924Board.org

[Porver9two4]

I am in the process of helping to get a longtime idle 924 back on the road...
It has come to me with absolutely no history as a non-runner of some years, but has clearly been 'fiddled' with in the past.
It has literally had every possible problem under the sun, pretty much everything has been tampered with (badly) and I am really having to dig deep and draw on all my prior 924 experience to make headway.

Just some of the things I have had to fault find and rectify include removal of an immobiliser and alarm system, ignition switch wiring, removal of flying hard-wire bodge lead direct to the fuel pump and restoration of correct current path through fuse box and DME relay, wrong spark plugs, ignition timing miles out, rebuild of fuel metering head (previous cack-hand had been in there and ruined ALL the o-rings amongst other delights).... and so on and so on.... It seems that if it could be fiddled with it has been, so I have to assume nothing is 'safe'.

My hunch is that whoever was butchering it previously was misguidedly chasing a non-start issue (probably originally caused by a faulty immobiliser). In the process they created a secondary problem that masked the first, then created another and another as they tried in vain to 'fix' it... ultimately leading to a total clusterf***

HOWEVER, headway has been made and it now runs .... and runs pretty well considering. I am pretty confident I now have the electrical side of the wiring sorted, the fuel pump(s) are working correctly (through the DME relay), the cold start injector is working and the ignition timing is correct.

When cold it fires up on the key easily, although initially it is a bit reluctant to rev and bogs down as you open the throttle (like it's under-fueled) - it will tick over happily though. Pretty quickly that reluctance clears and it revs and sounds fine. Ticks over fine and drives fine, even at wide open throttle. It stays that way all the way up the temperature range and will warm up to where the radiator fan kicks in. BUT, around this time, once up to temperature, the engine will die at idle (as you pull up to a junction say) and it will not restart. Checking spark at this time shows spark is good, but pulling an injector shows the injector dry and it doesn't produce much more than a drip of fuel as you crank it on the starter.

At this time it will bump start and drive with great reluctance but will die again if not actively kept revved.

If left to sit for a while it will fire up on the key as if nothing has happened and run happily again...... until the next time it sputters and dies....

I am starting to wonder if the fuel pressure has been 'fiddled' with at the WUR and it is being starved of fuel when the engine gets hot. I don't have a fuel pressure test rig to check though. I guess it could also be metering plate to metering plunger adjustment as I know one of the prior problems created by the cack-handed fiddler was catastrophic over-fueling owing to metering head balls-up....

What do you guys reckon? would the wrong control pressure at the WUR give the symptoms of dying when warm as described? whilst allowing it to run ok otherwise?

Investigations so far seem to point to insufficient fuel, so what else might be causing it to die when warm?

[Fasteddie313]

Yep, could definately be the WUR..

You should be waiting for it to come up to full hot operating temp before you adjust the AFR screw, and idle screw, and timing..

Even if the WUR control pressure is wrong, you should probably be able to get it to idle ok when warm with the AFR screw.. Then adjust the idle air bypass screw, then the AFR screw some more and back until you get a good idle at proper RPM.. I'd adjust the AFR screw towards rich until it started hurting the idle and then back lean a touch just to where it idles good so you are a little on the rich side when done..

If that doesn't work then something is indeed wrong somewhere and you really need a method of pressure testing..
You can buy one or I just made a permanent install one for my car with 3mm compressions, T block, Gauge, and a valve, and resold my Hoffman tester..



If you want to make one perminent or removable you just have to figure out a way to get a gauge and valve in the middle of your WUR line, not rocket science..
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80 Turbo - Slightly Modified