720 hard to start after sitting

[TimmyG]

'84 720 with z24 electric choke Weber 32/36. After truck sits for a week or two it takes quite a while to fire up. I can press the gas pedal to the floor 3x, turn the key and hit the starter and it took probably 10 seconds straight or more to fire up. Runs smoothly once fired up and will crank up quick, fast, in a hurry when engine is warm. And I mean immediately. Worth mentioning I usually don't let it sit for 2 weeks without starting it.

 

Battery was not low (charger), nor did the starter slow down. Maybe I need to adjust my choke? Its colder here now and I adjusted it previously...but the truck would stumble hard and run rich at first cold start up so I backed off the choke some. Now it doesn't stumble on cold start up or smell so rich, but that last cold start after it sat for probably 2 weeks was excessive on the starter. It took a WHILE to fire up. 

 

Does the fuel pump actually kick on and prime the lines with the key ON? Seems like the fuel pump only starts to flow fuel once I'm turning the key to spin the starter. It doesn't seem to help at all by leaving the key in the ON position before starting.

[datzenmike]

When you step on the gas (3X) the accelerator pump should squirt enough gas in to make it rich enough to fire up... even if it stalls right away.  Take the top off the air filter off next time and check this happens. Also on the first step the choke flap should snap closed.

 

The carburetor should have enough gas left in it to drive half way round the block. It should start even without the fuel pump working.

[TimmyG]

16 hours ago, datzenmike said:

When you step on the gas (3X) the accelerator pump should squirt enough gas in to make it rich enough to fire up... even if it stalls right away.  Take the top off the air filter off next time and check this happens. Also on the first step the choke flap should snap closed.

 

The carburetor should have enough gas left in it to drive half way round the block. It should start even without the fuel pump working.

 

Thanks, Mike! I will check this.

[banzai510(hainz)]

if I let mine go a week it takes a little bit to get the gas to the carb. 2 week even worse.

[datzenmike]

When I had my Hitachi I had the same thing, never solved it. Thing is the carb float chamber should have half a cup of gas in it. Enough to start and drive away. Pumping the gas should squirt enough from the accelerator pump to fire up. WTF? why wouldn't it if sitting for a few weeks? Where'd the gas go??? Or did it?

[TimmyG]

10 minutes ago, banzai510(hainz) said:

if I let mine go a week it takes a little bit to get the gas to the carb. 2 week even worse.

 

Same.

 

 

2 minutes ago, datzenmike said:

When I had my Hitachi I had the same thing, never solved it. Thing is the carb float chamber should have half a cup of gas in it. Enough to start and drive away. Pumping the gas should squirt enough from the accelerator pump to fire up. WTF? why wouldn't it if sitting for a few weeks? Where'd the gas go??? Or did it?

 

 

 

......and same. 

[datzenmike]

Gas can't siphon up hill out of the bowl and back through the pump. Winter so can't evaporate.

 

It would start with the starter, eventually. After 3 or 4 five second cranks. Maybe more. Ive squirted gas directly into the carb after one 5 second crank and I know it isn't going to start and it immediately fires up! and quits but if I use enough gas so I can half way rev it up, it will catch and keep going. So it acts like it is completely dry and has to suck gas all the way from the tank and I don't see why.

[TimmyG]

Just now, datzenmike said:

Gas can't siphon up hill out of the bowl and back through the pump. Winter so can't evaporate.

 

It would start with the starter, eventually. After 3 or 4 five second cranks. Maybe more. Ive squirted gas directly into the carb after one 5 second crank and I know it isn't going to start and it immediately fires up! and quits but if I use enough gas so I can half way rev it up, it will catch and keep going. So it acts like it is completely dry and has to suck gas all the way from the tank and I don't see why.

 

That's exactly how mine acts. Never bothered pouring any gas in, as it will eventually fire up if you stay on the starter. Still don't like it, though. Kinda cringy feeling while I'm doing it. Poor battery and poor starter. Lol. 

 

Will check accelerator pump soon and report back. Should be able to do this myself from under the hood using the throttle linkage, right? I mean I don't really need to be in the truck stepping on the gas pedal plus an assistant. 

[Madkaw]

Pumps don’t have any check valves ? Pumps not priming the circuit properly?Weak pump or check valve.  He level of the fuel in my Weber is pretty low , maybe 4 oz of gas - maybe . The carb is higher than the tank so siphon is possible - at least most of the supply line .

Does your pump come on as soon as the key goes on or only during cranking . 

I run a Carter pump from a RX-7 thru a regulator . 

