GQ TB42E manifold valves & hoses - pictures, explanation, thinning the useless stuff.

There is hardly any info on the TB42e - especially the fuel/inlet system. Thought I'd share what took a long time to find out.
Had to repair a water leak at the back of the block (heater hose outlet) which was almost impossible to get to due to the inlet manifold and all the junk attached to it.
Figured the best way was to remove the inlet manifold to get to the heater hose - what a stupid "Mitsubishi" design (thought I'd sold my Delica ? )

Anyway the vacuum hoses, water hoses and control valves can be greatly simplified - allowing easier future access and a less junk crammed engine bay.

Sorry there are no pictures of "before", but if you want "before", open your bonnet/hood.

Attachment 68738
This is your fuel pressure regulator - it senses manifold vacuum and regulates the fuel injector rail pressure to be a set amount above the manifold vacuum/pressure - to provide a fixed amount of difference between fuel pressure and manifold vacuum .
Necessary for proper control of the fuel injection system.
No matter how big a "racing fuel pump" you fit, this valve just bypasses the extra fuel supplied to return to the fuel tank.

Attachment 68737
These valves are your Idle control valve (green plug) and your air-con fast idle valve (purple plug)
If the air-con valve doesn't work it just means you don't have additional fast idle for running the air con system.
The Idle control valve doesn't work you're in trouble - it regulates your idle speed and compensates for extra load placed on the engine when you place it in "drive" (auto transmission) , when the engine is cold, and can even compensate for a failed air-con fast idle.
It regulates engine deceleration and has a "high vacuum bypass" built in which is a pain when you are trying to use engine braking compared to a direct throttle control system.

Attachment 68739
This one is your "cold start" or "Air control valve" - (nissan speak) It hides underneath the inlet manifold and blocks access to the heater hoses, oil filter and oil pressure sender.
Unless you are living in the Snow country where it is regularly below 12 degC, this is just useless junk.
It operates on startup like the Auto choke on the carby tb42. A thermo spring opens an air valve to allow a faster idle than the (green plug) Idle control valve can allow by itself. 12v current taken from the fuel pump circuit, heats up the thermo spring to turn it off.
For most Aussies, this valve and it's pipes, brackets and hoses can be junked - the ECU doesn't even register it's missing.

Attachment 68740
Here is the "cold start" valve on the floor along with it's vacuum hoses/pipes, water hoses to the inlet manifold (for heating the inlet manifold and throttle body to prevent "icing" - hardly a problem in Australia),
Also are the vacuum pipes for the brake and clutch booster (which for some reason go all the way across the firewall to the passenger side of the engine bay to the tiny vacuum booster reservoir, and then back across the firewall to the boosters - there is probably more capacity in the pipes than the reservoir)
Also are the original heater hoses, rusted out heater pipes and barb fittings.

Here is the engine with all the junk removed

Attachment 68741
Removal of the Cold start valve is easy - a couple of bolts and blank off the pipes into the manifold with some 1/2" rubber blanking caps.

Attachment 68742
You're better off without all the rusty pipes. Replace the welch plugs while you're at it (and you have access)
Attachment 68743

Attachment 68744
Run 5/8" brass barbs, tee fittings and 5/8" hose throughout for simplicity.
In the gas converter I spun up a restrictor (8mm hole) to fit inside the 5/8" barb so flow is restricted for the gas converter and biased toward the heater/demister core.
The heater hoses are fitted high on the firewall to allow access to the back of the engine.

Attachment 68745
The Vacuum piping for the boosters now runs direct to the boosters. Seems to work just as good as original. If I need an additional reservoir I'll mount it between the battery and the brake booster on the inner guard.

Attachment 68746
Did the valve clearances, new rocker cover gasket (was leaking oil at back of motor) and threw in some iridium plugs while access was easy.
"DO it ONCE, do it WELL"

Attachment 68748
Now all that remains to be done is to ditch the spastic clutch bleeder extension (what idiot designed this ? ) and clean up the confusion of wiring and earth leads (how many earth leads do you need ? - really ! )

Clutch bleed line removed a few nights ago.
Spun up a brass plug to fit inside the original flange nut of the bleeder line.
Filled it with fluid and bled it clean in 3x pumps.

