Resurrecting Someone Elses FJ80 Project (1 Viewer)

[IowaEngineer]

I found a project 1991 FJ80 that was local and at a good enough price that I picked it up. The PO had purchased it as a project for him and his son to work on with the intent to use it for light offroading, but it seems that they only made it as far as buying new wheels and tires before the son lost interest. He had purchased it in 2019 and it had been sitting in his driveway since. At some point between then and when I purchased it from him in early July 2023, it had developed an issue in the fuel system and was not running. I have been weekend warrioring the baseline/repair since then. I bought this because I needed a hobby/time pit to keep me busy. I am aware that the meandering path of fixing it up may not be the most expedient or cheapest, but cheap and fast isnt really my goal.

Fuel:
dropped and cleaned out fuel tank
replaced fuel pump and strainer
replaced fuel filter
replaced fuel injectors with the ebay osidetiger 12 hole injectors
on order: fuel pressure regulator, fuel pulsation dampener

Electrical:
replaced missing fan relay
replaced blown then resoldered fusable link
replaced distributor cap
replaced distributor rotor
replaced plugs
replaced plug wires

Engine:
verified compression (130, 125, 145, 130, 125, 130 no oil added to any of the cylinders)
replaced air filter
removed smog system
cleaned sludge out of valve cover and top of head (it was very bad)
set valve clearance
removed oil pan to inspect and remove any sludge buildup
changed oil filter and oil (added seafoam to hopefully helpo dislodge whatever sludge is left, will change again in a few hundred miles)

In the queue once I have it running:
new radiator/radiator hoses
new waterpump
new thermostat

Additional known issues:
wire to water temperature switch is broken at the connector (jumped with a test lead for now)
water pump is leaking
diagnostic code 41 for throttle position sensor shorted high/low (TPS tests fine by FSM standards, so I expect I may have a short between it and the ECU)

Where we are now:
I can get occasionally get about 3 seconds of running before the engine dies if it starts at all. It still agressively cranks and will sputter a bit after those three seconds, but will not fire. I believe I still have a fuel delivery issue. If I use the diagnostic jumpers to test the fuel pump and crack the banjo that that feeds the fuel return line from the pressure regulator, I get no flow or dripping. Cracking the banjo to the cold start injector gets a nice spray of fuel. This makes me think that the FPR may be seized close.

 

[leonard_nemoy]

Nice, welcome to the forum

 

[BILT4ME]

Look up posts from @jonheld . There is a link in his sig line to properly diagnose issues with the 3F-E.

I am guessing it is your VAF that is the issue. Hopefully no one has pulled the two screws and yanked on the harness, as that breaks things.

Follow the FSM and check it out.

Welcome! Great to have another Iowagian here.

 

[IowaEngineer]

Thanks for the hint on the VAF. Just to ensure that I am not losing something in the acronym. Does VAF refer to the airflow sensor? If so, I checked based on the FSM and all resistance measurements were within specifications. Would there be another indication of a fault that I should look for?

 

[BILT4ME]

Thanks for the hint on the VAF. Just to ensure that I am not losing something in the acronym. Does VAF refer to the airflow sensor? If so, I checked based on the FSM and all resistance measurements were within specifications. Would there be another indication of a fault that I should look for?

Vane Air Flow meter.
This is the aluminum block in the air intake tube just after the air filter housing. This is what allows the fuel pump to turn on. The fuel pump won't come on until that flap moves showing airflow.

You've already checked most of it.
Get Jon's list and step through it.

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

 

[IowaEngineer]

I do have CEL. I also went through the full chain of fusable link -> circuit opening relay back when I was initially diagnosing the dead fuel pump. Everything electrically appeared to be operating as expected. I also would think that I've elimated the VAF as a likely cause based on no change in start behavior with or without the fuel pump diagnostic jumper in place. Am I missing something in making that logical leap?

Numbering is based on Jons 3FE tune up steps:
1. Spark plugs replaced
2. spark plug wires replaced
3/4/5. dist cap/rotor/gasket replaced
6. skipped
7/8. PCV valve and grommet replaced
9. Air filter replaced
10/11/12. N/A EGR system is removed
13. All 3mm vac lines that were removed in order to take off the intake manifold are replaced. Have enough 3mm to replace remaining hoses, but have not done so yet.
14. Cold valve adjustment done
15/16. Replaced valve cover gasket and grommets

 

[ppc]

Never, ever skip step #6.

