Triple carb install = won't start!!??

[EricB]

I've checked for spark by arcing one of the spark plug wires to the shock tower bolts - that works fine.

I've checked for fuel - pulled off all three weber dcoe 40 covers and looked inside and the fuel level is identical in all three and pictured below.

I've tried to start the car while pumping gas and it overflowed a bit, leaking a couple drops out from where air horn goes into carb body - let it sit and tried and again and did not work.

starter is cranking over normally

engine is turning because i do hear air exiting out of my header (yes I am running only header for right now).

I had the full '73 flat top su shenanigans on there up until last night when I yanked them off.... the only two wires that were plugged up then but no longer are now are the backfire valve and the XXX??? valve (see pic below also...)

Any clues?

Does it just take a long time???

All main jets, idle jets, pump jets, accelerator/discharge valve, needle valve, and matching gaskets are brand new - as for size of each item I went with what Alan (HS30-H) recommended on my totally stock L24.... I don't remember all the sizes by heart but I can sure look them up and post if needs be....

Clues?

Here come the pics:

[EricB]

here's pic 2

[EricB]

here's pic 3

[EricB]

here's pic 4

[Phred]

Eric,

After cranking, check all spark plugs to see if they are all the same, i.e. gas fouled or dry. Also, with a mirror & light, look down each carb to verify each squirter/accelerator pump is functioning. While peeking down there make sure all throttle plates are opening equally. It won't keep it from starting, but I didn't see any Isolator 'o' ring plates between carbs and manifold. These are part of a mount kit which keeps the carbs isolated from engine vibrations, which keeps the float level from splashing fuel up into the air corrector jets which causes flooding, and poor performance. Let us know what you find. good luck.

Phred

[Mike]

Also check all of your electrical connections to make sure you are getting low voltage through the system. I've accidentially disconnected a single wire at my resistor and the whole car wouldn't start.

Of course, you did say that you have spark. So, that might not be your troubles.

Go back to the basics.

1) Fire (electrical)

2) Air

3) Fuel

Does it just continue to spin over or does it try to kick every now and then?

If it doesn't kick at all then you are missing one of the 3 key components above. Because if there's fuel in the cylinder, then the spark will ignite something.

Put it this way... fuel is getting TO your webbers, but, is it going from the webbers into the engine?

Have you ever worked with Webbers before?

PS: You'll want to check into getting a heat shield to help reflect the heat away from the bottoms of your webbers. The heat from the headers can get pretty hot and it just rises up and will affect the performance of your carbs.

[EricB]

Phred...

By "isolator o=ring" do you mean a plastic spacer with a rubber ring washer on either side? yeah they came in the box of used parts but I do not have them on... i just have a paper weber gasket between each carb and the cannon manifold....

The carbs are held to the manifold by 12mm nuts with funky spring looking washers - not the usual split locking ones - I thought that would be enough?

Does the fuel level look correct?

Mike - like I said the only two wires I have unplugged are the backfire valve and the other valve pictured above (emissions?)

All jets are brand new and if I pump the accel pedal too much i get a little dribble out of the velocity stack on carb #2 and carb #3 so gas is making its way out of the accel pump/jets...

I have checked out that the butterflies open all the way with the gas pedal pressed all the way down and that it closes all the way with the pedal depressed.... should i be feathering the throttle at all when trying to start the car with triples??

I'll pull each sparkplug and look at it - last time I did - 2 weeks ago - they were all in perfect shape (they're NGKs not that it matters)....

New fuel filter too I've installed.

Oh and the only Weber book I have is the Speedpro Weber DCOE/Dell'Orto DHLA one - and the only thing they tell me about starting is to back out the idle mixture screws 1 and 1/4 turns from fully seated which I have also done...

And yes this is my first ever set of Webers...

-e

[EricB]

Another thing....

look at the 4th picture down... go straight back (towards the valve cover) from where the jets are on any of the three carburettors... see that lever that is poking up and to the right (ie towards firewall) it looks like it should have a wire?? or something going through it which would then pull it forward (towards the radiator)...

lemme see my weber exxploded view....

brb....

oh yeah it's called the choke cover.... :stupid:

is that supposed to be hooked up? how? they are REALLY hard to move.... should they move freely? should they be moved towards the radiator (ie forward) for the car to start? why did I think webers did not need chokes????? How do you hook them up?? i know, I know.... lots of questions.....

