V12 starting issues

[nigeld]

Im in the process of attempting to revive a UK spec v12 FHC that has stood for a while. I have drained the fuel to replace with fresh fuel, checked the fuel filter at the pump and cleaned/rebuilt the carbs on one side (will get to the other two but need to get the car running to move now). There seems to be a good spark at the plugs but at present the car will only start with a generous spray of EZ start. Once running it seems to run ok.

1. I have noticed that some of the vacuum hoses (including the vacuum advance from the distributor) have come loose, deteriorated and cracked. Would this effect starting?

2. Any thoughts on what to look at next in terms of diagnostics? I'd just like to get the car into a state that it reliably starts so that I can move it to a better workspace. The EZ start suggests its still a fuel issue I think?

TIA (my other car is a single cylinder motorcycle so the V12 is a little overwhelming!)

Nigel

[angelw]

Nigel Wrote:

I have drained the fuel to replace with fresh fuel, checked the fuel filter at the pump and cleaned/rebuilt the carbs on one side (will get to the other two but need to get the car running to move now). There seems to be a good spark at the plugs but at present the car will only start with a generous spray of EZ start. Once running it seems to run ok.

1. I have noticed that some of the vacuum hoses (including the vacuum advance from the distributor) have come loose, deteriorated and cracked. Would this effect starting?

2. Any thoughts on what to look at next in terms of diagnostics? I'd just like to get the car into a state that it reliably starts so that I can move it to a better workspace. The EZ start suggests its still a fuel issue I think?

Hello Nigel,
If it runs OK once started (and presumably warm), I'd suggest the choke unit is not functioning correctly. Typically, the V12 with Stombergs need a very rich mixture when cold to start and that's what you're providing with the EZ Start.

The vacuum hoses won't make any difference to starting, but I would ensure that the hose connecting the carburetor equipped with the choke mechanism is connected with the one that does not. Only one carburetor per side has a choke and feeds the fuel enriched mixture to the one that doesn't via a short connecting hose. It will depend on which side of the engine the carburetors were rebuilt as to whether it is the Front, or Rear carburetor that has the choke unit.

It also depends on the definition of rebuilt. Some just replace the diaphragm in the vacuum chamber and needle and seat in the float chamber and call that rebuilt. If not done, I would be stripping the choke unit and ensure that the fine holes in the rotary plate are clean, as is the rest of the unit.

Regards,

Bill

[nigeld]

Hi Bill

Thanks for the help. That makes sense so I will focus on the chokes. I did rebuild the choke on one carb and the little holes were slightly obstructed. I will take a look at the choke on the other side. Also I will check the adjustment of the rebuilt choke - not sure I have got the cable as tight as it should be - was a fiddle to get it done up securely.

Is the summer/winter adjustment on the chokes crucial? I set the rebuilt one to winter but assume the other side is still set to summer. Based on what you say about V12's needing a lot of choke I guess it will help.

Nigel

[Woolfi]

Does the motor have a good idle when it is hot ? If the idle is good, there es no leak for air at the hoses.
If the motor pulls air through a hole, the idle is bad.
Regards Wolfgang Gatza

[nigeld]

Thanks Wolfgang. I need to investigate the idle when hot fully - it was hunting a little but that could be due to the rebuilt carbs requiring balancing plus so far I have not run it with the air box (and various vents) reinstalled.