Nissan GU Patrol Diesel Lift-Pump

As a bit of background, many diesels, especially trucks, use a diesel fuel lift-pump in or near the fuel tank to provide better fuel flow to the engine’s fuel filter, which is usually located near the engine. When the fuel has to travel quite some distance and the height between the fuel tank and fuel filter is significant, then a lift-pump takes a lot of strain off the main fuel pump used to pressurise injectors, or a fuel rail in common rail diesels. You can find lift-pumps in even smaller vehicles of one form or another especially 4WDs but many, like my Patrol, don’t have a lift-pump and so it’s quite common for owners to install one to assist with fuel flow and fuel pump longevity. So I did the same in 2014 with my Patrol but, unfortunately, on one of our High Country Cruises in 2016, the lift-pump unceremoniously failed, stopping fuel flow to the engine. Thankfully that wasn’t a particularly difficult job to remove, as I’d specifically installed the lift-pump so that it was easy to access.

Diesel Lift Pump - Good when it's good, bad when it's not.

Diesel Lift Pump – Good when it’s good, bad when it’s not.

The pump that I used back in 2014 was a Carter P4600HP, one that’s often recommended by other Patrol owners, and it worked quite well until it failed (isn’t that always the case?). That said, the first one that I bought made an awful racket, so much so that it nearly drowned out the engine at idle and so I contacted the seller and they sent me another one (the one that eventually failed), which was a lot quieter, but still not really quiet. I’ve heard other lift-pumps on Patrols and they too can be very loud and, quite frankly, obnoxious to listen to when the vehicle is idling. But as the Carter was one that was highly recommended, it was the one that I bought. It came as a complete kit with everything required bar the extra fuel line and certainly appeared to be a very well made unit. One of the features of the Carter pump was that if it failed, it had a bypass that would allow fuel to still flow. But so much for the bypass.

Carter P4600HP Lift Pump

Carter P4600HP Lift Pump

Fitting the lift-pump to the vehicle came with its own issues, as space was at a premium when trying to fit the pump near the fuel tank. In my case, every spot that was ideal was full of other things that couldn’t be moved, so I eventually sought out a spot where the pump would fit and then went about manufacturing a suitable bracket. That didn’t turn out to be as difficult a task as I’d thought it would be, but it took a lot longer than expected as there was a lot of measuring, then forming, drilling and fitting involved. But eventually things came together and the bracket was made and it fitted quite well, as you can see in the first photograph above. The pump mount was attached to the chassis rail as well as the bracket that holds the exhaust mount at the rear of the Patrol. I also incorporated a inline filter with the pump so that it didn’t pick up any debris that could cause failure (not that it helped). The way I’d made the bracket provided rigidity so that it wouldn’t fail from the jolting expected on bush tracks and it also provide protection from rocks etc flicking off the tyres. Overall the design worked very well and did what it was supposed to do.

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Nissan GU Patrol Diesel Lift Pump

Following the failure of the lift-pump, I decided not to replace it and went back to the standard fitment. But recently I started having starting issues early in the morning (the engine needed far longer cranking than normal) and so began an exercise in trouble shooting. The first thing I did was replace the starting battery which was getting pretty old, but that didn’t solve the issue. Next were new glow plugs, as they were nearly 200,000km old and that didn’t solve the problem. I checked the glow plug relay and the voltage across the glow plug power rail and both were fine. I then checked the alternator output and a few related things and they were all in good order. I put in a new fuel filter (because that was due for a change anyway) and the problem was still the same. I checked the spill tubes on the injectors and the fuel pressure relief valve, but both appeared to be in good order, especially as I wasn’t losing any noticeable power under full load. So everything that could possibly cause the issue came up fine. On a side note, when checking the fuel pressure relief and spill tubes, I realised that you could block the pressure relief valve without replacing the valve itself, as many do when they install aftermarket chips to boost power that increases fuel rail pressure. All you really need to do is blank off the end of the spill tube banjo bolt that attaches to the fuel rail and you achieve the same effect without the complications.

