Rough running after starting

BX Tech talk
Post Reply
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Rough running after starting

Post by Rich »

My 19 Auto petrol (with manual choke conversion) has developed a problem over the last week....

In this warner weather it seems to like to be started with a couple of pumps on the throttle, no choke and then held at about 1200 rpm on the throttle for a wee bit before driving off. However, in recent days, once it has fired and ran for a few seconds held at 1200 rpm, it starts to chug badly as if it is being over choked. I also noticed a wiff of dark smoke (unburnt fuel???) whilst it was chugging this morning. On driving off it seems ok and once warm it ticks over smoothly.

I also noticed that sometimes if it is started from hot, after a short distance it goes through a period (maybe 10 or 15 seconds) where it seems to hesitate. Related???

Any advice gratefully recieved.

Rich.
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
User avatar
Tim Leech
Over 2k
Posts: 15565
Joined: Tue Apr 15, 2008 11:12 am
Location: Derbyshire
My Cars: Various
x 141

Post by Tim Leech »

Have you tried starting it with a small amount of choke and not touching the throttle?
Lots of Motors, mostly semi broken....
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

Hmmm!... You may be on to something here Tim.

I tried this this morning and the chugging did not appear. It did need to turn over for maybe 8 to 10 seconds (which I understand is not a problem???) so maybe I've been too premature to pump the throttle to make it bust into life. I guess I'm just used to my 2cv's starting at the flick of the key.

I'll give it a week and report how I get on.

Thanks Tim :)
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

It ain't starting at all now!

It has been left unused for 3 days outside my house and this morning wouldn't start at all :(

It occationally fires, runs for 1 second and then dies again.

Any ideas before I scrap it! :?
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
User avatar
Tim Leech
Over 2k
Posts: 15565
Joined: Tue Apr 15, 2008 11:12 am
Location: Derbyshire
My Cars: Various
x 141

Post by Tim Leech »

Rich wrote:It ain't starting at all now!

It has been left unused for 3 days outside my house and this morning wouldn't start at all :(

It occationally fires, runs for 1 second and then dies again.

Any ideas before I scrap it! :?
Have you tried with the choke out fully and not touch the throttle? I take it theres plenty of fuel in it.
Lots of Motors, mostly semi broken....
User avatar
maxgreenwood
BXpert
Posts: 830
Joined: Wed Aug 15, 2007 9:44 pm
Location: Dublin, Ireland

Post by maxgreenwood »

at the moment with no throttle, mine starts for a second and dies straight away. I have to give it a quarter to half throttle or one pump of pedal before starting and then feed it some more gently. You must have tried all sorts, does feeding it like that work?

I'm sure i'll get to the bottom of it one day. Doesn't bother me but would another potential owner.
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon
User avatar
Tim Leech
Over 2k
Posts: 15565
Joined: Tue Apr 15, 2008 11:12 am
Location: Derbyshire
My Cars: Various
x 141

Post by Tim Leech »

I would AVOID pumping the throttle when starting from cold, the auto-choke Max should take care of it, as soon as it fires then give it a few revs for a second of two.
Lots of Motors, mostly semi broken....
Linegeist
BXpert
Posts: 788
Joined: Thu Oct 27, 2005 6:35 pm
Location: Anglesey - out near the nuke power station!

Post by Linegeist »

I suspect that what you're describing is classic fuel drainback - and I have a hunch you've got a similar problem to me. Your petrol's draining back to the tank when the car's stood for more than a day or so.

If you fill a small bore pipe with fluid, hold your thumb over one end and suspend the pipe vertically, the fluid will stay in the pipe because air can't get in to allow the fluid to drain out.

The BX fuel system, when the engine's running, continually draws petrol from the tank, pumps it around a closed loop (off which the carb float valve sits) and back to the tank. This ensures that a supply of cool petrol is always in the fuel lines and helps to prevent vapour lock - where the petrol evaporates inside the pipes due to engine heat soak. The problem is, the fuel tank's much lower than the carburettor and the reason the petrol doesn't all drain back to the tank when you switch the engine off is because the fuel lines are sealed - there's no air can get in them.

However, if there's a pinhole air leak upstream in one of the fuel pipes, or maybe a poor joint, air will leak in and allow the petrol to leak back to the tank over a period of time. When you try to start the engine, the only petrol the engine has available is in the carburettor float bowl - and that's been evaporating for several days. If that runs out (giving you your few seconds of running) before the pump's drawn fresh petrol all the way from the tank (and uphill) then you have no petrol for the engine to start.

An easy way to check for this is to take off the rubber hose on top of the carb venturi and, while peering into the carb throat, operate the throttle linkage a few times. You should see neat petrol being squirted into the manifold by the accelerator pump. If it isn't, then the chances are you have fuel starvation due to drainback.

