Wednesday, October 10, 2012

DT Project Car Update: It's Alive!

by CFlo

Just over two days after rescuing the DT Project Car Volvo 242, we are glad to say that as of Tuesday night, it runs! We had been doing some fuel & spark troubleshooting after replacing the spark plug wires, distributor cap and rotor on Sunday shortly after the purchase. The investigation was fruitful and uncovered fuel pump power wiring that needed replacement. Once that was done, it started - and after a check of vital signs we took this sweet honey out on the road and are happy to report that it drives very well for its age. Big thanks to our readers for the comments and suggestions on the intro post. This car holds a ton of promise and we can't wait to keep going with it!

Back to the repairs...when replacing the broken plug wires didn't fix the starting issue, we turned to the fuel system. Jumpering fuel pump fuses and powering the pumps directly in several ways, we discerned that the in-tank "transfer" fuel pump is dead. However, this alone will not usually cause a 240 to stop running, although it should (and will) be replaced.

We applied 12 volts directly to main high-pressure fuel pump under the car and found it to be in good working order, yet we could not hear it prime when the engine was cranking. A functional check of the fuel pump power circuit showed that there was an issue with the wiring to the main pump, however, and it was not getting power. We replaced the pump connectors with a fresh set, crimped and heat-shrunk the wiring - and while we were double-checking for spark with a timing light, the engine fired and settled into a healthy idle. Great success!

Out on the road, our initial observations were:
  • Almost everything works! The electric overdrive, horn, all lights, and even the air conditioning system are all healthy and functional.
  • There are no major vibrations from the wheels or suspension; it's a smooth cruiser.
  • The high compression, pulsed-EFI B23F engine is a peach and a big improvement over earlier K-Jet engines. It has plenty of low-end and midrange torque that will make this white refrigerator a fun daily turismo.
  • The M46 manual transmission shifts very well, and the clutch is smooth with no chattering or slippage.
  • It's easy to induce oversteer with these little stock tires on 14-inch wheels - lack of grip and neutral balance make it a natural low-speed drifter.
  • It has no problem maintaining 85 mph on the highway.
All in all, we are excited to dive further into the project and have respect for the car already. Stay tuned for more DTPC (Daily Turismo Project Car) updates to come.


  1. ~ i've owned several M-46 OD equipped 240s, and i like them quite well. but i just recently had a two week reminder course in how nice the M-47 true 5 speed transmission is to drive. 29mpg, from a 1980s 244.

  2. Sounds like you scored on this. The non-running status could have been a much bigger hassle to resolve.

    For all of us not does the electric overdrive work, what are the differences between electric overdrive and a typical 5th (overdrive) gear), and what is the advantage of electric overdrive?


  3. The electric overdrive unit that Volvo used for many years was a way for them to get the advantages of a 5th gear for highway driving without having to redesign their transmissions entirely. The M46 trans is a 4-speed standard unit, with 4th gear having a 1:1 ratio. The electric overdrive unit is a planetary gear set (like you'd find in a conventional automatic trans) bolted to the tail of the trans, that when engaged via electric solenoid, reduces the ratio in 4th to something like 0.8:1 - so engine speed is slower than driveshaft rotational speed - hence the term overdrive. In operation it works exactly as a conventional 5-speed manual does, except in order to engage 5th you press a switch on the shifter while it's in the 4th gear position, instead of moving the shift lever. There are no real advantages over a conventional 5-speed self contained gearbox, except that you could disengage the lockout switch and be able to engage overdrive in any gear, effectively getting an 8-speed transmission (not sure why you'd want to, but it can be done). The disadvantages of electric overdrive are reduced reliability and increased complexity - more parts to fail on a 30 year old car. The advantage vs. a conventional 4-speed is better mileage on the highway and a higher geared top speed. We are just glad it works!

    1. Thanks for the info, CFlo. I guess the part I found a little odd is why Volvo wouldn't just add a 5th gear with a sub-1:1 ratio (like everybody else did), rather than purchasing what is likely fairly complex and expensive system and then engineering it into their existing mechanicals and structure. Seems like a lot more work to get the same effect. Unless, of course, they actually thought people might want utilize the available gear reduction in 1st, 2nd or 3rd, which as you said, why would they do that?

    2. ~ @ Larry, the true 5 speed (M-47) transmissions are becoming somewhat more difficult to source. when you find - hoard!

    3. @Larry: even the Volvo experts at ipd don't understand it: "Why in the world Volvo chose to use an electronic overdrive instead of a real 5 speed manual transmission is beyond us, but they did and we have all suffered that decision!"

      From this article, which is a good overview of the "cons" of our favorite brick:

      If these cars were perfect, we wouldn't have so much material for our project posts!

    4. "If these cars were perfect, we wouldn't have so much material for our project posts!"

      Perhaps, but I'm sure we'd find something to complain about.

  4. ~ iPd offers an Automatic Over-Drive Solenoid Bypass Kit, applicable for Volvo's AW-71 automatic transmission, unit eliminates relay and solenoid failures.


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