New Carby - New Tpoic - Zenith Carby

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AustHaflinger
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New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

New Zenith carby is on and runs well except.

I have set idle at 850 revs and idle mixture screws are 2 1/2 turns from being wound right in. Engine starts with or without choke but with choke on it needs to be taken off soon after start.

Engine idles OK and the Haffie runs well. Except after running for 20 minutes or so (so engine is hot) and on a hot day (haven't had any cod days to check) and you come to a stop light it idles Ok but when you go to take off when the lights change the engine hiccups and stalls (feels flooded/rich) and will not start for quite a long time - normally need to switch off the fuel pump as it just fills up the fuel bowls as cranking empties them. Without the pump filling up the bowls the excess fuel in the system slowly clears itself and the engine fires up.

I increased the idle to 1300 rpm and the problem goes away with no hesitation when the accelerator is applied at the lights. There is no vapour lock and on a 31°c day the rocker covers were 61°c, the carby was 31°c, the inlet manifold was 50°c (indicating the carby heat tubes work) and the fuel pump 40°c. It is clear that while the engine gets plenty of air via the fan, the rest of the engine bay gets quite hot as there is no air circulating. The above temps were taken after a 20km drive with the top engine hatch open.

What I think is happening is that the idle mixtures are a little rich and when at correct idle, the action of the accelerator pump when you go to take off the from the lights is causing an excessively rich mixture that kills the engine - the floats may also be a bit high so the engine is not able to clear the excessively rich mixture as the fuel pump is continuously topping the bowls up so when the pump is turned off, cranking the engine clears the system of the excessively rich mixture. If the pump pressure was too great it would flood the engine at idle which it does not.

They are my thought but I am open to alternative ideas.

The car is going in to a tuner with a dyno next Wednesday so I want to give him some aspects to look at in addition to the normal tuning process.

Cheers

Garry
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heinkeljb
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Re: New Carby - New Tpoic - Zenith Carby

Post by heinkeljb »

Gary,

Are the accelerator pump jets in your ex Mog carb the same size as the original Haflinger ones? I know your engine is larger cc, but as a starting point the originals should work.

I agree it does sound like the moment you put your foot down, the pump squirts neat petrol down the bores making the mixture ultra rich. I think 850 rpm is a bit slow, have you tried 900rpm? Lurch is a bit temperamental about idle revs for exactly the same issue, pick up is kangaroo like if idle is too slow.

Was there a reason for having the engine hatch open? I am sure you want things to work with the top hatch closed and the little flap folded down, the oil cooler bypass open all the way with those sorts of temperatures.

John
Haflinger 703AP LWB 1973 - (Once owned by Lady Sutherland & Sons.) Now called "Lurch" !

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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

John the jets are all haflinger - I was able to get the Zenith centre block with all the jets from Haflinger Technik.

What do you think the idle should be? The new carby will sustain a 600rpm idle but the engine does not have the torque to pull away cleanly. The question of idle speed has been raised here before but everyone seemed to have a different idea what it should be.

But yes, I have increased the idle to 1300rpm (higher than it should be) and while there is just a little hesitation it does not stall and will start if stopped so that is a bonus.

You mentioned - kangaroo - driving the Haflinger around on hot summers days brings in the smells of the country - particularly the smell of baking dead roo road kill in the hot summer sun. You don't notice it when in the climate controlled comfort of the car - the Haffie is a bit different.

I just checked the handbook as I did not recall a oil cooler bypass - idle is 700 rpm and my car has the oil cooler bypass removed so the oil cooler gets a full blast of air in all conditions.

A question for the learned forum - is the carby header really needed in warmer climates - it does not actually warm the carby but the inlet manifold in the area just under the carb but not much heat would get into the carb.

