ALFAGTV6.COM

[Bruce]

Hello all,

Every 75 (3.0 litre) I have had, all suffer(ed) from the same problem; difficult / jerky / misfire after restart. This occures with a hot engine.
I have checked the carbon canister, valves, filter etc with no fault found.
I have noticed that during the cranking period there is a hissing or drone from the petrol tank; sometimes releasing the vapour pressure by opening the petrol cap elevates some of the problem.
Any idea what the problem is?

[ar4me]

Assuming this is an L-Jet car (and not a later Motronic) I would check the cold start thermo time switch and cold start injector (at back of plenum). The hissing at re-start (kinda sounds like a jet passing?) is pretty normal, I think. I have it and have had it on a number of 3 liter milanos/75.
Jes

[Bruce]

...it is motronic, the last 3 I had where L-jet..

[ar4me]

If it is a Motronic then the 164-guys are probably a better source as no gtv6s and relatively few 75s were Motronic. I'm not sure if it is the same Motronic version as on the 12v 164s, but you could try the 164 forum or the 164 section on the Alfa BB.
Jes

[Zamani]

Motronic just changes the pulse width of the injectors instead of a cold start injector.

Sounds like vapor lock? But vapor lock should be almost non-existant in an EFI car. Something tells me that there's something wrong with the "breathing" of the fuel tank. I'm not very good with these types of problem.

Try opening the fuel cap and starting your car, does it start without problems?

[Mats]

Whan did you change the plugs? Often overlooked and can make a HUGE differance.

[Bruce]

I think it is a vapour lock or percolation / heat soak issue.
I always thought the fuel tank was a pressured closed loop system with any vapour or excess pressure released into the manifold on start up.

Plugs are OK.