-e

[EricB]

this is the last post for a while (i promise) as i have to go to a wedding this afternoon....

Mike to answer your other question, the starter spins the engine freely but the engine gives no sign of wanting to start - it doesn't stumble and die at all.... it just doesn't start period.

PS: out of the blue question: do triples need stronger than stock spark to work? do i need to invest in an aftermarket ignition??? I know it is RECOMMENDED but do I NEED it to run ??

-e

[HS30-H]

Hi Eric,

First of all I think you should calm down a little and stop worrying about updating your ignition system. If it was fine before you fitted the Webers, then it will still be fine now. However, those "mysterious" left-over wires need to be put out of the equation somehow. Not having seen a Z with all the Californian smog-control equipment, I am afraid I cannot advise you what to do with those wires. However, if you have a spark at the plugs then they should not be affecting things too much.

Second thing to do is to take off the carbs and install some "proper" o-ring equipped gaskets ( one of the most popular brands being called "Misab plates" after their maker ). The people who supplied you with the jets should be able to supply you with these. Please do not try to re-use the old ones, unless they are in TIP-TOP condition. As you have been advised - these are necessary to stop the carbs from "foaming", which is something that the DCOE style of Weber is rather susceptible to. This will not stop your engine from starting, but they need to be on there and you might as well do it now as it will change all of your throttle-stop and linkage positions when you space them out. These will also help you to ensure that you have not got a massive vacuum leak on the joint between carbs and manifold.....

Those funny washers are also mandatory; they will help you to avoid overtightening the carbs on the manifold. You might not believe it, but the Webers need to "move" on the manifold, or at least have a little "give", so that those o-rings are allowed to do their job and isolate the carbs from frequency-induced foaming of the fuel in the float bowl. The "Cotton Reel" type of rubber washer seems more common here in Europe these days ( a rubber cotton-reel shaped washer with a cup washer at either end ). Again, this is to help you to avoid overtightening the joint between carb and manifold. Whatever you use, make sure that you do not tighten all the way.......

Third thing to do is to resolve a question regarding the "Starter Devices" on the carburettors. Some people refer to these as the "chokes" - but in fact the chokes on the Weber DCOE are the removable venturis that govern the amount of air that the carb sucks in ( you will remember that I advised you to keep them down to about 30mm or 32mm for an other-wise stockish L24 ). The "Starter Devices" are on the manifold-side of the carbs, and you will see a little lever with an arrangement for attaching a cable to pull them into an "on" position ( ie: choke "on" for starting ). Unfortunately for us and our Nissan / Datsun "L-series" engine, these need to be pulled toward the FRONT of the car to engage them - and consequently the stock choke control cable is difficult to utilise without having a long looping curve on the cable. NEVERMIND, as in California you really ought not to need to have the Starter Devices operational at all. Here in the rainy and cold streets of London, I used to use a 40DCOE-equipped L24 every day for a few years. Just two pumps on the throttle pedal was enough to start the car from cold, with just a light feathering of the pedal for the first thirty seconds or so being enough to give me a good idle. So, you do not need to have the Starter Devices to be operational, BUT the fact that you have mentioned that you can hardly move them is most worrying indeed. The lever operates two pistons, lifting them off their seats to reveal the starter circuits. If these pistons are stuck in the "off" position ( ie: seated at the bottoms of their bores ) then it would be OK - the carb would work normally. However, if they are even just slightly off the seat, or one of them is, then it will cause you grief in tuning the carbs. If I were you, I would take off the Starter Device covers and investigate fully why they are not moving. They may be gummed up with old fuel and black deposits, and they DO stick. The pistons are made of brass, so be careful with them; if you scratch or score them they will be even worse.

The fact that you mentioned that the Starter Devices are seemingly stuck makes me worry whether all is well with the provenance of the carbs. They look very clean indeed ( I am sure that you cleaned them etc ) but did you go RIGHT through them? Did you fit new springs to the Accelerator Pump Rods ( attached to the butterfly spindle )? The Starter Devices are right next to these, and I am sure that you must have seen them.The pistons need to be removed and the bores cleaned right out to make sure of doing the job 100%. The operation of the Starter Devices can be tested with the carbs off the car. They should be quite free, but you should feel a little resistance as the pistons push against their springs as they come off the seats.

