Fuel pump control unit/relay

[matrophy]

Lately I've had to crank the starter several cycles to get gas to the fuel bowl. I wasn't really paying attention but I seem to recall that when I turned the key to 'on, you could hear the relay buzzing/clicking which I guess meant that the fuel pump was pumping gas to the carb before the key is turned to 'start'. If that's true, then is it possible that the relay has malfunctioned where it allows the pump to operate with the the key at 'start' but not at 'on' like I think happened before?

[weldingrod]

My carb is hooped, leaks among other things but I find if I turn ignition on (I hear the pump clicking) for a minute or so, then pump the gas a couple of times, it starts right up. sounds like a carb problem but this will hopefully solve your day to day issues until you can deal with it.

[matrophy]

Thats' what I'm thinking - that the ignition 'on' doesn't turn the pump on any more - only with 'start' so I have to crank the starter several cycles before I pump the accelerator to squirt fuel into the carb. Trying to figure out if it the pump relay is somehow gone bad

[datzenmike]

You don't need the pump on, to start the engine. This isn't EFI. The carburetor holds half a cup of fuel in the float chamber from the last time it was running.... more than enough to start the engine and drive down the block.

 

Look at the sight glass on the front of the carburetor, gas should be at the half way point. Take the top off the air cleaner and hold the choke open. Have someone pump the gas pedal. You should see the accelerator pump squirt gas into the primary side. If no gas or weak stream then the accelerator pump needs replacing.

[matrophy]

It's a Weber so no sight glass but I'll check the acc pump before turning the key to see if there is fuel pumping OK.

 

So - what is the noise that the pump and/or relay makes when the key is 'on'?

[datzenmike]

Is it coming from the fuel pump relay? or one of the other relays just below it? Clicks once or chatters???

[matrophy]

It's not making any noise now but I "thought" it was the fuel pump relay working normally before but I think that may be a red herring. 

 

 

 

[datzenmike]

Again, a click or continuous chatter?

 

The auto choke heater relay is actually above the fuel pump relay. The auto choke relay will chatter is the battery voltage is low.

 

There is also an interlock relay if you have an automatic.

 

 

1/ If ignition turned on and engine not running the fuel pump is OFF.

2/ During start the fuel pump is ON

3/ Ignition ON and engine running... if there is loss of either oil pressure or the alternator stops charging, (oil light OR charge light ON) the fuel pump should be OFF. This shuts the fuel supply off in the event of an accident to prevent fuel spillage.

[Stoffregen Motorsports]

Weber DGV can have a fuel cut solenoid. I suppose it could make a clicking noise. Probably not a buzzing noise though.

[matrophy]

We got off track here a little. I thought I remembered hearing a weird buzzing/clicking with the key on early on and was told recently that it was the fuel pump and/or relay that was on before starting the engine. 

 

  That appears to have been a myth and not the cause of my difficult starting.

 

 The original issuse is that I have to crank the engine several times before pumping the accelerator and getting the engine to start.

 

I'll check that there is fuel in the bowl after the vehicle has been sitting and check the accelrator pump output.

[datzenmike]

If everything is working properly, when starting a cold carburetor equipped engine, step on the gas once and release to set the choke, then use the starter. If it gets colder out try two steps on the gas pedal and if really cold 3 or more. This pushes the accelerator pump to squirt raw fuel into the carburetor and intake for an initial richer start mixture.

 

If engine is warm just use the starter.

 

If you are having trouble starting a cold engine make sure the choke is working as it should.

[Thomas Perkins]

I have a Weber and it runs perfect.Here is a good video on how to set your fast idle speed.It's for your cold start everyday.But once it has been driven for the day,you don't have to do this.When I get off work everyday,I just turn the key and it fires up,never press the gas pedal,and it idles at 1100 rpms,then I can just drive off  or set for a minute or so and tap on the gas pedal again and it will go to 850 rpm's and it will idle at 850 rpm's when I am at a stop light,that is what I have it set at.You can do this hot or cold,if you do it hot,you do it like he did it with your hands,when cold,you just press gas pedal to lock in cam and it will fire up,set it at 2000 rpm's,just cut it off and make adjustment till you get it set at 2000 rpms.I use a idle cut off solenoid cause mine won't stay idling without it.Are you using the blue wire to your choke.

 

Edited October 21, 2022 by Thomas Perkins

[matrophy]

Can I clarify what choke working as it should means?

 

Right now, When cold -  I step on accelerator and choke snaps shut

When it finally starts after cranking several times - regardlesss of weather - it runs at 1500 rpm

After a few minutes, a blip on accelerator drops idle to 550 rpm-ish suggesting that the high idle setting is correct

Choke ultimately opens right around normal operating temperature

 

When warm, engine starts right away with no accelerator pumping

 

Am I missing anything?

[Thomas Perkins]

1 minute ago, matrophy said:

Can I clarify what choke working as it should means?

 

Right now, When cold -  I step on accelerator and choke snaps shut

When it finally starts after cranking several times - regardlesss of weather - it runs at 1500 rpm

After a few minutes, a blip on accelerator drops idle to 550 rpm-ish suggesting that the high idle setting is correct

Choke ultimately opens right around normal operating temperature

 

When warm, engine starts right away with no accelerator pumping

 

Am I missing anything?

