make a bubble flare on the hard line ( google it - lots of info available).

This will give you a good seal with the hose.

Hey all,
Thanks for the responses. The leak is happening at the rubber line -> hard line junction; sorry i didnt make that more clear in my original post. There is a flare on the hardline, i think the fuel line has either degraded or the hose clamp isnt tight enough. I think im going to replace/add a new hose clamp for now and see if the leak goes away. It doesnt seem to be a very fast leak so it should be OK for now. I do plan on putting the correct fuel pump in at some point, but i want to address it immediately for safety.

Thanks!

bobd wrote:If the leak is where the rubber hose connects to the hard line, make a bubble flare on the hard line ( google it - lots of info available).

This will give you a good seal with the hose.

That's a good idea......but. Here comes the but.

Doing the bubble flare will make the hard line no good with the stock setup. Right now the hardline including the nut is still intact making for an easy conversion back to a stock fuel pump.

anhizer wrote: The leak is happening at the rubber line -> hard line junction; sorry i didn't make that more clear in my original post. There is a flare on the hardline, i think the fuel line has either degraded or the hose clamp isn't tight enough. I think im going to replace/add a new hose clamp for now and see if the leak goes away. It doesn't seem to be a very fast leak so it should be OK for now. I do plan on putting the correct fuel pump in at some point, but i want to address it immediately for safety.

Thanks!

Good idea. I think a new rubber fuel line and good clamping BEHIND the flare will work just fine till you convert to stock.

The Saga continues.

So, i replaced the rubber lines as discussed & fixed the leak. I drove it a bit and still smelled gas- pulling away from a light i noticed COPIOUS AMOUNTS OF GAS ON THE STREET. I assumed it was a leak from the hose at the clamp or something, but determined that wasnt it. I did some poking around and determined that the gas was coming from the fuel bowl overflow. I pulled the top off one of the fuel bowls and inspected the valve- it looks like its in good shape so its probably not the issue.

Long story short, the fuel pump i have puts out about 5psi of fuel pressure, way too much for the carbs to handle. According to the guy at Z therapy these carbs should be getting around 3.5lbs max.

So I have decided to order a mech. fuel pump (and spacer) and return it to 'original' ish.

Check your floats. If you have brass, they are most likely infested with minute cracks which leads to them filling up with gas.....then they don't float!

Plastic ones are better. Check them by pulling them out and give 'em a shake. you will hear the gas sloshing around if they are filled up.

The most likely scenario is you have sunken floats, which causes the fuel spillage.

The float i checked was replaced with a plastic one (no leaks) & the valve seat looked good. Gas flows from both carbs and a fuel pressure gauge inline with the electric pump confirmed the 5+ psi. According to the guys at Ztherapy the SU carbs are overwhelmed above 3.5 causing the bowls to flood and vent.

I thought about buying a fuel pressure regulator but a decent one is $40 minimum and it would be a bit of a bandaid. I decided to go with a mechanical fuel pump and see if that fixes the issue. Worst case i need to replace the valves on both carbs.