3FE ground location Code EC air intake chamber? (1 Viewer)

[92bruiser3FE]

Hello mudders! I've been after an occasional long crank / no crank problem with my 92 FJ80 3FE.

I've been reviewing the electrical and Haynes manuals. There is a ground EC that is supposed to be located on the air intake chamber.

Is this the intake manifold or could that be Toyota speak for the firewall considering the cab gets it's HVAC air from this location.

I've replaced FPR and Damper and swapped in a known good pump at this point. Pump is powered and spark is verified. Grounds have been cleaned and additional ground from battery to block added for good measure. New ground from starter to frame as well.

I believe I found the problem was a loose ground on the passenger kick panel was not letting the injectors open. The electric manual doesn't specifically show ground EC location.

I always have check engine light. Just for reference.

Appreciate any input and want to thank contributors as I have used this site as a resource for many issues. So again thank you!

 

[jonheld]

I've been after an occasional long crank / no crank problem with my 92 FJ80 3FE.

These are 2 different issues. The starter circuit (no crank issue) is isolated from just about every other system on the vehicle. It has nothing to do with any EFI component.
A long crank before start could be as simple as the vehicle needing a regular old tune-up. How old is the rotor/cap/plugs/etc.?
When was the last time the valves were adjusted?

"I believe I found the problem was a loose ground on the passenger kick panel was not letting the injectors open."
That's not how the injectors work on a 3FE. Injectors are supplied with a constant +12 on 1 pin and the ECU grounds the other pin to energize the coil. The injectors are fired in 2 groups of 3 into the intake manifold.

 

[92bruiser3FE]

Honored to have you reply Mr Jonheld. Have reviewed many of your replies to other threads. Thank you for the wealth of knowledge.

Appreciate the reply and the information.

I agree, based on the schematic and was trying to understand how the loose ground could cause a no crank issue. The way I saw it the starter should crank with the ground completely unhooked.

Could the ignition switch be at fault?

Tuneup has 3k miles

Cap and button new OEM / Yec

Wires aftermarket but tested fine / longest being less than 15k ohms. Will be upgrading to yakazi. Will report back.

Plugs new but autolite that came with the truck. Gapped to manual spec. Will replace with denso or ngk and update.

Valves adjusted 3k miles ago. Per manual spec.

Just to clarify, your saying that a loose ground near the ecm could in no way affect the outcome of the injectors opening?

I haven't tested the ecm to verify what terminals are grounded to what outputs. But hypothetically speaking if the ground on the passenger kick panel correlated to the injector circuit could that not at times not provide sufficient ground to prevent the injectors from opening?

Certainly not trying to contradict you, just want to fully understand what's happening when this truck cranks and won't start sometimes and other times fires right up. Appreciate your insight!

 

[92bruiser3FE]

Just wanted to update. Ground location EC is on the driver side intake manifold under the cold start injector fuel line bracket as pictured. I'm going to clean it with deoxit and see if it makes a difference. For good measure I'm replacing the ignition switch and next step is cleaning the neutral safety switch. I'll follow up as I make some progress.

The electric manual doesn't show the location of EC. It is pictured on page 24 but it is not labeled. I'll add a pic in a bit for reference.

 

[jonheld]

Could the ignition switch be at fault?

Possibly, but I would try to diagnose the issue rather than throw parts at it. The starter circuit is pretty simple on these trucks.
Battery positive; fusible link AM1; 50 amp fuse AM1; ignition switch; NSS; starter solenoid. The starter motor is a direct connection to the positive battery terminal.

Just to clarify, your saying that a loose ground near the ecm could in no way affect the outcome of the injectors opening?

The ECU is grounded through connector E4-13; E4-26; E5-16; E4-24, all of which terminate at ground point EC on the intake. If this was an issue, the ECU would not function. Yes, the injectors would not fire, but you would not get a CEL either as the ECU would be dead.

I haven't tested the ecm to verify what terminals are grounded to what outputs. But hypothetically speaking if the ground on the passenger kick panel correlated to the injector circuit could that not at times not provide sufficient ground to prevent the injectors from opening?

That ground has nothing to do with the ECU or injectors.
From the EWD:

 

[92bruiser3FE]

Thanks for the clarification. Upon further review of the electric manual I also found that the passenger kick panel ground is unrelated to the ecu or injectors. Certainly appreciate the information!

