DTPC Update: Wiring Nightmares, or How I Learned to Stop Worrying and Love My Multimeter

by CFlo

When we last left the saga of the DTPC, our 1983 Volvo 242 DL, we had announced we were entering ipd’s $25000 Build Off for Volvo project cars. Lucky for ipd, clear heads prevailed and we didn’t win a spot although we were amongst the top 5 finalists in the RWD category, of around 300 total entrants for the contest. Despite lacking the big budget injection that winning $5k would have provided, our plan is to follow fairly closely to the “Bizarro Alternate Universe Trans-Am” concept, but also update the car mechanically as well. We’ll need to be carefully shiesty misers of our own money as opposed to gleefully squandering someone else’s, so the project will be sticking closer to the true DT ideals by creating a cool, interesting, hot-rodded and cheap daily driver.

Of course the first step in creating a Daily Turismo after dragging home a dead or dying “classic” has to be getting the damn thing to run right. Now join us as we descend to the 8th circle of Volvo electrical hell and attempt to appease a heady cadre of Teutonic, Capitalist and Norse gods as we wrestle with Bosch fuel injection, Chrysler ignition, and Scandinavian Wasabröd cracker-based wiring insulation.

If you remember back to October of last year, our 242 wasn’t starting when we brought it home. Despite the initial setback we had it up and running in a matter of a few hours of work. After fettling with some wiring and changing out the distributor cap, rotor, and spark plug wires, the original B23F engine ran well enough to serve daily driver and rainy-day drifting duties for a matter of months, which was surprising really. But it was obvious this thing had never received more than cursory attention and the occasional tuneup or minor repair.

It had archaeological amounts of crud, grease and grime covering the block, intake manifold and just about everything else. Because it was trouble-free for a while we delayed getting the CA smog test done… I mean hey, why do something today when you could do it tomorrow? As college freshman-esque procrastination reasoning tends to go, the plan backfired…and so did the engine. The B23F developed some severe ailments; it was misfiring, running on some non-integer number less than four cylinders, and was pig rich, belching black soot out of its clattering free-hanging exhaust system. Now it’s getting down to crunch time for the smog inspection and we’re up soot creek without a paddle, so we break out the tools and start rooting it out.

After poking around in the wiring harnesses again and not finding any obvious issues like disconnected connectors or missing spark plugs, the first order of business to get it running right was replacing the notoriously flaky (literally) main engine EFI wiring harness. The originals are terrible, but we found a much improved aftermarket upgrade in the turbobricks classifieds for $150 shipped. This may seem drastic as a first step but banishing the original harness would save hours of hair pulling and take countless unknowns out of the equation.

Before getting elbow deep in greasy electrons I have to say every shop/garage/driveway needs a helper dog, and at my house Brodie the Skye Terrier is never far away when the tools are busted out. His thick Scottish coat keeps him warm on the foggy overcast days common in LA’s coastal South Bay area.

Diagnostic tools that are handy for a job like this include: multimeter (volts, ohms, continuity), electrical contact cleaner, screwdrivers, needlenose pliers, a brass bristle wire brush for cleaning crusty contacts, a piece of 180 grit sandpaper for cleaning rusty grounds and corroded connectors, paper towels, and assorted sockets & combo wrenches. Volvo’s engineers planned well in advance for such failures, providing the shadetree mechanic a handy workbench / tray in the form of the nearly 12″ wide core support panel.

The factory service manual is another invaluable tool for diagnosing ailments on an old fuel injected European car (or any future Daily Turismo). Bentley is the licensed publisher of the FSM for the Volvo 240 series, and luckily the first year covered in the book is 1983. Also helpful for understanding the engine management system is this book, How to Understand, Service and Modify Bosch Fuel Injection & Engine Management (by Charles O. Pobst, SAE), which explains the principles and specifics of each generation of system and goes into detail on all of the sensors and their function. Understanding how it should be working is kind of necessary before determining why and how a complex system isn’t working…

Under the hood it’s best to start with the easy stuff first; we couldn’t hope to get an automotive electrical system happy without solid power supply and grounds. The main Bosch LH-Jetronic power wire piggybacks on the main battery positive terminal, and in our car it was pulling out of its crimped ring terminal due to vibration, heat, and abuse. An easy fix – I cut off the offending terminal, stripped insulation back to expose clean wiring, and crimped on a new ring terminal that matched the wire gauge.

Even though this early EFI system does not handle ignition (there is a separate Chrysler-sourced spark control computer and wiring harness to the distributor) the primary coil power is supplied by the main fuel injection relay, which is in turn connected to the main EFI wiring harness. These gray wires to the #1 coil primary terminal had been crimped spliced and taped in the past. The quality of the repair work was questionable, meaning that contact may have been intermittent here. This got binned with the rest of the harness.

The injectors on this LH-Jetronic 2.0 system (LH2.0 for short) are all fired at once making it a “batch fire” EFI as opposed to the more finely controllable timed sequential port injection that came later. The wiring for each injector branches off from one main source and there is only one injector driver in the Bosch ECU, which adjusts pulse width based on a variety of factors. Above we can see the common fuel supply rail with injectors below it, and decaying boots around the connectors.

The LH in LH-Jetronic stands for “Luftmasse-Hitzdraht” which translates literally to air mass hot wire, referring to the Mass Air Flow sensor (MAF, also referred to by Volvo as the Air Mass Meter). The cylindrical aluminum bit with the wiring connector is the MAF sensor housing, which was a pretty advanced piece of kit when introduced in the early ’80s. It contains circuitry that heats an incredibly thin electrical wire suspended in the intake air flow. As intake air passes over the heated wire, there is a cooling effect, which decreases the electrical resistance through the wire.The electronic whizmos contained within the MAF housing work to maintain the temperature of the wire by increasing the current flow through it, so therefore the air mass flowrate is proportional to the hotwire current. 

