Replaced virtually every component but seems worse... suggestions?

[abgwin]

When I first got my '81 FI 2.0 coupe, I found fuel in the oil, so went about replacing all the major components in the fuel system: injectors, cold start valve, thermo time switch, temp sensor. It actually ran worse than before, so I went back through and found the connector to the temp switch was worn and cracked, so spliced a new one in and got incrementally better results.

It's incredibly cold natured and won't idle till the temp is well off the peg, just dies unless revved.

The other connectors look fine. Should I assume they're bad and replace them anyway? Is there a method to test them to see if they're working?

One other bit of data: when I replaced he cold start valve, I noticed that there's a seal for it advertised but there was none in place. There didn't appear to be room for one; the surface of the valve seemed designed to mate to the intake. Should there be a seal, and could the lack of one cause the problem?

Oh, and while we're at it, now I'm getting a wisp of smoke between the cam and firewall after it runs for a bit. I've replaced the cam cover gaskets; what else would leak oil onto the exhaust? I think the seal between distributor and cam is bad, as the distributor's underside is filthy - might that be the source?

[rossocorsa]

Auxiliary air valve probably kaput, this is a temperature dependent device that feeds additional air during the warm up cycle, they stick when old causing stalling when engine isn't fully warm.

[Neil-yaj396]

The smoke will be oil leaking onto the exhaust from the Cambox gasket (between the camshaft and the cylinder head). A really common problem.

[Ammy]

Smoke could also be head gasket failure allowing oil under pressure being sprayed from joint on to exhaust..  How do I know-- because I've had it happen to me.

[abgwin]

Thanks for the advice.

I pulled the aux air valve - the mount is a little corroded and the bolts weren't very tight - but it shows 48 ohms resistance at room temp. I've been told that a dead one would show no continuity at all.

I'm not sure if it needs a good ground to work right, or how to know if it's working at all.

[peteracs]

Hi

You could try disconnecting whilst running and see what happens?

Peter

[rossocorsa]

Will try to check up if I find time, trouble is NA spec is slightly different to euro

[rossocorsa]

Someone else correct me if I'm wrong as I am not sure but I think the aux air valve uses two sources of heat, it is based upon a bimetalstrip and a sliding plate tensioned with a spring (which could be broken). When engine is totally cold it will be fully open starting the car causes a current to pass warming the bimetallic strip which starts to close the valve by pulling against the return spring. The valve is also partially dependant upon heat from the engine and this further contributes to the bimetal strip drawing the plate further until the air flow is blocked at operating temperature. With age the valve can become sticky giving erratic behaviour and stalling when the engine is not fully warm also the bimetal strip will deteriorate with age. Check if there is a free flow of air through the valve when off the car if not it is definitely defective. Measuring the resistance of the valve doesn't help a lot as it is probably the mechanical parts of the valve that are showing old age. I hope that this solves the problem however must admit from what you have said I am not sure it will! As regards a new valve if you can't get the exact match you may find that a similar unit off another Bosch injected car will work well enough (if you are lucky).

[rossocorsa]

Another possibility is that the valve is permanently fully or partially stuck open, if so someone may have adjusted the warmed up idle to suit which would again cause stalling and poor starting when cold. If the valve is working the car should start from cold with no pressure on the throttle pedal at all.

Hope that all makes sense I find it difficult to explain properly sometimes!

[abgwin]

I'm lucky to have a VW and Mercedes mechanic on tap, as he's an expert on L jetronic.

He's told me how to adjust the valve (you're correct that it should be open when cold and gradually close as it warms) so I was able to test fit it and got another incremental improvement.

Beta won't quite idle on her own, but it's substantially less work to keep running.

I assume that more diligent attention to vacuum and air lines, along with determining whether there's really a seal on the cold start valve, and perhaps a look at timing might get me past the hump.

Thanks, all.

[abgwin]

Another update:

Some adjusting of the idle control, and she's running much much better. I think a few more (or several) passes of the vacuum lines and we'll be right.

However, still a very long time cranking until she fires at all, at least 30 seconds and sometimes more. Once she coughs, she almost always catches soon after and we're good.

I'm wondering if the fuel rail isn't holding the fuel and all this time waiting is for it to repressure, except that it doesn't seem to matter if I let the pump run for a bit before cranking.

Would this indicate the pump weakening? It's supposed to be new (or newish, according to previous owner) Or perhaps another indicator or vacuum problems?

[Neil-yaj396]

Might be worth getting the fuel pressure checked? It does sound like a fueling problem. The fuel should be there ready to go, unlike a mechanical pump that sometimes has to re-fill the carburettor before the engine will start.

[MattNoVAT]

Sounds like air is being drawn into the fuel rail when the engine is stopped after running.  Then its taking time to pump fuel back up, I have similar problems with an old diesel engine with a leaky injector, it used to fire up first time every time, but now the injector leaks its taking its sweet time after 15 seconds of turning over,