‘93 FZ80 Engine shuts down randomly only after it’s warmed up… (1 Viewer)

[SUMMIT CRUISERS]

When replacing fuel pump did you replace the fuel strainer/sock with new or use the old one? If old one, that is more than likely your issue.
Ask me how I know.

 

[TomH]

i will try this next time it shuts down...if it works this shows that i need a new FP resistor, correct? Meaning the old one is getting too hot and stops working until it cools down....random insight, i don't know know if its connected but i notice when i open the hood after a shutdown it restarts faster

I suggested this because it’s a quick test without tearing a bunch of stuff apart. Providing 12V directly to the fuel pump bypasses the whole fuel pump logic that comes from the ECU and forces the fuel pump to run. This assumes power to +B which can easily be checked with a meter, should have 12V with key on. Doesn’t necessarily mean the resistor is the problem. It may also be a way to get the truck running if it won’t start.

One thing to keep in mind is jumping the fuel pump means you have power with key on and not just when cranking/running. Worse case is you get in an accident with the pins jumped, rupture a fuel line, and the pump keeps pumping fuel.

I went through a similar issue with my SC400 where it would just die while driving. Jumping FP and +B always allowed it to start. I tracked the problem to the fuel pump ECU which I replaced and that solved the problem. The SC ECU is a little different than the Land Cruiser resistor but similar. In the SC world, many run with the fuel pump ECU bypassed, meaning power to the fuel pump with key on.

 

[Nbndallastx]

When replacing fuel pump did you replace the fuel strainer/sock with new or use the old one? If old one, that is more than likely your issue.
Ask me how I know.

it came with a new sock and i added it...but i haven't replaced the fuel filter? i have a new one but the old one looks like it was replaced recently...should i give that a go? Just wouldn't think it would kill the engine like in my vid? it doesn't seem like it sputters when it dies...anyways might do it, just in case. Sorry for the steam of thoughts, haha...

 

[Nbndallastx]

I don’t think anyone has mentioned specifically the engine harness near the EGR. It becomes “crispy” with heat and age. But it’s also source for electrical shorts due to breakdown of insulation of wires routed together at that spot. Harness goes from engine to firewall.

its definitely a concern...but i inspected the wires only near the pipe...no frays or tears...i put heat tape and a heat guard foil wrap from Amazon that is made for high heat on that area...now that the egr is gone, it should be cooler than the last 2yrs. I might come back to this if other things don't pan out...thanks.

 

[Nbndallastx]

i don't want to get ahead of my next two tasks...jumping fuel pump logic and/or swapping out the coil pack BUT....

Any thoughts that a bad ECT sensor could be causing this? i have a new OEM one at home that was part of my PM plan but never installed it...could it be telling the ECU the engine is too hot and shut it down in this manner? I don't want to inject too many new variables now that i can replicate the shut downs (kinda)...i'm assuming my OBD1 wouldn't identify if the ECT sensor was bad as well...again just thinking out loud.

 

[baldilocks]

Pump the brakes dude…… one thing at a time.

 

[Nbndallastx]

Pump the brakes dude…… one thing at a time.

i just want my fzj80 back lol

 

[Sc0-]

Had a similar problem with a '86 22RE, ended up being a bad AFM.

 

[SUMMIT CRUISERS]

it came with a new sock and i added it...but i haven't replaced the fuel filter? i have a new one but the old one looks like it was replaced recently...should i give that a go? Just wouldn't think it would kill the engine like in my vid? it doesn't seem like it sputters when it dies...anyways might do it, just in case. Sorry for the steam of thoughts, haha...

Not thinking a fuel filter would cause this. With that said it’s either spark or fuel related. If you have another person, try testing for spark when it happens. Spark plug tester lights work great and are cheap. Next would be to squirt some starting fluid through a vacuum/intake hose if you have spark. As @Sc0- just mentioned might be AFM. AFM controls fuel pump. Got a buddy with one you can swap out for a day? Or wire up the fuel pump temporarily to run with key in the ON position to bypass AFM as discussed.

 

[bubfuji]

do you know if the OBD1 would identify a bad Coil pack with a CEL?

i recently changed my battery clamps, fusable links and cleaned up all the old wire loom and inspected wires to the ALT and Starter...they look good. Testing the ECU is probably over my head for right now...i still have the ground wire to the engine firewall. It will restart if its not too hot(ambient heat not coolant heat) right away if its hot...

yes this did happen before the ERG was removed and after.

coil pack is the next place i'm looking at, thanks!

OBD1 would not flag a failing coil. The FSM shows a list of CEL codes and definitions.
The spark plug wires and coil wire can go bad. The Toyota OEM wires are really good wires. That being said, when spark plug wires go bad. It is usually in the form of increased high Ohm resistance or leaking spark energy (cracked wires). Adding engine heat multiplies this effect.
You mention the ECU was swapped. Check the 3 harness connectors that plug into the ECU. Pull each connector one at a time, look for corrosion. You can clean the connectors with electrical contact cleaner (usually CRC safe for plastic).

Does the rig just die? or act like it is running out of gas?

Also there is a main engine relay in addition to the fuel pump relay.

Witts End sells the OEM 80 series engine harness.

 

[Nbndallastx]

Had a similar problem with a '86 22RE, ended up being a bad AFM.

god i hope its not my VAF...i think that's a tough/expensive part to find...

 

[Nbndallastx]

OBD1 would not flag a failing coil. The FSM shows a list of CEL codes and definitions.
The spark plug wires and coil wire can go bad. The Toyota OEM wires are really good wires. That being said, when spark plug wires go bad. It is usually in the form of increased high Ohm resistance or leaking spark energy (cracked wires). Adding engine heat multiplies this effect.
You mention the ECU was swapped. Check the 3 harness connectors that plug into the ECU. Pull each connector one at a time, look for corrosion. You can clean the connectors with electrical contact cleaner (usually CRC safe for plastic).

