The back 3 injectors on 7m Toyota dont work?

I have a Toyota 7m engine and i have a problem with my injectors. I have got spark from my distributor and the spark continues to the sparkplugs but there is no combustion on the rear three cylinders. I know this because when the car is idling i can remove spark cables from distributor and there is no change in how the motor idles. Cables 4,5,6 are the ones i can remove. I have tried switching the impulse wires as well as the power to the injectors but it still doesn't work..Can anybody help?The back 3 injectors on 7m Toyota dont work?You don't tell us the year but from the sound of things you've tried supplying the plugs different spark plug wire feeds, plus you've switched the injector feed wires and still the same cylinders don't fire.



Sounds like either you've 3 injectors that are faulty or the wiring going to them is the problem.Basically a injector will work via a two wire system or it has a negative and positive feed, the comp system will send a ground usually to each injector when it wants that cylinder injector to turn on.So this means that every side of each injector connectors is a live feed once the key is in the start position and the comp then sends the pulse turn on signals via the other wire.



You can conduct a ohms test if you know where the ends of each injector wires go to, for example one mite go to ECM pin 10 and the other wire maybe connected up to a relay or fuse.If it was a fuse that is hot or live all the time then you know every side of the injectors should be getting power from this fuse or battery positive post feed. That means that with the negative battery post disconnected and you used the positive ohms meter lead wire to touch the battery positive post and the negative to the injectors same wire connector.So with the inject unplugged or the lead wire pinching touching this wire the ohms meter should be giving you a reading, for example the old dial meters mite be giving you a zero reading.This says the wire is making at connection at that injector and the battery , unless it's a fuse that switches on once you turn a switch like the ignition switch, then you'd need to use the test lead not at the positive battery post but where ever the wire goes to such as one side or pin of a relay or fuse.



What you can do is a basic resistance test unplug a injector one at a time and compare 4,5,6 to 1,3,2. With nothing but the positive and negative ohms meter test lead wires being connected straight up to the connectors on the injector the reading should be according to the normal resistance of that injector design. Meaning the factory and service manuals etc will have the resistance readings you should get when using a ohms meter.For example just say injectors 1,2,3 are giving you say 11-12 ohm readings but the other 3 aren't doing that in fact the reading is either zero or why different.This would tell you that whatever injector I get the odd readings from when unplugged that they must be faulty.



If you could trace or know where both of each injector goes to then it might be as simple as having all the injectors plugged in with the battery disconnected and each set of injector wires should basically being you the same readings as the last unplugged injector tests.Note if you've can't really gain access to all the injectors plug in connectors then it's best to get the fuel delivery, fuel system, ECM pin/wiring schematics/diagrams from either online at autozone.com or try going to part source stores for free print outs and free trouble shooting info too.







Hope that helps and best of luck.By the way due to the designs and different types of wiring harness's that run things like the fuel injectors, the wires must run into the hot engine areas in order to be able to connect up to each injector.Also if the system is either feeding all the injectors from one feed that means it's one main wire spliced and made into a wire that is part of several wires all spliced at certain spots and one of these splices or junctions may have a bad wire or bad junction.



It all depends on the design but even a fuse could cause that issue or a relay but if it's a old engine and the injectors are part of a engine wiring harness those could end up with hot and even damaged or melted or broken connections, all bec they may be joining up to or more then 4-8 wires to one splice. If the harness has junctions and bends in it the harness may have more tension and if the harness is routed around the engine or hot exhaust systems the heat and hot/cold seasons over the years the wires end up just like ground junctions/connections/wires they all tend to rot/corrode/rust and even internally rot.





Last note unless you've money to spend on brand new fuel injectors don't bother with new find a U pull auto wreckers pull all 6 out and get the wiring harness or harness;s.They can be expensive on some makes they run from 200-800 bucks each when their brand new so if you can get 6 used say 100 bucks or so it's worth it bec you'd have some kind of warranty and probably spares injectors.The back 3 injectors on 7m Toyota dont work?Is it clogged use a fuel treatment