aceofsnett

I have a 1991 3vze, 4wd / 5 speed with an intermittent hard miss / no start condition that has been going on for several years. I've posted about it before, but now I'm stranded with it not starting. I've replaced the vfm, coil, igniter, distributor, efi relay, plugs, wires, cap, rotor and more. The ecu is getting power, but not sending power to the igniter. Could the ecu ground be bad? Could the VFM harness be bad? Please help!

aceofsnett

I should add the following information.. The B+ connector has power with the ignition on, but the FP connector does not.

93toyrunner2

Are you getting fuel to the rail? Are you getting spark? Codes? Have you pulled the TPS plug to see if that helps? There are about 100 things that could be wrong. Need more information on what you have checked to help you with what else to check.

aceofsnett

The truck actually started just now, randomly. I can't believe I forgot to mention that this is a no spark issue, having checked several times for spark. As for fuel, you can clearly smell fuel dumping out the exhaust. (I have a cherry bomb exiting right behind the driver's door)

The TPS tests out fine, although I have not checked it recently. Every other part of the ignition system except for the ECU has been replaced. The ignition switch also tests fine. The harness for the VFM appears to be in good shape. Could it be a corroded connection at the ecu, or a bad ground? I know that if the ecu is not receiving a signal from the VFM the engine will not start. The truck also has a tendency to run lean, which could theoretically be due to the vfm connection at the ecu being corroded, couldn't it?

I should also add that the truck only flashes a code when it misses, and only for a split second. At the same time, the shown rpm drops to zero. I have not checked for stored codes.

93toyrunner2

Could be. Do you have a water leak at the ECU area? If not, then you more than likely have a wiring issue. Time to break out the voltage meter, set it to continuity, and trace wiring to the VFM, checking if there is a short or bad wire from the ECU. Pin outs can be found in the FSM, wiring section. IME, an occasional no start condition is bad wiring, bad ground, or shorting wiring in the Engine harness. If it were an electrical part, then it would usually just get worse every time, until it just quit.

aceofsnett

I do have a water leak at the ecu area due to the massive rust hole that has appeared under the ECU. The only visible corrosion is on the two power connectors, but the ecu seems to be getting power just fine. I am going to attempt to trace the E1 ground, as well as clean up the various terminals on the ECU itself and see if that helps.

TNRabbit

Also check ALL major grounds, & I mean take them apart, clean, & re-install. These trucks are getting old, so all electrical wiring is subject to corrosion degradation. I've had SEVERAL issues related to bad contacts due to age/corrosion.

sharpy46

im havin a similar issue....every thread here ends without a solution......i wish folks wouild post after they fix sumthing...but anyhooo...check the round connector to the ignitor....mine was pretty nasty with corrosion. im still chasing this issue.....ill be shure to post if i have any luck.

aceofsnett

Anyone have a good list of the major grounds? I'm especially interested in where the ECU ground is. I heard it was on the passenger's side door pillar, but I have not yet found it. I'm also curious about what ecu will fit which truck, as I'd like to try replacing it.

MudHippy

They're all bolted to the firewall in the engine bay, or bolted directly to the engine itself. Near the fuse box and battery, near the ignitor, directly behind the engine, and various places on the engine. No grounds for any of the engine controls/components are inside the cab that I know of. I know for sure the ECU isn't grounded in there.

As for the ECU, I answered that in your other thread.

aceofsnett

Thanks for your help. The truck is still stuck at my parent's house. I'll get to cleaning up the grounds as soon as possible, before I start messing with replacing the ecu.

It does seem like no one outside of Japan knows where the stupid ecu ground is. Looks like I'm buying a 75,000 mile 86 2wd 22r tonight, so at least I'll have something to drive in the meantime.

93toyrunner2

Try looking at the FSM, "electrical", "ground points"
http://www.ncttora.com/FSM/1990-1995...o/groundpo.pdf
If you look at page 3, you will see that the ground point for the ECM is "EC" and if you look at page 4, it tells you where it is located, exactly. No need to contact Japan.
Download your copy of the FSM today from the link in my signature!