Datsun Roadster Forum-311s.org

Hello good friends,

I'm back with my '69 2000.

In our last thrilling episode there was no power--after consulting the forum wizards, wiggling some things under the hood, and making a few tests in the cockpit, magic returned and the car cranked!

And then I couldn't help myself and drove it! around the block once! around the block twice! then got the kids and drove a third time, and this is the time it stalled...

Which are exactly the same symptoms from three years ago when I decided the fuel pump must be failing...but this is a brand new fuel pump, so I suspect my troubleshooting is suspect.

I don't know if it's a clue or not, but the cycle seems to be that it will start/idle/run from bone cold for about 10-15 mins. Then die. Leaving it and returning anywhere from 20-40 mins. later gets me 3-5 mins. run time. Then dies again.

When it's cold and I crank it I can see fuel bubbling into the clear plastic filter, when it's stalled much less so. I can see fluid coming in, but it's sporadic at best, and where when cold the filter seems to be about 1/3 full of fuel, when stalled it seems to be either dry, or perhaps 1/8th full...

Knowledgeable friend suggested I might have a plugged fuel line/sludge in tank that was causing fuel pick up from tank to be restricted/cut off as heat motion build/agitate the tank. Correcting this seemed much simpler than rebuilding carburetors...

I dropped my tank, and heard an odd clunking in there, as though there were a small bar of metal slamming around in it. Sent it off to be cleaned and lined, and have it back now. Metal bar was removed, fuel sender apparently tested good (perhaps electrical gremlins moved from cock pit to tank?)

1.) My "tank hanger bolts" were rusty beyond belief and one broke during removal--does anyone know where I can get a new one?

2.) There was a vent hose on the top of the tank---seemingly vinyl tubing from the aquarium store, yellowed, dry, brittle with age, and a sharp kink in it--that ran to the bottom side of a small pipe fitting screwed into the trunk floor. From the trunk floor to the side of the fill neck it was proper PCV/Fuel Vapor line. Is there any chance the yellowed line was stock from the factory? I'm planning to replace it with PCV hose at the moment (and kind of hoping I've actually found the problem...)

--I'm wondering if it's possible this bent hose is causing some kind of vapor lock?

2a.) The little piping bend that connects the tank vent through the trunk floor seemingly had a gasket of some kind at one point, possibly paper? Seems a good idea for metal pipe carrying fuel vapor to be insulated from abrasion and wear, is there an individual gasket here, or is it part of the fitting?

3.) Is it weird this tank vent returns to the side of the fill neck UNDER a non-vented cap? When I removed the vent line from the floor of the trunk, there was a distinct whooshing sound as though pressure were being released, although my gas cap is extremely difficult to fit and remove--there are only a couple degrees of turning where it seems to be sealed the way it should, and the rest of the circle it's just flopping about in some grooves--although it's still extremely difficult to get it off the fill neck at all even when floppy.

4.) I have two outlet fittings on the forward part of my tank, which per my Scott Sheeler Roadster Manual is as it should be. One of them was pretty large and the other about two wrenches smaller.

What purpose does the smaller of the two pipes serve?
Where does it go?
If it were blocked, would my engine be fuel starved somehow?

My fuel pump doesn't seem to have a return from it. All smog equipment was gone when I got the car, and since my car came from Washington State originally, I don't think it ever had a charcoal canister for the gas fumes...?

5.) The previous owner of my car attached the fuel sender protective plate in the trunk floor with an assortment of fasteners of different sizes--can someone tell me what they should be? I suspect that won't help much as two of the four holes have been reamed out by the self tapping sheet metal screws the previous performance enthusiast put in there..."these screws are good for another 10 horses on the top end sir, all the racers are using them..." (not.)

Thanks again all.

Best regards, Nic Close

I'd pull the cover in the trunk, then pull the fuel tank sender and see what you see in the tank. You might have some crud floating around and eventually getting stuck on the pickup tube blocking it.

There is no return from the fuel pump, but there should be one coming from the rear carb. (Assuming you have SUs.) It would have a rubber hose that connected to a metal tube that runs under the cowl to the passenger side, then down the firewall and back to the tank next to your fuel inlet line. Does the fuel filter fill all the way up (bad) or stay at a partly filled level?

Do you have a heat shield under the carbs? That will also make a huge difference in whether or not the car runs well.

Lastly, when it cuts out, check your coil. If its hot to the touch, that might be your culprit. I've had similar issues to yours that turned out to be a bad coil. It would get hot and stop conduction electricity and therefor killing the spark. Let it sit for half an hour and it would start and run fine, for 5-10 min before doing the same thing.

