Jordan Covert

Hey all,

I just did an engine swap on my 1988 4runner v6 and I'm having some issues with my fuel injector's I was hoping y'all might have some answers to. The injectors aren't firing, and so my engine won't start.
I've tested that they're getting power, and they are.
When grounded, the injectors do cycle, so the injectors aren't faulty.
It seems the issue is that the injectors aren't being grounded. I've checked the local ground in the wiring harness, and that's grounded, so I'm at a loss at what the issue could be.
My EFI fuse is also still working so that's fine.
The only error codes I'm getting are 41 and 51 which both have to do with the TPS, which I'm assuming is more or less unrelated.
Any thought's on why the injectors aren't getting grounded?

-Thanks

Jordan Covert

Oh also, even though I swapped the engine, these are the old injectors and old harness (including old injector connectors). So they worked previously and now they don't! And the EFI main relay is still functioning.

Terrys87

iTrader: (1)

You do know that 88 injectors are a one year only? When you swapped motors, was it an 88 as well? I do not know the 3.0 to well but I think Toyota used the same principal for the fuel system. To see if you are getting a signal from the computer https://www.yotatech.com/forums/f116...t-22re-270857/

Just because you are getting a signal from the computer, does not mean the injector will fire. 85-88 trucks have a poorly designed wiring harness. Toyota used a wire crimp in the harness. I have seen the crimps so corroded that it will let the signal pass but not enough voltage to fire off the Injectors.

I seen your post earlier and just now noticed you updated your post with using the same harness and injectors. Here is what I went thru on Non Firing Injectors https://www.yotatech.com/forums/f199...l#post51897320 Even though it is for the 22re, I would think the diagrams and operation is the same and would check the harness,signal, and connections.

Jordan Covert

Yeah the swap was to an 88 as well, but it was made in Japan. I've used the noid lights already and they haven't been flashing at all for me. I can check the crimps and such, but honestly I've kept my harness in such good shape I kind of doubt that's the issue.

But I did do further testing. It turns out that I'm getting 12 volts to each prong in my injector connectors... really really strange. Any thoughts on this?

RAD4Runner

The injectors will get 12V to one side when Ignition is on. The ECU switches ground to the negative side. As mentioned ^^^ the wiring between the negative side of the injector and ECU is known to have problems.

You can spend time doubting things, or you can actually do something to make sure they are good.

Jordan Covert

So went through the wiring harness and all the splices are fine, no corrosion at all.

As far as the 12v to each side goes, I believe it has to do with the way the injectors are wired. Seems to be batch fire on each side, right and left, which is really interesting.

I've checked ignition coil and module and it's modulating ground, but neither side of the injectors are. My cold start injector also modulates, so I'm really at a loss as to why my injectors won't. Any advice is hugely appreciated!

Jordan Covert

Hi all. So here's what I've looked at so far...

1) I pulled my harness apart and found the crimps to the ground side of each bank. They all look fantastic, doesn't appear to be an issue.
2) I removed and sanded down the ground connection to the rear of the lower intake, the upper intake, the ignitor and the driver side fender/exhaust manifold. All look good and check out with ohm meter.
3) I took the computer out and inspected the pc board to see if there were obvious signs of trauma (burned spots, smell of magic smoke, etc). It was clean and looked good (I know this isn't a great validation of the health of the ECU but it is all I can do for now).
4) I've swapped every sensor from my old engine to the new engine (including the distributor).
5) I've checked every fuse in the drivers side kick panel with an ohm meter - all good
6) I'm running the factory harness and injectors.
7) I ran a ground from the battery to the ECU case.

Here are my observations:
1) I get a quick pulse from the cold start injector when I first crank the engine.
2) I don't get any modulation on the injector harness while cranking. 12 volts to both sides only. When in the complete dark I can see a super faint pulse of the light, not sure what to make of that.
3) I'm not getting any relevant codes from the ECU.
4) I'm getting good spark from the distributor.

I'm going to buy a new ECU tomorrow and hope that it solves my problem. The engine ran before it blew (300k, bottom end died) and although it has been sitting for a good 9 months, I have a hard time believing it just died. So I don't expect that the new computer will solve my issues. If it does solve my issue I'm worried that I don't know what killed the computer in the first place and I'm doomed to kill the new one as well.

Questions:
1) Are there more fuses I should check other than the ones on the driver side kick panel?
2) What tells the computer to fire the injectors? Ignitor? The tests I've run say it is functioning but I'm not sure the tests have been effective.
3) What am I missing?

I feel like my issue is a) my computer thinks it is grounding out the connections to the injectors but it's ground source doesn't exist so nothing is grounding or b) my computer isn't even trying to ground my injectors (which makes me think there would be some codes explaining why or c) my computer is fried (hard to believe...).

Thanks all for your help - I really appreciate it. I need to get my truck back on the road, I start a new job next week and need this thing to be running!!