I am trying to track down an air leak in the fuel system of my 83 240d. The car has good compression and fires up readily. Idle is smooth, but has an intermittent miss. The miss seems to increase in frequency proportionate to the throttle up until about 2000rpm+-, then smooths out somewhat. There is white/gray smoke at idle and a lot of smoke when the engine is revved. I have set the timing by drip method and by an unapproved ip installation. The valve adjustment is done. The timing chain has been corrected by woodruff key, 4 degree elongation.
I got a new flexible line from the primer pump to the filter. Unfortunately. the line is semi opaque. I put a clear hose from the feed line to primary filter, no air. I installed a new bosch primer plunger and no change. I can see no fuel leaks. When I installed a clear hose in place of the cigar hose, I see some small bubbles coming through the line, but not many. If I pump the primer pump with the engine running, I see foamy bubbles in the line, more if I pump quickly. I also made flexible lines with saab fuel line to my banjo fittings. They seem good and secure, but no effect.
My question(s) are what procedure(s) are effective in tracing an air leak. Are there any shop tips and methods to help with this problem? Are certain fittings and areas more prone to leaks?
The car seems right to me under the miss and smoke issues.