Cheers

Garry
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HaffyHunter
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

Hi Garry,
The manifold heater tube on the left side had a block-off plate on tropical (APT) models. This part is shown in the Parts Book. As I only drive my Hafi during summer in Canada I have installed this block-off plate. My truck seems to work better this way but takes a few more seconds to warm up for smooth idle. The other benefit is that I'll not likely ever need to repair/replace the manifold heater tubes again on my truck.
Cheers,
Steve
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

Thanks Steve - I had noticed that plate on the book and just assumed it was the gasket but they had forgotton to drawn in the circle on the inside - the description did not enlighten me but now that you have pointed it out to me I might make a plates to go in there.

Thanks

Garry
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heinkeljb
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Re: New Carby - New Tpoic - Zenith Carby

Post by heinkeljb »

Sorry Gary,

Maybe my terminology isn't quite the same as the book / other peoples.

The oil cooler bypass i am talking about seems to have been fitted to later Haflinger and allows the hot air collected from the oil cooler to be diverted to the outside world rather than heating the left hand cylinder barrel. It exist the left hand rear of the vertical engine flap. I think originally from factory the flap was painted red.

The other side of the vertical engine flap has an air intake flap, equivalent to the muffs Landrover owners put in front of the radiator on cold days to stop the air from going through the radiator. I believe tropical (maybe only some) versions had a completely different rear vertical engine cover with the vents on the top surface at the same sort of hight as the platform.

I don't know what temperature(s) Lurch operates at but next week one of the local supermarkets will have on offer an infrared non contact thermometer :

http://www.lidl.co.uk/cps/rde/SID-430D5 ... =9087&ar=1

So I will get one and try to get the same point readings as your post above.

John
Haflinger 703AP LWB 1973 - (Once owned by Lady Sutherland & Sons.) Now called "Lurch" !

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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

John - understood what you were talking about. I have the flap in the engine door that you close when really cold to cut off about half the air going into the engine bay.

On my Haffie, the air from the fan obviously goes down and over the barrels and out the bottom. Also through the oil cooler and out the rear of the vehicle - as mentioned the red restrictor on the pipe that takes the air out the back is not in mine. I am surprised how little air can get to the left cylinder but I suppose the oil cooler provides enough restriction to force the air to the cylinder.

I have a similar temp gauge and now wouldn't be without it.
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

What I think is happening is that the idle mixtures are a little rich and when at correct idle, the action of the accelerator pump when you go to take off the from the lights is causing an excessively rich mixture that kills the engine - the floats may also be a bit high so the engine is not able to clear the excessively rich mixture
Hi Garry,

Have you followed the Zenith directions for adjusting the accelerator pump lever to correct volume as well as float level? Both of these adjustments are critical to acceleration, consistent idle speed and fuel consumption rate. Also be sure to check the pump suction valve & pump pressure valve at the bottom of the accelerator pump chamber. In particular, make sure the rubber seal in the face of the pump pressure valve is in good condition.

A good reference paper on rebuilding and tuning Zenith NDIX carbs was written by Ron LaDow and it can be found on several Porsche 356 and 'Mog websites. I have a .PDF copy I can send you if you can't find it on line.

Cheers,
Steve
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

HaffyHunter wrote:Have you followed the Zenith directions for adjusting the accelerator pump lever to correct volume as well as float level? Both of these adjustments are critical to acceleration, consistent idle speed and fuel consumption rate. Also be sure to check the pump suction valve & pump pressure valve at the bottom of the accelerator pump chamber. In particular, make sure the rubber seal in the face of the pump pressure valve is in good condition.

A good reference paper on rebuilding and tuning Zenith NDIX carbs was written by Ron LaDow and it can be found on several Porsche 356 and 'Mog websites. I have a .PDF copy I can send you if you can't find it on line.

Cheers,
Steve
Hi Steve and thanks for the information.

I have no idea about adjusting the carb that is why it was rebuilt and statically set up by a supposed carby expert. I have the Ron LaDow document and when my vehicle goes in for its final tune and carb setup this Wednesday I will give them a copy of the document.

If you have any other docs I could review I would appreciate it.

Thanks

Garry
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

The haflinger is in for its tuneup at a tuner whop also has a dyno. I just had a call saying the engine is running incredibly rich - so much so that that there would be enough fuel in the cylinders to wash the bores.

