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I have an 88 early model year ( built in 87 ) 4runner that I put a motor from an 87 in. With everything in place, it will only run off the cold start injector for a couple seconds and die. Right now, the setup has the 88 computer, a resistor box under the hood, and 87 injectors spliced into the harness. From my understanding the early 88 injectors were the same as the older ones other than the plug.
After this, I tested wiring and have 12 volts before and after the resistor box, matched to ground, and twelve at one leg of each injector plug. The part that confused me is the other leg of the injector plug on each wire shows 9 volts, which i assumed would be either zero or grounding depending on the ecu injector pulse? The obvious problem would be an issue with the harness, but I want to make sure my setup is not the problem before taking apart the harness, or at least have a better idea where to search.
Anyone have any ideas? Thanks
Theres your problem. 1987 injectors do not work with '88 ecu. The ecu switches them on by grounding them. You always have 12vdc on the hot side. 1988 is an odd ball year, you have some parts that are not compatible. Also check the ground at the rear of the head to chassis ground on the firewall, I bet you its busted.
88 is a one year only injector. You may see them referred to as Red Top Injectors. Red Top Injector can be misleading as the 89-94 injectors have Red Tops on them. 85-87 are a White Top Injector. 85-87 White, 88, Red, 89-95 are Red, but each group has a different resistance value. I don't know if it is true, but I have read that the wrong injector can ruin the computer. Each injector connectors have tabs to keep them from being able to connect the wrong injector to the wrong connector.
Where in IL are you? I have another set of 88 injectors and harness that has been hacked but the injector plugs are there.
I'm just west of Peoria.
I understand the resistance values are slightly different between years but are the circuits different enough that this could cause the ground side to read voltage?
Also I tested the set up with an 87 ecu without any help.
I'm testing the ecu's in another truck tonite to make sure one or both isn't bad.
Okay I tested in another 4runner and both ecus will run an 87. I got the splices exposed on the harness and they also look good. The b+ to E1 terminals show 3 volts. B+ to ground is 12, e1 to pos is 3 too. So this would point ecu ground?
How can i tap in to run a good ground straight to the computer?
Okay reset everything checked codes, only one is a #12 - rpm signal.
I swapped igniters and distributor, and no change still only fires off the cold start injector.
From here I suspect possibly a wire? How can i check this wire from the igniter to ecu?
I don't think running a ground to the computer will do anything. The computer some how electrically grounds the injectors. Also I have read some of the rock crawlers move their computer to the glove box to keep it out of water, and I have just had my computer just laying in the floor for testing.
I think the Igniter does have a part in timing on the injectors, I just am not able to read diagrams well enough to trace it out like that. It looks easy on the diagram, but getting to it physically is another story.
I've tried running a jumper wire now from both igniter leads and the negative side of the Fuel injectors to the ecu and still now luck, same thing where it starts and only runs a few seconds and dies.
My next try will be another distributor if a can find one off another truck to fit.
This things driving me nuts, I'm about to just throw a carb at it and make a dang 22r
code 12 is most likely the problem. The computer uses the distributor signal the fire the injectors. Test the pickup sensor on distributor. Next would be the ignitor, then closely inspect wiring.
The b+ to E1 terminals show 3 volts. B+ to ground is 12, e1 to pos is 3 too. So this would point ecu ground?
I would say your problem is here. E1 sounds like it's floating, in which case the fuel pump relay (circuit opening relay, or COR) will not be powered by the VAFM switch. In that case the fuel pump shuts down as soon as you release the start key, and the engine dies almost immediately.
Measure the resistance of E1 to ground. It should be down around an ohm or so. My guess is it will be much greater than that. You need to fix that. If you temporarily run a jumper from E1 in the diag port to ground I'll bet the engine will run.
Your code 12 may be just collateral damage. That E1 ground goes to a lot of places in the ECU control systems, and if it's floating all bets are off as to what will work and what won't.
I'll check the readings again tonight but I believe when I took that reading that showed 3 volts the plenum and its ground was removed, causing the lack of ground.
10-07-2015, 08:48 AM