Does the rig just die? or act like it is running out of gas?

Also there is a main engine relay in addition to the fuel pump relay.

Witts End sells the OEM 80 series engine harness.

got ya on the list of CEL codes so its a safe assumption its all in compassing list, thanks! i've got some time today so we'll be troubleshooting for a little bit will inspect wires and ECU again. The rig just dies, but no sputter like its running out of gas or air...i posted a youtube link, not sure if its working for ppl. Anyways, i hope its not the engine harness...more to come

 

[80t0ylc]

its definitely a concern...but i inspected the wires only near the pipe...no frays or tears...i put heat tape and a heat guard foil wrap from Amazon that is made for high heat on that area...now that the egr is gone, it should be cooler than the last 2yrs. I might come back to this if other things don't pan out...thanks.

If your troubleshooting finds nothing in other areas, you can remove tape and inspect each wire for missing or damaged insulation. Adjacent wires with damaged insulation can short out and cause “twilight zone” problems. Random dash “idiot lights” are a symptom of this sometimes. The damage may have happened before the installation of heat tape.

 

[Nbndallastx]

Update: this morning we installed a new coil pack it fires up per usual then warmed up at idle for 15mins (sounds great) - I drive it around the neighborhood and it dies (exactly like the YouTube vid link)…it won’t restart, strong cranks…so did the bypass fuel wire (B+ to FP)…doesn’t fire up. I let it sit with the hood up for 3-4mins and go fires back up perfectly idle for 5mins this time then dies…with the bypass fuel wire

Same shutdown symptoms with or without fuel bypass…so tgat should rule out fuel issue right?

Reminder - no CEL codes, CEL comes on when starting, so EFI relay is working…

I haven’t touched the TPS should I look here?

When it dies it just quietly dies, no sputter - like it ran out of air or fuel…

 

[Nbndallastx]

Oh I tested all the grounds with multimeter and they passed just fine…

 

[bubfuji]

OBD1 would not flag a failing coil. The FSM shows a list of CEL codes and definitions.
The spark plug wires and coil wire can go bad. The Toyota OEM wires are really good wires. That being said, when spark plug wires go bad. It is usually in the form of increased high Ohm resistance or leaking spark energy (cracked wires). Adding engine heat multiplies this effect.
You mention the ECU was swapped. Check the 3 harness connectors that plug into the ECU. Pull each connector one at a time, look for corrosion. You can clean the connectors with electrical contact cleaner (usually CRC safe for plastic).

Does the rig just die? or act like it is running out of gas?

Also there is a main engine relay in addition to the fuel pump relay.

Witts End sells the OEM 80 series engine harness.

I was able to see the video.
It does not look specifically fuel related.
Maybe not the coil/wires. However you need to go through the steps.

The engine dies gracefully...
No sputter, cough, rpm jumping, or rough idle
Runs fine and then not.

Your temp gauge shows a warm engine. Your idle is too high. Should be 650 +/- 50 and might be related to engine shutting down.
check your intake tube for cracks or air leaks.
Cracks form in the bellows area and are hard to see without taking off the intake tube.
leaking or bad IAC valve. If you haven't, go through the trouble shooting pages in the FSM. There are 3 pages.

In an earlier post, "Sc0-" mentioned replacing his VAF under similar conditions.
The VAF cap is plastic. You carefully cut the silicone around the plastic cap and VAF body. And look inside. When the flapper moves, it also moves a contact patch along a copper strip (actually a half circle strip). The copper strip wears out around the engine idle point creating a dead spot. When the engine cranks, the flap opens. This starts the fuel pump. If your idle moves up/down 50/100 rpms? Your VAF may find this dead spot.

 

[TomH]

Same shutdown symptoms with or without fuel bypass…so tgat should rule out fuel issue right?

This should rule out the fuel pump circuit.

 

[Nbndallastx]

The Good, the Bad, the Ugly today after work…

Good - swapped in a brand new shiny ECT sensor with washer

Bad - didn’t fix my engine shut downs

Ugly - take a look at the old ECT sensor…has to be original I would think…

 

[Nbndallastx]

I was able to see the video.
It does not look specifically fuel related.
Maybe not the coil/wires. However you need to go through the steps.

The engine dies gracefully...
No sputter, cough, rpm jumping, or rough idle
Runs fine and then not.

Your temp gauge shows a warm engine. Your idle is too high. Should be 650 +/- 50 and might be related to engine shutting down.
check your intake tube for cracks or air leaks.
Cracks form in the bellows area and are hard to see without taking off the intake tube.
leaking or bad IAC valve. If you haven't, go through the trouble shooting pages in the FSM. There are 3 pages.


View attachment 3113777

In an earlier post, "Sc0-" mentioned replacing his VAF under similar conditions.
The VAF cap is plastic. You carefully cut the silicone around the plastic cap and VAF body. And look inside. When the flapper moves, it also moves a contact patch along a copper strip (actually a half circle strip). The copper strip wears out around the engine idle point creating a dead spot. When the engine cranks, the flap opens. This starts the fuel pump. If your idle moves up/down 50/100 rpms? Your VAF may find this dead spot.

Thx for the insights! Yea need to go back through the troubleshooting pages…the IAC keeps popping up in the steps, I thought I tested it correctly but I think I’ll double check it again - I might have missed something

Anyone near ATX have an extra VAF they’d let me plug n play to determine if this is my culprit?

 

[ajax1]

Pop the fuse box in the engine bay and see if any of the relays are super hot, also on 93s the main wire has had issues under the fuse box