240 General: Mysterious Starting/running Problems

[sunnyvic]

What make of petrol do you use and could i be rude in saying is it dirty petrol causing the problem..regards just trying to help//..sunnyvic

[leftfootleashed]

Originally Posted by stephend

Edit: just re-read your original post. As, prior to replacing the injector seals, it would cold-start

Just to be clear, the cold starting problem was there before I did the injector seals.

This suggests that working properly (assuming your AAV is) the idle speed should be constant (as I would usually expect of any car)...

Originally Posted by stephend

mine has always started immediately on the key, no matter how cold, but has never gone to a fast idle. Instead, it ticks over, perfectly happily, at about 800 rpm while the engine starts to warm up (e.g. while I go round and scrape the ice off the windows).

...whereas this suggests working properly you get the fast "warm up" idle:

Originally Posted by Paul240480

^^^. Mmm, mine never went to a 'fast idle' until I bought a replacement (2nd hand) AAV from 'suterman' when he broke his GLT.

Since fitting that one, when it is really cold the revs do go up to around 1400rpm and as it warms up drop to 850-900rpm.

I always thought that a correctly working AAV would make the car do just that?

Hmm... somewhat inconclusive. I guess it's quite possible that stephend's is faulty but doesn't cause a problem, because, as Paul points out, we don't live in Sweden (unfortunately).

I have been tweaking the idle speed since I cleared the PCV blockage, and I think it might be running better - I've got it to idle at what sounds a reasonable speed (~1000rpm) without it seeming "starved" on starting. I started it this evening for the first time since Wednesday, and it started no problem. Unlike when I left it for a similar period (Thursday-Monday) a couple of weeks back when I left it in the car park at a festival and it took ages to start. Only difference is it was wet then (I've tried cleaning and drying the dizzy cap before, but it seemed to make no difference - I'll make a point of trying this again next time it won't start after it's been wet).

Not sure what to try now - may just leave it for a bit and see if the problem re-occurs. Maybe the PCV unblocking was all it needed.

Might also try unplugging the AAV electrical connector seeing if I can discern whether or not that's making a difference at all. Hopefully I can at least answer the question of whether it's that that causes the "warm-up revving". Will report back.

[leftfootleashed]

Originally Posted by sunnyvic

What make of petrol do you use and could i be rude in saying is it dirty petrol causing the problem..regards just trying to help//..sunnyvic

Whatever's cheapest! Not a policy I apply to many things, but with petrol I didn't think it made a difference. I've only once before heard the opinion that branded fuel was better for your car than supermarket fuel but that was years ago. I've heard newer engines are more tolerant of differing fuels though, so you may have a valid point.

I don't know how I'd check this other than by buying different fuel for a while.

Appreciate your help, someone's got to think of these things!

[stephend]

Originally Posted by leftfootleashed

Unlike when I left it for a similar period (Thursday-Monday) a couple of weeks back when I left it in the car park at a festival and it took ages to start.

Lateral thought: could this be a fuel starvation problem? Back in the days of mechanical fuel pumps, it often took a bit of cranking to start the car when it had been standing for some time, and I always understood it was because all the fuel in the fuel lines had drained back to the tank. At the other extreme, on modern injected engines, you hear the electric fuel pump prime as soon as you turn the key, and you get an instant start if you wait for the second or so it takes to prime before you operate the starter (it cranks a bit if you don't wait).

Now, on my 740, the main pump (the underfloor one, not the lift pump in the tank) always kicks in a second or two after the engine fires, never before or during cranking. Again, I don't know if this is how it's supposed to work, but it doesn't seem to be a problem! I don't know what the pumping arrangement is on your 240, but could this be some sort of low fuel pressure issue...?

[Paul240480]

^^^ a good thought... B200e will have an in tank pump. They often fail. The car will still run..... for years, erm mine did for 3 before I replaced the in tank one.
Symptoms will be the main pump get noisy from ,say a third of a tank or less.

Can't say (because I can't recall) if having a duff in tank one made a difference to starting though .

Obviously it is good practice to replace tha in tank one as leaving it just make the main one work harder and wear more.

Keep going, interesting thread this one

[sunnyvic]

Many years ago in fact back in the 1980 s i had a 164 and actually found that if i used Esso my car would run no problem but if i put in shell or one of the other brands my car would be hesitant have you tried to put a good dose of injector cleaner through the system,personally i would start at the tank and clean right through and change any inline filters and use only one brand of petrol ,i could be talking rubbish as in previous years i was a seaman on British oil tankers collecting oil from far east and delivering same oil to any of the big companies in the uk part to one company and the rest to another of course a lot depends on the way its refined regards sunnyvic

[leftfootleashed]

Started up yesterday having not moved it since Friday, and even then just rearranging on the driveway. Started first time, and it wasn't warm (the thermometer on the college I drive past said 9 degrees). Either unblocking the PCV has solved the problem, or the problem's more complicated than I thought. Hoping the former.

Originally Posted by leftfootleashed

Might also try unplugging the AAV electrical connector seeing if I can discern whether or not that's making a difference at all.

I did try this once. Started with the connector unplugged and it steadily revved up to over 2000rpm - higher than it would normally go - before I shut it off. My theory is that the increase in engine speed is caused by it warming up and therefore running more efficiently, etc. and that the AAV should counteract this by reducing air intake (presumably modern cars do this in the ECU). If the AAV's faulty, e.g. it's resistance has increased, therefore the current through it has decreased for a given voltage, so it heats up slower and closes slower, you get this increase in revs.

On the other hand, I could be talking out my arse

Haven't got round to listening for the in-tank fuel pump yet :/

[leftfootleashed]

Haven't updated this thread in a while. My current thinking is that a fuel supply problem is to blame. The car's still taking an age to start, but always does so. I'm worried that I'm ruining the battery cranking it for 30 seconds or more.

I'm pretty sure I can hear it in the back so it's working to some extent. I would have said it was particularly loud, but maybe the fact that I can hear it at all when I'm sat idling is not a good thing. Unless I'm hearing the main fuel pump - where is that? I haven't noticed a particular difference between a full and empty tank.

My friend suggested a leak in the fuel system that's allowing air in, which would explain why the problem is worse after the car's sat for a few days as the fuel runs back into the tank. Any particular areas I should check for this? Injectors? Fuel filter (replaced a few months ago)?

[Paul240480]

The main pump is basically under the rear nearside passenger seat. Stick your bonce under that area and you'll find it. If its 'tired' or your in tank one had died you'll hear it, as mentioned when fuel is low. It may well be 'grumbling' but not hearable from inside the car, so have a look/listen whilst its running.
I am sure you will have heard it already if it is 'grumbling', it is quite an un-missable 'buzz' once it gets going......

You should also be able to hear the in-tank pump, again whilst running slip the fuel cap off & stick your ear close to the filler tube....

[leftfootleashed]

Cheers Paul, I'll have a closer listen now my ear is better informed!