Will

1. The J bolts?

2. Clear tubing is stock. The one in the trunk I believe has a spring inside.

4. One fitting should be the fuel return line from the carburetor.

5. The inspection plate has rectangular capture nuts on the bottom side of the trunk floor. For my low window car they are 8-32 or 10-32, don't remember which at the moment. Not sure if they changed them to metric, probably not. Your body bolts should be SAE inch.

wmckid68 wrote: Sat Sep 12, 2020 1:54 pm 3.) Is it weird this tank vent returns to the side of the fill neck UNDER a non-vented cap? When I removed the vent line from the floor of the trunk, there was a distinct whooshing sound as though pressure were being released, although my gas cap is extremely difficult to fit and remove--there are only a couple degrees of turning where it seems to be sealed the way it should, and the rest of the circle it's just flopping about in some grooves--although it's still extremely difficult to get it off the fill neck at all even when floppy.

You should have a vented gas cap for a 69.

The large line is the return and the small line goes to the fuel pump.

As others have stated, Check your coil for being very hot and leave your gas cap loose to see if its a vent problem.

To determine if it's fuel you could bring along a can of starter fluid to see if the engine will run on sprays of that. If not, then it's spark.

Is the car back together now? The most typical cause of your symptoms is crud in the tank which should be ok after the cleaning.

Hopefully, you have cleared out both the fuel and return lines.

Get a thread gauge -

https://www.boltdepot.com/Product-Detai ... U2EALw_wcB

You will find this helpful as you have both metric and SAE threaded fasteners and many are close enough to start threading in but bind up quickly.

McMaster-Carr is your friend or a well stocked hardware store.

Per your questions, a kink in the vent line could be causing a vent issue, you should have a vented cap. The whooshing of air is a big clue that you have a vacuum situation and that the tank is not vented properly. The empty fuel filter, and bubbles also point to a fuel starvation/vacuum situation. Post a picture of your gas cap - if that's incorrect that could also be contributing to a seal/vacuum situation. Lastly check all fuel lines, particularly any rubber lines as when they get old they crack and while they may not visibly leak, they can suck in air through the cracked line again resulting in fuel starvation.

Happy Sunday everyone, thanks again for collective wisdom!

Will check fuel return from carb--thanks for hipping me to what that is and what to look for.

Heat shield is present.

Have not performed "hot coil" test while I was stalled out, but coil is brand new East Coast Roadster component supplied with my snazzy new Electronic Distributor, and has less than 100 miles on it.

Yes--I think I broke a "J-Bolt" when removing the tank

Glad to know vinyl tube is stock, it seems well beyond its service life now (going to try and attach photo)

Thanks for tip about inspection plate hardware sizes!

Have photo of gas cap--car was delivered with matte black generic, replaced with Chrome generic from a roadster parts vendor--cap does not seem to be vented, I'm intrigued by this angle of attack for sure. Thanks to all who pointed out/corroborated the vented cap need.
Car not back together yet--need to find J bolts... Had planned to try and blow fuel lines out with compressed air while the tank is out, but have NOT done that yet.


Photos below show the small connector for the vent piping that comes through the trunk floor--it had some oily paper on it and seems like it may have had some kind of integral gasket with it when new? There seem to be small copper collars around the attachment holes and the paper bits seemed pressed into these? Anyone seen this before? Should there/was there some kind of something there when car was new?
Will get thread gauge--thanks!

When car stalled three years ago, while waiting for tow, I walked off, got a can of starting fluid and got going again that way. Made it most of the way home before it stalled again. These symptoms are what prompted my seat of the pants "fuel pump!" diagnosis, and my somewhat humorous (in hind sight) struggles to obtain and install said new fuel pump... I now think perhaps I had simply waited for the tow truck long enough for the fuel/engine/tank to cool enough to release its vacuum/vapor lock, and got fooled by my own hubris. Always be learning...

Will investigate/replace all soft fuel lines--many were done by my mechanic when they were waking it from it's previous long slumber: It's new hose from tank hardline to fuel filter input, filter out to pump in, and pump out to carbs, but I'm nearly certain the carb return line was NOT changed out.

Once again, deep gratitude to everyone for your thoughts, ideas, help and suggestions.

Watch this space, will keep you posted.

Best regards, Nic

Your non starting Problem is either gas or spark. First thing I would do when it stalls is to check for spark at spark plugs. If no spark work backwards to distributor then coil. If you have spark at the plugs then it’s time to look at fuel. Before it has time to cool down disconnect fuel line at front carburetor. Have a jar or some kind of container that will hold the end of the hose and contain the fuel. Be sure that no fuel can land on the hot engine. Having a fire extinguisher at this point would be advised. Crank the starter for a few seconds and observe the fuel flow. If no,or very low volume Of fuel flow then check for obstruction fore and aft of pump. If you have good flow at the carb end of the hose then I would tear into carbs. These cars are very simple and if you just take it a step at a time you will find the source of your problem.
Good Luck!

I like your attitude. Despite your car problems, you seem pretty game for figuring it out with humor and patience. Good job so far!
Lots of great tips to keep you busy and you have followed thru on the suggestions too. Lots of smart people on here so take advantage so that you can be motoring soon with your evident enthusiasm! Pics appreciated, with kids
Linda