Isuzu Trooper Owners Club UK™

plant man · Newbie Joined: 21 Dec 2016 Posts: 9 Location: sheffield

Hi,

I have just got myself a 96 bighorn with the 3.1 but while checking it over i have noticed that some of the vacuum lines are not connected some look a little perished so not sure it they have been took off or fell off Confused

The main thing im not sure about is that under the air filter there is a bunch of vac lines that are off (next to a blue looking electrical connector)so was wondering if anyone had a picture of how they go so i can start putting it back together. Very Happy

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Rhanagar · Posted: Thu Dec 22, 2016 0:18 Post subject:

Depending on your opinion, 99% of the vac lines on the 3.1 are redundant. A lot of them drive the EGR's and QWS (Quick Warmup System). On MK.III (1995-1997) models you also need vacuum for the front axle part of the 4wd system.

Now a lot of people (myself included) do away with all the vacuum stuff. The only hose I have on mine is the boost line from the intercooler to the fuel pump. I have a Mk.II (1992-1995) model so slightly different. The EGR's are of no real benefit on these engines. They just coke it up and without them you will find the engine runs cleaner .. therefore more efficiently and better emissions MOT time. Don't worry about increased exhaust gas temperatures. I have never seen a difference. The QWS system on the 3.1 is dire. There is a flap in the exhaust that shuts when it is switched on. This labours the engine when it is cold and helps it get to temperature quicker. I have never found it makes much difference. Also on the 3.1 the flap has a tendency to stick shut causing all sorts of hassle.

Yours is a 1996 Bighorn auto Mk.III I am assuming. I will guess it has the newer electronic fuel pump. This means that you won't need the boost line, but you will need the vacuum system from the vac pump on the back of the alternator to the front axle part of the 4wd system.

If it were me I would strip everything off the truck and replace the lines for the 4wd system. If you look at the back of the alternator there is a vacuum pump. On that pump there is a small vacuum hose. It should have a branch coming off it that goes to the front axle and off that a branch to the vacuum reservoir on the nearside chassis rail under the passenger front footwell. What you will need is about 5-6m of 3mm ID silicone hose and plumb as per this diagram:

Vac pipes on the front axle

As for the rest .. they can all be removed.

Some reading:

Vac pipe removal This is a Mk.I 2.8 but the principle is exactly the same:

http://www.itocuk.co.uk/forums/viewtopic.php?t=19621

Hope this makes things clearer .. or muddier lol
_________________
1990 Isuzu Bighorn LWB Mk.I 2.8TD Manual Lotus Edition
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto Lotus Edition

Deceased
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto LS

plant man · Newbie Joined: 21 Dec 2016 Posts: 9 Location: sheffield

Thank you.

Yes it does make sense. I shall get some fresh tube and get busy.

Yes my bighorn is a 1996, it has the newer shape dashboard, if that makes any difference.

I had seen about the egrs and wondered wether to block the vac on them so thanks for confirming that.

When i have put it in 4wd the light doesnt come on but im presuming that will be part of the reason with vac hoses been perished ect.

Rhanagar · Posted: Fri Dec 23, 2016 18:26 Post subject:

Yeah .. lots of people have bypassed/removed the EGR's, myself included. It doesn't hurt and you may see an improvement in performance and economy.

If you relpace the vacuum lines as per the diagram above then it should solve your 4WD issue.

The only thing you should be aware of is confirming what fuel pump you have. If you look at the offside of the intercooler, just in front of the inlet from the turbo is a small port. Yours should be blanked off .. Port "1" in this picture.

_________________
1990 Isuzu Bighorn LWB Mk.I 2.8TD Manual Lotus Edition
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto Lotus Edition

Deceased
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto LS

plant man · Newbie Joined: 21 Dec 2016 Posts: 9 Location: sheffield

Brilliant. I shall check that out. You certainly seem to know your troopers Very Happy

I was expecting to get chance today but alas that wasnt to be.

I did however get chance to have a look at where the speed sensor is, as i noticed my speedo has died....or wether it worked before i picked it up, i never noticed anyway....it has been stood for about 14mths so im expecting the odd issue to crop up. Needless to say a new one has been ordered via our most fav auction website Wink