Now for the wiring - will post more photos when it's done.
At the moment it's a dogs breakfast of relays, unused plugs, fusible links, little fuse blocks and clumps of wiring plugs attached to brackets - and that's genuine Nissan!!
Makes me love my old Nissan Cabstar - 5x wires to the engine = fuel cut, temp sender, oil sender, alternator (x2). "God I love dinosaur engineering ! "

Hey mate sorry to bring this thread back up but I really need help with my tb42e motor. I bought it off a guy who has removed all this stuff and changed everyting. I'm trying my best to put everyting back to factory minus the carbon canister ? Preety much what you have done. Mines straight petrol .

It idles at nearly 2200 rpm and runs rough ect and I'm struggling to work out how everyting is put back corrrctly. Could you possibly take some photos of how you ran all the pipes that come off the motor from FICD, AAC, the air regulator and top of motor . Really really appreciate anything. I'm going crazy trying to get this motor to run right

Thanks , Jay
If it's any easier you could text everyting to me on 0474119060 . Thankyou

This is my first time post people, so if I get something wrong, my apologies and don't be backward at putting me straight. I have a manual GQ Ti running a TB42E with 302,000km on the clock. Runs well once warmed up but missing occasionally when cold/coming up to operating temperature. New plugs and leads fitted. Vac hoses checked (the ones I can see!) and replaced where obviously loose or cracked. I'm trying to diagnose components not directly identified by Arfa in his post. Close to my idle control valve assembly, and bolted on top of the tappet cover near the firewall, is a small unit that I cannot identify. I have posted a photo. Any idea what this unit might be or what it is/does? It seems to have two points for attaching a vac hose (but there are none fitted) and encases a cylindrical shape (some sort of coil)? It is powered via the same wiring loom that powers the idle control and A/C valves.

Hey Patrolman and crusty - sorry, just found my old password and was able to log in again after ages.
Patrolman - sounds like you have an air leak into the manifold or hoses that feed it. The oxygen sensor will regulate the fuel input to match the airflow, so will idle fast.
Crusty - looks like a vacuum solenoid to control any vacuum operated valve/servo. The TB42E runs like crap when cold on petrol. LPG is sweet and smooth no matter what the temp.

All my mods have been running sweet, inlet air, cooling, vacuum and clutch.

Did the wiring reduction to the clump of terminals and spaghetti near the battery feeding the engine. Added a fuse block and lost about 1/3 of the wiring. The original looked like a dozen seperate designs were used on the wiring and none of them agreed with the other. I've seen better jobs on farm utes with 240v house cables.
It's now slim, efficient and logical. Organised and labeled the mess of relays as well, and added an upgraded headlight harness, protected rear cargo power supply, reverse light override, relay fed driving lights and interlinked switch controls.

Thanks for this thread , I was struggling putting my car back together after leaving it to long to finish the conversion the pics helped a lot

Quote:

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Originally Posted by Arfa Brayne

Hey Patrolman and crusty - sorry, just found my old password and was able to log in again after ages.
Patrolman - sounds like you have an air leak into the manifold or hoses that feed it. The oxygen sensor will regulate the fuel input to match the airflow, so will idle fast.
Crusty - looks like a vacuum solenoid to control any vacuum operated valve/servo. The TB42E runs like crap when cold on petrol. LPG is sweet and smooth no matter what the temp.

All my mods have been running sweet, inlet air, cooling, vacuum and clutch.

Did the wiring reduction to the clump of terminals and spaghetti near the battery feeding the engine. Added a fuse block and lost about 1/3 of the wiring. The original looked like a dozen seperate designs were used on the wiring and none of them agreed with the other. I've seen better jobs on farm utes with 240v house cables.
It's now slim, efficient and logical. Organised and labeled the mess of relays as well, and added an upgraded headlight harness, protected rear cargo power supply, reverse light override, relay fed driving lights and interlinked switch controls.

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Arfa, thanks for your response. I am wondering then if it may be what the manual refers to as a "thermal vacuum switch". These are apparently fitted to some, but not all, evap equipped models. The relief air line into the top of my fuel evap. canister just feeds into the air intake before the airbox via an OEM junction but I see from photos of other setups I've found online that this same line snakes its way around the back of the airbox to a point I cannot see in the photos, and that the line into the OEM junction point also returns from there.

Thoughts?

By the look of it Crusty, it's surplus to your needs.
It's an electrical controlled vacuum solenoid. Could be for a dozen different uses including your suggestion for the vapour cannister.

Hey mate (or anyone else that's aware), when you're talking about deleting the 'Air control valve', are you meaning if you're seeing temperatures of below -12C, or below 12c?

Tossing up going this route for obvious reasons (holy crap it's a mess in this bonnet), but live in Gippsland Vic, so we definitely see some cold mornings in winter..