1995 2.0 Zetec Rough Running
Discussion
Calling all Zetec / Weber brains...
Anyone know what might be up with my 1995 silvertop zetec with twin DCOE 45's? Symptoms are:
Carb 1 (cylinders 1 and 2 front of car) sucking air fine
Carb 2 (cylinders 3 and 4 nearest cockpit) no air suction
... according to my carb balancer. All carbs are set as per set up instructions with mixture 2.5 turns out on all 4 cylinders, allowing the car to start and idle (just about!)
It does start and will idle at around 1,250-1,500 RPM but can hear the odd pop and bang and it just feels a bit rough.
I've had the carbs off to service them (gaskets, filters...) and appear fine, new fuel filter so clean fuel, new head gasket and compression is a little on the low side but even across all 4 cylinders.
Not quite sure where to turn next...
Anyone know what might be up with my 1995 silvertop zetec with twin DCOE 45's? Symptoms are:
Carb 1 (cylinders 1 and 2 front of car) sucking air fine
Carb 2 (cylinders 3 and 4 nearest cockpit) no air suction
... according to my carb balancer. All carbs are set as per set up instructions with mixture 2.5 turns out on all 4 cylinders, allowing the car to start and idle (just about!)
It does start and will idle at around 1,250-1,500 RPM but can hear the odd pop and bang and it just feels a bit rough.
I've had the carbs off to service them (gaskets, filters...) and appear fine, new fuel filter so clean fuel, new head gasket and compression is a little on the low side but even across all 4 cylinders.
Not quite sure where to turn next...
quantum_man said:
Carb 2 (cylinders 3 and 4 nearest cockpit) no air suction
... according to my carb balancer. All carbs are set as per set up instructions with mixture 2.5 turns out on all 4 cylinders, allowing the car to start and idle (just about!)
Are you sure? the first sentence in my quote and the start of the second sentence seem to be at odds with each other, if a carb is not sucking then how have you balanced them.... according to my carb balancer. All carbs are set as per set up instructions with mixture 2.5 turns out on all 4 cylinders, allowing the car to start and idle (just about!)
Sounds like you probably have a leak somewhere on the inlet side I would suggest that maybe the rubber seal between carb and inlet is displaced and allowing air to bleed in.
I maybe read that differently..are you saying that the carb balancer is showing no draw on 3/4?
Leak is always a good call, although both barrels is slightly suspect. Have you checked the balance screw between the two carbs hasn't backed out allowing the rear carb to close completely perhaps?
Leak is always a good call, although both barrels is slightly suspect. Have you checked the balance screw between the two carbs hasn't backed out allowing the rear carb to close completely perhaps?
Thanks for the replies,
I'm pretty sure the gasket's are good as checked the seal and bolted both carbs on pretty tight with a view to backing them off a bit (rubber anti-vibration) once I'd proven all carbs were sucking air.
The balance screw's worth checking again actually, good point! The balancer can't be used yet other than to prove the float moves on cylinders 1 and 2 but nothing on 3 and 4.
Do you think this sounds like a carb issue (including seals) rather than something engine related. Wondered if it was to do with the valves but hoping not, but have read that the silvertop zetec is prone to sticking valves...
Engine's done 8,500 miles from new and is about 17 years old. It's always run fairly rich so there's a fair amount of carbon deposit but it's not caked.
I'm pretty sure the gasket's are good as checked the seal and bolted both carbs on pretty tight with a view to backing them off a bit (rubber anti-vibration) once I'd proven all carbs were sucking air.
The balance screw's worth checking again actually, good point! The balancer can't be used yet other than to prove the float moves on cylinders 1 and 2 but nothing on 3 and 4.
Do you think this sounds like a carb issue (including seals) rather than something engine related. Wondered if it was to do with the valves but hoping not, but have read that the silvertop zetec is prone to sticking valves...
Engine's done 8,500 miles from new and is about 17 years old. It's always run fairly rich so there's a fair amount of carbon deposit but it's not caked.
Double check the balance screw first, then if that looks OK, do a quick compression check with the throttle wide open would be a sensible next step I'd think.
ETA, forgot to say, I always put 5W30 in ours. Used to use Titan Pro Race but last oil change (this weekend just gone as it happens) put some Ford synthetic in it. I know followers can be sensitive to oil grade, and very low miles over a long time can also be problematic I guess, but losing 2 cylinders like that does seem to suggest a problem on one carb as the simplest answer.
ETA, forgot to say, I always put 5W30 in ours. Used to use Titan Pro Race but last oil change (this weekend just gone as it happens) put some Ford synthetic in it. I know followers can be sensitive to oil grade, and very low miles over a long time can also be problematic I guess, but losing 2 cylinders like that does seem to suggest a problem on one carb as the simplest answer.
Edited by CorseChris on Monday 22 April 16:10
Just wanted to update - turned the balance screw in a turn and a half and backed off idle for cylinders 1 & 2 and increased idle for 3 & 4 and guess what, got some rather nice suction on carb 2!
Getting the hang of cabs a bit more now thanks to your advice
I've read the tricky thing is actually balancing all 4 cylinders for smooth running and idle around 1,000 RPM. Would you suggest experimenting with idle screw and balance screw until it sounds about right? The balancing tool appears to be very hard to get accurate!
Getting the hang of cabs a bit more now thanks to your advice
I've read the tricky thing is actually balancing all 4 cylinders for smooth running and idle around 1,000 RPM. Would you suggest experimenting with idle screw and balance screw until it sounds about right? The balancing tool appears to be very hard to get accurate!
It's a bit of an iterative process. Balance each carb to itself, then adjust the main carb balance screw to match the two, tweak the idle as required, then rinse and repeat until you have all 4 barrels at the same draw and the idle speed you want. I always used to use a couple of colour tunes when doing the webers as well, to get the mixtures the same on each barrel as there is always a bit of interaction between the adjustments.
I also had the float type gauge and yes, I agree, a bit fiddly, but they do work once you get the hang. The classic webber balancer is better if you can get one though. Either that, or go old-school and use a chunk of pipe in each choke to listen to it.
Getting there, well done.
I also had the float type gauge and yes, I agree, a bit fiddly, but they do work once you get the hang. The classic webber balancer is better if you can get one though. Either that, or go old-school and use a chunk of pipe in each choke to listen to it.
Getting there, well done.
thescamper said:
You could always build yourself a 4 channel U tube manometer, there used to be a design on-line but I can't readily find it. All you need is a bit of board, some clear platic pipe and a few other bits and pieces.
Sounds epic! Will have a hunt around for the guide online but please post it here if you find it first. Bank holiday coming up too, always good for a bit of DIY and this certainly beats putting a wardrobe together or painting!4 channel U tube manometer - sounds like something from Wallace and Gromit
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