Fuel Pressure Relief Valve and Banjo Bolt

Fuel Pressure Relief Valve and Banjo Bolt

So back to the lift-pump. After doing all of this and nothing seeming to improve the starting issue, I thought I’d try the lift-pump option once more in case the fuel was draining out of the fuel filter and requiring the engine to turn over longer to get the fuel pressure up to the rail and injectors. But I wasn’t going to use a Carter pump again and went on a hunt to see what other sort of pump could deliver the volume and pressure of the Carter, which wasn’t all that high as far as fuel pumps go. After some research, I came across a HO12-428 Holley Mighty Mite Electric Fuel Pump that ran at 7-10psi and 129 lt/hour (close to the Carter specifications – slightly lower volume and slightly higher pressure). It was deigned for petrol and diesel engines up to 400hp, well above that of the Patrol. It was also self-priming, had a lift capability of 127cm and produced 65db of noise when running.

HO12-428 Holley Mighty Mite Electric Fuel Pump - (source: Holley)

HO12-428 Holley Mighty Mite Electric Fuel Pump – (source: Holley)

The fitment of the Holley was much easier than what I experienced with the Carter, notably because it was quite a deal smaller and the connections were much simpler. All I had to do was crimp the existing wires I’d left in place, after the Carter pump removal, to the Holley pump wires and replace the fuse on the relay in the engine bay (the pump would only start running when the ignition was on). And once again I can’t recommend Rivnuts highly enough, they make the installation of so many things just so much easier. Now I have to say that after a bit of testing the Holley works very well, is quiet and doesn’t appear to cause any restriction on power. In fact, after all the changes that I did, the Patrol seems to have a bit more go than previously, so maybe adding the lift-pump has provided some benefit after all. I’ll just have to hope that the Holley pump lasts longer than the Cater pump did.

HO12-428 Holley Mighty Mite Electric Fuel Pump - (source: Holley)

HO12-428 Holley Mighty Mite Electric Fuel Pump – (source: Holley)

HO12-428 Holley Mighty Mite Electric Fuel Pump Guard

HO12-428 Holley Mighty Mite Electric Fuel Pump Guard

But after all of that, the Patrol is still slow to start on very cold mornings. If I turn the glow plugs on and off three times it starts with fewer turns, but not like it used to start almost on first crank. But once it’s warmed up, it starts like normal, so I’m still baffled by what could be the cause. I even tried connecting my auxiliary battery at start up to see if that helped, but it made no difference. I also remember that I double checked the glow plug numbers to ensure that they were the same as the originals and not 24V, which could cause less heating.So as a last act of desperation, I bought a battery charger/jump starter off eBay to see whether that would make any difference to starting. First of, the charging test seemed to indicate that the battery was in fairly good condition (I think) because the charging indicator started to fall fairly rapidly after it was connected. But when I switched on the starting mode and turn the ignition on, did that make a difference. The engine had barely made a full turn before it fired up.

Rossmark Car Battery Charger/Jump Starter - (source: eBay)

Rossmark Car Battery Charger/Jump Starter – (source: eBay)

So I’m now faced with a conundrum, even with a brand new battery, there doesn’t appear to be sufficient cranking voltage/amps to give a clean start. What is causing this, such that with the assisted starting, things work fine? The search continues for an answer to this cold start problem. These sorts of issues are absolutely frustrating when nothing seems to resolve the problem and I have yet to find anything on the internet that comes remotely close to giving me an answer. But as a final word, anyone contemplating installing a lift-pump on a Patrol, the Holley seems to be a pretty good option as the two weeks that I’ve had it, it’s worked very well.

Update 1. OK, problem solved. Even though I’d checked the batteries several times, there’s one thing that I hadn’t done when it came to the auxiliary battery and that’s to check the voltage after not driving the Patrol for a few days. I’d always checked the voltages after having gone for a drive and it always showed around 12.7V. So one morning before starting, I checked the voltage and it showed 10.5V, not good. So after a drive, I again checked the voltage and it was back to 12.7V.

However, after not driving it for another day, the voltage was back down to 10.5V. So the battery was clearly dead and, at the same time, I noticed a completely melted fuse and fuse housing that connected to the battery isolator. So after replacing the auxiliary battery and fuse, the next morning came the acid test and the Patrol started immediately. So clearly the dead auxiliary battery was affecting the main battery and the starting. I’m not concerned about buying the jump starter, as I still plan to use that when we get those freezing mornings where every bit helps; but it turned out to be a simple thing after all.