Struggling to get it to idle

[Dunc]

Hello all, various of you have been helping me with a transmission problem over the last week or so, but I am discontinuing that thread for now at least, because I now realise (thanks to forum help) that before I worry about transmission, I need to get my 66 to idle properly. It won’t. 
On choke it revs highly and sounds ‘fit’ albeit noisy, but as I reduce choke and the revs come down it reaches stall point. Although I have no tachometer, I would say it begins to struggle at well over 1000 rpm. So I have the options of  ‘revving like mad’, or’stalling’ but I cannot get the engine to calm down and keep running. This afternoon I have had the carb off again and cleaned/blown/flushed through every channel I can see and access, in order to get the idle circuit working but to no avail. One particular channel through the carb was choc full of crap and I thought I had solved it, but on returning the carb to the engine and starting up, still the same problem - revving it’s balls off or dying! It starts too brightly for ignition timing to be miles out, it’s got new plugs and I have cleaned the points. 
So, I am left thinking that I replacement carb might do the trick (anyone got one they’d sell me?) or there’s some other reason that it’s 1500 rpm or nothing?!?
Suggestions on a postcard please.......

[Richard DAF Webmeister]

OK, hang on in there!

Is there a capacitor (looks a little bit like a spark plug) screwed into the side of the carburettor, with a thin (white from memory) wire attached?

That is a slow running/emission reduction device, and it is quite common for this to shake/work loose from the carb, and/or the wire is not attached or loose.
If any of the above happens, it causes the engine to run very poorly and cause it to stall at anywhere near tickover speeds. Only choke or full throttle enables it to keep going, and even then usually in a rough uneven way.

I and others have had this on our water-cooled and air-cooled DAFs over the years.

I'm sure others will come in with their suggestions.

[bobdisk]

Jan 15, 2021 21:39:06 GMT Richard DAF Webmeister said:

OK, hang on in there!

Is there a capacitor (looks a little bit like a spark plug) screwed into the side of the carburettor, with a thin (white from memory) wire attached?

That is a slow running/emission reduction device, and it is quite common for this to shake/work loose from the carb, and/or the wire is not attached or loose.
If any of the above happens, it causes the engine to run very poorly and cause it to stall at anywhere near tickover speeds. Only choke or full throttle enables it to keep going, and even then usually in a rough uneven way.

I and others have had this on our water-cooled and air-cooled DAFs over the years.

I'm sure others will come in with their suggestions.

That is a solenoid. It controls the petrol path when energised. The white wire to it comes from the + supply to the coil. Check that it is a good connection and there is 12v at the solenoid., it could be open circuit or stuck and not operating when the 12v is there. Listen for a "click" from it when the 12v is applied. While these diagrams are for VW carburettors, the Daf carbs are similar.

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A capacitor (old name condenser) is an electronic component and is part of the ignition, and lives in the distributor

[andrew]

The above comments sum up things pretty well. I'd just add the following thoughts: As explained, the solenoid that screws into the side of the carburettor is "ON" when the ignition is on and "OFF" when it's not. This is fitted to prevent "running on" and for exhaust emission & environmental reasons. When you switch on there ignition you should hear a "click" as the solenoid energises. If you don't, it's not working and so therefore the idle jet in the carburettor is not open and the engine will then only run properly when the accelerator is depressed, thus opening the fast-running jet. These solenoids hava a habit of shaking loose, particularly on the air-cooled Dafs, and it's the first thing experienced Daf mechanics look at when diagnosing a poor tick-over.

There is also a micro-switch fitted to the carburettor, which is operated by a cam on the throttle linkage. This switches the change-up valve in the transmission "ON" when activated. It's possible this may be malfunctioning, thus weakening the mixture, but as I think you have blanked off the opening at the back of the inlet manifold anyway, this shouldn't make any difference at the moment.

[starider]

Hi, could be wrong but I don't think the electro magnetic jet was fitted to any of the Renault engines,but not having spent as much time working on them I stand corrected. Several good sources for carburettors[indeed any spares] within the club.

[Dunc]

Thanks all, I read the above with interest as the description is precisely what I am struggling with. Unless choke or throttle are activated, it runs roughly - kind of lumpy - and if revs go down anywhere near idle, it conks out immediately. Trouble is, I don’t see anything electrical or electronic anywhere near the carb. As Starider states - maybe mine wasn’t fitted with the solenoid that controls petrol flow at tickover. It certainly needs one though!

