ICQ>

Here's a description of a problem and an example of how easy it is to be mislead by the data.

During the last several weeks, I've been helping a friend solve a problem on an '87 non-turbo 740. He owns a one-man, Volvo-only shop. The car, not registered, came from a body shop that had bought it to fix up and resell.

We solved the problem (finally), and I'm passing on the symptoms, information, and data -- and final results -- to everyone. There's a lesson or two. After several days, I'll post our findings and success.

Here's what the customer (body shop) said:

"It ran and drove fine before we replaced the fender."

"It wouldn't start after we worked on it."

"It starts and runs if you squirt gas into a vacuum line."

"We checked everything we can think of under the hood."

"It cranks GREAT!"

Here's our work, observations, tests, etc.:

(I might have one or two of these steps out of order.)

- Gas tank almost full, told it was fresh gas (it was).

- Cranks like crazy.

- Has excellent spark.

- Ignition timing at about 10 BTDC (+/-) while cranking.

- New plugs, always come out clean, fresh, dry.

- New fuel pump relay.

- Replaced injection module.

- Checked voltages at injection module harness connector -- all OK.

- Checked grounds at same connector -- all OK.

- Checked and retightened grounds at injection rack.

- Checked for 12 volts at pin 1 (signal from ignition module) -- 11 volts -- close enough.

- Swapped ignition module anyway.

- Plugged both modules and relays in known-good and running '87 -- all parts OK.

- Checked for voltage at injectors -- ZERO VOLTS.

- Found cracked (broken) connector at plug (up inside the insulator) to suppression relay!!

- Replaced connector -- cranked like crazy.

- Fuel pressure measured at about 2.7 kp/cm (at injection rack using Volvo gauge).

- Plugs still look clean, fresh, new. And dry. No smell of fuel.

- Detected pulsed ground at injector plug.

- With stethoscope, able to hear injector clicking during cranking. (Compared favorably to test car, while cranking, with coil wire pulled.)

- Pulled injectors and rack -- injectors spray fine while cranking.

- No gasoline smell at exhaust pipe.

- Reinstalled injectors, cranks like crazy, but won't fire.

- No fingerprints around timing belt cover.... nobody's been in there recently.

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We made one more (very basic) test, made one simple addition, and had the car running in 5 minutes.

As I said, this is an example of how to be misled and how to miss the simplest data.

So here's the pop quiz:

What did we measure, what did we add, and what had happened?