72 142e power drops / Electronics magic

This has been happening for a little while but seems to be getting more pronounced. Whenever I have my 72 142e on the highway over 60mph its like the motor hiccups. A loss of power for maybe half a second like a momentary fuel cut. This started happening like once a day but now it may happen 1-3 times per drive if I am on the highway. The strange thing is besides that everything is cool besides when its around or below freezing and my temp/fuel gauge/cluster lights won't turn on until about 3-5 minutes into the first drive of the day (alternator is at 12 and jumps to 14.3 when everything else kicks on). Any suggestions as always would be appreciated!


TLDR - Volvo be coughing and electronics be cray cray

Check the junction in the engine compartment. The ignition switch gets power from it and the alternator charges the battery through it. Disconnect the battery first, though. It's behind the left headlight near the battery and it looks like this.



Be careful with the cover. It's fragile and NLA, although I have a 3D printed repro if you need one.

There's also a fuse for the fuel pump relay under the hood. It's exposed to the elements so the contacts may need to be cleaned. Some dielectric grease on the contacts will help prevent corrosion in the future.

The transition from 12 v to 14.3 volts may be occurring because you have a bad wiring connection to the field winding on the alternator ( or the voltage regulator is sticking if you have the original style alternator and regulator). Bad electrical connections are the bane of vintage Volvos and a double bane on vintage Volvos with D jet.

The junction block identified above is an excellent place to start. With the battery disconnected, pull it apart and clean up all the connections. I recommend applying a little Oxgard grease to the connections, goes along way to improving electrical conductivity (available from Home Depot, Lowes ...). Dielectric grease is an insulator. It will protect the connections once they are in good condition; but, does not improve conductivity. Oxgard improves the connection and helps to seal it. The Djet controller gets its 12 v supply from that distribution block (through the main FI relay) so if the connections on that block are bad - then you definitely have problems.

Have a look at the connections on the back of the alternator and the voltage regulator. Check the condition of the wires - check for missing insulation and broken wire strands. Clean up the connections and apply a little Oxgard to the spade connectors and stud / ring connectors.

Your momentary hiccups might be caused by momentary loss of 12 v power to the D jet system or the ignition system. Does the momentary loss of power occur when you hit bumps? One of the first things to check would be the ignition switch. As they get old they can become intermittent. Other things to check

- connections to the ignition coil primary and the connection to the distributor.
- check the spade connections and wiring on main FI relay - clean up and apply a little Oxgard
- check the fuel pump fuse and the fuel pump relay connections - clean up and apply a little Oxgard. If the fuse is original replace it - the ends of the festoon style fuses tend to fret and wear with vibration leading to flaky connections.
- check the connection from the coil + terminal to the main FI relay

When I ran D-Jet, hiccups while cruising were often a result of a worn out throttle position switch. Don't go throwing parts at it randomly, but something to test.