My other problem unfortunately goes back to the transmission. I have managed to get it to stay running albeit roughly at fairly low revs and any attempt to guide the transmission lever into forward or reverse is met with the grinding sound that suggests that the clutch is engaged. It is probably running at about the speed you would expect it to run at when it’s on choke in the morning, not revving highly but up around 1000 or maybe 1100...... I would have expected it to be possible to engage a gear under those circumstances?! Surely you don’t have to fully warm it through and get it idling at 750rpm before setting off?? Maybe I am wrong, but if I can get it ticking over at 750rpm it feels like it would still grind and graunch rather than engaging happily. Should that be the case, what is wrong and how do I investigate?

So, 2 questions there - carburettor/tickover - what could be wrong or missing? And transmission grinding even when revs are fairly low, what could that be and what should I look for?

[Richard DAF Webmeister]

Jan 16, 2021 8:57:58 GMT andrew said:

The above comments sum up things pretty well. I'd just add the following thoughts: As explained, the solenoid that screws into the side of the carburettor is "ON" when the ignition is on and "OFF" when it's not. This is fitted to prevent "running on" and for exhaust emission & environmental reasons. When you switch on there ignition you should hear a "click" as the solenoid energises. If you don't, it's not working and so therefore the idle jet in the carburettor is not open and the engine will then only run properly when the accelerator is depressed, thus opening the fast-running jet. These solenoids hava a habit of shaking loose, particularly on the air-cooled Dafs, and it's the first thing experienced Daf mechanics look at when diagnosing a poor tick-over.

There is also a micro-switch fitted to the carburettor, which is operated by a cam on the throttle linkage. This switches the change-up valve in the transmission "ON" when activated. It's possible this may be malfunctioning, thus weakening the mixture, but as I think you have blanked off the opening at the back of the inlet manifold anyway, this shouldn't make any difference at the moment.

Correct - solenoid, not capacitor - I'd had a long day!

[Dunc]

Ok folks, after a third session of poking things carefull through every orifice I can see on the carb, it is ticking over well enough for me to turn my attention elsewhere. For what it’s worth, my carb has no electric gadgetry attached at all - idle is achieved solely by air passing through tiny pilot channels in the body and picking up traces of petrol along the way.

Transmission.

If I start up in Park, the engine will fire up but you can kind of feel that there’s something binding - a bit like the clutch is at biting point. It turns over though, and starts and runs. From Park, if you pull the selector back into Reverse, it goes in quite nicely and you feel sort of ‘proper’ engagement through the transmission system. Needless to say, it also reverses fine. Pop it into Neutral however, where the engine feels free of any binding, and from this position, you can’t select either Reverse or Drive. As I gently push the stick towards either direction, I hear the micro-switch click (the one that’s designed to stop you starting up in gear) and then you feel/hear cogs beginning to grind. I have only pushed gently on the selector - I’ve not forced it into gear, but it really is acting like the centrifugal clutch is engaged. I am at pains to avoid taking the engine out or the transmission off (especially this) unless absolutely unavoidable. What further investigation can I do to bottom out whatever is not working??

For what it’s worth, there’s a little vacuum device attached to the bellhousing on the passenger side which has a cable/pulley gizmo protruding from one end of it. This cable is slack when engine off, but pulls tight when engine running. The vacuum pipe goes to a small plastic thing attached to the driver’s side inner wing. I have not yet deduced what all that is, but if it’s attached to the clutch bellhousing, it must be something to do with the clutch right.....?

By the way, I promise I’ll leave you all alone once I get this car running and driving!

[andrew]

Hum...

Yours is a Volvo 66, not a DAF 66, so I should explain at this point that I have worked on quite a few DAF 66 cars, but only one Volvo 66, and that wasn't a transmission problem. That said, what you have described sounds and feels like a "normal" (inasmuch as anything Daf related can be described as "normal"...) "clutch not disengaging" problem. I suspect the car's clutch is the culprit, and if, by putting the car in neutral and starting it, there's no problem, it suggests the clutch isn't disengaging at tick-over as it ought. If the car has stood for a significant time the clutch may be stuck, so a wooden chock and a hammer might free it off! This has worked for me on other cars in the past.

Hope this helps!

[paull]

Hi Dunc,
The plastic thing on the drivers inner wing is a solenoid valve that should control the clutch - you should hear that click when you push / pull or tilt the gear selector handle.
From what I read the Volvo clutch I has a centrifugal mechanism but with the vacuum override for selecting gears with the choke out and a fast idle.

My guess is that you could check the clutch freeness with the engine off and gears in neutral by trying to turn the prop shaft and if you had a vacuum pump it could be connected to the actuator on the bell housing to see if that made any difference.