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

[benn9090]

Oops, forgot something - those 2 wires are meaningless. They are the EGR solenoid 12V output and ...uhhh .... I don't remember what the other one is. They output 12V based on the thermo switch. Just insulate them.

[spudz]

Hi Eric,

Some people will shudder when I say this,

but try a squirt of starting fluid into the

carbs. Just a small squirt to see if it will

fire. If it does fire on start fluid then

more in likely it is something in the carbs.

Mike

[Phred]

Eric,

I've been rebuilding and tuning Webers for years, And I agree with all that Alan (HS30-H) said. For parts and expert advice in your area. go to: www.piercemanifolds.com

(408) 842-6667

Gilroy, Ca.

Order: Isolator kit #99005.146 (3ea.)

Phred

[EricB]

thanks for all your replies guys....

i'll answer all as best and concisely as i can.

i'll first check the condition of the set of isolators I got before i order more - incidentally it is from pierce that all my rebuild parts came from....

ben9090 sure i can check timing on it again to be sure...

alan the fuel rail that came with the triples was steel as per stock but of course with three outlets, i don't think it was the nismo unit you mention because it does have a fuel return end as the stock SU fuel rail does.

also alan: yes the spark plugs are in the correct order - i did not remove them during the install

and yes i did take them apart myself, clean every item i could get my hands on with fuel/carb cleaner before re-assembling... i tried to make some progress with the choke cover/starter devices but didn't get very far...AND since I found nothing specific about them in my literature I didn't bother with them all that much... guess I'll go right back to them then....

PS: If all else fails, does any one recommend a Weber go-to person/shop in the LosAngeles area I could take them to for a more qualified opinion then my own?

-e

[Mike]

Eric,

Check one more thing for me. Did you remember to put the rotor back in the distributor? Been there.

I'm skeptical because you are getting absolutely NO kick over at all. Remember to check for the basic necessities. How about starting fluid? If you squirt some of that in the intake, does it try to sputter up? It should. If it doesn't then you have some other problems.

Timing is also key here. If the distributor isn't kicking a spark to the cylinder at the right time then it just won't work.

This might be difficult to do, but, set all of the spark plugs out of the engine on a table next to your Z. Don't disconnect them, but, try to crank the engine and look for the proper firing order. I don't remember it off the top of my head, but, it might be 1,5,3,6,2,4. Please double-check that.

Oh, one more thing, pull the fuel supply hose and crank the engine... does fuel shoot out of the hose?

When you're done with this whole thing... you'll realize that it's the SIMPLEST answer. So, don't go out and buy anything new parts yet.

PS: I also agree with Alan and think 1.25 turns out might not be enough to get it started. Try to loosen them another turn. It might be too much, but, maybe they aren't working right? Just an idea.

[EricB]

Ok here's what is new:

first i pulled off the top covers and re-checked the range of motion of the floats. I am SURE I have the droop set to 15mm on all three. I will admit to having trouble setting the closed value to 7.5mm (in point of fact I think they hover more around 5mm)... which leads me to the first set of questions:

_ to set the floats at the right droop you bend the tab which hits the needle right, and to set the right closed value you bend the brass arms the floats are at the end of, right? or vice-versa? do you guys have a good trick for bending the requisite pieces?

second I forgot to mention that my car came with an aftermarket external electric fuel pump located outside of the tank (it actually hangs underneath the car betweent the tank and the spare tire well) so there ought to be no fuel pressure problem

third with the covers still off i made a little experiment with the accessory power on (and fuel pump on of course) to see if movement of the floats did correctly allow fuel to flow into the bowls - no problems there whatsoever.

while i was at it i also checked over what Alan called the "starter devices". They were indeed stuck in the off position. The front two carburettors were stuck much more than the last one. Well I got them loose and moving relatively smoothly. After doing so I pushed them back to their off position (towards the firewall, not towards the radiator)

then i refitted the covers and turned the accessory power back on and with mirror and flashlight watched down the the bores of each carburetor what happened when i turned the throttle open by hand. Here's the first WEIRD thing which to me indicates that I do not understand the functioning of my Webers very well... If I waited long enough with the fuel pump working then I would eventually get quite a bit of fuel dribbling out of the "jet" (correct name?) inside the chokes of each barrel of the front two carburettors. The back one did not have this problem provided I didn't pump the throttle arm. So let me make this crystal clear: with the electric fuel pump doing its thing, and if you wait long enough, and you do not touch the throttle, fuel will drible out of the jets inside the chokes of both barrel of each of the front two carburettors.

I think that because of the amount of fuel dribbling in these two the car would not start because it would automatically flood itself the minute I pressed on the gas.

So i got a can of starting fluid as was recommended by both Mike's. I sprayed that into all three carbs and tried to start the car again. It almost INSTANTLY came to life and boy was it LOUD...

