Found some bad wiring and think it might be causing my no-start scenario (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Aug 5, 2020
Threads
11
Messages
104
Location
Oakland, CA
Hi All,

My head gasket went out last October on my 1993 80 series. After a bunch of personal drama I finally got it reassembled earlier this month but it won't start. There is no spark and no fuel despite it running when I started disassembly in Nov'21. The truck cranks strong with a brand new X2 Power AGM battery. I found a bad Circuit opening Relay and EFI Main Relay. These likely are the source of the no fuel issue but I'm bought a new fuel pump just to be safe and will put that in as preventative maintenance.

What I'm struggling with is the no spark issue. I replaced the spark plugs, spark plug wires, rotor, dist cap, and ignition coil all with OEM or Denso units. I ohm'd the new coil just to be certain and checked the air gaps in the distributor. I also checked the resistance of the distributor per the FSM. I've checked all the fuses and they are all good. Fuseable links are good. I get a CEL with key on. I have not yet checked the VAF or the TP but it sounds like those should be checked.

I have a few questions

1. Should the tach bounce around a bit during cranking (mine is not and to my understanding this points towards the igniter).
2. During the disassembly I found this wiring splice from one of the 7 previous owners. I replaced these spade connectors with butt connectors and hoped for the best. These run from the end of the fuel rail to wire harness junction just behind the battery. Does anyone know what these wires go to? I have a FSM but am not great at wiring diagrams so I figured I'd ask here before I dive into the diagrams.
3. Does anyone have any pictures of all of the ground wires for the engine that I can reference? I'm wondering if I just forgot a ground wire or something simple like that. I'll be going back and squeezing/pulling every connector this weekend.

IMG_20220117_161054577.jpg
 
Check the wiring connector on top of the distributor for broken wires and connections.

Do you have a CEL with the key in the "RUN" position?

Odds are the VAF / AFM on the intake by the air filter has been damaged. Have you removed the two screws on that wiring harness and tried to unplug the harness from that VAF/AFM?
 
Check the wiring connector on top of the distributor for broken wires and connections.

Do you have a CEL with the key in the "RUN" position?

Odds are the VAF / AFM on the intake by the air filter has been damaged. Have you removed the two screws on that wiring harness and tried to unplug the harness from that VAF/AFM?
I'll double check the distributor wire for issues.

Yes, CEL is on in "RUN".

The VAF was sitting in a box for a couple months in my garage. It likely got bumped around a bunch. No I did not touch the screws. Just unplugged it and removed it while connected to the top of the air box.
 
I'll double check the distributor wire for issues.

Yes, CEL is on in "RUN".

The VAF was sitting in a box for a couple months in my garage. It likely got bumped around a bunch. No I did not touch the screws. Just unplugged it and removed it while connected to the top of the air box.
With a CEL on and the key in the RUN position, the computer has all the sensors and inputs it needs to run.

The fuel pump will only run when the engine is cranking. You should pull the relay and short the fuel pump to test it for operation.

You need to check for spark.

Do a diagnosis of the AFM to determine it is giving a proper signal at all positions to indicate airflow.

If you have the FSM, use it to follow diagnostic procedures.

If you don't have it, download the free copy from the RESOURCES tab above.
 
With a CEL on and the key in the RUN position, the computer has all the sensors and inputs it needs to run.

The fuel pump will only run when the engine is cranking. You should pull the relay and short the fuel pump to test it for operation.

You need to check for spark.

Do a diagnosis of the AFM to determine it is giving a proper signal at all positions to indicate airflow.

If you have the FSM, use it to follow diagnostic procedures.

If you don't have it, download the free copy from the RESOURCES tab above.
I'll try shorting the fuel pump to test operation tonight.

I've checked for spark 3x times now based off the FSM procedure. Holding the spark plug against the intake manifold next to the ground point results in no spark from the ignition coil. I have not done the ECM checks though. That will happen tonight.

The VAF just measured/checked out good per the FSM test. Same with the TPS. It's looking like it's the igniter or ECM unless someone else has any other ideas.
 
I'll try shorting the fuel pump to test operation tonight.

I've checked for spark 3x times now based off the FSM procedure. Holding the spark plug against the intake manifold next to the ground point results in no spark from the ignition coil. I have not done the ECM checks though. That will happen tonight.