Do you feel I'm on the right track with the ignition switch and cleaning the neutral safety switch?

 

[jonheld]

Thanks for the clarification. Upon further review of the electric manual I also found that the passenger kick panel ground is unrelated to the ecu or injectors. Certainly appreciate the information!

Do you feel I'm on the right track with the ignition switch and cleaning the neutral safety switch?

Again, I would be testing with a meter before replacing parts.

 

[92bruiser3FE]

Thanks for the clarification. Upon further review of the electric manual I also found that the passenger kick panel ground is unrelated to the ecu or injectors. Certainly appreciate the information!

Do you feel I'm on the right track with the ignition switch and cleaning the neutral safety switch?

The starting circuit appears sound. I haven't changed the main wire to starter or fuse able links. They did however pass voltage and resistance tests. I have not tested under load. I will perform these tests directly but as of now it's starting every time.

 

[92bruiser3FE]

I sincerely appreciate your input and patience.

 

[92bruiser3FE]

Tested battery voltage at battery key on start position versus voltage at the starter solenoid wire key on start position

Key on 12.36 v at battery.
Key on start position 12.2 at battery
Key on start position 11.8 at starter solenoid wire


Also I watched the voltage " build " (at solenoid wire) while I held the key. Just like when you have to hold the key for a couple seconds on a delayed start.

I think my next move is clean and adjust the neutral start switch. I'll update asap.

 

[92bruiser3FE]

Just wanted to update. I started to remove and clean the neutral safety switch but wanted to test it first. There is a connector on the passenger side near the firewall approximately where the bell housing meets the engine.

I tested it for resistance and found I had approximately 100 ohms. It looked a tiny bit green so I cleaned with deoxit. Upon testing again I now had 0 ohms. So even though the neutral safety switch could probably stand to be cleaned it is not the source of my hard start.

So upon reviewing the 3fe service manual I stumbled upon the troubleshooting section. I noticed that if giving the truck gas pedal helped get it going that the isc was suspect.

Fortunately I just happened to have a spare so I tossed it on and it fired right up. I've only started it twice so far and several times I have thought I had it whipped only to find a hard start at a later time. I will update after I have about 20 good starts.

Now, all that being said I tested my old idle control valve ( isc ) and it's resistance was within specs 10 to 30 iirc. I had about 20 per test. All 4 tests were identical resistance.

I took it apart and it looked pretty clean. Before I disassembled I tested per the manual and had no movement. After disassembly I tested the motor with the cap loosely fitted / not tightened to the housing, and it moved. But only slightly. For grins I removed the wave washer to reduce potential drag from a tight fit. It "worked" but the movements were so small I doubt it is working correctly.

In summary, as of now, I believe the isc was the culprit of my extended / difficult / non starts.

The quick and dirty test for the isc is to shut off the engine and listen for the unit to click. Seems like it clicked 4 or 5 times. The click was significant and I believe the old isc is completely shot. Again after hearing how loudly the isc clicked I don't think there is any way the isc I removed could be any good. Just seemed really weak during testing. Possibly the removal of the wave washer could let it function but I think it's adjusted idle for the last time.

I wasn't specifically listening for the old isc to click but I think I would have heard it as much as I've been fooling with this thing. During my initial testing it wasn't moving at all.

Finally, the resistance test in this case was pointless. I could have done resistance test and thought oh this is a good unit and it certainly was not.

 

[92bruiser3FE]

Tested battery voltage at battery key on start position versus voltage at the starter solenoid wire key on start position

Key on 12.36 v at battery.
Key on start position 12.2 at battery
Key on start position 11.8 at starter solenoid wire


Also I watched the voltage " build " (at solenoid wire) while I held the key. Just like when you have to hold the key for a couple seconds on a delayed start.

I think my next move is clean and adjust the neutral start switch. I'll update asap.

Upon reviewing the service manual these readings are within spec

 

[92bruiser3FE]

Just wanted to update. After months of trouble shooting and testing and not wanting to replace parts unnecessarily I finally pulled the trigger on the ignition switch. I think dirty contacts was letting power through (testing good) but insufficient power to provide the required spark for the truck to start consistently. Since replacing the ignition switch the truck has started every single time, the first time I hit the key within a couple revolutions. At this point I'm starting to believe with the age of these vehicles the ignition switch is basically a maintenance / wear item. Best of luck to all in your trouble shooting adventures!! This baby has finally been put to bed!