Is this normal?

[Hubbell]

Hi Everyone,

My van is a funny old thing. When its cold and I use the choke to start it it really plods along and then I turn the choke off and i suddenly get a power boost (bonus). Anyway when the choke is on it almost feels like its lost a cylinder? Anyway last night I took the old girl for a drive and spin and it as if turning the choke of had no power boosting effect intact it got worse and it feels like its running in two cylinders. It's back firing, shaking and generally looking as if its got some issues. I'm fairly handy when it comes to engines and carbs and other mechanical things but whats going on? Could it be that the carb is all gunked and needs a clean or is it more likely that Ive got a dodgy coil, leads spark plugs etc? Strange events...
What I'm trying to get at is before I start changing stuff on the distribution side would it be a better bet to work on the carb first?

 

[Panky]

Sounds like it's running quite rich but I'd check the points, plugs and leads first. If the points are OK and it's still running rough try pulling one plug lead at a time off while it's ticking over and see if it makes any difference, if it doesn't check that plug and lead for issues. You'll generally find out if a lead is OK because you'll get a belt as you pull it off

 

[greg]

Could be what I get....snakeskin from the petrol tank
possibly caused by ethanol in modern petrol, starving your engine of fuel.

 

[THE ICEMAN]

Sounds to me like the carb/choke setup needs looking at. Usually when cold pulling out the choke should result in increased revs and perhaps a bit of 'hunting' if it is a bit to rich. Could be that it is set to rich overall and pulling the choke out is swamping it which will make it run very poorly. Pull out a plug and see if it is sooty or even a dark brown. It should be a light tan colour. Have a look at the end of the exhaust, is it all black and sooty? Is it the original zenith carb? An SU conversion is SO worth doing!
I would start with setting up the carb, new plugs and a check of the points etc as panky says. Well worth also checking for snake skin and dont forget the filter in the pump.


I just need a good rootes...

 

[Hubbell]

I totally get you ice man! I think it is a carb issue. That's exactly what I thinking in regards to the choke lifting the revs but the engine performing poorly in response must be a case of over or under fueling? It is an original zenith. I was planning the SU conversion later in the year when I've got a but more dough, but I would like to keep the van running in the mean time. I might just strip the zenith down and refurb it just to tide me over. Would this kit be ok?
http://item.mobileweb.ebay.co.uk/viewitem?sbk=1&nav=SEARCH&itemId=321298887241

 

[Panky]

It looks OK but as it says in the listing the jets may not be the same as yours.

 

[Aussie Commer]

I had the same problems with my original Zenith, kept fouling plugs and making the motor run rough. Once they start playing up they are very hard to get back right. Overhauled mine, worked fine for a week then started playing up again.[!]
I fitted the Webber conversion from Speedys, its a massive improvement on the Zenith and never gives me any trouble and has all adapters etc in the kit.

Although its not as good as an SU, Its an easy and not too expensive fix & the Webber is also a good carb.

Wherever we roam,
we still call our Commer home!
www.commervanoztour.blogspot.com

 

[greg]

This was my worst example of snakeskin at the fuel pump filter

Petrol just about got through though

Swarf got the next filter just above the carb needle valve

And petrol flow was severely reduced this time[xx(]

I am running a Ford carb however
Regular cleans and we run just fine

 

[Hubbell]

I'm not sure if I should own up to this level of stupidity. Before I go any further I would just like to say I'm fairly mechanically competent. I rebuilt my first engine at 18 and I went on to successfully modify my first renault 5 so that it was super fast. I've also rebuilt motorbikes and generally fetteled with every vehicle I've ever owned. So upon driving my van last week it was shaking awfully under excelleration and back firing. It felt like a missfire for sure. However.... I drove it again tonight and as I realised the nearside was vibrating more than the offside and the it crossed my mind - do I have a flat tyre? No, I thought surely not, but to my surprise when I pulled over I did indeed have a flat! As my suspension is shortened the flat tyre was causing some serious vibration and I'd imagine preventing the engine from excellerating causing the back fire?

 

[Panky]

First time I've heard of a flat tyre causing a miss fire
If it was me I would have said I'd found a dodgy lead

 

[Hubbell]

Is a back fire a miss fire? I'll get the spare on this saturday and see how the old girl performs.

 

[Panky]

A back fire is a lot louder Usually caused by unburned fuel igniting in the exhaust[B)]