924Board.org

[nesty]

Hi

I got a cold starting problem with my 924. I looked in the FAQ and thought I'd put it in to my local garage for inspection. They are a VW/Audi Specialist garage and it was displaying the symptoms below.

At cold takes about 3 or 4 attempts to start. Then it idles not though not great. I can't apply any gas until warmed up, otherwise it will stall. Once warmed up drives ok.

They phoned me up and said it's the fuel metering distribution head & said they cost a arm and a leg to repair, so not worth my time. I gather that it's bad news, as they are hard to come by?

Anybody got any advice can I get a reconditioned one from some where. I have seen on ebay there are a few good 2nd hand ones.

Any advice appreciated, it's a real pity if I have to get rid of it as a real good condition 924.

Nesty
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Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera

[Mike924]

If it's running OK warm, chances are the metering unit's fine.

More likely, the fault is a stuck WUR. Very common problem at this time of your car's life.

There's a bloke on a BWM site reckons WURs can be repaired. I'll dig out the link. New ones are very expensive these days and EBay one are likely to have similar problems...
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[924RACR]

I'd be more suspicious of the warm-up regulator. If the metering unit itself were bad, it would not likely ever be driveable.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Mike924]

Is this deja vu?

Nesty, face facts, mate: it's the WUR.

Buy the Porscheshop one. £130 is a good price for the right unit. Believe me, you'll be glad you did!
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[nesty]

Thanks for replies. I meant to say also that it was pointed out that the metering unit is slightly leaking as well from inbetween the joins.

Just both items are expensive just want to be sure before buying.
_________________
Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera

[Mike924]

Where exactly is it leaking from?

If it's just the banjo joints, that's easy to fix with new copper/aluminium washers.

Serious leaks are from around the plunger down into the air-box (a tiny amount is acceptable, even inevitable, given that there is no seal) and from between the two halves of the fuel dist. unit (square bit on top).

If it's leaking from either of those places, I'd replace the whole unit. You can pick one up from Ebay for not too much money. I'd be more prepared to trust a second-hand fuel dist rather than a WUR...
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[nesty]

The mechanic reckons its leaking from in-between the joins on the square bits. I am going to clean up the area at the weekend and see if this is the case. If it was leaking from the joins I'd expect the engine to be running a lot rougher, as would be a vacuum leak?

How easy is it to replace the whole unit. Looks like a case of undoing the fuel and injector pipes and the 6 Allen bolts on the base? I have seen a few on ebay, so most probably go 2nd hand unit, if have to replace. Though my reckoning as people say I reckon it's the WUR, as when car warm it picks up rather well.
_________________
Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera

[Mike924]

There's very thin steel gasket between the two halves of the square fuel dist. Once this starts to leak (fuel), there's not really much that can be done.

It won't cause a vacuum/air leak. The air seal is a rubber O-ring between the fuel dist and the rest of the metering head.

Metering heads are easy enough to extract and replace, allowing for the number fuel line connections. Perhaps the easiest thing to do in your circumstances (i.e. a leaky dist) is just to replace the dist block, leaving the rest of the metering head in place.

The fuel dist is only held on by two screws. Undoing these allows you to remove the dist (having undone all the fuel line connections) and replace the O-ring (good practice). The replacement dist will then just drop in.

Two things to take note of: (a) there is nothing that holds the plunger of the fuel dist in, once it's free of the metering head. If it falls out and get grit on it, it's pretty much written off. Plungers are not interchangeable between units. (b) the torque spec on the two bolts is quite low (can't remember what exactly, now). Do them up evenly gradually and not too tight.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[nesty]

OK thanks for this.

Is there a trick of taking off the unit without allowing the plunger to fall out?

I have seen a 1983 unit head on ebay. Person asures me it's ok, Would this fit a 1981 model. I take it there was no change in these between the 1981-83 years?

nesty
_________________
Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera

[Mike924]

I don't think there were any changes throughout the production life of the car. They're all the same (except for very early ones (pre ~1979?) that had a cut-out switch fitted to the air meter).

The real trick to not letting he plunger fall out is to be aware of it in advance. Just slip a finger around underneath to hold it in place as you lift the dist away and do the same in reverse as your fitting the old one. Once the plunger's in contact with the air vane lever you can relax.

When separated from the air meter, hold and store the fuel dist upside-down to keep the plunger in, preferably with a clean rag over it to protect the mounting surface and the valve/plunger orifice from contamination.

It's not tricky to do - the trick is in remembering to do it.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[nesty]

The block is leaking quite visibly from between the joins now. I'll have to replace it, possibly this weekend. Hopefully replacement will make it run a bit better and might cure the cold start problem.
_________________
Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera

[Mike924]

It won't cure the cold start problem. That's a broken WUR.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[gohim]

Don't forget that a cold start problem could also be a symptom of a blown head gasket. Is the car losing coolant? Next time you go to start the engine cold, turn the key to spin the engine, then pull out the spark plugs one by one and look for liquid on the spark plug tips. A leak (fuel or coolant) will short out a/some spark plugs so they won't fire. If you find a liquid, determine if it is fuel or coolant. If you can't tell by sniffing it, put a match to it. If it burns it's fuel (leaking injectors) and if it boils off it's coolant (blown head gasket).

I would fix replace the leaking fuel distributor first to see if the cold start problem is actually a symptom of the leaking fuel distributor. Bosch CIS Mechanical Fuel Injection uses fuel pressure to fire the fuel injectors and if the pressure bleeds off through the fuel distributor, the fuel injectors will not fire untill they are properly repressurized. This would cause an extended cranking period while the fuel pump repressurizes the fuel lines (forcing the air out (lumpy engine idle will be a symptom, if the engine actually starts).

No need to buy a WUR, until you confirm whether a fuel pressure bleed is causing the extended starting by replacing the leaking fuel distributor. then checking for leaking fuel injectors.

[nesty]

Thanks for replies.

Actullay the car has lost a little coolant, but I have been using it quite a bit and the loss was minuimal. I checked the oil dipstick and there was no bubbles or milkyness on it that often related to blown head gaskets. Apart from the cold starting it runs ok. Though I have noticed that the warmer is it the easier it to start.
_________________
Porsche 924 2.0 Litre (1982 model),
Porsche 911, 3.2 Carrera