When you pump the throttles ( by hand is best, with your head and eyes down the throat of the carb so that you can see the jet end exposed where it comes out into the venturi ) can you see the pump jets squirting fuel? I would be inclined to manually test them individually when they are off by putting some fuel in each bowl and pumping the throttle. Are they squirting neatly and evenly with a nice sound? If they are, then the engine really ought to start at least. Running at idle is another matter.

Did you rebuild / recondition the carbs yourself?

Your fuel level in the bowls looks OK - but that is no way to measure them. You really need to set the float-height accurately as per the diagram in the Weber gasket kit. You need to bend those tabs on the float for both open and closed positions. Float height and consequently fuel bowl level is VERY sensitive on the Weber DCOE. Please do not underestimate this. The Webers are precision measuring devices, and will not tolerate any inaccuracy in set-up. You have the "old" style brass floats, in keeping with your "old" style "flat-top" pre-emissions DCOEs ( thats good ), but they can be fiddly to bend the tabs up and down on.

Taking out your spark-plugs will of course tell you whether you are flooding the engine ( causing it to be reluctant to start ) or not getting any fuel in at all. I would have thought that something quite simple ( and hopefully easy to fix ) is wrong, as you really ought to have the occasional "kick" from at least one or more cylinders as they try to fire. Stupid questions such as firing order ( did you take off the spark-plug wires when you fitted the carbs and manifold? ) should be eliminated of course.

Lastly, and this should have nothing to do with your inability to start the engine, I would advise you to think about an electric fuel pump and deletion of the return pipe to the tank. Mine was all the better for this ( the Webers need a constant PRESSURE - not necessarily a constant flow.... ) and you will find that there might be instances when your stock mechanical pump cannot keep up with demand. You will notice this especially on starting, as you will have to keep on cranking the starter to pump fuel up into the fuel bowls ( they tend to drain down, due to evaporation caused by a hot engine as much as anything else ). Remember that your return line to the fuel tank is lowering the PRESSURE at the carburettor inlet valves. The Webers would prefer about 3 to 5 PSI constantly, which your stock pump will not always be able to supply. Again, not necessarily related to your non-starting woes - but worth thinking about.

Don't start pointing the finger at things that you think might be culprits yet ( such as the jet sizes etc ) as I can assure you that you are well in the ball-park there. You might also like to back out those mixture screws a little more than 1 or 1 and a quarter turns; maybe two or two and a half from the seated position, as long as they are all the same. The final adjustmant will take time and you may not be happy at first..............

I would certainly sort out the O-ringed gaskets and Starter Devices questions first. Shame I can't just jump in my car and come over, as I feel it would be MUCH easier that way!...

Sorry for the long post....

Good luck,

Alan ( HS30-H )

[HS30-H]

Sorry, I just noticed something from your photos.

I can't quite make it out ( maybe tired eyes ) but how have you connected the fuel supply for each carburettor? I can see the "front" two have got hoses on them individually, and I presume that the third one has too - but what are they connected to?

If you are using your old standard-spec. metal fuel-supply rail, then it only has two OUTlets for the old SU carbs. The other ( smaller diameter ) pipe is the return to the tank. I am worried that the final carb is connected to the return pipe - I hope that I am wrong.

Anyway, you might like to try blocking-off the return pipe until you get the problem sorted, as if it is still operational it is losing you fuel pressure from the stock mechanical pump.

With a single electric pump rated at around 3 to 5 PSI, you would be able to delete the stock fuel rail and use either the NISMO fuel rail for triple carbs ( three outlets and no return ) or run your own flexible fuel pipe from the pump or filter up to the carbs. As long as the pump pressure is not too high then you would not need to have any return pipe whatsoever ( but you need to block the return to the tank, otherwise you will get a fuel leak if you overfill the tank or park on a slope.... ).

Good luck,

Alan. ( HS30-H )

[benn9090]

A.) Try removing and plugging the vacuum advance. Make sure your brake booster vacuum line does not leak.

B.) Take the 2-6 plugs out, ground plug #1, crank the engine and check the timing.

C.) Hotter ignition helps, yes. My Webers would not start on the stock igntion, but would start with a Jacobs aftermarket unit.

Just finished Weber install, definitely not sorted out yet, but it DOES start and run,

Mark