Cutting out - air in fuel line?

Technical questions and answers about the Mazda Bongo

Moderators: Doone, westonwarrior

Post Reply
TonyBongo
Bongonaut
Posts: 66
Joined: Sat Apr 30, 2016 5:42 pm
Location: Nr Marlborough, Wiltshire

Cutting out - air in fuel line?

Post by TonyBongo » Wed Apr 19, 2017 9:34 pm

After sitting unused in my garage for about 7 years, my diesel Bongo has been back on the on the road for nearly a year.

The only problem that I've been encountering is fine particulates blocking the banjo filter. I fitted a 40 micron glass filter after the fuel filter hoping it would eventual resolve itself after a few tanks of diesel, but it has continued so I'm now planning on dropping the tank and cleaning it out or replacing the fuel tank altogether. Pending this, I've been popping out the banjo filter every 200 miles or so, cleaning it, popping it back in priming the fuel line by pumping the pump on the top of the fuel filter and tightening up the banjo bolt.

Over the past few week, I've noticed that the pump on the top of the fuel filter has become easier to pump, that the fuel is slower to rise to the banjo bolt (before I tighten it), and that the fuel line does not feel like it is pressurising (the pump used to become harder to pump after a few presses). Today, after cleaning the banjo filter as above, the van started but cut out shortly afterwards when idling. The van started again, but then died after less than 1/2 a mile. This has never happened before and I initially put it down to me not priming the fuel line properly and leaving air in it. I primed the fuel line by pumping the pump on the fuel filter and managed to get the van going again before driving home 200 miles without any problem - even when idling.

When I got home, after switching off and leaving the van for a while, I was unable to start the van again without pumping the primer and revving it.

I suspect that the problem is an air leak in the fuel line, specifically in the priming pump on top of the fuel filter (http://lushprojects.com/bongopartsmk2/c ... no=.html#4) - probably as a result of me 'overusing' it every time I've had to clean the banjo filter and reprise it.

Does this make sense, and does anyone have any tips for diagnosing and resolving it? I'm guessing that there is a diaphragm in the priming pump on top of the fuel filter, but I don't know whether it can be replaced. Perhaps a whole new assembly is needed, but I'd appreciate any advice on what to check/try first.

Ta

Tony
User avatar
Northern Bongolow
Supreme Being
Posts: 7713
Joined: Mon Mar 15, 2010 11:33 pm
Location: AKA Vanessa

Re: Cutting out - air in fuel line?

Post by Northern Bongolow » Thu Apr 20, 2017 4:26 am

sounds like your about right with the filter housing primer, either the diaphragm in it has split or the 2 little crude flap valves have rubbish in them.

https://www.google.co.uk/search?q=pic+o ... Own6llWBdM:.

its similar to this old mechanical pump on the inside, it may even have an internal filter too, try reverse flush cleaning it with the pipes off, and blow back to the tank gently with your mouth down the removed pipe, there is a pickup filter in the tank, this could be partly restricted.

https://www.google.co.uk/search?q=pic+o ... CdU6s5Qk0M:
rita
Supreme Being
Posts: 3284
Joined: Tue Sep 15, 2009 7:11 pm

Re: Cutting out - air in fuel line?

Post by rita » Thu Apr 20, 2017 8:42 am

I am afraid there is usually no Shortcut to this problem You need to completely Clean out the tank and fuel/suction lines and NRV, make sure that the tank is scale /rust free. It is not advisable to blow back the suction lines to the tank for obvious reasons.

Good Luck.
TonyBongo
Bongonaut
Posts: 66
Joined: Sat Apr 30, 2016 5:42 pm
Location: Nr Marlborough, Wiltshire

Re: Cutting out - air in fuel line?

Post by TonyBongo » Sun Apr 23, 2017 9:05 pm

Thanks for the pointers.

Had a quick look at things at the weekend. I now suspect that the leak is from the banjo bolt as I think I saw a trickle of diesel from by it when I primed it using the pump on top of the fuel filter. I'm wondering whether I've either lost one of the washers while cleaning the banjo filter, or after removing/replacing the banjo bolt repeatedly I've crushed the washers so frequently that they no longer provide an adequate seal.

There was also trickle of diesel dripping off the bottom of the diesel pump, but I'm hoping that this had just ran down from the banjo bolt rather than being the diesel pump seals.

Does anyone know the size of the washers used around the banjo bolt? Are they just standard copper washers (they are referred to as gaskets in the mech drawings on lushprojects).

Ta

Tony
User avatar
Northern Bongolow
Supreme Being
Posts: 7713
Joined: Mon Mar 15, 2010 11:33 pm
Location: AKA Vanessa

Re: Cutting out - air in fuel line?

Post by Northern Bongolow » Mon Apr 24, 2017 12:59 pm

if you ring allens veh services or lawsons diesels in edinburgh they will know the size and poss send you some, they are standard bosch parts
Post Reply

Return to “Techie Stuff”