 

[lp2k]

Kudos for taking a chance on this project and applying your skills to repair and bring this one back. The 3FE when running AND maintained is a strong engine.

 

[Broski]

Step 6

 

[Broski]

Welcome to mud !!!

 

[IowaEngineer]

Kudos for taking a chance on this project and applying your skills to repair and bring this one back. The 3FE when running AND maintained is a strong engine.

It was the reputation of the 3FE's reliability that had me take the chance. To be honest if I'd know the sludge disaster that was under the valve cover, I might have though a bit more before taking the plunge. I can't blame the PO because he obviously had not had it apart so I doubt he knew either and taking off the valve cover is a bit outside of a normal pre-purchase inspection, so it just is what it is at this point.

 

[mudgudgeon]

.

It was the reputation of the 3FE's reliability that had me take the chance. To be honest if I'd know the sludge disaster that was under the valve cover, I might have though a bit more before taking the plunge. I can't blame the PO because he obviously had not had it apart so I doubt he knew either and taking off the valve cover is a bit outside of a normal pre-purchase inspection, so it just is what it is at this point.

Run diesel engine oil in it for a few changes. It'll help de-sludge it.

 

[jonheld]

Couple of thoughts.
The new injectors might be faulty or the fuel rail might be clogged with poop.
Those fancy 12 hole injectors will give you zero gain over the OEM ones. I would send the OEMs out to Witch Hunter or the like and have them cleaned and flow tested and reinstalled.
You have compression.
Have you verified spark?
Have you verified that the distributor is seated correctly and you're not 180 out or a tooth or 2 off?
The 3FE will spit out aftermarket ignition parts as fast as you can put them in. Stay OEM for all this stuff or you'll just be doing it again.

 

[YMT]

Also, don't forget to inspect/replace your intake hoses. They are prone to splitting, due to age, and sitting for extended periods doesn't help. The more you manipulate them, the more likely to crack/split.

 

[IowaEngineer]

Couple of thoughts.
The new injectors might be faulty or the fuel rail might be clogged with poop.
Those fancy 12 hole injectors will give you zero gain over the OEM ones. I would send the OEMs out to Witch Hunter or the like and have them cleaned and flow tested and reinstalled.
You have compression.
Have you verified spark?
Have you verified that the distributor is seated correctly and you're not 180 out or a tooth or 2 off?
The 3FE will spit out aftermarket ignition parts as fast as you can put them in. Stay OEM for all this stuff or you'll just be doing it again.

Really apreciate the help Jon. Point noted on the injectors. They were bought more because I was impatient than because I was chasing more power. I'll get the OEMs sent off for a rebuild soon. I did verify that the fuel rail was clear of obstructions when I had it off to swap the injectors.

I've verified spark by the FSM procedure. I did not consider to check the distributor since I had not removed it. Thats a good idea.

Everything that has gone into the engine bay this far has been OEM except for the fuel pressure regulator and the injectors.

I did also just try disconnecting the injector lead from cylinder 1 and connecting it to one of the OEM injectors that I removed. I could not feel it clicking at all when I cranked the engine over. Does that make sense or should I take that as reason to investigate the electrical that fires the injectors?

Also, don't forget to inspect/replace your intake hoses. They are prone to splitting, due to age, and sitting for extended periods doesn't help. The more you manipulate them, the more likely to crack/split.

I've already had to replace the 'lower(?)' hose. The one thats closest to the filter had broken off the port that connects up to the IAC. I'll add the upper hose to the to do list.

 

[jonheld]

I did also just try disconnecting the injector lead from cylinder 1 and connecting it to one of the OEM injectors that I removed. I could not feel it clicking at all when I cranked the engine over. Does that make sense or should I take that as reason to investigate the electrical that fires the injectors?

I would do some basic diagnostics on the injector harness.
All 6 injectors are fed a constant +12 on pin 2 (black/green stripe). That +12 comes from fusible link AM2 through the ignition switch when in the ON/START positions.
The ECU grounds pin 1 of the injectors to fire the coils in 2 groups of 3 (white/light blue stripe on injectors 1-3 and yellow on injectors 4-6).
With injectors in place and connected, you should see +12 on BOTH pins of each injector with the key in the ON position because you are reading across a coil.
You would need a oscilloscope to verify that the ECU is grounding pin 1 during start.