A further check is dumping a teaspoonful of neat petrol into the carb throat. Don't go mad here - you don't want to hydraulically lock the engine. A teaspoonful's just enough. If the engine fires, then it's a petrol problem. If you're really tricky, you can gently dribble petrol into the carb until the engine catches, and keep it dribbling until the fuel pump's drawn enough petrol up from the tank for the carb to take over on its own. If you set light to your car doing this then you never heard this trick from me. Deal? :?

I had precisely this problem with my Athena, which often goes weeks without being driven. Rather than cane the starter motor for several minutes every few months, I fitted an electric pump in line with the mechanical pump and operated by a push switch on the dash. Operating the electric pump for 10 seconds prior to starting the engine after a long layover ensure a first time start every time.

Worth a thought?
User avatar
maxgreenwood
BXpert
Posts: 830
Joined: Wed Aug 15, 2007 9:44 pm
Location: Dublin, Ireland

Post by maxgreenwood »

thanks Bob, sounds like it could be it, i'll get investigating, and i still need to check out the other vacuum pipe/diaphragm thing too.
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

A question...

IF it is fuel drain... Why would it fire and die several times?

Surely it would fire and die once as the fuel is used up in the carb and then not at all.

Another idea:
IF the ignition module is playing up... What would be the symptoms?

PS Thanks for all the help so far... Very much appreciated.

PPS: I ain't really going to scrap it.... Not yet anyway!
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
User avatar
Tim Leech
Over 2k
Posts: 15565
Joined: Tue Apr 15, 2008 11:12 am
Location: Derbyshire
My Cars: Various
x 141

Post by Tim Leech »

Rich wrote:PPS: I ain't really going to scrap it.... Not yet anyway!
You best not! :lol:

Remember its a 20 year old car so expect these foiables!

Did you try the choke without touching the throttle method?
Lots of Motors, mostly semi broken....
Linegeist
BXpert
Posts: 788
Joined: Thu Oct 27, 2005 6:35 pm
Location: Anglesey - out near the nuke power station!

Post by Linegeist »

Rich wrote:A question...

IF it is fuel drain... Why would it fire and die several times?
Because petrol sits in several locations in the carb. There'll be an amount in the float chamber, another deposit in the throttle pump chamber and a small amount in the various drillings inside the carb body. There might even be a small puddle or two lying in the inlet manifold. It only takes a tiny amount of fuel in an air charge to make a cylinder or two fire - and give an impression of starting but, once the engine takes a big, combustion-induced gulp, the supply dries up and the engine dies once more.

This is why I suggested trickling a little petrol into the carb venturi, see? :)
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

Roverman wrote:
Did you try the choke without touching the throttle method?
Yes Tim I did... It worked fine last week when I was using it every day... I did have to turn it over for longer than I was comfortable with... Maybe 15 seconds before it would fire.

However, as soon as I have left the car for 3 days whilst using my bike to get to work... It ain't starting at all... What ever I do.

I must say that I have not even opened the bonnet yet as I've been too busy but I will have a good look at the weekend.

I main worry at the moment is that I drove my Red and White 2cv last weekend for the first time since it's year long body resto and broke the Gearbox (third gear synchro ring has broken up). So with the big 2CVGB shine and show weekend starting next Friday... I really would like it to be there... One quick 'box change coming up.
Last edited by Rich on Thu Jun 23, 2011 3:50 pm, edited 1 time in total.
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

Linegeist wrote:
Rich wrote:A question...

IF it is fuel drain... Why would it fire and die several times?
Because petrol sits in several locations in the carb. There'll be an amount in the float chamber, another deposit in the throttle pump chamber and a small amount in the various drillings inside the carb body. There might even be a small puddle or two lying in the inlet manifold. It only takes a tiny amount of fuel in an air charge to make a cylinder or two fire - and give an impression of starting but, once the engine takes a big, combustion-induced gulp, the supply dries up and the engine dies once more.

This is why I suggested trickling a little petrol into the carb venturi, see? :)
Thanks for the advice Bob :)
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
Rich
BXpert
Posts: 213
Joined: Thu Oct 14, 2010 11:35 pm
Location: Northamptonshire

Post by Rich »

BX love resumes :D

I finally got the chance to lift the bonnet this evening. After 15 minutes fiddling... The ol boy burst into life.

The problem?... Three of the HT leads pulled off without any resistance so needed a nip up with a pair of Pliers and the plugs were in a right old state and needed a clean :oops:

So a new set of plugs and HT leads are on the shopping list and I'm glad I started with the simple stuff. I'll probably have a look in the dizzy cap at the weekend as well.

Hopefully all will be well now... Time will tell.

Thanks again for all the help... it's very much appreciated :D
'86 2CV Dolly
'81 2CV 007 Drummer
'82 HY Shorty
'77 Smurf blue Ami8
'92 TZD Hurricane (keeping it safe for a mate)
Post Reply