Hi all, hoping someone can throw some light on this for me - 2.0 Pinto installation in my NG, car didn't run when I got it & had obviously been considerably messed with in the past, timing belt was a tooth out, reset points (remember those?!) timing, tappets, etc. put some fresh fuel in & dropped some down the carb &hey presto, it ran, however, had very obvious carb probs, I whipped the carb off & stripped cleaned, blew out all jets, checked diaphragms for splits etc & reassembled, it runs better, but still nowhere near right.

Even when completely warm the choke flaps at idle are as pictured below, only slightly open,

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Carb Chokes [/img]

as soon as the throttle is opened the choke flaps also pull open fine & at revs, it runs perfectly, at idle, it hunts & I'm unable to significantly affect it with the idle screw. The really odd thing is that, despite the chokes being a lot further closed than you'd expect it is clearly running weak at idle, if I partially cover the chokes with my hand, blocking the air supply, the idle picks up & it runs much more evenly. The float level had been set waay high, presumably cos someone had worked out it was running weak, that's been reset to standard, didn't make any noticeable difference

I'm currently going through the procedure for resetting the vacuum pull down for the choke, the choke phasing & the fast idle, but I'm sure that's not going to sort it-

I've noticed when looking at the vac pull down that I think there's an issue that the linkage may be bent - see pic below

[img]
Carb choke [/img]

Surely the little arm should be behind the yellow "plug" so that the yellow bit pushes it along when the vac diaphragm pulls it? I still don't think that's enough to hold the chokes so far closed & what could be wrong at idle that it runs so weak?

I can't find a schematic for the carb, but I'm pretty sure the idle screw only controls an air passage & even with the screw right in it's still running weak, exactly which jet is it pulling fuel from at idle? I don't think it was clear in the manual, tho' I'll take another look.

The auto choke spring feels like it's wound on way too tight, but there's no mention of adjustment for that part of the choke anywhere I can find. It looks as though the 2 halves of the choke housing should separate, but the bolt appears to be seized in the housing, if I can get it free, I might be able to slack the choke off, but that's just gonna make the idle even worse!

I don't suppose anyone has a decent Cortina/Sierra twin choke they no longer want or a set of bike carbs suitable for conversion for reasonable money? This has got me tearing my hair out - I used to make my living 30 years ago fixing exactly this sort of stuff, but don'rt ever recall coming across anything quite like this b4!!!

I am no expert on these, but it does sound like a classic [manifold] air leak problem.

I fitted a 2.0 pinto with manual choke Weber carb like that in my MK Indy. It wasn't the carb the engine came with in the donor Sierra. Engine started and ran, but just wouldn't go through the revs above 3,500. Also stalled very easily. Having it rejetted on a rolling road by a local expert Airey Tuning made a world of difference. Opeed up the full rev range and stopped the stalling.

Your problem does seem air leak related + you've already had it apart and serviced/cleaned it.

The autochoke is held in position by a circular clamp ring with 3? Fixings, when its hot slacken them off rotate the housing til the choke flaps open fully. Are you sure you have cleaned the idle jets thoroughly, there should be 2 one for each choke and when you remove them give a good blast of carb cleaner down the drillings.

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Originally posted by gremlin1234
I am no expert on these, but it does sound like a classic [manifold] air leak problem.

Deffo not an air leak, have been all over it with a stethoscope, clamped off vac hoses to distributor, servo & breather. Breather made slight difference, others none at all, you'd expect the breather to make some difference .....

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russbost - 30/4/24 at 06:01 PM

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Originally posted by Dingz
The autochoke is held in position by a circular clamp ring with 3? Fixings, when its hot slacken them off rotate the housing til the choke flaps open fully. Are you sure you have cleaned the idle jets thoroughly, there should be 2 one for each choke and when you remove them give a good blast of carb cleaner down the drillings.

