sollyburton

I've been fighting this for 4 months now. Truck ran perfect until the battery cable came undone when offroading. I hooked it back up and it has ran terrible since. It is getting a good spark, getting fuel and the motor has great compression. I took a video so you can see and hear the problem. Any help is appreciated.

ldivinag

you can replace the idiot lights one by one.

at the dealer, each one is like $8... yeah i know... i know.

but from i heard/read, you can just buy the bulb and not the bulb and the holder. i didnt know this a few years ago when i replaced one of mine.

once you R&R the idiot lights, you should be able to read the codes...

good luck.

BamaYota1

It almost seems like you have a grounding issue since half of your harness doesn't seem to be doing anything. I assume you have checked all fuses in all locations? What year is your truck?

sollyburton

My truck is an 89. I tried checking all of the grounds and even took a jumper cable from the negative side of the battery and tried grounding it everywhere I thought might be a problem with no luck.
I am pretty sure my idiot lights didn't burn out, because why would 3 of them go at once?

sollyburton

Yeah, I've checked all the fuses about 3 times.

rustypigeon

..............

sollyburton

Here's another thing that has confused me. I bought another ECU for my truck because I originally thought that was the problem. My truck is an 89 and the ECU I bought was out of a 90. According to what I've read everywhere it should interchange. So when I put the 90 ecu in my truck it wouldn't fire at all.
At first I thought I wasted $100, but decided to go to a neighbor's house and try it on his 1990 truck. My 90 ecu worked in his truck but my 89 ecu wouldn't fire in his truck, it flooded it! I immediately smelled fuel when he ran the starter and he had a hard time getting the truck to start again when he put his ecu back in because it was flooded.

Any ideas on this?

Co_94_PU

iTrader: (-1)

Which cable came loose. Either cable coming loose can/may/will damage the ecu among other things. OMG don't unplug your ecu while it's running, and don't touch it if it's not fully grounded to the chassis.

You can check the codes at the diag port with a test light(yank a running/parking light and use some spare wire if you're a real redneck)

At the end when you have most of the stuff disconnected it's only running off the cold start injector. Notice when you were altering the throttle it smoothed out, does it react the same with all the stuff attached? Attach a test lamp or meter to the main injectors and see if they are firing.

Nice video even If i was crinching every other second

sollyburton

It was the positive cable that came loose.
It ran the same with all the stuff connected, so I guess it is only running on the cold start injector.
How do I check the diagnostics with a test light? Which pins should I connect the light to?

Bigblock

Either wire.One will flash during cranking and the other is ground.You also need to check(unwrap some of your body wiring harness)for melted wires.CSI should only light up for a short time then go out. Just unplug it and see what happens.Also try your buddies VAFM. Let us know.

sollyburton

I checked out my circuit opening rely today. It passed all of the resistance tests but the one between +B and Fp. I took out the circuit opening relay from my 86 truck and it showed the same reading on the ohmmeter. I put it in the truck and it did not help the truck either. On the VAFM, I tried the tests in the Haynes manual and it showed no resistance between E2 and Vc. Also I turned om the key to see if the wire going to the VAFM had power and the only one that showed power was Vc and it only showed 0.7 volts. Could this be my problem? When I open the VAFM by hand with the key on I do not hear the fuel pump run. Will the VAFM on my 86 toyota work on the 89? Or is the problem that it isn't getting enough power?

XtraSlow_XtraCab

A lot of the defects you mention share a common ground "under the left front pillar". Look for that and check your ENGINE fuse. Under left piller probably means near the driver side kick panel (near fuse box). There should be a couple of decent size wires with an O-connection to a bolt.

I believe this problem includes a major circuit, not just a relay.

Co_94_PU

iTrader: (-1)

Yeah thats bad news, this means the whole system got the alternator output/current.

Pretty sure the lamp is in the DLC also but it's "w" on the ecu so you don't have to pull the dash apart.

FSm diagnostics Eg1-121 shows the schematic.
FSm ecm pin out is here

Full fsm link

"W" is located on that first plug you pulled out, right next to the battery power for the ecu your trucks running in the "start mode" where the ignition is directly controlled by the distributor sensor "ne".

There are some unknown variables here.

What is the manufacture date on your truck, from the door placard?
Please give the part numbers for both computers and indicate which is the original.
Count the pins on both ecu's or provide a photo of the plugs.

Co_94_PU

iTrader: (-1)

P.S. If you have an ESD safe work space, or don't care and have the sense not to poke around in it. Pull the lid off the dead (original 89) computer and post a clear photo of the board, might be a simple fix like soldering a blown pcb trace.

sollyburton

I checked the ground under the left pillar and it was good. The Engine fuse was good too. I checked for power where the engine fuse plugs in and got 12v.

The date of truck manufacture on the door is 9/88

The original ECU (1989) is 89661-35150
175 600 0501

The ECU from the 1990 is 89661-35150
175 600 0502
They both have the same number of pins - 10P 18P 14P

Co_94_PU, are you saying I need to ground the "w" pin on the ecu? and which pin is it on the first plug in?

sollyburton

I see that there is a W pin at the diagnosis plug in, but it is just an empty hole, there is nothing there. Do I need to access W at the ecu with the lid off?

Co_94_PU

iTrader: (-1)

yeah I thought i saw that plug in the DLC but it doesn't show a wire in the schematics. not sure which harnesses get that wire to the DLC..

With the lid on, clip the test lamps clip to the body and put the probe on the (W)arning lamp. eg stick the probe in the back side of the wiring harness while it's attached to the computer. I'm not sure of the polarity offhand but so long as it's a regular bulb not an led it won't matter.

Those ecu's appear compatible at a glance, but I didn't look up the interchange information.

The manual section that gave the computer pins has a voltage and resistance check, can you handle that? The resistance check will help diagnose the harness. The voltage tests diag' the computer.