BUT: I had to almost immediately shut off the engine because the revs came up very very fast and almost instantaneously.... I tried a couple more times and the same thing happened. I don't think it was because of the ether (starting fluid) alone... What I think is happening is that the ether helps it kick over but then with all the fuel dribbling out of carburettor 1 and 2 the engine wants to go to wide open throttle right away... I shut it off almost immediately on all three occasions because the revs in those couple seconds showed NO sign of slowing down or petering off... If I left it on I was afraid it would rev to god knows where and drop a valve....

So.....

(sorry for the ultra-long msg)

I understand the needle valve along with the floats regulates how much fuel is in the bowls at any given time. I understand the main jets get their fuel from the bottom of the well, below the bowls. But how does opening the throttle make the main jets squirt fuel into the barrels then and only then? Vacuum? And is the fact that I am getting this dribbling problem a result of the fuel level in the bowls of carb 1 and 2 (my floats' closed position not being set correctly) being too high???

Thanks a mil friends,

-e

[benn9090]

E-

Skimmed your message very very quickly, but in regard to your fuel dribbling, I suspect your fuel pump may be overpowering the Weber's float valve with too much pressure. I believe the books will recommended you use 2.5-3.5 psi, and the typical way to do this is with a fuel pressure regulator. The regulator is a chrome dial affair, adjustable from 1-5 in .5 psi increments - should cost about $28, brand names are Purolator or Fuel-Pro.

I am a few steps ahead of you in the same process - my Webers are installed and running, but I have to get the @!#$% brakes working before I can do any serious road testing and jetting.

FYI, if you decide to tear down and rebuild, I found that Pierce Manifolds had the best prices on rebuild kits.

Regards,

Mark Bennett

'74 260Z

'85 Supra

'93 Supra TT

[72zcar]

Maybe you have the linkage set to full throttle... i don't have webbers but i did manage to get the linkage reversed one time(that was enough) on my su carbs so when it started it was full blast... no fun

[HS30-H]

Hi Eric,

Well at least you got it started with the spray - so now you know you can narrow it down to carb trouble........

Sounds very much to me like you do indeed have carb float level problems and / or problems with the needle valves. Benn9090 has a good point about fuel pressure regulators, and I did not mention about these because I thought you were using the stock mechanical pump. As he says, they are the best way to make sure that you are not over-pressuring the fuel supply at the needle valves ( they CAN be overcome and flood the carb ).

In my experience, about 4psi pressure right at the needle valves is not enough to overcome them and will help to ensure that you still have enough pressure at high rpm and times of high gas use like climbing a steep hill. Don't get this psi rating mixed up with flow rates - which are a different thing altogether.

I honestly think that a Bendix-type electric pump ( which are usually rated at around 5 to 6psi I think ) situated near the tank would drop enough pressure down the length of the fuel line to only give you around 3 or 4psi at the needle valves. Added to this, you are using that special three-outlet fuel supply pipe with a return pipe still connected - which would certainly be acting as a sort of fuel pressure regulator anyway. So, I don't think you have a problem of too much fuel pressure per se - but you might like to eliminate it anyway by installing a fuel pressure regulator. My current car does without one, and runs a Mitsuba pump rated at 4psi with no return to the fuel tank.

While you are ticking off possible causes of problems, you might like to check out any identification on that electric pump body to see if it is indeed the Bendix-patent type, and not something with a high pressure rating ( like the type of pump on an injected car ). I think its very unlikely, as your car was running fine with the SU carbs that were on it before.

The float level is the most likely suspect, and at this point you can concentrate on the setting for the float when it is shutting off the needle valve - ie when the float is high. This is where you might find that your needle valves are not shutting off, and fuel is leaking into the overflows and into the inlet tracts at the back of the butterflies. If you turn on your ignition ( electric pump "on" ) without cranking the starter, and fuel is leaking / dripping anywhere then TURN OFF and get to the bottom of the problem. The carbs should be DRY and not dripping / leaking unless you are cranking the throttle. The vacuum of the engine draws fuel and air through the jets, and you should not get any fuel dripping unless you are activating the accelerator pump jets by cranking the throttles / accelerator pedal. Even then it would take a real lot of pumping to get a real dribble going, so I reckon you are still looking at a needle valve / float setting problem. You might like to try setting the tab on the float to shut off the needle valve whilst you are blowing into the fuel pipe for that carb ( you will need four hands to do this ) and then measuring the gap at the point where the flow stops and you cannot blow anymore. You can bet that the tabs will need to be bent so that the fuel flow shuts off when the float is "lower" ( as its shutting off too high at the moment ).That "blow-through" test is a good way to make sure that your needle valves are working correctly anyway ( and that you remebered to put the aluminium crush washer between the needle valve body and the carb top cover ).