The jet block with jets installed was provided by a Haflinger parts supplier and assembled into the rest of the carby (unimog 404) and refurbished.The jets are supposedly:

Venturi 22mm, main jet sizes 110 (but taken out to 115), idle jet 45, air correction jet 240, idle air jet 80, pump jet 40, starter jet 190.

Given that all the jets are fixed except for the idle mixture there is something weird going on.

Any ideas??

Thanks

Garry
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

Hi Garry,
My first suggestion is to closely inspect the Pump Suction & Pump Pressure valves as mentioned in my previous post.

Secondly is adjustment of the accelerator pump lever for proper volume per Ron LaDow's instructions. Also, its location on the bellcrank arm must be on the outermost hole. Is it the correct accelerator pump piston for Haflingers? The shaft for the Haflinger's accelerator pump piston is shorter than that used in the Unimog and Pinz version for the NDIX carb.

Of course, correct float level is also critical.

Lastly is the "choke" (starting circuit) disk installed in the correct orientation? This is an easy piece to get installed incorrectly and the parts diagrams do not give very clear direction for this piece in my opinion. Having the disk installed incorrectly allows fuel to flow freely through the larger start circuit jet.

Cheers,
Steve
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

Thanks Steve,

On the accelerator pump - I am no expert here and I have given LaDow's instructions to the tuner for reference and mentioned to him that this does need checking. It is rich even when the running at steady revs when the accelerator pump is not being used.

I understood the Unimog accelerator piston is OK for the Haflinger as long as the outer hole on the bell crank was used which it is.

Float level will be double checked but was initially set up by the rebuilder and the car works quite well at very steep angles offroad so if it is not right it is not far off.

On the choke disk - I have absolutely no idea - again was rebuilt by an expert. I just pulled the unimog one apart and it has been pulled apart so I "assume" he checked the arrangement on the unmog part when he reassembled the haflinger choke disk.I can see how the brass disk could go back the wrong way around.

As you can see I do not have a lot of carby knowledge and that is why I have been using experts to do the work for me in the hope it will all work out - unfortunately the Haflinger and the carby is an unknown to most experts here.

Maybe that is the reason that the previous owner changed to the Solex carb which is a known quantity. Interestingly in another thread I complained about the 18mpg I was getting with the Solex - I am now getting 25mpg with the over rich Zenith so at least that is a step in the right direction.

Cheers

Garry
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Re: New Carby - New Tpoic - Zenith Carby

Post by ogdenenterprise »

I had my zenith carb cleaned and supposedly set up by professionals twice, both times the said it was set up perfectly . I later found out they had set it up on a 6 cylinder engine ,every time I tried it on the haf it would not run correctly, they had put the bell crank link arm in the inner hole and bent the link rod to fit . When I eventually found the problem I went back to see them but they had gone out of business, I wonder why?

Dave
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

ogdenenterprise wrote:I had my zenith carb cleaned and supposedly set up by professionals twice, both times the said it was set up perfectly . I later found out they had set it up on a 6 cylinder engine ,every time I tried it on the haf it would not run correctly, they had put the bell crank link arm in the inner hole and bent the link rod to fit . When I eventually found the problem I went back to see them but they had gone out of business, I wonder why?

Dave
Yes I am beginning to think I just should have done it all myself on the basis of information provided here and on the Real 4x4 forum.

Cheers

Garry
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

I understood the Unimog accelerator piston is OK for the Haflinger as long as the outer hole on the bell crank was used which it is.
Hi Garry,

I've not heard this before and have never tried it but have heard quite the opposite information.

That aside, my money's on a problem in the Suction valve and/or Pressure valve. If these aren't sealing properly they will continuously feed fuel from the accelerator pump chamber regardless of throttle position.

Cheers,
Steve
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

Thanks Steve - I am going to ring the tuner and pass on the informatio.

A well know Haffie engine builder in the west of the US indicated that the pump is same as Pinz or Mog, however, link location is furthest out.