[Charlie69]

Every 32/36 I have owned on L and Z motors and even on my 50 Willy's pickup has had this problem the float bowl dries up and the pump has to refill the carb bowl before the engine will start.  Also when you hit the throttle pedal one time it gets the auto choke up on the high idle cam of the carb.  when engine starts idle will be at about 2000 rpm and as the engine warms up the idle slowly drops back unless you hit the pedal again then it will drop off the fast idle lobe of the auto choke cam.  I have never had to pump the throttle pedal on a proper running and tuned Weber. 

 

If you drive the Weber daily you will not experience this dry bowl condition.

Edited January 11, 2020 by Charlie69

[620slodat]

It sounds to me like you need a secondary electric pump. It will need to be flow on fail like the electric pumps on the 90's era Chevy and GMC diesel. These pumps are stock on them, are used as primary pumps, but will still flow fuel if they fail and the pump on the IP needs to take over. The pump probably should be wired so that when you turn the key to start the motor the pump will run, and then shut off when the motor starts and the starter is shut off. Flow on fail so that fuel continue to flow when the electric pump shuts off and fuel will still be pumped by the stock pump.

 

The electric pump is a metal canister like a king sized fuel filter, with inlets and outlets on each end,  so it would be easy to add in line just after the fuel tank. It will need to be wired through a relay that is triggered by the wire that triggers the starter solenoid. I think this would fill the fuel line faster so the stock pump will work quicker and reduce the time the starter is engaged. If you use the pickup/car as a daily driver it sounds like the electric fuel pump won't be needed.

 

Don

Edited January 11, 2020 by 620slodat

[datzenmike]

12 hours ago, Madkaw said:

Pumps don’t have any check valves ? Pumps not priming the circuit properly?Weak pump or check valve.  He level of the fuel in my Weber is pretty low , maybe 4 oz of gas - maybe . The carb is higher than the tank so siphon is possible - at least most of the supply line .

Does your pump come on as soon as the key goes on or only during cranking . 

I run a Carter pump from a RX-7 thru a regulator . 

 

Yes the carb is above the tank but once in the float chamber, the gas can't climb up and through the needle valve above it. The pump has one way valves so fuel should stay in the lines all the way to the carburetor. Most likely the pump valves are not perfect (with age) and over weeks all the fuel, except the carburetor, could siphon back into the tank. Hmmm if this is the case the fuel filter would also be empty. Something I should look at.  Right now I have R-1 carburetors on my L20B and it's the same. It sits for weeks in the winter and it cranks for a long time with the 'choke' on but fires up eventually.  

 

A more rugged in line one way valve should fix this.

 

Yes an auxiliary electric pump would work but only for those who let their Datsun sit weeks at a time. I would wire it to the ignition not the starter, you want several seconds to prime the lines and carb before trying to start. Perhaps a relay connected to the oil pressure sender. Once there is oil pressure the relay turns the pump off.

[TimmyG]

5 hours ago, Charlie69 said:

Every 32/36 I have owned on L and Z motors and even on my 50 willys pickup has had this problem the float bowl dries up and the pump has to refill the carb bowl before the engine will start.  Also when you hit the throttle pedal one time it gets the auto choke up on the high idle cam of the carb.  when engine starts idle will be at about 2000 rpm and as the engine warms up the idle slowly drops back unlees you hit the pedal again then it will drop off the fast idle lobe of the auto choke cam.  I have never had to pump the throttle pedal on a proper running and tuned Weber. 

 

If you drive the Weber daily wtou will not experience this dry bowl condition.

 

Gives me one more reason I don't like these stupid 32/36. Why doesn't everyone run a 38 like the one I had back in the day? Fuel mileage depends on your RIGHT  FOOT. (End rant). 

 

Yeah, I am setting the fast idle cam with the first press of the pedal to the floor. That is working properly after I adjusted the choke. I only meant I tried flooring it 3x gently before starting instead of the usually 1x since it was sitting for 2 weeks. You're right. If you drive it daily it fires up quick. Sits for a week and it takes a while to fire up. Sits for 2 weeks and it's very difficult to fire up. 

[TimmyG]

15 minutes ago, datzenmike said:

 

Yes the carb is above the tank but once in the float chamber, the gas can't climb up and through the needle valve above it. The pump has one way valves so fuel should stay in the lines all the way to the carburetor. Most likely the pump valves are not perfect (with age) and over weeks all the fuel, except the carburetor, could siphon back into the tank. Hmmm if this is the case the fuel filter would also be empty. Something I should look at.  Right now I have R-1 carburetors on my L20B and it's the same. It sits for weeks in the winter and it cranks for a long time with the 'choke' on but fires up eventually.  

 

A more rugged in line one way valve should fix this.

