Priming a 93 diesel Hilux

This morning the old girl would not start. It had been sitting for 2 weeks since a big weekend of use. Would crank over fine but not fire. Checked everywhere for loose wires/fuel lines, rang NRMA & waited 2hrs. Started thinking it was a fuel problem, got on Dr Google, discovered there is a primer button on top of the fuel filter, pumped it 5 times and hey presto, it started fine and has done another 2 times since.

Decided to wait for the NRMA guy anyway to ask him why this happened. He said probably a small leak in the fuel system, which meant all the diesel drained back into the tank, hence the need to pump it back through.

Does this mean a trip to the mechanic to fix the leak as air in the system could cause damage? Or can I just prime it if it happens again? I need it to go bush over Xmas & don't want to get stuck.

I've also heard about 'bleeding' the system, but have no idea how to do that. However, it seems to be going OK now, took it for a few laps of the block and it ran as normal (i.e. like an old rowboat, but offroad it is epic ;)).
cheers
 

billolga

Well-Known Member
You can prime as much as you like.
I had a problem with my Patrol a couple of years ago when it would go fine until I tried to get it up to 100 kph & it didn't have the power.
A mechanic told me he couldn't look at it as he was too busy, but had several Patrols with an air leak through the Primer itself - I installed a replacement (around $100), two bolts & two screws with a new one & I was back to full power.
 
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Hoyks

Well-Known Member
Yeah, if you do CPR on the primer a lot, then they can crack and let air bleed in, rather than bleeding it out.

What can cause it to leak air? A cracked diaphragm, of course. Old hoses that are starting to perish or have squashed over time so the clamp doesn't seal as well as it should. In my experience the main culprit is generally the fuel filter. If it has been replaced and not tightened up quite enough or spun on dry so the rubber seal twists a tad, then air can get sucked in over a few days. There are also some small O rings in the water drain in the bottom of the filter, if these perish and split. If the drain isn't turned off properly, then air can also get in.

Priming is pretty much bleeding. Newer vehicles are happy with just pumping the fuel so the filter is full and the injection pump has something to push. Older and less operator friendly setups you would have to loosen off the pipes on the injectors and pump the fuel through the filter and injection pump until you got bubble free fuel coming out at the injectors. It was messy, smelly and had you pumping away on that primer like no tomorrow and needing a spare hand to clamp off pipes before air got back in.

My current ride has a boost pump in the tank, just change the filter and turn the key to ON, wait 45 seconds, turn it off and repeat two or three times until it stops gurgling. Much more civilized
 

CruisingSned

Active Member
Yeah, if you do CPR on the primer a lot, then they can crack and let air bleed in, rather than bleeding it out.

What can cause it to leak air? A cracked diaphragm, of course. Old hoses that are starting to perish or have squashed over time so the clamp doesn't seal as well as it should. In my experience the main culprit is generally the fuel filter. If it has been replaced and not tightened up quite enough or spun on dry so the rubber seal twists a tad, then air can get sucked in over a few days. There are also some small O rings in the water drain in the bottom of the filter, if these perish and split. If the drain isn't turned off properly, then air can also get in.

Priming is pretty much bleeding. Newer vehicles are happy with just pumping the fuel so the filter is full and the injection pump has something to push. Older and less operator friendly setups you would have to loosen off the pipes on the injectors and pump the fuel through the filter and injection pump until you got bubble free fuel coming out at the injectors. It was messy, smelly and had you pumping away on that primer like no tomorrow and needing a spare hand to clamp off pipes before air got back in.

My current ride has a boost pump in the tank, just change the filter and turn the key to ON, wait 45 seconds, turn it off and repeat two or three times until it stops gurgling. Much more civilized
Used to work for a generator Hire company and customers used to run the generator out of diesel, refuel it and stand cranking till the battery died. Used to be my pet hate as I had to change a heavy battery and then get covered in diesel. Gotta love boneheads.:rolleyes:
 

cam04

Well-Known Member
Used to work for a generator Hire company and customers used to run the generator out of diesel, refuel it and stand cranking till the battery died. Used to be my pet hate as I had to change a heavy battery and then get covered in diesel. Gotta love boneheads.:rolleyes:
Various Lister models came with the injectors on the inside of the crank case, so once you've primed the fuel system and each injector individually, you have to change the newly contaminated engine oil - british engineering at its very finest right there.
To the OP, If it is like any of the older Toyotas I had, there will be a bleed screw which needs to be loosened for each down stroke of the primer pump, and tightened for the up stroke. Continue until no air bubbles are present. Check your manual. Yes, you have a small leak somewhere.
 

Batts88

Well-Known Member
How old is the fuel filter sometimes air gets through the rubber seal. This has happened a couple of times to my patrol I usually change the filter around 20,000km but sometimes sooner if the vehicle gets hard to start after sitting for days. Just smear some diesel on the rubber seal before installing.
 
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