Nevertheless I will also raise this aspect with the tuner.

I appreciate your input - has been very valuable.

Garry
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

Armed with all this information that has been provided and the old Mog jet block I went out to the tuner - I showed him the disk inside the jet block and talked about the Suction valve and/or Pressure valve aspect - he was most interested and will have a look at that.

He said that the idle mixture is about right and as revs increase it starts to lean off a little but then from mid range up it is full on rich with lots of black smoke coming out the exhaust. Also I had asked him to look at the ignition as I felt it was maybe a bit advanced - it has a 123 Electronic ignition system - he said that his instruments is showing 41 degrees BTDC at higher revs where the standard curve should have it at about 30 degrees BTDC and the 123 system should have it at about 30 degrees on the milder settings and about 35 on the more aggressive settings so there may also be an issue with the ignition as well.

Thanks to everyone for then input.

Garry
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

He said that the idle mixture is about right and as revs increase it starts to lean off a little but then from mid range up it is full on rich with lots of black smoke coming out the exhaust.
Hi Garry,

This definitely sounds like a problem with the pressure valve. There is a small rubber ring in the top of the valve which seats against the bottom of the accelerator pump plunger shaft as the accelerator linkage is depressed. The result is that as RPM is increased the air/fuel mixture is leaned. Adjustment of the pump's linkage controls the travel distance as well as the timing of the leaning relative to throttle position. It is very common that the rubber ring hardens with age and therefore does not seal correctly or eventually crumbles away so there is no seal at all. The other issue which might be preventing the correct timing of this seal is incorrect pump linkage location on the bellcrank arm or incorrect pump shaft length as in Unimog or Pinz pump plunger.

One note of caution when working with the suction valve or pressure valve. These are very prone to fuel leaking and are located very close to the hot intake manifold heater tube so the resulting fire will be quite spectacular. If you remove the valves from the carb body be sure to check them frequently after reinstalling the carb to be sure no leaks exist.

Cheers,
Steve
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AustHaflinger
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Re: New Carby - New Tpoic - Zenith Carby

Post by AustHaflinger »

HaffyHunter wrote:It is very common that the rubber ring hardens with age and therefore does not seal correctly or eventually crumbles away so there is no seal at all. The other issue which might be preventing the correct timing of this seal is incorrect pump linkage location on the bellcrank arm or incorrect pump shaft length as in Unimog or Pinz pump plunger.
Steve
I would have assumed those parts are part of the rebuild kits and replaced as part of the rebuild the carby has just been through.

Here is a pic of the accelerator pump linkage.
Image
HaffyHunter wrote:One note of caution when working with the suction valve or pressure valve. These are very prone to fuel leaking and are located very close to the hot intake manifold heater tube so the resulting fire will be quite spectacular. If you remove the valves from the carb body be sure to check them frequently after reinstalling the carb to be sure no leaks exist.
We have constant 40°c temperatures this time of year and will stay hot for the next two months (is 40 out on my verandah at the moment) so as to discount any overheating of the carby, the heater tube is blanked at both ends. If I lived on the coast it could probably be OK to run with it blanked all year around but it gets cold here in winter so depending how the engine runs I may have to remove them in June and hopefully all the issues will be fixed by then.

The tuner has to some higher priority work so I have given them the OK to work on these cars and do mine when the other work is complete - so may take a week or so.

The tuner has taken input from me (based on your advice) very well and seems to have the right attitude so I think we will get there in the end.

Cheers

Garry
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Re: New Carby - New Tpoic - Zenith Carby

Post by HaffyHunter »

I would have assumed those parts are part of the rebuild kits and replaced as part of the rebuild the carby has just been through.
Hi Garry,
None of the NDIX carb kits that I've found have included the Suction Valve or the Pressure Valve.
Your tuner guy will need to review the adjustment on the accelerator pump linkage to determine if the plunger base is seating on the rubber ring on the top of the Pressure valve and at the correct throttle position.
Pressure Valve.jpg
Cheers,
Steve
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