Fuel Injection Electrical Schematics for 2.7L Engine, 1996 Toyota Tacoma, MT 4x4

I'm looking for the electrical schematics of fuel injection system, to ECM, for a 2.7L, 1996 Toyota Tacoma, Manual Trans, 4x4? any links or diagrams for checking this system?
Schematics of specification of the fuel injection system for trouble shooting?

 

This is from 95 - injectors are controlled by ECU, so not much diagnostics in there (they fire at will of the computer).



The brown wire is from +12 ignition (before IGN fuse).

The only simple checking on the injectors is resistance - at 20C should be between 12 and 16 ohms. The rest is using a tester connected to computer - the tester will fire injectors and you measure the volume of gas allowed.

I don't know what you are trying to find.

 

Engine is currently running roughly and appears to be missing. Disconnected # 1 injector with notice very minimal change when this was done. I'm currently running electrical checks on the fuel injection system to ECM.

I just replaced all the injectors on my truck as two injectors were out of specs. New injectors were checked and all were currently 14.5 ohms prior to install.
Using volt-ohm meter .

Currently, I ran diagnostic checks for positive battery voltage on disconnected harness plug terminals, on #1, #2, #3, and #4 injectors, and these injectors terminal wires, ( B-R wire ) for each injector is showing 12.4 volts.
The negative wire ( W-R) at the disconnected plug terminals terminal at the injectors, for #1 and #3, was reading 12.25 volts negative. The #2 and #4 ( W-R) plug white erminal with red stripe, at injectors had low reading for negative voltage.

According to the wiring diagram schematics, the W-R (white - red ) wires should be ground.



Send me the lower portion of page and the other page, thank you.

 

Everything else seems to be irrelevant to injectors - if ECU does not have a ground there will be much bigger problems . It is possible that injector is clogged or faulty so even it has 14 ohms, the fuel does not run through it. You can manually check the injector (has to be removed) by connecting 12V to it for very (I mean very!!!) short time. injector gets 12V on black-red wire you can check if ECU is trying to fire it but that probably will require oscilloscope. Or using acoustic method by connecting 200ohm speaker in parallel with injector - if speaker ticks then ECU is firing injector. But unless some rodent had a feast in your wiring I doubt it is electrical - my personal bet would be faulty or clogged injector.

Anyway here are all pages attached (all 4 high resolution pages in the zip). Good luck.

 

I did install 4 new injectors ( 1st set of injectors, in March) prior to the 4 new injectors (2nd set of injectors, now in April), currently on engine. the 1st set of new injectors had two defective injectors. The original set had one bad injectors.
Decided to replace all original injectors, because of 23 plus years in engine.

Just completed electrical test to the white with red strip wire and white wire running from ECM.
I disconnected the fuel relay at fuse panel, to eliminate fuel pump engaging pump.
With Key On: #1 and #3 wire at fuel injector reading above 12 volts, and reading above 7.4 volts when cranking engine over.
With Key On: #2 and #4 wire at fuel injector reading below 0.1 volt , and reading below 2.3 volts when cranking engine over.

I'm going to need to hook up the battery charger, as cranking volts are a bit low at this point.

I'm going to reconnect the fuel injector wires terminal plug in and the fuel relay at fuse panel, and check for ticking noise at injector while engine is running. I'm hoping I don't have another defective fuel injector.

Can you send me page 36, as it refer to connection I10 on page 79. I'm curious on checking these connections if quickly accessible.

 

There is nothing on that page really - I10 is a splice basically passing through a grommet on the right side to 4 plugs going into ECU. This is from 1999 but shows the same picture (the pdf is much better than printed book 1995 I have)

 

#2 and #4 should never have 0.1V with key On. Brown/black should be 12V and white should be 12 too. When you crank the measured voltage may drop one volt (on average) and it will be grounded via ECU for the injector opening time. If Brown/black is 0V then maybe wire is rotten at the plug. I have never heard of factory splice go bad.

 

All brown wires at fuel injectors harness do have positive voltage above 12.1 volts.
Its the #2 and #4 white wires showing no negative volts at the injector harness (terminal plug ins).

if the negative ground, white wires is spliced together at I10 (pages 36, and 76), for W-R and W wires, but has individual wires going to ECM/ECU (refer to C and G connection at ECM, on pages 36 and 76, which refers to page 29). Can you send me this page 29.

With engine stethoscope, I can hear a ticking noise from each fuel injector.

I pulled all plugs and ran cylinder compression test, all cylinders were within 5 psi of one another, with no leak down observed per cylinder as well.

Valve clearance checks were done earlier, as all eight exhaust valves were below specifications, and one intake valve below specs.
Replace with new valve shims, after checking with micrometer to verify correct shims. After R&R valve shims, rechecked valve to cam clearances and all are with specification for valve clearance of engine now. New valve cover gasket was replaced along with new seal of gasket on half moon plates for camshafts in front of engine.