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Can't rotate the choke housing as it can only move slightly B4 the water hoses hit the rocker cover.
Must admit haven't specifically targeted the idle jets with carb cleaner, but they appear clean & have blasted through with compressed air .....

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nick205 - 1/5/24 at 09:05 AM

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Originally posted by russbost

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Originally posted by Dingz
The autochoke is held in position by a circular clamp ring with 3? Fixings, when its hot slacken them off rotate the housing til the choke flaps open fully. Are you sure you have cleaned the idle jets thoroughly, there should be 2 one for each choke and when you remove them give a good blast of carb cleaner down the drillings.

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Can't rotate the choke housing as it can only move slightly B4 the water hoses hit the rocker cover.
Must admit haven't specifically targeted the idle jets with carb cleaner, but they appear clean & have blasted through with compressed air .....

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Give them a proper good soaking in carb cleaner and ensure ANY claggy old fuel deposits are properly dissolved away. You mentioned putting fresh fuel in the vehicle. There may well be chance the old fuel went nasty sat in the jets.

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SteveWalker - 1/5/24 at 10:50 AM

I'll second that. My pinto engine (38 DGMS carb) wouldn't even attempt to start. Adding fresh fuel did not help, until I'd drawn off around 20 litres of fuel (it came out looking like milk at first). Even then it was not running right, so I completely drained the tank and pipework and refilled with fresh fuel. It is now running beautifully.

I also had a similar problem with a Matiz that has sat for a number of years. Again emptying and refilling quickly solved the problem.

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adithorp - 1/5/24 at 06:55 PM

Thinking waaaay back, I seem to remember a common issue, that I think was caused by the bi-metal coil inside the thermo housing becoming loose on its central fixing.
Remove the three screws and pull it back on the hoses. Memory says you could work out where it had originally been located from the original fixative (flat on the shaft?). We stuck them back using loktite bearing fix (603?). As long as its close to original position you can then adjust by twisting the housing.

Memory isn't what it used to be so could be talking nutsack

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russbost - 4/5/24 at 08:11 AM

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Originally posted by adithorp
Thinking waaaay back, I seem to remember a common issue, that I think was caused by the bi-metal coil inside the thermo housing becoming loose on its central fixing.
Remove the three screws and pull it back on the hoses. Memory says you could work out where it had originally been located from the original fixative (flat on the shaft?). We stuck them back using loktite bearing fix (603?). As long as its close to original position you can then adjust by twisting the housing.

Memory isn't what it used to be so could be talking nutsack

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You've got me wondering now, whether it could be 180 degrees out, because that would fit the feel of correct preload, I'd not thought of the spring coming off & being put on 180 deg further round, I'll check & see if it will come off.

Still leaves the issue of exactly how that vac pull down works, really need to see an unmolested one!

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russbost - 31/5/24 at 10:23 AM

Update on this in case it's of use to anyone else -0 sooooo many different issues!

The small arm within the vac pull down for the choke was indeed bent, I straightened it & it fits in behind the yellow plastic collar pictured, in cleaning the first time I had actually missed the 2 idle jets - Doh! as they look like locating screws, so these were removed & blown out. The choke spring was 180 degrees out , someone had obviously removed t previously & replaced incorrectly

With all this done & float levels again checked etc, it all went back together - it would obviously run fine now - Yeah?

Well it started & ram but was lapsing onto 3 cylinders, I'd already had the plugs out - which looked almost new - & cleaned/burnt off excess fuel several times, but tried once more, ran better, but still misfiring, rechecked ponts gap, cap, rotor, etc. all correct, so decided to order a fresh set of plugs.

Well, I can only assume they'd been fouled so many times previously that there was something that was never going to clean up - with new plugs it runs fine -I wouldn't say perfect, but certainly acceptable & satisfactory until I get it to the stage of a road test

The joys of stuff that's previously beam messed with by the incompetent

Thanks for your info & suggestions - the comment re the choke spring was invaluable!

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