Bleed back/cold start dramas (12ht) (1 Viewer)

[melias24]

Hi guys, I feel a bit silly asking for help as I'm an apprentice mechanic and should be able to work this out on my own but I really can't. I rebuilt the 12ht for my truck (fj62). Everything's new but the turbo. Now the drama I have is it seems to be bleeding back I assume, I can pump the primer on the injector pump (which is usually firm enough i would think) and it fires up pretty much straight away. If I don't, it'll crank for a really really long time and will need throttle to stay running.

I have checked injection timing 3 times, replaced all copper washers, replaced the rubber hose from the fuel filter to the pump and checked overall lines and clamps. Being it was petrol now a diesel I'm unsure if perhaps there is a drama there causing it to bleed back? I didn't encounter these dramas with this pump PRIOR to reconditioning. Any other suggestions? Is it possible for the pump to be the blame? Thanks guys.

 

[Indestructible 47]

The primer pump on the 2h/12ht are notorious for leaking air into the fuel system. Heaps of people swap them out for a Bosch one, I just can't find the part number right now. Sounds like your issue is air in the fuel line, so check that all hoses are new, clamped, replace the primer pump with a Bosch one and you should be good.

 

[SPVTony]

I come from diesel background.
There is likely a small air leak between primer and chassis rail flexible hose. Could be a filter, housing or as mentioned hose not clamped. Annoying issues like this wont always leak fuel.
If you have no joy.
Try three things..
1/ fit a clear tube just before lift pump on injection pump and see if air drags back.
2/ carefully blow back to fuel tank then pressurize the fuel tank slightly.
3/ set up a small fuel canister with very clean fuel and bleed system.
If all the above fails, fit a temporary electric lift pump.
There isn't an auxiliary or second primary filter fitted? 90% time it will be the issue.
if runs on forced fuel, points to primer or lift pump.

 

[roscoFJ73]

Replace the primer, these types are the problem 50% of the time. Check ends of fuel lines for cracks, it can leak air pretty bad through fuel line cracks.

 

[Rock40]

Air is getting in somewhere for sure. I had a lift pump fail on a Land Rover once. It actually ran fine but was super hard to start as it was sucking in air. You may try bypassing the filter/primer to rule it out

 

[melias24]

Air is getting in somewhere for sure. I had a lift pump fail on a Land Rover once. It actually ran fine but was super hard to start as it was sucking in air. You may try bypassing the filter/primer to rule it out

Thanks, i replaced the fuel primer as i requested the diesel shop fit a bosch closed fuel primer but they fitted the screw down type. I replaced that and still the same.

 

[roscoFJ73]

Any primer should have worked if that was the problem

 

[KamarulF]

Try doing a diesel fuel treatment to flush out all deposits and air out. Whilst at it, check if there is any pressure loss as well. If there is, there is definitely a leak. If still persist, you might want to do fuel calibration as well

 

[Greg_B]

When the 12HT was fitted into the FJ62 was the fuel pickup/fuel return fitting at the tank replaced, or how was the fuel return line routed? The 6*'s fuel pickup can develop rust then let air in right at the bend where it comes out the fuel tank. The pickup/return fitting (12HT style) is still available, if that ends up being what it is.

hth's
gb

 

[roscoFJ73]

Hi guys, I feel a bit silly asking for help as I'm an apprentice mechanic and should be able to work this out on my own but I really can't. I rebuilt the 12ht for my truck (fj62). Everything's new but the turbo. Now the drama I have is it seems to be bleeding back I assume, I can pump the primer on the injector pump (which is usually firm enough i would think) and it fires up pretty much straight away. If I don't, it'll crank for a really really long time and will need throttle to stay running.

I have checked injection timing 3 times, replaced all copper washers, replaced the rubber hose from the fuel filter to the pump and checked overall lines and clamps. Being it was petrol now a diesel I'm unsure if perhaps there is a drama there causing it to bleed back? I didn't encounter these dramas with this pump PRIOR to reconditioning. Any other suggestions? Is it possible for the pump to be the blame? Thanks guys.

How is your fuel return set up?

 

[melias24]

How is your fuel return set up?

I have it running return and supply using the original petrol return and supply lines, i did read that people T it back into the supply line but doesn't seem like a great idea having hot diesel going straight back into the system.

 

[roscoFJ73]

Did you try a temporary fuel supply in the engine bay. You have to do this to isolate the problem btween engine and elsewhere or you are just chasing your ass around.