Clicking constantly

[helibrian]

I have a 91 l300 and it starts normally the problem is it randomly has the glow plug clicking sound while I'm driving sometimes it does it after 30 minutes of driving and other times it does it for a minute then stops for the rest of the trip. The voltage on the voltmeter goes to around 12 volts when it clicks then back up to 14 volts on the second click. Can anyone point me in the right direction for the quickest and cheapest fix.

[Growlerbearnz]

It might be the temperature sensor failing, but more likely the glow plug ECU.

Electrical diagrams and fault finding here: http://www.delica.ca/forum/viewtopic.php?f=17&t=7333

ECU repair thread here: http://www.delica.ca/forum/viewtopic.php?f=94&t=15336

[helibrian]

Ok thanks I'll look into it tonight and post what I find.

[helibrian]

I looked at the relays the ecu and the water temp sensor. All looked good the resistance on the sensor was 630 ohms and the engine was warm. I drove home and no clicking maybe a wire was chafing or maybe it will be back tomorrow. Maybe it's gremlins.

[vernacular]

i've had such intermittent weirdness from the various connectors being corroded, check the strip connector plug in the loom front of the battery, the fat connector plug from the alternator power lead halfway up from the alternator itself, located in front of where the air cleaner is , the plugs into the relays behind the air cleaner, and the plug onto the temp sensor. spray with oxidation solvent. (contact cleaner).

alternately, your checking of things if it involved unplugging stuff may have restored the electrical conductivity of the joins

[helibrian]

Does anyone have the 6volt glow plug wiring diagram?

[helibrian]

Maybe it's not the glow plugs. I just assumed because it makes the clicking sound like the glow plugs.it happens almost all the time below 1500rpm and then seems good above that so maybe it has something to do with the alternator or voltage regulator.any thoughts?

[Growlerbearnz]

The 6v glow plug circuit is on page 2 of the wiring diagram (if you have it). Mitsubishi call it the "super quick glow system". You've got two relays- one of them applies 12V directly to the glow plugs, the other runs the power through a resistor block which drops it to 6V. The ECU applies 12V first to heat the plugs up quickly (since they're 6V plugs), then drops back to 6V. Once the engine is running, if it's cold, the 6V relay will pulse on and off to keep the glowplugs warm and improve the idle. The rate at which the 6V relay is pulsed depends on engine temperature and RPM, but cycle times vary in the range 2 seconds to about 6 seconds.

If your clicking is slow (2-5 seconds between clicks), and (as you said) happening only below 1500rpm, it suggests the ECU thinks the engine is cold, which is usually a failed temperature sensor.

600 ohms sounds a bit high for a warm engine, the chart on page 45 of the engine electrical manual suggests 300ohms at 80C. You're measuring the correct terminal of the 2-terminal temperature sensor, right?

[helibrian]

I measured at pin b and the body with the sensor installed. The weird thing is that it starts no problem.

[Growlerbearnz]

Hmm. My next test would be to put a 300ohm resistor in place of terminal B (between the wiring harness terminal B connector and the engine block), which should permanently fool the ECU into thinking the engine is hot. If your clicking goes away then it's the sensor at fault- if the clicking remains, then the sensor is probably not the problem. Then again, I have a bunch of resistors just lying around. YMMV.

When you first turn the key on, you get the initial 12V click- it lasts about 4 seconds if the engine's cold, and as little as half a second if the engine's hot. When your engine is hot, how long is that initial click? If it's 3 or 4 second long, then the ECU definitely thinks the engine's colder than it is.

[helibrian]

I will try that tomorrow I have a potentiometer that goes up to 800ohms. Hopefully it will lead me in the right direction. I also have owned the van for almost 8 years and have never changed the glow plugs. Could the glow plugs cause the clicking sound?

[Growlerbearnz]

Maybe. I suspect the ECU measures the resistance of the glow plugs to determine if they're up to temperature- I fitted aftermarket 6V glow plugs once, and the ECU refused to turn them on. Switch back to genuine Mitsubishi plugs and they worked just fine.

[viajeros4x4x4]

We got that clicking since 2000. It happens almost every time after crossing a stream (we assumed it was that some wiring got wet) and it stops half a minute later (when we suppose it gets dry). We never payed a lot of attention to it. It's a part of our Delica character.
A year ago we've changed the 6 volts plugs to 12 volts, we disconnected the computer and preheat the engine manually (thanks Jay). But even now, sometimes it starts to click, mainly in cold mornings.
We accepted it as part of our Delica, a.k.a. 'The Cockroach', character.
I don't know if this story about our Deli helps, but it's there.
Cheers from Newfoundland.