91 q45 plenum

[tx91q45]

I'm currently doing a 91Q45 plenum job and the information on NICO is great! I have taken my fuel injector off the plenum but it's still attach to the fuel rail. It is possible to ohm an fuel injector with the plenum off?

thanks

[Q45tech]

Important to understand that each fuel injector connector [on the harness] need to be inspected [cleaned inside and refilled with dielectric grease to protect against corrosion and oxidation].

To me a better way is just to replace all the hoses [EVERY SINGLE ONE] and harness under the plenum along with brand new knock sensors and any injectors which show any even minute deviation from the mean.

Flip the rail over and examine the pintel plastic spray director cover for presense and cracks.

The things you don't change will be the things that fail soon because we know that new these components mostly lasted 100k or 7-8 years anyway.

[goody90q45]

I have taken my fuel injector off the plenum but it's still attach to the fuel rail. It is possible to ohm an fuel injector with the plenum off?

Not only is it possible but it is the preferred way to ohm an injector since it takes the wiring for the harness out of the equation. Put both probes on each of the injector pins and take the reading. A range of 10.0-14.0 is acceptable. Good Luck.

[tx91q45]

q45tech,

thanks for your prompt reply. I'm indeed planning on replacing ALL the hose under the plenum. I will also take your advice on the replacing the knock sensor. I have read that you can indivdually ohm test each fuel injector BUT i'm getting mixed messages. If my fuel injector is off the plenum but still on the fuel rail. Can I still effectively ohm test each fuel injector? and what is the most effective way to test it? thank you

[tx91q45]

Mike,

thanks for the quick reply. As soon as I posted my second question. I saw your post!! Man, you guys are good. thanks

[goody90q45]

Are you going to be sending your FI that ohm within spec in for refurbishing or replacing them all?

[Q45tech]

The reason Nissan spec 10-14 ohms is to avoid warranty, and to allow for variances in ohmmeters their batterries and the temperature of the injector coil.

Once temperature stabilized all should be within +- a few tenths of an ohm because all the coils have exactly the same wire and number of turns.

I measured 6 new injectors they all read the same with +- 0.1 ohms.

Obviously meters have different accuracy so the exact ohm number is not important JUST THAT ALL INJECTORS READ THE SAME when tested.

[tx91q45]

I'm actually replacing ALL my 91 fuel injector with a 95 fuel injector. I was planning to ohm it and send it off Deatschwerk for professional cleaning. I had read somewhere (forget where) but if I was going to replace ALL my 91 injector, then I can replace with with a newer model (like a 95). Please let me know, if this a wrong approach. I read that the 94-96 injectors are better than the 90-93 model.

[maxnix]

The later injectors use a rotary valve instead of a single pintle. Better, maybe, but one should be aware of the differences in intake path design in the heads.

TexasOil has the post for which you are searching. The later injectors are not a straight bolt on.

I can highly recommend Deatschwerks personally.

[StarPD]

The reason Nissan spec 10-14 ohms is to avoid warranty, and to allow for variances in ohmmeters their batterries and the temperature of the injector coil.

Once temperature stabilized all should be within +- a few tenths of an ohm because all the coils have exactly the same wire and number of turns.

I measured 6 new injectors they all read the same with +- 0.1 ohms.

Obviously meters have different accuracy so the exact ohm number is not important JUST THAT ALL INJECTORS READ THE SAME when tested.

I have long wondered why so many Infiniti injectors go bad. Generally speaking,since there are no moving parts in electronic devices, barring manufacturing defects and/or physical abuse (shock and extreme thermal environment), electronics have a good reliability record. Electric motors also have good reliability record, and generally, only excessive current flow or physical damage harms windings. I would think that the designers of Infiniti fuel injectors would have taken into account the temperature fluctuations present in an automotive application, and the repeated shock/vibrations of a device close to the combustion chamber. Strangely enough, it is usually not the moving parts in Infiniti fuel injectors that fail, but rather the windings in the operating coil.

I can understand how electrical connections can become loose or corroded, and how complicated electronics circuit boards can develop minute cracks, but even these things are not so frequent that they ALWAYS die within typical time periods as do Infiniti fuel injector windings.

It seems that these injectors only last for a given length of time before failing. Interestingly enough, I'm familiar with other manufacturers whose fuel injectors almost never fail.

So what is it that causes Infiniti injectors to "not ohm out? What causes the windings to short or open, and why after so many years of this phenomenom has Infiniti not addressed and fixed it? Finally, is there anything owners can do to prolong the life of injectors? Their failure involves great expense in parts cost and labor, and is one of the most frequent and costly parts of maintenance that is a part of Infiniti ownership. I see no reason why injectors cannot be made to last as long as pistons/rings, bearings, and valves, all of which take a terrible beating in their normal function , yet unlike fuel injectors, last for hundreds of thousands of miles.

[Q45tech]

Better is a relative term. With proper maintenance the 90-93 injectors can last 312,000 miles if you utilize the as designed gasoline and clean them regularly.

Nissan warned CARB that the 1994 update would still fail after 100k if exposed to non standard gasoline.

THe injector sizes [diameter] and the lower runner are a match set so determine how you intend to do the swap?

[tx91q45]

maxnix,thanks for your reference to Texasoil FI swap between a 92 and 95 Q. Looks like it will work.

q45tech,Can you please explain what you mean by "lower runner"? I'm new at this and don't know all the lingo.

[ScottJackson]

312K miles max? That's quite a specific number! Maybe someone will make an adapter fuel rail that adapts the lower part of regular Bosch style injectors to the lower intake and then you'd just need some simple custom rails to feed the tops of the injectors.

[Q451990]

Of course, the trick is finding "standard" real fuel in most parts of the country. We've been lucky in dixie so far!

Heath

[Q45tech]

312k is the maximum number I can recommend* as that is mine today and I know of 2 others that exceed that number with as built injectors- In Atlanta Metro.* I ohm test all 8 on Monday they were perfect 12.1 +- 0.1 ohms...............more than I can say for harness or plastic connectors.

WE never bother to keep injectors in stock as the failure rate is so absolutely low in all 3 shops.

[maxnix]

Can you please explain what you mean by "lower runner"?

Lower intake manifold runners are on what the injectors mount and to what the upper plenum runners mate.

[tx91q45]

thank you, i'm learning new stuff all the time. All work that I have done on my car (mostly for the first time ever) , is based on this sites and others. very helpful

[maxnix]

Get the 1994 FSM. There are some differences, but more similarities.

http://www.phatg20.com