The VAF just measured/checked out good per the FSM test. Same with the TPS. It's looking like it's the igniter or ECM unless someone else has any other ideas.
The most common no spark reason I've see (with a CEL at key on) is the plug on the top of the distributor.

Any codes registered on the OBD1? I realize the battery has been unhooked or a while, but it would be worth checking to verify no codes.
 
The most common no spark reason I've see (with a CEL at key on) is the plug on the top of the distributor.

Any codes registered on the OBD1? I realize the battery has been unhooked or a while, but it would be worth checking to verify no codes.
I haven't checked for codes but definitely adding that to the "to do" list.

Thank you for all your suggestions and help!
 
This is from the 1994 EWD; I think the '93 is the same:
1645740072626.png


1645741523072.png
 
Last edited:
This is only a guess, but it looks like those are the EFI leads:
1645740566571.png


The colors are right and they appear to be bundled together. The R wire (red wire) should be connected to terminal "4" in EB1 (see above). The Y/R wire (yellow wire, red tracer)should be connected to terminal "1" in EB1. The R/Y wire (red wire, yellow tracer) should be connected to terminal "3" in EB1. Looks like someone cut that connector off the harness, and used the spade terminals to replace it.

"EB1: is a waterproof, 5P (5 pin) connector housing:
1645741935501.png
1645742004630.png

(female on left, male on right) You can either buy these from Toyota, or rob them from a 1993 Camry (or something near the same year). Be aware, though, Toyota only sells the bare housings; you then also have to buy the terminals (I like Mauser or Ballenger; you also need a crimper) and seal plugs. Not a big deal, but you need the whole kit (and kaboodle). Looks like about $40 to put it back right.

PM me if you need help with this.

If I'm right, the dark red wire (which is BR above) is a ground. I cut off the EWD above that point.
 
Last edited:
The R/Y (red wire, yellow tracer), from the EFI main goes to the connector marked "EB1", terminal "3" on the EWD:
1645740987226.png
 
The Y/R wire (yellow wire, red tracer), feeds all this crap:
1645741144861.png
 
...and last, but not least, the Fuel Pump relay, via the COR, in the driver's footwell:
1645741209585.png

the "Circuit Opening Relay" is here:
1645741323521.png
 
So you don't confuse the two, the Fuel Pump Relay is here:
1645741416642.png
 
@Malleus Thank you so much! Considering that these wires seem to run to the relays that I measured to be out of spec I'm now concerned that if I put in new relays they will go bad. Thankfully I bought spares so I can try plugging them in to see if I can get fuel pressure. But doing a better repair than my crimped butt connectors sounds good. I have some crimping tools but I'll see if I have the right tool for those pins for the factory plug.
 
@Malleus Thank you so much! Considering that these wires seem to run to the relays that I measured to be out of spec I'm now concerned that if I put in new relays they will go bad. Thankfully I bought spares so I can try plugging them in to see if I can get fuel pressure. But doing a better repair than my crimped butt connectors sounds good. I have some crimping tools but I'll see if I have the right tool for those pins for the factory plug.
If those wires are the culprit, your solution is a good one, as long as the connections are good. The only reason Toyota put a removable connector there was to allow you to remove either side - the engine harness (for example to pull the head or engine) or the load side.

If I had to guess, I'd bet on the ground being bad.
 
If those wires are the culprit, your solution is a good one, as long as the connections are good. The only reason Toyota put a removable connector there was to allow you to remove either side - the engine harness (for example to pull the head or engine) or the load side.

If I had to guess, I'd bet on the ground being bad.

I figured I'd respond to close out this thread...

The issue of cranking with no start was my fault. When I was fixing the wiring from my first post in this thread, I mixed up the two small gauge wires. When I fixed it, the 80 started right up.

Now I just need to sort out why my new fuel filter is leaking like crazy.
 
I figured I'd respond to close out this thread...

The issue of cranking with no start was my fault. When I was fixing the wiring from my first post in this thread, I mixed up the two small gauge wires. When I fixed it, the 80 started right up.

Now I just need to sort out why my new fuel filter is leaking like crazy.
The banjo bolts need new crush washers on both sides of the fuel line; that means 4 new crush washers with a new fuel filter.
 

Users who are viewing this thread

Back
Top Bottom