Fuel problem in 4bd1

**rar110** · 21st December 2006, 08:01 PM

Hi all. thanks for the further info.

I straightened out the kink in the pick up a bit. It seemed to improve the flow. This plus replacing the fuel line from the tank to the sedimenter seems to have fixed the problem.

I was down to 1/4 of a tank and inline file got suddenly very dirty.

I checked with the Isuzu engineering place and another mechanic about fitting a filter before the pump and all said no problems. It there is crap in the tank the mechanic suggested running both the inline and cav type filter before the tank.

I bought a cav type filter assembly with glass bowl from ebay. Seems pretty good. I have fitted that and the bubbles have returned to the inline fileter but dont seem to be affecting the motor this time. The amount of air in the inline filter seems pretty constant - mystery to me. I was told that air will sit in an inline filter and slowly disappear as the filter comes to the end of its life.

Anyway I took it for a run and it goes. I went for a low rev drive in 2nd up a long steep hill, went beautifully.

peter.

**mattmac** · 29th April 2014, 05:23 PM

I just removed the small plastic filter under the fuel pump to see if it was blocked - the banjo bolt/washer fell on the ground- not easy screwing back in with limited space- I assume it would be best to replace the sealing washer- BTW-is there 2 sealing washer-one on either side of banjo fitting?

**Phil B** · 21st July 2014, 03:59 PM

Hi Gents,
My Perentie was incomplete/inoperable when I bought it as a project.
One of the things that was missing was all the fuel supply and return lines.
My thought process was that the fuel supply should come out of the tank, through the sedimenter and then to the lift pump, returning directly to the tank via the return pipe.
I could not bleed the system once I was finished installing the pipe work and so decided to check here and on REMLR.
Upon checking the EMEI for Unit repair in the REMLR library it very clearing shows in group 4 Fuel System that the fuel flows directly from the tank to the lift pump and then returns via the sedimenter.
In this Thread it seems that the fuel flows the other way round.
Now I am really confused, not that me being confused is particularly difficult!
Could someone please let me know which is correct.
PS thanks for the information in this thread. I would never have found the "forgotten" filter below the lift pump without it.
Regards,
Phil.

**isuzurover** · 21st July 2014, 04:11 PM

Originally Posted by Phil B

...
My thought process was that the fuel supply should come out of the tank, through the sedimenter and then to the lift pump, returning directly to the tank via the return pipe.

You have missed out the filter on the inlet manifold, which I use as my bleed point.

Fuel flows from the tank through the sedimenter (see threads on here about making this a combined filter+sedimenter), then through the lift pump, then the filter on the inlet manifold, then the IP.

There are 2 or 3 returns, and you don't make it clear how much piping you have. There is a return from the pump, plus a return from the injectors, and IRC there is also a return from the filter (need to check tonight).

Are you trying to bleed using the hand primer? These have been known to die/leak and are available as a separate unit from the lift pump.

**Phil B** · 21st July 2014, 05:06 PM

Thanks for that reply,
I am using the hand primer. That is leaking air/fuel and I have ordered a new one.
The pipe work (supply and return) is all still in place on the manifolds with the filter etc. It was missing from where the steel tubing ends and the nylon starts below the brake and clutch MC's.
I am still confused that the EMEI's for that vehicle issued by the Army for maintaining the Perentie show the return pipe going to the sedimenter.
Maybe the Perentie is set up differently from the Civilian 4BD1.

Regards,
Phil.

**isuzurover** · 21st July 2014, 05:13 PM

Originally Posted by Phil B

...
I am using the hand primer. That is leaking air/fuel and I have ordered a new one.

...

In that case there is no point attempting to bleed until you have the new one installed.

**mattmac** · 7th August 2018, 08:40 PM

I think you're correct as i recently replaced my sedimenter(which was bit corroded inside) with CAV filter/water trap-seems like good idea at the time and believe many have done same but the other day engine died like was out of fuel only to discover that cause was blocked CAV filter which had only been on for about 1000km -will be going back to stock sedimenter.

Originally Posted by Larns

Yea it's not a real good idea to have a filter before the lift pump of a diesel. The reason they have a sediment bowel is because they don't create a resistance. Plus the lift pumps are designed to tolerate crap in the fuel, and the filter the Isuzu runs on the manifold is a pretty good one. If you do have the impulse to throw a different type of filter in, replace the unit on the manifold, don't add extra ones, especialy before the pump.
You could also try replacing the washers on the banjo bolts, as these are more often than not overlooked and are more often than not the problem. The banjo fitting only has to be a little twisted off center to create an air leak, and the rubber coated Isuzu fuel washers are a one use only item.

Never heard of the pick ups in the tanks cracking, new to me. Have seen people mixing the supply and return lines when re-plumbing, that leads to only having 3/4 of your tank usable.

Good luck though

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