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Air in fuel system?

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Air in fuel system?

Postby 96IsuzuBighornNZ » Mon Jun 12, 2017 6:09 pm

1996 Bighorn 4JG2-T

Hey guys and gals, I've been through a lot of these posts and made quite a bit of progress with cancelling things out about this problem I have, long story short, I have air in my fuel system somewhere, revs were all over the place and ran rough as hell, bled the hand primer which didn't fix much.

Tonight I bled the fuel injector pump, started her up and she ran like a dream straight away, took it for a drive and it ran soo much better, perfectly for a while, after a few minutes started very minor twangs in the revs, nothing like what it's been doing recently, just very minor and gradually building slightly, am I right in saying this points to a slow air leak in a seal somewhere or could it be residual air that will escape over time?

I'm new to the fuel system stuff but handy on the tools and I just don't wana go forking out $$$ for things that ain't broke. Any suggestions to most likely or what makes sense MUCH appreciated.

So far the threads on the site suggest to me maybe fuel filter o-rings etc? I'm hoping it's on the fuel filter side of things anyway.

Cheers all!
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Re: Air in fuel system?

Postby geeves » Tue Jun 13, 2017 6:38 am

Easiest check for where the air is comeing from is get a meter long length of clear plastic hose Remember this is not fuel rated so you cant leave it in the system. First replace the hose between the filter and pump. If it shows bubbles your issue is in the filter assembly or the fuel line to it If not its in your pump. You can put a length of pipe on the other side of the filter or pump to verify but you will need to make an adapter
Places that can leak air Fuel filter at either seal Water drain on filter Primer pump Fuel lines. Low fuel. Front seal on pump. Split hose between filter and pump. All can be done in place but the front seal on the pump means taking the timing gear off. If a garage was doing this they would try to convince you to do a full rebuild of the pump which may fix other things that could cause running issues.
My wizard used to start fine but if it had been sitting it would run for 30 seconds then miss etc sometimes stalling for 20 or 30 seconds before settling down. It developed a leak in the rear plate so I had it fully rebuilt ($1200 including new injector tips) and it ran fine
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Air in fuel system?

Postby 96IsuzuBighornNZ » Fri Jul 07, 2017 4:19 pm

Thanks for all that info! I've been away for work but will hopefully have time this weekend to get into it and figure something out! It's still starting but running like a pig so hopefully things go well :)
96IsuzuBighornNZ
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Re: Air in fuel system?

Postby 96IsuzuBighornNZ » Thu Sep 28, 2017 2:25 pm

Late reply, but in the end it was a lack of pressure in the fuel pump causing it, new fuel pump in, problem solved
96IsuzuBighornNZ
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Posts: 23
Joined: Tue Sep 30, 2014 6:49 pm
Age: 30
Country: New Zealand
City: Auckland
Vehicle: '96 Bighorn 4JG2-T


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