I have an 88 pickup with a rebuilt 86 motor with about 30 hours on motor. When the swap took place I did a heater/ac bypass, New radiator, gm altenator swap,premium clutch kit,New battery,coil,plugs,and wires.did a csi timout bypass.New fuel pump, filter, and line.newer dist cap and rotor. New stock ecu compatible 4 port injectors.ran amazing for around 5 hours with all that on it.now injectors aren't pulsing. Each has correct power and ground is fine as far back as the 4-2 ground splice in harness. Have not traced ground farther back than that.truck starts fine cause of CSI but once that fuel is used its done. What else can keep it from pulsing? Can I bypass the ecu and make it ground manually straight off the injectors?( yes I know I'd have to wire it to only ground on the crank and running that's not an issue)

 

The distributor times the pulses.

 

Where and how would you suggest testing this?

 

csi as in cold start injector? i've never heard of anyone doing a "timeout bypass" on it.

if you stripped the harness back to the splice, did you replace the spliced area? it's well known to corrode there, and not carry enough current to fire the injectors.

 

CSI is cold start injector and many people have bypassed the timeout switch especially if they are toys... did not need to replace splice in harness it looks brand new I just peeled it back because of its reputation

 

Power and ground to the injectors are fine? How do you figure? You should have 12v on all injector connector terminals with the key on / engine not running. No grounding of the injectors- the ECU does that internally, switching one (two actually)of the lines from 12v to ground to fire them.


What type of injectors did you install... high or low impedance? Either may have been installed by the factory- I think 88 was a cutover model year when that occured. A tell-tale indication is the presence of a resistor box on the right-hand fender well, meaning the engine had low-impedance injectors. If you do not have the resistor box and installed low-z injectors, chances are you've blown the output transistors in the ECU.

 

I do not remember the voltage of new injectors, when I ordered them they were listed for x year to x year and mine was in that range and it noted that they were compatible with the ecu. As far as the resistor box on the fenderwell, I'm assuming the finned one, yes I have that. Yet lets say I fried that part of the ecu for whatever reason, is there anything stopping me from a manual grounding system Perhaps?

 

I don't trust anything, any more, that says "applies to XXXX-YYYY". There were at least 3 different ignition igniters and I think just as many ECU's used on 88 22RE's. I match part numbers now.

The ECU grounds the injectors to fire them so no, there's nothing easy you can do IF the ECU is the problem.

I'd say check the impedance on the injectors with an ohmmeter, making sure that if you have the resistor box the injectors are ~1-4 ohms resistance. If that checks out, go back to checking the wiring, verifying 12v on all the injector terminals with the key on/engine not running. Sometimes things with related symptoms but un-related causes can occur and add to confusion.

 

Also if the airflow meter has faults same problem, The fuel pressure dropping off really fast because the fuel pump shuts off after the key is released from start possession.

 

You can't just ground the injectors. That would turn them on continuously and drown your engine in fuel. The ECU calculates the length of time the injectors should be on for each revolution of the engine to get the fuel-air mixture just right.

 

AFM checks out fine...I know a continuous ground would flood the engine but if all it needs is a ground to run,I can wire a series of relays and switches to only let it ground when it needs to run (though that is a lot of work) it can be done if the injector fires same length and amount at all times... voltage at the injector is whatever the battery is at, which should be normal. However the ohms is reading 8. Not the 1-4 you suggested it should be. I do not believe its the harness or wiring itself,I believe its a relay,ecu, resistor, transistor, act of god, hopes and dreams or whatever Toyota needs to run

 

"All it needs is a ground to run" is a gross oversimplification. It needs a precisely timed "ground". I don't think you're appreciating the complexity of electronic fuel injection. Arguably the most important task the ECU does is to manage the fuel injectors (managing ignition timing is the other important one), and you can't really substitute for its sophisticated control. The ECU pulses the injectors each engine cycle, by grounding the low side of the injector (as you propose to do with relays and switches) using a solid state switch (transistor).

The injectors are pulsed on each revolution for about 1 mSec (1/1000 of a second) at idle, and up to 10 mSec at full throttle, and everything in between, depending on engine load. The ECU recalculates the proper length of the pulses every engine revolution. Those pulse lengths are far too short for relays to switch accurately, if at all, and even if you could use relays, the relays would wear out in about 5 miles. A solid state switch is essential.

One could conceivably get the engine to "run" without the ECU by designing a solid state switch to pulse the injectors, and controlling it with a one-shot pulse generator triggered by the ignition and with a pulse length proportional to throttle opening. Throttle response would be terrible, emissions would be through the roof, and power and fuel economy would be abysmal - but with enough tweaking one could probably get it to limp along.

But what you really need to do is to track down why the ECU isn't firing the injectors. Causes, in general order of likelihood, are:
- bad wiring between the injectors and the ECU. - Verify with your ohm-meter.
- some sensor giving the ECU bad info telling it not to provide fuel. Check the TPS and VAFM, and the wiring between them and the ECU.
- Bad ECU - swap with a known good one. Working used ones are available at salvage yards - they usually survive accidents just fine, unless the front passenger side got T-boned.

 

88's are a one year only injector. A lesson I learned the hard way is even if it passes a resistance check for continuity, doesnt mean enough electric can flow thru to fire the injectors. Basically it would be like breathing thru a straw. You get some but not enough.

A Haynes Manual will help get you thru some of the test. https://www.yotatech.com/forums/f199...l#post51897320 Things I checked.

 

I had an issue with injectors not firing once. Turned out to be as simple as poor battery ground.

Check that your injector resistor is reading the right resistance as well.

 

It's possible your new injectors are the high-resistance version, which don't need the external resistor box. Since you do have the resistor box, you might have double the resistance total, which will limit the current such that the injectors will rarely, if ever, fire. Higher battery voltages may allow them to work, whereas if the battery is low they won't.

 

Agreed!