Starting issues with our Dmax

Not long after getting our 100k service done on the Dmax (despite it only having 77km on the clock, but that’s another story), I went out to start the car and found it would crank over, but not turn on. After a couple of turns it would go on, and I found the priming valve took forever to go hard when you pumped it.

On top of this, I could hear air bubbling or moving in the fuel system, and knowing that Isuzu had replaced both the factory fuel filter, and the 30 micron diesel care fuel filter, I had my suspicions. I knew that if this isn’t done correctly (pinch the o ring or anything else) you can end up with a minor air leak that will make it hard to get the vehicle going, but once its running you’d be fine.

Provent 200 install
I could hear air from the pre filter, and the primer wouldn’t come hard quickly

However, due to a myriad of fun circumstances I dropped the vehicle off with the fuel light on, and when I picked it up, I realised the trip metre had been reset because the dash was removed for the Dmax aircon problems, so I had no idea how much fuel was actually left. With the long range tank it’s a bit hard to tell exactly what you have left anyway, but generally with the fuel light on you have 30L or so, which should be at least 250km, although we’ve never run it that low.

Regardless of this, I had a mate drop off a 20L jerry can of diesel (as I couldn’t leave due to isolation) and I threw it in. From then on, we had no issues, and I filled it all the way up on our way out to Serpentine Dam, and we left a week later to go north.

We’d done about 600km to Mt Magnet, and I pulled in to get fuel, filled up and hopped back in the car and it wouldn’t start again! 3 tries and it finally went, and we drove to the playground for a while, then another 700 odd kilometres with no issue.

At the playground I did give the fuel primer a few pumps, and about 10 pumps later it came good, so I thought we’d see what it did after another day of sitting, but it seemed awfully strange. When we finally had some reception, I watched a couple of videos showing how to replace the fuel filters in the diesel care units, and the factory filter, in case I needed to play with it further. I had decided to basically leave it unless it caused further grief, knowing fuel systems are not my forte.

We had a few more starting issues randomly, and on a quiet afternoon at Meentheena Veteran Retreat, I decided to have a play with the system to see what was wrong. I checked the factory water drain wasn’t loose, the pre filter fuel fittings were tight, and that the hose clamps were all good on the pre filter, before moving to the line that goes to the Isuzu factory filter.

Meentheena camp
On a quiet afternoon at Meentheena I started to tinker with the Dmax

I gave the hose clamp a little tweak and felt it strip. I replaced the hose clamp, and moved back to the diesel pre filter where I removed the top to see if there was any damage to the O ring, and undid the bleed screw on the pre filter to see if I could get it to prime better.

Each time I pumped the primer, I could hear air get pushed out, and then sucked back in again, which had me completely stumped. I could get a bit of diesel out, but the air just wouldn’t leave.

I could still hear air in the system, and the priming unit just didn’t want to go hard unless you pumped it hugely, and even then it wouldn’t stay hard for long. Listening carefully again I was positive it was related to the pre filter, and stuck my hand underneath to the water drain fitting, and the second I touched it I heard the bubbling noise change. Struggling to fit my giant hands underneath, I tightened the fitting up, and immediately the noise stopped.

A few pumps on the factory primer and it was hard again, and stayed that way. I ran the vehicle for a while and it started first go with no issues, so hopefully its completely resolved.

I suspect it was as simple as whoever changed the filter didn’t do the drain up tight enough, and this allows for a tiny amount of air to be sucked in (as the pre filter would have to be under vacuum).

Frustratingly, the next day it struggled to start again, and despite an obvious change in noises around the pre filter something still wasn’t right. I removed the filter from its bracket when we got back, and as soon as I tilted it I could see air bubbles start to run through the drain, and into the filter!

The moment I tightened it further they stopped, and all it took was a prime, a small drive and the starting issue was completely resolved. I knew it was good too, as it would crank over and start immediately, instead of the delay that’s probably been growing for some time!

30 micron pre filter
The drain on the bottom of this filter was loose

It just shows a tiny amount of air in your fuel system regardless of where it is can either make your vehicle not start, or even worse, not run at all!

Despite having me quite concerned, with us being in a remote part of the world often not seeing people for days, and having no reception, I was glad to see a resolution and learn something in the process, and I was also glad that this wasn’t another thing to add to our list of Isuzu Dmax Problems, being caused by an aftermarket part.

Dmax fuel draining manual
Reading through the manual for draining water out of the fuel filter


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  1. Hey Russell,

    If everything is done correctly you shouldn’t ever have this issue. I’m actually fascinated that it ran and only presented an issue sporadically. Certainly something worth knowing about though!

    All the best

  2. G’day Aaron. I have not had this problem with my Dmax, and hopefully won’t. This was a really interesting read and good information to know about.