 

Yes an auxiliary electric pump would work but only for those who let their Datsun sit weeks at a time. I would wire it to the ignition not the starter, you want several seconds to prime the lines and carb before trying to start. Perhaps a relay connected to the oil pressure sender. Once there is oil pressure the relay turns the pump off.

 

I will have to take a look at my clear inline filter at the tank before and after starting the truck as well. 

 

Seems like I'm just gonna need to continue to remember to crank her up every weekend even if I don't go anywhere. 

[TimmyG]

13 hours ago, Madkaw said:

....Does your pump come on as soon as the key goes on or only during cranking?

 

Seems like it only come on when starting, not with key ON. I tried priming the system with key ON and I didn't hear anything, nor did it help. 

[datzenmike]

It's governed by the fuel pump relay and needs certain conditions to be ON.

 

TWO CONDITIONS

1/ It can be on with the  key in the START position

2/ With the key in the ON position it can only be on if there is oil pressure OR alternator output. Basically the engine must be already running to keep it on.

[TimmyG]

4 hours ago, datzenmike said:

It's governed by the fuel pump relay and needs certain conditions to be ON.

 

TWO CONDITIONS

1/ It can be on with the  key in the START position

2/ With the key in the ON position it can only be on if there is oil pressure OR alternator output. Basically the engine must be already running to keep it on.

 

Makes sense. This is what i have experienced with mine. Fuel pump is working normally. 

[Charlie69]

When my truck sits for a while and I suspect the fuel bowl is empty I turn my switch barely into the start position and I can here the fuel pump come on but this does not engage the starter, I keep the key in this position for a few seconds to fill the fuel bowl, I release the key and hit the throttle pedal 1 time to set the choke and I start the truck.  This prevents the dry bowl cranking.

Edited January 11, 2020 by Charlie69

[DanielC]

In winter the gasoline formula changes, to have more volatile liquids.   The more volatile formulas run better in cold temps.  But they also evaporate quicker leaving the float bowl emptier, and what is left behind is less volatile and is harder to vaporize, and run the engine .

Easy solution, start the engine more often.

[Crashtd420]

If you dont like cranking it so long to get fuel to the carburetor, how about simply adding a momentary push button switch and a relay to temporarily power the fuel pump.... 

Push the button to activate the pump and fill the carburetor .... start the truck and the factory relay works as normal...

[620slodat]

This may be the best solution. I didn't realize these motors had an electric fuel pump stock when I suggested an aftermarket electric pump. A momentary switch for the stock electric pump and bypassing the stock wiring would be an easy solution.

 

Don

[datzenmike]

Connect a momentary switch between the L (Nissan for BLUE) and the White/Black stripe wires on the fuel pump relay. The relay is just above the right (passenger side) kick panel beside the glove box. It's a black box. This will give you pump operation when the ignition is on

 

 

[TimmyG]

Definitely a few good ideas here! I have confirmed the accelerator pump is working. It squirts gas into the carb every time. Visually confirmed 5 squirts in a row....just because. 

 

Might try Charlie's method before I decide to wire in a momentary switch. Both are great ideas. I'll have to see if my ignition will allow me to lightly access the START position without the starter engaging like Charlie said. 

Edited January 12, 2020 by TimmyG

[Madkaw]

On 1/11/2020 at 11:04 AM, TimmyG said:

 

Gives me one more reason I don't like these stupid 32/36. Why doesn't everyone run a 38 like the one I had back in the day? Fuel mileage depends on your RIGHT  FOOT. (End rant). 

 

Yeah, I am setting the fast idle cam with the first press of the pedal to the floor. That is working properly after I adjusted the choke. I only meant I tried flooring it 3x gently before starting instead of the usually 1x since it was sitting for 2 weeks. You're right. If you drive it daily it fires up quick. Sits for a week and it takes a while to fire up. Sits for 2 weeks and it's very difficult to fire up. 

 Not sure a bigger carb is he answer. Not sure the 38 would have a larger bowl. The 32/36 is more than adequate on a stock motor if jetted correctly. 

 

Edited January 13, 2020 by Madkaw

[datzenmike]

On 1/11/2020 at 8:04 AM, TimmyG said:

 

Gives me one more reason I don't like these stupid 32/36. Why doesn't everyone run a 38 like the one I had back in the day? Fuel mileage depends on your RIGHT  FOOT. (End rant). 

 

 

 

 The 38/38 is a six cylinder or small V8 carburetor, so too big for a 4 cylinder engine. Sure it will work, if you learn how to 'step into it', (the 32/36 is the same way) but engine will display all the symptoms of being over carbureted above idle and at low speeds. It would work better on a larger displacement Z24 than an L20B. The 32/36 would work better on an L20B than an L16 and so on.