If this still doesn't work, and you still have fuel leaking out of the carbs with the fuel pump switched on, then I do not know what to suggest apart from taking all three carbs off and stripping them completely to make sure that they have not been mis-assembled or have parts missing. You can never trust an unknown previous owner not to have messed with them, and if its your first time to strip and clean a set of DCOEs ( I don't know how far you stripped them, and I'm hoping you did not have any parts left over ) then you would have to admit to the possibility of human error. It sure took me a long time to learn about them, and I made plenty of errors along the way................

Did you put the proper o-ringed gaskets between the carbs and the manifold yet? I am presuming that you did this by now.

PLEASE be careful of fire. It is so easy to get one started with fuel leaking and live electrics nearby.

Good luck and KEEP AT IT! You will feel like a million dollars when you get on top of it.

Fingers crossed for a good result,

Alan T.

[byunique]

I have had those o-ring gaskets and one thing I want to say is once you get them in there and torque it down. If you ever take it apart, the rubber o rings no longer fit into the spacers. You really have a heck of a time re-assembling it. I bought HKS solid spacers, very costly, they are brown and made of phenolic. The have gaskets on both sides and are solid so you don't create further problems with the carb linkage. Having orings in there causes the carb to manifold interface to be not so solid.

Like your pics show, you are running the system w/o air cleaners? I had a similar problem as yours at one time because I had installed the ITG filters on incorrectly blocking the floatbowl breather holes. That allowed the car to turn over but not run more than a couple seconds.

If you install a electric pump, get a good one. Those cheap things from Kragen burn out every year or so and leave you stranded. I opted for using a old Mazda RX-7 pump, mounted inline near the gas tank. They are low psi and you can get them from the junkyard for $10 a piece. At that price, get two and have spare.

A pump like that you can run w/o a regulator as I have done but it is always better to be precise as possible with a regulator.

[benn9090]

Got around to reading your questions more carefully - as for setting the float level, I try not to bend the float arms themselves much at all, but only the tabs. I take the float off and bend the short arm (for the level) and the long arm (for the droop) toward each other just a little too far, then I put the float back on the lid and flex things around until it matches the specs. I used drill rod of 5/16 (level) and 9/16 (droop) because I don't have metric drills. With these I iterated back and forth to set the levels. I takes perhaps 5 minutes per carb if you remove the lids and work on a nice bench.

My carbs are brass-float 40DCOE18s on a Cannon manifold. All the jets and other calibrated parts match what the Haynes Weber book lists as the parts included with the stock Weber conversion kit.

Engine is L26, mild port/polish on E88 head, mild Schneider 274 cam, N42 280Z exhaust manifold and head pipe only (like you, I do not have the exhauist fabbed yet).

I have the stock 260Z fuel rail (2 outlets) and I have the return line hooked up. Alan seems to think this is not optimal, but I am telling you this only because my car starts and so I don't think it is your main problem.

I have the stock electric pump and a Purolator style electric pump in the engine bay, the mechanical pump removed, and the regulator set to 3 psi. Not optimal, but again my car starts OK.

My floats levels are set, but the car started even when they were WAY off.

My idle screws are 3/4 turns out.

The car starts no problem without the starter valves, much like Alan described - 2 pumps and 30 seconds of nannying the throttle.

My timing is 10 deg BTDC with vacuum advance disabled.

I have done no synchronizing, jetting or mixture adjustements yet.

Things that made the car NOT START until I fixed them:

-Weak stock ignition coil

-Vacuum leak through the distributor advance dashpot. I would block off both brake booster and dizzy vacuum just to make sure. I have the unpreferred o-ring style gaskets, but I got new O-rings and used elastic stopnuts ordered from www.McMaster-Carr.com.

At all times the car at least popped and fired, however.

-Mark

[benn9090]

Alan, Phred, others that may know what the @#$%@ they are doing-

Many questions, perhaps when Eric and I both have our cars running nicely we can compile this mess into a nice FAQ:

1.) Got my Synchrometer today! - With flow differences from one carb barrel to the next (within a given carb body), is the wise choice to average the two readings in order to match with the other 2 carbs?

2.) Is it typical to have barrel-to-barrel differences? I can imagine such differences being due to valve timing differences, compression differences, and/or a twisted throttle shaft.

My data:

Cyl# 1 2 3 4 5 6

compression psig 145, 145, 139, 150, 142, 150.

flow (kg/m^3) 5.2 4.8 6.5 4.8 5.5 5

As you can see, my biggest compression difference is between #3 and #4, which is also the carburetor with the largest flow difference.

I read somewhere it is typical to sync off the front barrel only.

Any advice or comments????

-Mark Bennett

Cleveland, OH (<-- nobody knows what a Weber is around here)