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Diesel no starts: the new rules

Tuesday, March 1, 2016 - 08:00
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Another part of the preliminary checks is to verify power and ground at the fuel pump, fuel pressure at the fuel pump and the rail (using the correct tools, gauge and service information) and make sure there are no obvious restrictions in the intake or exhaust systems – which can happen if the vehicle spends most of its life idling or is often driven at low speeds. Don’t just rely on the gauge on the side of the air cleaner box; remove the element and actually check for restrictions to be sure.

And of course, make sure none of the “override” switches have been tripped and make sure there’s fuel in the tank (it happens) – resetting the switch or priming the fuel system may be all that’s needed to fix the problem.

The most common problems and fixes

If the vehicle won’t crank, from experience the most common cause of the problem on diesel vehicles is a weak battery, especially if the vehicle was parked in the cold overnight – but that doesn’t mean just dropping in a new battery and sending the vehicle on its way. That’s asking for trouble. From experience, in these cases it’s good practice to charge and check all of the vehicle’s batteries as well as the charging system, and also make sure the block heater and cord are OK, and finally ensure that nothing was left on to drain the battery before releasing the vehicle back to the customer. Fixing the same problem twice is embarrassing and costly.

No doubt poor quality (or incorrect) fuel can cause no-start conditions—but is it the most likely cause?

One interesting note is that a battery doesn’t need to be all that weak to cause starting problems. Many no-start diagnostic trouble charts state that both batteries must be charged to at least 12 volts and they’re not kidding around. Anything even slightly less than that may cause problems.

In fact, batteries that are slightly discharged but still as high as 12 volts can and do result in no-start conditions.

One excellent dealer tech says he’s seen some newer Ford diesel engines make a disturbing clanging sound as the vehicle tries to start with a battery that’s not quite fully charged but still at nearly 12 volts exactly and that charging the battery a bit – or even just plugging in the heater – for a few minutes stops this problem (along with a proper charging system check, of course).

Pulling out the dipstick to insepct the condition, level, and scent of the oil can save time later on—be careful though, the cable part is known to fray and can stab you.
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