Car stalls intermittently on motorway journeys!

Post by **december_boy** » 31 Mar 2005 02:39 pm

Hi all.

I have a '88 340 DL, manual choke.

About a month ago, it developed an issue where intermittently on longer journeys, the car would start to drink petrol, slowly become more and more unresponsive and then grind to a halt at the side of the motorway.

After a min or two, it would restart then the same thing would happen about 15 miles later.

During this whole time, the car would be drinking petrol like a fish - maybe using half a tank for a 40 mile journey.

Then the next journey, it will drive just fine!

I've had a mechanic mate of mine look at the obvious things, cleaned the filters etc to no avail.

I've now replaced the Weber Carburettor, again to no avail.

Any ideas? I've had a look round the forum but I have not found this specific issue. By the way, this can happen any time of the day or night.

Is my car buggered?

Stephen

Post by **5lab** » 31 Mar 2005 02:50 pm

try the carb fix at the top of this thread.

if that fails, check the fuel tank breather hose isnt blocked.

Post by **december_boy** » 31 Mar 2005 02:54 pm

Hi there.

Thanks for such a prompt response.

As I mentioned in the message, I've had a new carb fitted and tightened on.

I had a question around your suggestion about this hose - how would such a blockage make the car run so rich? I'm not a mechanic - just curious.

Stephen

Post by **5lab** » 31 Mar 2005 03:04 pm

how d'ya know its running rich?

i wasn't working on that symtom - just that that can make a car stall intermittently on long journeys...

is the choke mechanism all working ok? check that the air input is fine too - ie that there are no blockages in the air filter, or any of the pipes leading from there to the engine.. it *could* be that if the car is running uber-rich that the engine is simply flooding..

Post by **december_boy** » 31 Mar 2005 03:07 pm

HI.

I know it's running rich because when this issue occurs, I can virtually see my petrol tank emptying! The car will use a half a tank of petrol travelling 60 miles.

I had all the pipes and filters checked when the problem first happened.

Would it be fair to assume that the mechanic did not do a great job?

Stephen

Post by **foggyjames** » 31 Mar 2005 03:37 pm

Was it a brand new carb?

You might be looking in the wrong place...how fresh are the plugs / leads / rotor arm / dizzy cap?

cheers

James

Post by **december_boy** » 31 Mar 2005 03:43 pm

No it was a refurbished carb, not a new one.

I'm bring the car back to the garage on Saturday and I'm trying to make a list of things for him to check as this is an intermittent and extremely dangerous problem.

Any hints would be appreciated - or ideally if someone has seen this problem before.

Stephen

Post by **5lab** » 31 Mar 2005 03:57 pm

well my obvious thought is - perhaps the carb is pissing fuel out somewhere? it definatly sounds like a leak, so if not enough fuel is getting thru, at higher consumption times, eventually the float may empty. try leaving your car running over some newpaper or something, and see if any petrol drips out anywhere.. also sniff around to see if you can smell any. it could be that the carb itself is leaking fuel - for instance from the float chamber.

Post by **foggyjames** » 31 Mar 2005 04:24 pm

Definitely investigate the ignition side too. The intermittance makes it a little unlikely, but it's still highly possible - especially if it's the leads.

The big problem with those Weber carbs is that they literally fall apart - a refurbed one might have all new jets, etc, but if it's leaking air...the acid test is to see how much the carb waggles (independantly of the engine - the whole lot will waggle together because the 1.4s engine mounts always seem to be soggy!) when you try to move it via the air filter pan.

Is there any correlation with any other factors? Hilly terrain, weather, engine temperature, fuel tank level, etc, etc?

cheers

James

Post by **december_boy** » 31 Mar 2005 04:30 pm

No there doesn't seem to be any correlation with other events. I've been trying to piece together why this might be happening to no avail.

The only real clues are that the car only does it on longish journeys (though sometimes it's fine), it drinks petrol, it always starts again and then it happens again maybe 20 miles later. You can tell that it is going to happen after about 10 mins of driving when you can feel a slight judder on acceleration. It's a gradual loss of power until the car literally crawls to a halt at the side of the road (quite dangerous on a motorway).

The car starts easily first thing in the morning.

It's not a cold weather thing as far as I can tell. And I can't predict when it is going to happen other than to say it does it regularly.

Post by **foggyjames** » 31 Mar 2005 04:58 pm

Hmmm....curious....I have a couple of theories, but I'm clutching at straws really.

How steady does the water temperature (temp gauge) sit?
Did the refurbed carb improve things at all, even if just for a few days?

cheers

James

Post by **december_boy** » 31 Mar 2005 05:10 pm

Temp gauge seems to stay steady.

I thought the new carb had fixed things... the car ran beautifully for a week.

Post by **foggyjames** » 31 Mar 2005 05:26 pm

AHA!

Right, I think you're looking at blocked jets. Look in the trusty Haynes manual for advice on removing the jets (probably the main jet in this case), then blow them through with compressed air....although there are probably other ways. I think my carb has a very small quantity of dirt in it, but if it gets bad it just gets a 30 second 'Italian tune-up'...which tends to work

Once it's done, try replacing the fuel filter(s?) with a new one rather than washing it out. I'm sure you don't do this (but I know I do!), but running tank down low on an older car is a bad move, as the dirt from the bottom of the tank gets sucked into the carb - filters are good, but not perfect.

cheers

James

Post by **december_boy** » 31 Mar 2005 05:29 pm

You reckon this is it?!!

But forgive my ignorance, but why does it drink fuel if there is a blockage?
Shouldn't it be the opposite?

Stephen

Post by **foggyjames** » 31 Mar 2005 05:44 pm

Well I'm no mechanic, but there is a limit to what it can be! The theory is that the 'new' carb was clean....for a week....until it got bunged up.

A carb has to provide metered fuel - once that metering goes off, you have to fight the car to retain power. My carb was set up to be lean for a long time, yet I was suffering from carbon deposits (rich running). It was because I'd had to (subtley) pump the throttle to make it go if it tried to die, etc.

These things can be a lot more subtle than you might think! The best thing to do it to take it to an expert...although for an hour of your time and a new fuel filter (and a good thrashing to blast the muck out!), it might be worth it!

cheers

James