Shock5

My buddy has a 1994 4 runner at the shop now and the mechanic says it has no injector pulse.
Anyone know what he is talking about? How to check for it? or What causes it.
Thanks in advance

dcg9381

Most likely cause is the inductive pickup at the distributor.
Have him test the distributor while turing over the truck.

^VooDoo^

The ECU gets its pulse from the distributor, Then sends a parralelled pulse to both banks of injectors.
The injectors are powered with the same B+ as everything else on the engine and the ECU controls the pulse via grounding the injectors.

Check the plug at the ECU, Maybe replug them in to eliminate oxidation
There are 2 sensors in the distributor, One is cam the other is injector/ignition pulse.

oldschool

Having the exact same prob on my 93 SR5 V6

Has good spark to plugs but no injector pulse

I've checked everything else and it's driving me nuts

dcg9381

If you have good spark, I'd start at the injectors.
When the ignition is on, you should have 12v at the injector measured between an injector terminal (one of the two) and ground.

Either the EFI relay isn't giving you 12v to start with or the ECM isn't ground the injector with the spark pulse. Any other recent work to your truck?
Note - a bad ground could cause this to happen also.

oldschool

There is 12v at the injectors as you described with the key on.
If i spray carb cleaner into the air chamber I can keep the engine running so I know there is good spark. Definiely a fuel issue and it seems to be the pulse to the injectors because I hooked up a small test lamp to one of the injectors and I can see it glowing when the engine starts momentarily and then I can see it fade out as the engine dies.

So what would cause the loss of the signal to the injectors?
This seems to be the problem. I guess it could still be the pulse generator inside the distributor since that is where the ECU gets its signal but like I said, it has good spark to the plugs.

^VooDoo^

Ohm both line from the ECU plug (C12 and C25) to the injectors or the to the blk/red wire on ether the ignition coil or the igniter (pls disconnect batery).

If shows infinite ohm THen I would say the fusable links are bad somewhere, If you get continuity then injectors are good and the ECU is bad.

dcg9381

The same signal that generates injector pulse generates spark pulse.
Quasi-educated guesses:
1) An ECU component has died.
2) Bad ECU / injector ground. The ECU has seperate grounds for components to isolate noise.

The FSM has a diagnostic procedure for no fuel conditions... Might start there.
As you mentioned you can put a test light on the injector and see if it's triggered.. having it die out is odd, especially if you've got spark.

oldschool

Pulled the plenum cover and ohmed out all the injectors. 5 are within specs
(15 ohms or so) but one is 2 ohms acros the terminals and also shorts directly to the injector body. None of the other injectors do this.
A knowledgeable mechanic told me this might cause all the injectors to lose their signal. Will find out tomorrow for sure...

oldschool

That was it - replaced the one injector and she runs fine now

Big thanks for the tips

Alford-brady

Need help I have a 1990 3.0 4Runner 4x4 auto i am not getting any pulse to my injectors I have power to them but no pulse I have replace distributor I have fire to plugs runs off starting fluid all relays and fuses have been checked I'm lost need help