It needs to be at 2000 rpm's,then when you tap on gas,after 10 seconds,it should go to 1100 rpm's,then wait a minute or so and tap on it again and your's should go to 700 rpm's on your 2 wheel drive,mine is 4 wheel drive so setting is higher,also adjust your idle screw to 700 rpm's

[matrophy]

5 minutes ago, Thomas Perkins said:

I have a Weber and it runs perfect.Here is a good video on how to set your fast idle speed.It's for your cold start everyday.But once it has been driven for the day,you don't have to do this.When I get off work everyday,I just turn the key and it fires up,never press the gas pedal,and it idles at 1100 rpms,then I can just drive off  or set for a minute or so and tap on the gas pedal again and it will go to 850 rpm's and it will idle at 850 rpm's when I am at a stop light,that is what I have it set at.You can do this hot or cold,if you do it hot,you do it like he did it with your hands,when cold,you just press gas pedal to lock in cam and it will fire up,set it at 2000 rpm's,just cut it off and make adjustment till you get it set at 2000 rpms.I use a idle cut off solenoid cause mine won't stay idling without it.

 

Hi, I have watched this video a few times and I feel that I have my high idle set correctly - Initial idle is at 1500 rpm and drops to 75-ish with a blip of the accelerator and idles at 750 from then on

[Thomas Perkins]

46 minutes ago, matrophy said:

Hi, I have watched this video a few times and I feel that I have my high idle set correctly - Initial idle is at 1500 rpm and drops to 75-ish with a blip of the accelerator and idles at 750 from then on.Try adjusting it to 2000 rpm's.Mine is set that way.Just like the video,drops to 1100 rpm's and then idles at 850 rpm's.It may help with your cold start up.Send a picture of your Weber set up.Are you using the stock Nissan fuel pump.I am.Also check all your fuel hose fittings to make sure you have no leaks,you have 2 by the starter,i had one leak there.I have replaced all my hoses starting at the gas tank.I think the rubber hoses are 5/16.Also had one leak at the fuel pump,it effected the start up.That is when I replaced them all with new clamps.Also change the fuel filter.I am a type of person,if my engine makes a wierd sound,I get my Sherlock Home's magnify glass out and find out what's going on.

 

Edited October 21, 2022 by Thomas Perkins

[matrophy]

I'm the same way. Probably a little OCD when it comes to my truck. Stock fuel pump with new filters all around in the past 2-3000 miles as well as an inline filter before the Weber. I had a tiny piece of something caught in my idle jet which took me forever to find so I added an extra filter. Fuel pump pressure when I checked it was 3 psi-ish. New fuel lines/clamps all around as well. I'll look at my fast idle to see where it is on the lobe and maybe go in half a turn or so. I rewatched the video and didn't realize that the high high idle should only go 10 seconds or so. I haven't tried kicking it off that early which I'll do. Appreciate the help.

[datzenmike]

1 hour ago, matrophy said:

Can I clarify what choke working as it should means?

 

Right now, When cold -  I step on accelerator and choke snaps shut

When it finally starts after cranking several times - regardlesss of weather - it runs at 1500 rpm

After a few minutes, a blip on accelerator drops idle to 550 rpm-ish suggesting that the high idle setting is correct

Choke ultimately opens right around normal operating temperature

 

When warm, engine starts right away with no accelerator pumping

 

Am I missing anything?

 

No that's fine. Stock carburetor is 1,800-2,200. This is designed to warm up the L series the fastest. If running a standard you don't need to kick the idle down just drive away. If the choke is warm enough it will release automatically while driving and less chance of stalling at a stop.

[Thomas Perkins]

1 hour ago, matrophy said:

I'm the same way. Probably a little OCD when it comes to my truck. Stock fuel pump with new filters all around in the past 2-3000 miles as well as an inline filter before the Weber. I had a tiny piece of something caught in my idle jet which took me forever to find so I added an extra filter. Fuel pump pressure when I checked it was 3 psi-ish. New fuel lines/clamps all around as well. I'll look at my fast idle to see where it is on the lobe and maybe go in half a turn or so. I rewatched the video and didn't realize that the high high idle should only go 10 seconds or so. I haven't tried kicking it off that early which I'll do. Appreciate the help.

You don't need that extra fuel filter,you have a super fine one inside the Weber that nothing will get thru unless it breaks the plastic filter.Mine is 6 years old and never ever had anything trapped in it.Just the big bolts smashes it in.My first Weber was a north American Weber which had the black choke on it,,came with a idle cut off solenoid.I have replaced my gaskets,and clean the inside a while back.Mine has never stalled.In the morning. I kick it down,it goes to 1100 rpms and 15 minutes later I am at work making printing plates.I have work there 30 years and my Nissan has got me there 28 years.Oldest and best vehicle in the parking lot.When you take the big air filter off,stuff can get in there.I clean mine with Dawn soap and warm water.I just looked,under the drivers sun visor, there is some writing which says after starting,wait 30 seconds then press your gas pedal.

Edited October 21, 2022 by Thomas Perkins

[matrophy]

On 10/21/2022 at 2:42 PM, Thomas Perkins said:

It needs to be at 2000 rpm's,then when you tap on gas,after 10 seconds,it should go to 1100 rpm's,then wait a minute or so and tap on it again and your's should go to 700 rpm's on your 2 wheel drive,mine is 4 wheel drive so setting is higher,also adjust your idle screw to 700 rpm's

Update: After rewatching Thomas' attached video, I got to thinking that my fast idle set to run at 1500 rpm may not be high enough so I tried increasing the fast idle setting probably 1/2 a turn and now it fires up right away after 2 pumps of the gas pedal before turning the key.