Battery voltage at battery and fuse panel are above 12.3 volts.
Battery had a low charge, from running different test, and currently on a trickle charge for the afternoon.
I won't be able to work on truck till tomorrow.

 

That page 29 is just a picture (same as on PDF I have) - just PDF is better visible. Reference to C and G is on page 79: C is E7 plug, G is E8 plug. C is used with Manual transmission, G is used if you have A/T. So these two sets of injectors are going to the same plug - which one depends on if you have A/T or M/T.



You will not be able to tell correct connections on injector plug when the plug is not connected to the injector. The ECU is "Open Collector" type. Basically if engine is not running the white or white/red wires are "open" meaning not connected to the ground (unknown voltage when plug is not connected to the injector). At the moment when ECU is firing injector that wire is grounded allowing 12V run through the injector. So you can only measure the voltage at the white wire (or red/white) when injector is plugged in - it should show battery voltage. When engine is cranking the white wire (or red/white) is momentary connected to the ground allowing current run through injector but that moment is so short that you probably will not read it with voltmeter (only by oscilloscope or with the speaker like I wrote previously).

When you hear injectors clicking but there is not enough fuel it is either fuel delivery (pump, fuel filter, fuel pressure regulator) or injector clogged or not opening correctly. Injector can be checked only outside with injector testing tool. I did not see your truck and condition it is but it is very unlikely that ECU does "funny things" or that wire harness is bad. If that part of truck was not messed up before I would check injectors (or fuel delivery). But that diagnostic from 6 thousand miles away is worth nothing anyway

 

I know RysiuM has already given you a ton of good advice, and even how to test your injectors, but if you want a device to support, I bought one of these.

https://tinyurl.com/qm4d2ed

 

That tool can be used for testing injectors including performance numbers. However it would have to be calibrated meaning you will have to know how much fuel should be delivered at given pressure and opening time. I'm sure these numbers are documented somewhere but I doubt they are published. But still there is a possibility of calibrating that tool using known good injector. Basically use known good injector to measure the the volume delivered at given mode and then compare the volume given by injector that is checked. Well doable.

 

One thing that came to my mind. I was always under impression that you should never connect the injector directly to the battery for longer than a split of second. But after reading FSM and the injector test procedure it appears that you can connect injector directly to the battery for at least 15 seconds without damaging it. Or I read it wrong?




SST 09842 - 30070 is just a pair of wires with injector plug on one end and aligator clips on the other end. So the injection volume is from the injector being continuously opened for 15 seconds and the full fuel pressure delivered by the pump (265-304 kPa, 2.7-3.1 kgf/cmz, 38-44 psi).

 

The W-R negative wire has me wondering why one side of the splice wire would have -12 volts and the other W-R wire has minimal negative volts. Not going to look into this at this time.

Battery is fully charged at 13.135 volts.
Earlier in the week the alternator went bad as well, R&R alternator, which ran down my battery charge.
Engine basically original, with no modifications to wiring or OEM Engine.

What started off with replacing bad fuel injectors, has led me into the engine and some other additional routine maintenances, I hadn't done. Engine now has 350k miles. Earlier, when the intake manifold was removed, to access the injectors and injectors rail, I cleaned out most of the carbon build up in the cylinder heads and intake manifold ports.

Fuel filter was replaced with the 1st set of new injectors. Fuel pump replaced around 2-3 years ago.
Currently completed fuel pressure test along rubber hose at fuel pressure regulator.
Fuel pressure currently at 10 psi, but engine is some how managing to start up and running roughly.
Back to checking fuel pump and fuel delivery system now.

 

Yes, that's low. With Engine not running you should get 38-44 psi. When engine is idling you should get 31-37 psi

 

Fuel pump pressure was 5 psi, not 10 (typo).
I double checked the fuel pressure in front of fuel filter, inline setup, while engine was running roughly, and had the same 5 psi pressure.

Replaced a couple of rubber vacuum hoses in engine bay, which where cracked and hardened.

Found the receipt for fuel pump and strainer, purchased on 7-2-2018, has lifetime warranty. Will need to R & R fuel pump, and take back bad fuel pump for warranty.

 

Dropped the fuel tank, and removed to old fuel pump.
Inspected inside bottom of fuel tank, and all looked very clean.

Attached photo shows old fuel strainer and old fuel line removed from old fuel pump.

Installed the new replacement fuel pump and new fuel pump strainer..

Started the engine, and fuel pressure in front of fuel filter, is at 5 psi.

I'm wondering where to check now.

 

How did you measure it?

 

From the fuel line between battery and brake master cylinder .

Checking fuel lines for kinks now.

 

Fuel gauge had been set up on the return fuel line, and that's were fuel pressure was measuring 5 psi. sight

I don't have the Toyota fuel banjo adapter to connect under the FPR.

I did hook up fuel gauge to fuel line going into fuel filter, but did not have adapter for continuous gas flow to engine.
Fuel pressure pegged the pressure scale, way above 100 psi.