1989 740 won't idle

[Laird Scooby]

Originally Posted by griston64

https://youtu.be/4GMnba1GC00

Video of 740 starting and cutting out

You've got the Permissions set to "Private" on the video Mark - we can't view it.

However, that's going to be popping, spitting, not pulling cleanly when it does rev and definitely won't idle! Here are 3, maybe 4 reasons why :



Reason #1 - Rubber sock top Jubilee clip not square on sock and loose

Reason #2 - As #1 but for the bottom of the rubber sock

Reason #3 - someone has adjusted the throttle stop screw to try bringing the idle speed up and the idle microswitch is no longer being made

Reason #4 - Idle bypass screw (the knurled one to the left of the throttle butterfly) appears to have been screwed in too far.

Reason #5 - i can't see any but if they've been hamfisted with the above, they may have split the rubber sock

Reason #6 - Again, can't see properly in any of the photos but the hose on the AAV (Auxiliary Air Valve, side of rocker cover) doesn't look right resulting in potential air leaks..

Reason #7 - throttle cable appears to be over-adjusted (tight) recently from the witness mark on the adjuster!

If it did indeed run out of petrol, there is the possibility (albeit a very slight one!) that it backfired through the inlet manifold and ripped a hole in the rubber sock. Again, this can't be seen and if it has happened, would prevent idling and/or running properly.

[griston64]

Deleted

[griston64]

https://youtu.be/q5a0zAwCh9I

Or this one ?

[Laird Scooby]

Originally Posted by griston64

https://youtu.be/q5a0zAwCh9I

Or this one ?

Still "Private".

[griston64]

https://youtu.be/q5a0zAwCh9I

This working ? It's saying public now Dave

[Laird Scooby]

That's better Mark! In the vid, 2 secs in roughly, as it tried to start but coughed and spluttered, there is spitback/fuel stand-off and it emanates from just under the inlet manifold on #1 inlet tract. Suggests the manifold gasket.

That's probably the primary cause of the lack of idle but someone has obviously tinkered with it as noted in my post above so (as far as i can see at the moment) a new inlet manifold gasket and it should in theory be capable of driving away, albeit with a high idle.

If there are other problems then you'd have to taeke them as they come but it might also be worth checking the tightness of the inlet manifold nuts, just in case someone has loosened them and not refitted them tightly.
Also if the inlet manifold was removed to fit the new injectors (can't think why but they can be reluctant to move after having been in a while) and they neglected to fit a new gasket or pinched the new gasket, that may also cause it. Could also explain the state of the Jubilee clips (well clip and a large cable tie, didn't spot it last night) on the rubber sock.

You know you want to rescue it!

[griston64]

I know it needs rescuing but not sure if I have the time or space with four cars already + the other 940 arriving next week

[Laird Scooby]

Originally Posted by griston64

I know it needs rescuing but not sure if I have the time or space with four cars already + the other 940 arriving next week

Can i make a suggestion then Mark?

Rescue it from wherever it is at the moment, new inlet manifold gasket, reset the accelerator cable, throttle butterfly and idle bypass screw (relatively easy) and fit a new rubber sock or just new Jubilee clips to the existing one if it's sound, new plugs, filters and oil change, check the dizzy cap + leads, breathers (maybe lift the flame trap up with a longer hose), cooling system flush and fresh antifreeze, give it some "Mark-Magic" cleaning and polishing, new MoT unless it already has a long one then sell it at a profit as a good base for a full rolling restoration and make yourself a bit of profit.

As it stands at the moment, it's essentially a non-runner so is likely to be only worth scrap money and you could in theory break it for more than it's likely to cost you.
From what i can see though it's worth more than that as a going concern and with a bit of luck should give you a quick turn-round as well.

[griston64]

Its actually got an MOT till July 2020 Dave.

I'll have a think about it tomorrow. I think I'll get the other 940 delivered up first and see how I feel then.

[griston64]

https://www.youtube.com/watch?v=YcgP...ature=youtu.be

She idles now but very rough