The power of the forum is needed - VX wont tick over

[lancialulu]

Synopsis:

Changed the weber 36 DCA 5/250 for another that was clean and overhauled (they are a simple carb easy to check all passages etc).

New carb would not run properly. It would start fine from cold but as soon as the engine got any warmth it died (at tick over).

Firstly suspected an air leak at the manifold - brake cleaner increased revs but could have been sucked in as running with no air cleaner (is this the problem.... running with no air cleaner?)

Removed carb and carefully replaced base gasket and used a smear of silicon refitting the carb. No different.

Put old carb back - same issues would start, rev cleanly but die at tickover even with the throttle stop screwed in.

Closed off all vacuum pipes (servo, distributor, carb water heater valve) - no difference

Measured fuel pressure - seemed a bit random 2-3psi (I have fitted a malpassi fuel regulator in place of the 2 Lancia "regulators" but it could for some reason not regulate). I have linked out the thermoswitch fuel limiting device just in case that was causing something

Did open pipe flow measurement of fuel pump (Bosch original) and got c 125 lph reading, also it read 3bar (only connected to a high pressure gauge nothing else). A Chinese copy which I had on the shelf did twice that.

Decided to buy another Bosch (Chinese copy does not seem to have built in one way valve). Fitted today. Same running issue remains but now I have a controllable pressure at Carb - set to 3psi.

Pulled plugs and they seem ok if a bit white on the central electrode. Checked timing (Valve and ignition both OK)

The auto choke works as it should, and float level is spec

It starts easy from cold, revs well but is splashy when throttle reduces. Just will not tick over - best I can do 1500 but its hardly steady and sometimes dies without warning.

At wits end... Is it the air cleaner???

[Ferrit]

I would normally say carb all day, but you have swapped it.  It does sound lean doesnt it, until the second choke/acc pump kicks in maybe?

[lancialulu]

I would normally say carb all day, but you have swapped it.  It does sound lean doesnt it, until the second choke/acc pump kicks in maybe?

On the VX the weber 36DCA is a twin choke both operating together i.e. at the same time.... I think it runs fine on the main jets but leans out at tick over meaning it is getting extra air (normally a carb gasket issue but having remade the joint severally and with new gaskets, hylomar, gasket sealant etc....)

It has the feeling of a larger strip down as the super charger system has many more areas it could be dragging air in; but I need to keep the car running to move it around to juggle other work.....

Also would want to strip it down coincident with a belt and water pump change and the broken cam carrier...

[stableblock]

when it dies doe sit restart immediately or does it have to cool down a bit first?  I am thinking there might be a dodgy electrical connection somewhere that is opening when warm and reclosing as things cool a bit.  Probably a nuts idea but you never know.

[lancialulu]

No it restarts immediately although you have to give it throttle as it is hot…..

If I screw the throttle stop right in it with run (not idle) splashy at around 1500rpm.

Its grabbing air from somewhere (all vac lines blocked, the over pressure valve on the manifold is not the culprit eitherj…..

[JASPER_40]

A smoke machine might be worth a go to find any vacuum leaks. It injects smoke under pressure through the intake and it will find any leaks or loose connections.

I have just used mine to track down an issue with my Aircon on the Beta which is all switched via Vacuum lines.

I invested in one a while back and has paid me back very quickly.

Mine is made by Ancel and you can get them on Ebay...just a thought

Cheers,

Steve

[WestonE]

This is granny sucking eggs time. Check and block every unused outlet/inlet to the carb. Non need for beauty. Bolts and spare hose will do. Go along all vacuum hose gently flex them looking for cracks. It takes very little extra air to ruin Idle. WD40 or easy start around the carb to manifold engine running for a sudden change of note. If you have a stable 3PSI and it runs with more load and revs your fuel supply is sound.
Do check the distributor under the rotor arm shield for burnt wiring on the pick up and pull back the king lead rubber boot and check you do not have corroded terminals. Make sure the pickup lead has a good positive connection to the amplifier. Squeeze the terminal if needed. Do not tolerate a burnt or corroded distributor cap or rotor or a stiff burnt distributor to amplifier lead. NB Montes like to breakdown thanks to old pick up wires. 
Good luck and if in doubt walk away for a cup of Tea and swearing and you might just notice what was hidden before. 

[lancialulu]

Another session...

Fired up from cold fine and smooth but needed throttle stop to be near maximum for it to run shortly after. Easy start was applied and it did not seem sensitive to where it was applied. Normally would expect manifold but I have gone through this with a fine tooth comb (flanges flat, gasket sealed).

Then I though as there is something odd about the DCA carburettor in that on other models (Talbot Simca for example) there are 2 "shut off devices" fitted one to each choke. The DCA fitted to the VX does not have these, just a plain disk (see photo). As both my carbs had been through an extended ultrasound  cleaning I just wondered if this could be the cause of the problem. Nothing was leaking out so I put an oily rag over them as best as I could to try to smother any air getting throughand the revs rose slightly.

I have decided to run some superglue round that area on both chokes and will check tomorrow that superglue has not bunged up the internals. Luckily it is a simple carb....

I will wait till tomorrow and fit this sealed carb. Fingers crossed.

[Ferrit]

I know everyone has another view, Classic Carbs told me not to use an ultrasonic cleaner as it sometimes leave residue in hard to get at places.  How about off and strip and blast out with cleaner, air and work through all the ports and jets with brushes etc?  My recent issue I eventually found it this way

M

[lancialulu]

I know everyone has another view, Classic Carbs told me not to use an ultrasonic cleaner as it sometimes leave residue in hard to get at places.  How about off and strip and blast out with cleaner, air and work through all the ports and jets with brushes etc?  My recent issue I eventually found it this way

M

Hmmm, dont really agree. These carbs in particular are ver simple. You can see all porting and I checked with an air line always after wards. Because I was have trouble with these I used a whole tin of carb/brake cleaner as well but it only showed the passages were already clean. I am sure Classic Carbs use ultrasonic cleaning…. Maybe their comment was directed at the use of cleaner with to smaller a bath size so the carb does get an all round clean. My cleaner is 10l and I turn the carb several times and use a proprietary carb cleaning fluid in the bath. I guess if the carb was really in a bad state poorly stored and or grossly dirty then there could be potential for blockages, but I have done this for a few years now (mostly on Fulvia twin chokes) and this is possibly the first instance of the u/s doing a better than expected job…. We will see Watch this space!

[WestonE]

Above your idle mixture screws you have 2 internal channel blanking plugs in brass. These might be the real access to the idle circuit drillings. I do not have the carb schematic to look unfortunately. If crud is dislodged in extensive cleaning it often heads for these drillings. The plugs are pull and throw away to get access then idle screws and anything else in those circuits out blow through. Of course you then need new plugs which often appear in comprehensive overhaul kits and get left unused. New plugs light smear of Loctite gently tap in place. If you know you have solid regulated fuel supply and rock solid spark. You are only left with air leaks or blockage. NB do look at the VX vapor vent pipes. These are meant to be extract only. I have a 1 way valve on my VX setup as the extractor pump died long ago. GC used to put float chamber valves into the pipes. The O rings that seat the extractor tubes rot over time. However those tubes are really fragile making replacement scary. I used aftermarket L and T piece plastic tubes with new O Rings.