90-93, 94-96 intake manifold interchange

[masoQist]

Hello. I recently acquired my first Q45, a 1990 model. Almost immediately a coolant hose located under the plenum started leaking. So far, so good. In preparation for removing the plenum, I identified one injector that failed to meet the resistance spec. I’ve decided to replace everything on the top of the engine that is a hose, or is fuel-system related. I’m also planning on changing the injectors to the 94-96 type. I read the thread on this update, which involves using the later rails on the early manifolds. I can certainly appreciate that this is a simple solution that works. However I’m thinking that Nissan must have had some reason for changing the rail-to-manifold seals for the new style injectors. So, I’m interested in the possibility of changing the manifolds to the later style.

My question: Will the 94-96 lower manifolds, rails, injectors and wiring harness bolt directly on to my 90 engine with no other modifications needed? If not, then what other modifications would be needed? Thanks in advance.

-Jon

[elwesso]

The reason theyre different is because the phyiscal dimensions of the injectors are different.. The 94-96 rails have a tapered fit where the 90-93 have like a stepped fit, if I recall correctly.

Theyre just rubber, so as long as you compress the bottom of the fuel rail into the seal enough they'll seal fine. If you take the plastic spacer and just use a washer under where the rail bolts to the manifolds youll be perfect..

You dont want to go to the 94 lower runners because they dont have the siamesed ports like the 90-93 does..

Just get yourself a set of 94 rails and harness, and you'll be all set!

[masoQist]

You dont want to go to the 94 lower runners because they dont have the siamesed ports like the 90-93 does..

Ah. I should have known. Thank you!

[maxnix]

Don't forget the KS and its harness.

[masoQist]

Don't forget the KS and its harness.

Forgot to mention that. Both KS's were dead. Car will get new ones, as well a new harness.

I just got one of my used 94-96 injector rails in the mail today, and have now had a chance to examine the old and new parts. In awhile, I'll post my observations to the original thread. zer...npics

[unknown007]

Make sure to check the new KS also and that they have ground contact.Mine are dead but brand new.Possibilities it can be the harness or it's not grounded right or it's just New dead KS.Just a heads up.

[Q45tech]

The KS are grounded thru the mounting bolt [metal ring on bottom of KS] to head, while the other audio wire has a grounded shield from ecu.

Correct mounting torque is critical to completing ground and to the sensitivity of the contact microphone/sensor. Too much and you add stress to housing speeding up cracking and too little allows oxidation between KS and head creating intermitents in future.

[Denver90Q]

Would a little dielectric grease when installing help with the corrosion problem?

[unknown007]

Also dirt under the KS can cause no contact.I don't think I made sure of that.When I get back down there I'll take pictures and hopefully it'll show why there was no contact.