Mechanical Fuel Pump

[greydog]

See if she runs if you feed the pump from a gas can at the pump.
That will show if the pump is moving fuel.
Dan.

[nismou20]

I have seen pumps where input/output were reversed. Should be able to pull vacuum from outlet side with hand held vacuum pump. Might just pop all the bolts off top and double check the diaphragm mounting. Spring?

[#009]

I had the same problem couple of weeks ago after replacing my fuel pump with another mechanical pump from ebay. My old pump is the type that can't be rebuilt hence buying a new one. What finally solved it was disconnecting the line from the tank to the filter, siphoned it by sucking on the fuel line till fuel came out. Reconnected the line to the filter, poured fuel in the carbs and started it.

[Linda]

Success, yay.
So first I went over every clamp with a small vice grips, then made sure pump screws were tight.
Then I ran car with intake hose in jar of gas. It pulled well I could see gas go down, car ran fine.
Then I reconnected hose, rechecked for tightness. Started and within 15 sec it pulled gas from the tank which I could see in the clear filter (new). Filter is very full but only a light bit of sand-like debris. So I will watch it.
Lesson learned is a screwdriver may not be enough to have clamps tight and new hose helps as well.

Nice rebuild kit from Sin City Datsun

IMG_20180204_122757376_HDR.jpg

Thx all
Linda

[Linda]

Yes you must reuse the spring and oil boot on the new diaphram when installing.
Nice to have new valves. I have replaced diaphram before but with current gas I don"t think they last as well.
Valves need gaskets. I found fiber gaskets at OSH size 5/8 x 3/4 fit great.
Also helps to have double nutted studs that you unscrew to take pump off, otherwise pump can hit the frame.
I am using 2 90deg fittings which are 1/8NPT X 1/4". Some use 1 straight fitting.
Some fittings are large which Rallye talks about and recommends 1/4".
Linda

IMG_20180204_151448570.jpg

[greydog]

Congrats Linda.
You stuck with it, thought logically and worked thru the possibilities.
Nice work!
Dan

[Linda]

Nice help, Dan!

[bobd]

I remember a thread a while back wondering why someone had installed one of these.

[jasmith1975]

Thread Revival #2

I'm having a stalling issue with my '68 2000. Before jumping into the details, here's a bit of background.

I replaced the points dizzy with an EI dizzy in the Spring. Car ran great and I was very happy with the improved performance. About a month ago I took a 15 min ride to the store. Came out 20 mins later and the car wouldn't start. I found the dizzy bolt was loose and ignition was out of time. Easy fix. The next ride out (again for 15 mins or so) the car ran fine. But again after 15 mins at the store, the car wouldn't start. Checked the dizzy bolt and it was locked down tight. After 20-30 minutes (with the hood open), the car started and I was able to get home. It was hot (mid 80's) and sunshine, so thought it could be vapor lock (although never had that issue before).

Fast forward and I'm still having problems. The temps are much cooler now (mid 70's) and I've been troubleshooting in the garage with the hood open, which seems to rule out vapor lock. I can recreate the problem every time...car starts, runs for 20 mins, then stalls; wait 20-30 mins, car starts again. Rinse and repeat. Here's what I've tried so far to troubleshoot without success:

1. replaced fuel filter (plastic cartridge type)
2. blew air back from filter to tank (heard gurgling in tank)
3. bypassed tank; hooked up fuel line (new) from gas can to filter
4. bypassed mechanical pump with 4psi electric pump (from gas can); used new fuel lines from gas can to front carb
5. tested fuel psi - starts at 3-3.5psi (4 with electric pump), then falls to <2

Based on PO receipts, the fuel tank was boiled out and lined (2012), fuel hoses replaced (2013) and aftermarket (mechanical) fuel pump installed (2015). I pulled the floats and noticed the front float has a crack on top. Wondering if that's contributing to the problem? Wouldn't a sinking float flood the carb and overflow the bowl? There's no evidence of fuel overflow/leak or excess gas in the carb throat.

I have a mechanic friend coming over tomorrow to take a look, but hoping to get some direction/ideas. Thanks all!

[Gregs672000]

Coil overheating?

[jasmith1975]

Coil overheating?

No, just warm to the touch and was installed with the EI conversion.

As an aside, fuel flow with the mechanical pump seems weak. I didn't check volume, but the filter is pretty much bone dry with fuel just trickling in. That said the car still runs for 20 mins before stalling out. With the electric pump the filter is nearly 3/4 full, but car still dies in the same amount of time.

[Bwk2000]

Pull your plugs right after it stalls - post a picture of them.
In the meantime, have your alternator bench tested and find a replacement used coil you can temporarily swap in (make sure its at least 3 Ohms). Wouldn't be the first time a new coil was defective.

[Gregs672000]

As above, next time it dies pull a plug wire or the coil wire at the dizzy and see if it sparks...that will clearly narrow down what system is failing. Use a screw driver to fit inside the plug or coil wire, then crank the engine (have a friend crank it) while you hold it a small distance away from metal (like the valve cover). Don't get too far away or touch the metal or you'll get shocked!

[jasmith1975]

Thanks for the tips @ Bwk2000 and Gregs672000. I pulled the plugs (before starting) and they're completely covered in carbon (which has been a prior issue). My mechanic friend stopped by and noted a few other areas of concern that need to be addressed.

1. Smelled raw gas on the dip stick
2. Plugs covered in carbon, resulting from excess fuel
3. A lot of play in throttle shafts and likely sucking air

He said the stalling issue could be a check valve in the fuel return line not functioning correctly. BUT to correctly diagnose, the carbs need to be rebuilt. Ugh...not what I was expecting.

So that leads me to my next question. What's the best approach to rebuild carbs? I've heard ztherapy is top notch, but I'm also trying to learn and do as much as I can. I see rebuild kits are available, but doesn't include bushings/throttle shafts. Thanks as always for the advice.

[Bwk2000]

You have several issues here - Let’s deal with them one at a time:

1st, don’t discount what Greg and I pointed out above (alternator, coil, spark check, etc). Test those FIRST, none of that costs anything to check and can help pinpoint the problem. Don’t start replacing parts just because - That can get expensive. Now, the rear carb will have the fuel inlet and check valve assembly you mentioned. It’s designed to reduce the chance of vapour-lock, but, it really is not needed (wasn’t included on earlier cars). This is not likely part of the issues you are describing since vapour-lock would not happen every time you run the engine and cause it to stall after exactly the same amount of time as well - Continue to investigate as per below.

2nd, black plugs and gas in the oil (your smell from the dipstick) are related (running way too rich). I recommend you install properly gapped new plugs (don’t just clean up the old ones) and change BOTH the oil and filter … Go ahead, we’ll wait until you’re done

3rd, now that ALL THE ABOVE have been checked/replaced, start-up the car, warm it up to OPERATING TEMPERATURE and CAREFULLY spray a small amount of ‘Engine Start’ directed at BOTH SIDES of the base of each carb (throttle shaft and gasket area) - Listen for a marked INCREASE in engine RPMs. If nothing happens, it’s not the throttle shafts or an air leak in the carb mounting gaskets, you may not need a carb rebuild after all just a proper adjustment, which is a nice segue to the next point …

4th, assuming you have SU carbs, go through Keith’s write up (link below) on how to properly adjust them and then have at it!

https://www.311s.org/su-setup/su-setup.html

5th, now that all the previous diagnostic/corrective steps are done, does it still stall after 20 mins? Let us know.

This may not be as big a issue as you think