Disco 1 '94 3.9L Missing hoses

[Mongrel]

Hi all,

First day working on my new purchase from last week - first LR but not first project car. While tracking down fuel issues have come across some hoses that appear to be missing I was hoping someone could help with. Haynes manual hasn't helped here and after an hour of searching the forum I thought I would ask

First one is the two coolant barbs at the bottom of the plenum chamber under the crankcase vent hose - there are no coolant hoses on there, assuming they have been deleted? Are these important? Can someone assist with where they go to and from?

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Second one is the vacuum line that comes from the cruise control, it goes to a T, one end back tot he firewall but I have a naked barb with no idea where that hose is? Has anyone got any ideas? It was resting on the washer bottle, I noticed the one on the firewall is split and pulled it up to find this.
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Motor is running rich, has a surge at idle and cuts out so looking for basic root cause before I start stripping down, fresh plugs haven't helped, leads seem new as it distributor cap and has Lucas rotor button.

Previous owner let it sit after giving up but he didn't try too hard. Has some strange wiring and had a dual battery setup I have to CSI the wiring on also but just would like it to run right for a start!

Thanks in advance

[PhilipA]

First one under plenum is a throttle body heater which leaks after a while and unneeded in OZ. Its to prevent throttle body icing in UK in winter.

Second should go to either a vacuum pump in the LH battery tray or to a vacuum source. RRCs had a globe/sphere which had non return valves in it to run the heater flaps when low vacuum and the cruise control went off that if aftermarket. The later factory ones had a vacuum pump in the second battery tray.

Regards PhilipA

[Mongrel]

Thanks for that! It seems the reason I can’t find where it plugs into is the vacuum pump is missing. The electric plug is there taped up so I guess that now goes on the list...

cheers

[Ronski]

Assuming that your ignition timing is correct and the vacuum advance is working, ( suck on removed tube.).

A couple of simple things to start and maybe get it running a bit better.

1. There is vacuum hose at rear of plenum for the fuel pressure regulator, these often wear or split at the end, check hose end etc.
clean end and suck on hose, this will tell you if diaphragm working ok, suck and block with tongue, you will tell.

2. If the intake system is dirty etc. you can adjust the base idle screw, located top of plenum, sometimes blocked by a plug, which needs removing first. then use a small allen key to adjust. There is a method described in rave, which involves blocking hoses etc. but I just do this.

If it's hunting or surging at idle, (rich) unscrew about a quarter of a turn at a time, it lets more air into system, check idle. If you unwind too far it will rev high when starting, but will settle down once the Idle control takes over. On my disco, it was idling up and down and stalling sometimes at lights, adjusting the base idle out a quarter fixed that. On another vehicle it had to be over a half turn out, it revved high at first. We reset base screw after removing plenum and throttle body and gave everything a good clean, things were a bit grubby in there.


This is temp fix, usually the idle control valve is dirty, throttle body, carbon deposits restrict opening etc. etc. needs cleaning.
Do check the distributer vacuum and the fuel regulator vacuum, then on to clean intake, MAF, etc and air cleaner.
These old V8' s will burn through fuel like a demon if left untreated.

If you decide not to have the throttle body heater, it's a good idea to block the open ends, just loop a hose between. The reason is, water and moisture from the air get in and corrode. You can see the rust scale in the picture. Left for a long time it can eventually corrode the throttle body from the inside.

hope this helps,

[pop058]

Cracked/missing cruise control vac lines are a very common problem as already mentioned. The actuator line goes to a T piece (one end to the missing vac pump as started). The other end goes inside to the brake pedal. When you touch the brake pedal, the switch/valve at the pedal opens and (sort of) dumps the vacuum dropping the cruise off. Fairly simply system but lots of little things that can stop it working.