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Diesel no starts: the new rules

Tuesday, March 1, 2016 - 08:00
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Preliminary checks on diesel no starts

Preliminary inspections are really important on diesel vehicles because they can save so much time and because so many no-start conditions can be accurately diagnosed and repaired in the early stages.

Even with regular maintenance, sludge builds up quickly and restricts critical air passages.

After verifying the problem, start by opening the hood and climbing up if necessary, and then checking that the battery cables and connections are clean, tight and secure. Check that the starting system connections and relays are securely in place and check that the glow plug and glow plug control module connectors are OK as well. It’s not uncommon to find one of these connectors has wiggled out of place or is compromised in some way.

10 preliminary checks for diesel no-start conditions

1.     Battery condition (both batteries)

2.     Fuses (especially if connected to accessories)

3.     Connections and wiring OK (oil soaked or chafed is not OK)

4.     Engine oil level and condition (and the correct type of oil used)

5.     Transmission range switch solidly in P or N (common on work trucks)

6.     Programming updates

7.     Plugged exhaust/restricted intake

8.     Glow plugs and control circuit OK

9.     Starter and fuel injection control circuit OK

10.  Check Engine Light comes on for bulb check

Here’s a tip: if you do suspect a fuse or wiring problem, quickly checking to see if anything else isn’t working and then finding out if those systems share a common fuse, splice or relay can save quite a bit of diagnostic time.It’s also very common on diesel trucks to find that accessories have been poorly wired into the circuits that supply power to the starting and fuel injection systems – and when the fuse protecting the circuit blows the vehicle subsequently won’t start, so it’s important to identify where those fuses are and then check them carefully early on in the diagnostic inspection, especially if the no-start problem just suddenly happened one morning.

Since high-pressure diesel fuel injection systems rely on a consistent stream of high-pressure engine oil to operate the fuel injection systems, engine oil condition and level are critical and anything that would affect this is worth noting. While under the hood, pull out the dipstick and inspect not only that the oil level is OK (way over full may indicate fuel or coolant leaking into the engine) but also actually sniff the oil for contaminants to help identify any problems. Be careful though, the dipsticks do tend to fray and the wires can stab your fingers.

Be suspicious if the oil looks like it was just changed – cheap oil changes are sometimes really expensive in the long run since using the wrong viscosity oil can cause a no-start condition. Also note any oil-soaked harnesses or connectors, which may be a symptom of the larger problem in the high-pressure oil supply system that should be investigated.

When the underhood checks are complete, turn the key on (engine off) and listen for the noise as the fuel pump turns on for a few seconds and pressurizes the system; also watch the instrument cluster to ensure the Check Engine light comes on during bulb check and check that the “WATER IN FUEL” light isn’t staying on (though, to be fair, faulty sensors are not uncommon). Any of these situations indicate larger problems ahead that you’ll want to be aware of. And be sure to check the transmission range switch, and even wiggle the shifter and see if the vehicle starts up. One of our customers has a fleet of Ford pickup trucks that often get mud build up around the transmission range switch, which stops the switch from going to park (and thus won’t start after it’s shut off). Cleaning away the mud fixes the problem quickly.


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