340 1.7 carb dont work!

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Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

340 1.7 carb dont work!

Post by Busicrx » 30 Mar 2013 04:15 pm

Hi, My car does not start good and it is not supported to the idle, rises and goes down returns and for. With the choke it is supported a little but for to the one that you try to accelerate. On having dismantled the spark plugs, they are dry and it does not seem that the car throws gasoline without being burning hot, but rather as if it was bringing in too much air. Thank you and a greeting

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mac
Posts: 1403
Joined: 19 Apr 2006 11:02 am
Location: Needham Market U.K.

Re: 340 1.7 carb dont work!

Post by mac » 30 Mar 2013 06:15 pm

Hi,

I understand the problem. It could indeed be an excessively weak mixture caused by an air leak through a warped carburettor base. This should be checked, as should any vacuum hose connected to the manifold and the crankcase breather pipe where it enters the insulating block.

I would also not rule out a problem distributor cap or rotor (a very weak spark will fail to ignite a (correctly) weak mixture).
I have seen several examples on the B172k engine where a "rich" carb. masked ignition faults - when the carburettor was correctly set the engine would not run or only badly.

A quick check would be to spray carb cleaner around the base plate and see if the idle changes (any leaks would draw the cleaner in).

Personally I would fit a new cap/rotor anyway (unless recently changed) you should look to fit new every 10,000 - 20,000km - they really only last that long. This may well improve things but if it does not cure the problem the next step is to remove the carb and measure the warp of the base (there WILL be some). It is possible to level up to 1mm but any more will require levelling and fitting the "green block" and rubber shim gasket.

Good luck - Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 30 Mar 2013 06:42 pm

I disamble carb, i see this broken, tomorrow more
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mac
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Joined: 19 Apr 2006 11:02 am
Location: Needham Market U.K.

Re: 340 1.7 carb dont work!

Post by mac » 30 Mar 2013 07:15 pm

This is the lower insulating plate - and known to crack!. If you fit one of the "green" spacer and rubber shim kits this lower plate is no longer used and can be dispensed with. (you will still need a gasket between the new block and manifold though.

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 03 Apr 2013 01:09 pm

The base isnt totally straight, the hole is not big, but its caused by the temp of the engine? The green block dont deform with temp?? I use the car go to track, and its operate hot.. I go to fit it with new handmade by me gaskets and ¿¿luiquid gasket?? Its go to works? Thanks

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 03 Apr 2013 01:10 pm

If i do a base with aluminium?

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mac
Posts: 1403
Joined: 19 Apr 2006 11:02 am
Location: Needham Market U.K.

Re: 340 1.7 carb dont work!

Post by mac » 03 Apr 2013 06:54 pm

As standard,
Carb sits on a black, thick, composite insulating block which reduces the transfer of heat from the manifold to the carb (reduces the risk of fuel vaporisation). Between this block and the manifold sits a thinner plate with a gasket bonded on each side.

Problem,
Heat and over tightening causes the base of the carb to warp causing an air leak between the thick block and the carb. Heat and time cause both the thick block and thinner plate to warp and often crack - again allowing air leaks.

Possible answers,
Reduce the carb distortion by sanding or machining, fit with good block and plate using new or newly made gaskets (I would avoid "liquid" gasket). If this cures air leaks all well and good.
Or, fit "green" block and rubber shim gasket - the rubber seal is designed to accommodate up to 2mm of carb warp. When using this kit the thinner plate from the std. setup is not used. You would need to make a gasket to go between the green block and the manifold and transfer the engine breather tube from the black to green blocks.

The need is to eliminate air leaks - exactly how is less critical but I would not make a replacement block from aluminium - this will promote not reduce heat transfer - if you use the car "on track" you would almost certainly run into fuel vapour problems.

Does this help?
Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 03 Apr 2013 09:30 pm

Yess !! 340pw i email webcon to buy the green block. I think the same think abou aluminium but better a second opinion :D .

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 03 Apr 2013 09:32 pm

Aaaah, the Nm to tighten the carb bolts to not distorsionate more? Thanks!!

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mac
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Joined: 19 Apr 2006 11:02 am
Location: Needham Market U.K.

Re: 340 1.7 carb dont work!

Post by mac » 03 Apr 2013 10:51 pm

The 4 inhex bolts securing the carb to the manifold should be tightened to 12Nm

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 05 Apr 2013 01:27 pm

A lot of thanks!! The green block is paid, now im waiting postman nesr the door all time!

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 07 Apr 2013 03:51 pm

I work in the carb but no soo much to not do the cabr "less strong".
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Finished
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There is little gap but i have fear to broke the carb

Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 07 Apr 2013 03:53 pm

Other more
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Busicrx
Posts: 41
Joined: 24 Feb 2013 12:25 am

Re: 340 1.7 carb dont work!

Post by Busicrx » 15 Apr 2013 03:13 pm

The green block is here!! Jejej
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macplaxton
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Re: 340 1.7 carb dont work!

Post by macplaxton » 15 Apr 2013 08:19 pm

Busicrx wrote:The green block is here!! Jejej
10 days is good! (I had a letter about my credit card - posted 20/3 arrived 12/4. 23 days to get from UK>IRL :roll: )
72 DAF 44 Estate 78 Volvo 343DL Black BeautyImageImage
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