 

[IowaEngineer]

I verified that I have 12v on both sides of injector 1. I also verified that with the battery removed and the ignition switch to on, I have continuity from the pos battery clamp through both the white/blue and yellow wires (A12, A25/ No10, No20) at the connector to the ECU. My Fluke 289 couldnt see any falling edges when set up to capture frequency. It should be able to register freqeuncies well into the kHz range, so that is moderately concerning. I'll have to borrow an oscilloscope tomorrow to chase that any futher.

I started going through all of the other diagnostic checks from FI-29 while I had the ECU exposed. I found 12v between IDL-E2 when at WOT rather than the expected 4-6v which would confirm the diagnostic code 41 from before. I apparently have a short to power somewhere in the wires between the TPS and ECU. Otherwise no surprises yet. The pins for battery, ignition switch, EFI main relay(M-REL), and EFI main relay(B+) all have ~12v to the computer ground. Air flow meter(VC), throttle position (VTA) both open and close were within spec referenced to the sensor ground (E2). I further verified that when manually depressing the vane inside of the VAF, that the fuel pump was running.

While digging through the dash, I also found a hidden Python 650 ESP alarm that I was not aware was installed. There is a collection of snipped wires and vampire taps up under the steering wheel that will all need to be addressed...

 

[jonheld]

I verified that I have 12v on both sides of injector 1. I also verified that with the battery removed and the ignition switch to on, I have continuity from the pos battery clamp through both the white/blue and yellow wires (A12, A25/ No10, No20) at the connector to the ECU. My Fluke 289 couldnt see any falling edges when set up to capture frequency. It should be able to register freqeuncies well into the kHz range, so that is moderately concerning. I'll have to borrow an oscilloscope tomorrow to chase that any futher.

I started going through all of the other diagnostic checks from FI-29 while I had the ECU exposed. I found 12v between IDL-E2 when at WOT rather than the expected 4-6v which would confirm the diagnostic code 41 from before. I apparently have a short to power somewhere in the wires between the TPS and ECU. Otherwise no surprises yet. The pins for battery, ignition switch, EFI main relay(M-REL), and EFI main relay(B+) all have ~12v to the computer ground. Air flow meter(VC), throttle position (VTA) both open and close were within spec referenced to the sensor ground (E2). I further verified that when manually depressing the vane inside of the VAF, that the fuel pump was running.

While digging through the dash, I also found a hidden Python 650 ESP alarm that I was not aware was installed. There is a collection of snipped wires and vampire taps up under the steering wheel that will all need to be addressed...

Attached is the full 3FE ECU schemo along with all the associated bits. This should help a bit.

 

[IowaEngineer]

Thanks Jon, but I cant seem to open that PDF with any of the viewers I tried. I do have print outs of most of the relevant pages from the WD085U wiring diagrams of the ECU and under dash electronics. I have not yet been able to find any sort of logic diagram for what signals and states the ECU uses to know when to command the two banks of injectors to fire. Does something like that exist so I could know which inputs to the ECU I should verify with the oscilloscope?

 

[jonheld]

Thanks Jon, but I cant seem to open that PDF with any of the viewers I tried. I do have print outs of most of the relevant pages from the WD085U wiring diagrams of the ECU and under dash electronics. I have not yet been able to find any sort of logic diagram for what signals and states the ECU uses to know when to command the two banks of injectors to fire. Does something like that exist so I could know which inputs to the ECU I should verify with the oscilloscope?

Here's a png of the pdf.
There is no document that I am aware of that goes into that much detail, but the FSM should lead you down the correct path. Again, if the CEL is illuminated with the key in the ON/RUN position before cranking the starter, the ECU is in a "ready" state and it should be all systems go.
Have you verified the correct position of the distributor yet?
Are you getting fuel to the fuel rail?
As far as the frequency of the ground pulses from the ECU, during startup it will be somewhere between 50 and 70hz, depending on how fast the starter cranks.
At 650 idle speed it would be 650/4=162.5hz.