Internal MAF circuitry interprets the current flow into a voltage signal that is sent to the ECU as a representation of the mass flowrate of air coming into the engine. In this way the ECU always knows how much fuel to inject by mass to burn efficiently with the amount of air flowing in, since this sensor compensates for air density and is accurate regardless of elevation, ambient pressure, and temperature. This sounds dense but is so much simpler than an electronic/vacuum controlled spaghetti monster carburetor like was still offered on some cars at the time!

The 242’s ignition system was electronic in 1983 (meaning no points to file) but still had a traditional distributor. There is a vacuum advance system but it’s integrated with the Chrysler ignition computer. Our distributor was replaced in 2012 with a fresh genuine Bosch unit, a nice surprise and a healthy upgrade in durability from the original Chrysler design. When we got the car some of the spark plug wires were actually loose in their boots so we replaced the wires, cap and rotor as a precaution. At the top of the above image we can also see the main ignition ground point on the throttle spool bracket (high-tech yellow circle), and one of the EFI ground points on the fuel rail bracket (red circle). The ground wires are bolted to the brackets; a quick removal and sanding down of the crusty contacts was in order here.

The physical act of swapping the wiring harness was not very picture-worthy; let’s just say there was a whole lot of grunting and awkward fishing for connectors under the intake manifold. I did end up cutting the old harness in several places as a shortcut to aid removal.

Once it was out some issues became obvious. Bare wires touching bare wires tends to be a recipe for getting low-voltage signals crossed to and from the ECU. The damage in the pics above & below is representative of the carnage; the main protective sheath around this bundle of wires has cracked and the insulation on each wire inside is crumbling worse than Greece’s economy.

But alas, simply swapping the harness did not cure the problem. Next on the list: busting out the multimeter and checking the original ignition harness for continuity, since it is separate from the main EFI harness and replacements are hard to find. Luckily every pin on the computer side of the harness was still electrically connected to the terminus of each wire its opposite end. Another quick test was to check for spark. This distributor has a Hall-Effect switch that can be easily validated by removing a spark plug, grounding it, and then jumpering two of the distributor signal wires. The test produced a clean, healthy spark every time, so the distributor itself was removed from the list of suspects.

Just to be safe I unplugged the ECU and tested for continuity and correct voltages between certain pins as described in the FSM. There is a big list of checks to make with the ECU unplugged to verify integrity of the main harness (which I had just swapped). Luckily everything checked out A-OK in this respect. I had no way of testing the LH2.0 ECU or the ignition computer, but assumed they were functional for this stage of diagnosis since they rarely go bad.

Us DT bunglers then tried swapping the spark plugs, wires, cap and rotor with known good parts from a running ’81 242 that also happens to be in my driveway. The situation seemed to improve from before; the DTPC was running a tiny bit smoother but still belching plenty of unburned fuel. It had only been running on the rear two cylinders prior to changing ignition parts so any improvement was welcome. But idle and part throttle were still rougher than a 2-cylinder diesel canal boat. Our fearless founder had the idea of unplugging the MAF to take that out of the equation and…it smoothed out quite a bit. Previously we’d checked the MAF using resistance and continuity checks found in the FSM and it seemed fine, but obviously there were deeper issues.

We are all about DIY repair here at DT, as it tends to save most gearheads money on straightforward jobs, and the more complex ones can be rewarding in their own way. But we are also just smart enough to realize when to turn a downward spiraling project car inferno over to the hands of an expert. Lucky for us, a veteran Volvo guru is only a 10 minute drive away.

Unplugging the MAF put the car into limp-home mode and made it run just well enough to drive it across town to Ian at Hi Performance Auto Service, who specializes in vintage pushrod Volvos but is glad to work on the “newer” stuff too. Ian immediately checked Lambda functionality, and found that adjusting the MAF did not seem to have any effect on idle mixture as shown from 0-1 volt on a multimeter with the oxygen sensor unplugged. He then changed out the metal-bodied MAF for a known good unit he had on hand, and power improved instantly. But by the hammer of Thor – it was still running quite rough, and missing on at least one cylinder. Just to verify the engine was mechanically sound, Ian checked compression and was satisfied at around 180 psi from all four cylinders…on an abused 290k mile B23F engine. Impressive.

After some high-voltage finger shocks (sorry man), Ian determined that the spark was jumping around inside my old used distributor cap and swapped it and the rotor out for brand new Bosch parts. With the cap off we could see that spark was actually arcing through the cap between the posts, leaving ashy evidence of its wayward tendencies. With the new cap cylinder #2 was still dead… so at this point, we are up to three cylinders. Luckily we then discovered that one of the injector wires had pulled out of the connector under the boot on my “good” replacement engine harness. Reconnecting was a quick job and now we’re back to hitting on all four, elated to have the solid basis of a drivable car that can be fine-tuned.

What about that hanging exhaust system that was dumped onto the pavement during Swedish drift lessons? Well it turns out a bracket had cracked and torn off of the rear muffler; a few quick squirts with a MIG welder and it’s held on well enough. It isn’t pretty but it is strong and as best I could muster welding rusty steel to thinner rusty steel, upside down in the driveway.

I’ll conclude this article with a Wheeler Dealers style cost tally so far, the only difference being the amount is shown in good old US Dollars instead of GB Pounds (and I’m disappointingly lacking in a charming British accent)…

Car……………………………..$1100

New ignition parts………….$89

Replacement harness…..$150

Total so far……………….. $1339



Stay tuned for the next exciting chapter: will we pass the through the ever-tightening noose known as California emissions testing?

Find all of the Daily Turismo Project Car posts here: DTPC Central