Hand fuel pump low pressure

Hi guys,

As some may know ive been going through hell with my Navara (owned it for 15 months, 7 of those have been at the mechanic), and the saga continues.

Friday just gone it was running like a dream, ready for me to pick up Monday. Mechanics mum is sick so was unable to meet me monday (all good, I get that a sick mum trumps a car), so he said he would drive it down yesterday. He arrived yesterday and found it won't fire. It turns over but won't fire.

The only thing that had changed since Friday was he had taken the battery out to put it on a charger.

Today he hs found some air in the fuel line. He has been hammering the hand pump but it doesnt seem to have enough pressure to push the air out of the lines.

Has anyone had this issue before? is the hand pump gone?

Any advice at all?

Thanks in advance

I've found that when I was getting air in the line that the hand primer will only prime slight pressure to the injector pump but not cycle the fuel through to get air out of the lines, you would have to bleed it from my experience.

nedm1989 said:

I've found that when I was getting air in the line that the hand primer will only prime slight pressure to the injector pump but not cycle the fuel through to get air out of the lines, you would have to bleed it from my experience.

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Thanks for that, I will let him know.

Can you think of any reason why it would now have air in it?

My original filter/primer housing was actually leaking in air, I'd say it was the primer diaphragm, sometimes it's a pin hole or crack in a line, or on the odd chance the the hose in the tank is cracked, you can't see it but it allow sucking in air, best way to diagnose it is to fix clear fuel lines on either side of the filter assembly to see the air and if it's getting in before the filter housing, what engine is in your nav?

nedm1989 said:

my original filter/primer housing was actually leaking in air, i'd say it was the primer diaphragm, sometimes it's a pin hole or crack in a line, or on the odd chance the the hose in the tank is cracked, you can't see it but it allow sucking in air, best way to diagnose it is to fix clear fuel lines on either side of the filter assembly to see the air and if it's getting in before the filter housing, what engine is in your nav?

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zd30

As above. If yours was a D40 I'd blame an aftermarket fuel filter straight away, followed by under- or over-tightened hoses, followed by perished hoses. These are things that can be inspected without expense (well not the filter in the D40, but ALL aftermarket D40 filters seem to be a problem!). Then there's the fuel pickup.

Clear hosing will show whether or not the air is entering around the filter or it's before or after that point. The primer bulb might have some cracking in its pump - so inspecting that is also a good idea.

Old.Tony said:

As above. If yours was a D40 I'd blame an aftermarket fuel filter straight away, followed by under- or over-tightened hoses, followed by perished hoses. These are things that can be inspected without expense (well not the filter in the D40, but ALL aftermarket D40 filters seem to be a problem!). Then there's the fuel pickup.

Clear hosing will show whether or not the air is entering around the filter or it's before or after that point. The primer bulb might have some cracking in its pump - so inspecting that is also a good idea.

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Thanks man, my mech is gonna bleed the lines and hopefully find the cause at the same time.

So, he bleed the lines and had no luck so has replaced the primer. Its now getting fuel into the injectors but still isn't firing.

Plugs are glowing all good etc, any idea what could be up now? Electrical maybe?


Thanks again

Does the zd30 have a fuel cut solenoid like the older qd32 diesel engines guys?

Diesels are essentially very simple. Give them air, fuel and some compression and off they go.

Let's assume there's air getting in - nothing blocking the snorkel/intake, air filter is clean, turbo is able to spin.

Now that fuel is getting in, the only thing left is WHEN the fuel goes in. That's governed by two things: the ECU to send the injector signal, and the CAS that tells the ECU where the crankshaft is so the ECU knows when to open the injector in a particular cylinder.

If you crank the engine over a few times and it doesn't fire, smell the exhaust. If you smell raw diesel, it's probably your CAS broken or out of alignment.

If you don't smell diesel, and you're confident that diesel fuel is getting to the injectors, I'd be checking the injector harness to make sure there aren't any loose connections, and checking the battery-to-engine earth point then the ECU-to-ground earth point.

