Topic: No Check engine light with key on 90 toyota 3.0

[Ctdogman1]

 Have a 1990 Toyota pickup 3.0 it runs Great "if it starts" when I turn the key the to the on position if the check engine light turns on it will start right up, if there is no check Engine light it will crank but won't start. There is No spark coming from the coil ( I did replace the coil and ing module) I changed the ignition fuse.

Also noticed when the engine is running, the EFI relay get to hot to touch and the wire coming from the fuse box to the POS side of battery is also hot, (Not sure if it matters but its a Toyota Motorhome)
 This problem started out with happened every once in awhile (thought i had it fixed) and then got worst, The last time I broke down on highway, i was sitting with the key in the on position and there was no "Check engine light" as I was calling for a tow with the key on I heard a click and the "Check engine light appeared, The truck started and i drove about 60 miles without a problem, Once home I shut off engine and no "Check Engine light and truck wouldn't start.

[Dingman.]

I had a very similiar issue with my 4runner after i did my 3.4 swap.  It ended up being a bad connection on one main wire in the main harness near the ecu.  So with my experience alone i would say to start wiggling different areas of the harness and see what section makes the light come back on, then move on from there.  Once i finally fugured out the problem area i was able to bend the ears slightly on the connector so it made better contact and that solved my issues.

[Ctdogman1 [OP]]

Thank you Dingman

 I pretty much wiggled all  the wires but will try again.

[Dingman.]

I know it is probably far fetched to think you have the same issue unless you recently did work involving the harness, but my issue was in one of the harness connectors that is located behind the ecu.  I wish i could remember more for you.

[gnob]

Sounds like maybe your efi relay is dying.
I have also seen sensors go bad on 3.0, the short pulls the computer down enough to keep the CEL from coming on.

[05sport4x4]

I had a problem with a 1989 22RE that would crank and not start randomly.  I replaced the ignitor which did not solve the issue.  I never noticed if the check engine light was on or off but the problem was a bad distributor.

[Willard]

I had a similar issue with my '90 4runner 3.0. It ended up being a bad ground on the firewall to the harness. It is a small rectangular connector center of firewall behind the plenum. Replaced the connection and as much wire as possible and no further issues on my end. Hope that helps.....

[Ctdogman1 [OP]]

 what sensor? gnob

[gnob]

Any of the 5V sensors. AFM, tps, ECT. Also make sure the o2 wires aren't chafed.
I would probably start at the efi relay. I did a job recently where the spades in the fuse panel were stretched and causing hot start issues for a guy.

[Ctdogman1 [OP]]

 Thank you everyone for your help, I'm hoping to be able to work on it this weekend, I will let you all know the outcome. 

[OOPS]

Could also be the main ground wires coming from the ECU to the back of the engine. They are located below the head on the passenger side of the engine in the back. Kind of a bummer to see and get to. I had forgot to hook them up when I did a body swap, no CEL no start.

[Tango Alpha]

Just another suggestion from an old guy that used to work on stuffs that have lots of wiring harnesses.

Wiggling harness means push and pull on the wire bundles SLOWLY and GENTLY in different direction while observing if the bad intermittent problem shows up.  Sometimes a wire that is subjected to long term vibration will break but still make connection with broken ends touching.  Same can happen when a connector pin has backed out a bit and has poor mechanical connection, but still maintain an operable electrical connection.  These poor connections can cause a temperature rise in the vicinity.  You can also have a high impedance short, like a power carrying wire insulation got chaffed and touching metal occasionally.  Shaking wire bundle SLOWLY and Gently can replicate some of those conditions and gives the symptoms again.

Good luck in locating that fault.

[OOPS]

Sometimes the grounds break loose at the splices in the harness, found one in mine!!

https://imgur.com/a/OvfcxAo

[Gnarly4X]

Just thinking out loud....  may not have anything to do with your intermittent issue? 

What condition is your battery in? 

Is the battery a wet cell with caps that you can remove to check cells electrolyte with hydrometer?

Have you checked and cleaned the battery terminals, cables and clamps at the battery?

Have you checked the output voltage of the alternator?

Gnarls. 

[Eygon]

Based on the description you provided, it sounds like there may be an issue with the electrical system of your Toyota pickup. It's possible that there is a problem with the wiring or a malfunctioning component, such as the ignition switch, that is preventing the vehicle from starting when the check engine light is not illuminated. It's also possible that there is a problem with the fuel system, such as a clogged fuel filter or a malfunctioning fuel pump, that is preventing the engine from starting.

One thing you can try is to check the fuel pressure to see if it is within the proper range. If the fuel pressure is too low, it could be an indication of a problem with the fuel pump or fuel filter.

It may also be helpful to have the vehicle's computer system scanned for trouble codes, which can provide more information about what might be causing the issue. An auto repair shop or dealership should be able to perform this service for you.

If you are unable to diagnose and fix the problem on your own, it may be necessary to seek the assistance of a mechanic or auto repair shop. They will be able to diagnose the problem more accurately and recommend the necessary repairs. If you are stranded and in need of emergency locksmiths se20 services or a towing service for help.