1980 124 FI vacuum / mixture issues

[ster1]

Hi folks, been awhile

I have a 1980 124 2000 FI that’s more or less a garage Queen. I don’t drive it very much. I recently fired it up to get the emissions checked and it failed. My CO (carbon monoxide) was too high. It was actually 10X higher than it was last year. I’m puzzled, so I did some checks. Valve timing is right on, ignition timing is it 10 btdc. The car runs great. I found my unregulated fuel pressure to be high at about 41. To pull the fuel pressure down to 28, the regulator needs 15” of vacuum. I don’t think that engine has ever produced 15” at idle, unless I advance the ignition to about 20 btdc and crank the idle up to about 1500 rpm, and unplug the advance unit. I haven’t checked compression or valve clearances yet, I suppose my problem could be internal. What kind of vacuum numbers are you folks seeing? Does anyone pull 15 inches? If not, how do you regulate the fuel pressure? What are your fuel pressures at idle looking like? Thanks for any help!

[rridge]

The Spider uses a 2.5bar fuel rail. With the manifold vacuum line disconnected from the pressure regulator and the engine spinning on the starter you should be seeing 2.5 bar (about 35 psi) on the hose to the cold start injector. Use the Bosch FI Diagnostic Manual for proper test procedures and reference specs.

[ster1]

As far as I know, it’s a Bosch L-Jetronic system, and according to the manual that I have, unregulated pressure should be 36 +_ 3 and regulated at idle should be 28. In order to get 28 on mine, I need to pull 15” of vacuum on my regulator, and also as far as I know, my engine has never made 15 inches of vacuum. So, that’s more or less the issue in a netshell.

[spider2081]

I have not checked engine vacuum to the fuel injection regulator however every Spider I have seen with high fuel pressure has been caused by a restriction in the fuel return line. Is the fuel pressure different with the fuel filler cap remov then when its inplace and properly tightened?