I'm not familiar with the adjustment of the EHA (yet), However, you stated that you set the digital voltmeter to 20volts and connected it in series with one of the wires to the EHA. I believe you intended to measure the current flowing to the EHA and thus the meter should be set to a current scale (ma or A).

When the meter, set at volts is connected in series, it has a very high resistance and blocks the current to the EHA. If this is what is happening, the EHA will not be functioning and may explain your starting/ running problems.

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1986 300E
1993 Volvo 940 Wagon
1984 Volvo 240 (daughter's)
1976 Dodge 1/2T pickup, gas hog