Im assuming your nav is a non-CR, with a VP44 injection pump. These need bleeding thoroughly, preferably through the pump return line. The pump has an on-board ecu and the only inputs are: Live and earth, CKP (translated to a square wave via ECM), CAN comms, and a fuel cut signal from the ECM, The pump control unit uses this info to control the spill valve and timing control valve. If you have CONSISTENT FUEL to the injectors, you can assume the spill valve (and by extension fuel pump) is operating adequately to enable starting. The pump circuit boards are fuel cooled so excessive dry cranking can cause electrical over-heat. These injectors will only open when sufficient fuel pressure is applied, so cracking pipes and seeing fuel dribbling out does not always mean fuel is entering the combustion chamber. Assuming you have good compression and proper fuel delivery, try blanking the EGR and disconnecting the vac hoses from the inlet throttle valves. As old tony says, fuel+compression+air=engine firing

Only one other thing to add would be to ensure there is not a voltage drop while cranking, as when the ecu and any electronics for that matter are supplied with a far lower voltage than their normal operating voltage they can either power off or reset constantly without you even knowing, seen this happen with many cars.

See what the voltage drops to while cranking, it may be that you might see low single digits which could also be adding to or causing the issue.

Thanks heaps guys I will take it up with mech tomorrow.

Its now officially been at the mechanic for half the time ive owned it.

So, story time...

My mechanic was out of ideas so called in a favor, from his friend a diesel mechanic. His mate agreed to come look at my ute, on his way to the shed he was in a car crash, he is now in hospital getting reconstructive surgery.

The fact that some poor guy is in hospital now aside, my mech is out of ideas and im now in the position of having to hire a trailer and travel over 100ks to get it home.

So, this is my prewarning that you will probably be bombarded with questions as I can't afford another mechanic.

Thanks in advance everyone.

Hopefully I can get an end to my 7 month saga. Owning a car for 14 months and having at the mechanic for 7 is painful

That's a terrible turn of events. Hopefully we can work some answers out and you can begin to enjoy the car.

Thanks Old.Tony.

I had a thought today that is more then likely a long shot, but when I got a key cut for our Kia Rio it would do a similar then when trying to turn over (crank but not fire). Now I can't even remember my keys its been that long, but pretty sure it would be similar.

Could it be an issue with the battery coming on and off, dying and being charged, being left off etc etc that has cause the key to "lose its code"?

I'm grasping at straws I know but hiring a trailer, taking a day off work, borrow a mates Navara to tow mine, and towing it back home (120k) isn't something I really want to do. (thats not including that 3k its cost me to not get the car fixed)

Thanks again

Wow - what a tale of epiciness... I really feel for you dude!

I had mine for 8 months, and 7 of those where at the mechanics.. I would literally get one thing fixed - and another would pop up.. The hardest one was a pesky CAS Fault.. It turns out it was a dry / corroded socket on the ECU.. GRRRRRRRR.. Spent THOUSANDS chasing it.. They found it by accident - after wanting to spend THOUSANDS more on "maybes"

As has been suggested - check earths and the Crankshaft / Camshaft sensors.. Untighten all earths and roughen the surface and re-tighten.. Unplug the ECU and check for any white corrosion.. re-plug.. Try the simple things first..

Flat batteries can cause all sorts of woes. You go to start the car, the ECU voltage drops below active level and it switches off - you'll get a couple of cranks and no start.

Jump starting it will help, and a battery test - or just to hell with it and replace it anyway - will be a good first step. Then you can get back to diagnostics, starting with the cheap and easy things like the previous poster suggests (connections!).

If you weren't far away (like within 200km of Newcastle) I'd come do it myself.

thanks guys and yeah i wish you were closer Old.Tony haha.

I will talk to the mech again today and suggest the advice above and fingers cross it starts.