3FE Speed Sensor and 5 speed (1 Viewer)

[mmw68]

On the 3FE engine the ECU uses a speed sensor. Can any one elaborate on this for me.
Is it on the instrument cluster? Or on the auto tranny? and If you drop in a 5 speed, or like I in my case, have a 3FE engine in a fj40, then were is this sensor?

Thanks - mark

 

[Aseif007]

I put a 3FE/H55 in my FJ-60 and did not have to make any provisions for a speed sensor.

 

[Elbert]

While I don't know specifics on the 3fe, most speed sensors are for automatic transmissions and sometimes deal with emission controls. Lockup torque converters...

 

[mmw68]

Hummm, Well Iam trying to solve a problem with my FJ40 with the 3FE engine and 4 speed.

Some times I have plenty of power in 1st and 2nd, and other times it just chokes and putters and even back fires. like it's not getting enough gas, or the fuel air mixture is wrong. I noticed that the VSS wire is not going to anything, so maybe this is my problem?

Another issue I thought was maybe the electric fuel pump, but It would work or not.

The TB has been cleaned, and has a new TPS, The timing is set to 850, and the engine purs when it runs, and at idle. Any suggestions would be help full.

-Mark

 

[RockDoc]

Try a search here, and maybe through google. The little bit I gleaned (but didn't look much) suggests that it is in the instrument cluster (tied to speedo?), controls emissions stuff at low speed, and is not missed in a manual swap.

 

[RockDoc]

If it is in the cluster, maybe that is the problem, manual swaps into a 62 have it still functioning, but dropping a 3fe in a different truck leaves you with no speed sensor.

 

[RockDoc]

gonna flip through the FSM and see what I can find, will attach if I find anything that clears it up.

 

[RockDoc]

The speed sensor feeds out of the speedo assembly. Gives 4 pulses of continuity per rotation of the speedo cable.

 

[mmw68]

RockDoc, Thank!! I owe you one.

Now all I need to figure out is what type of gismo I need. Downey has a few.. I have to call them and see which one will fit on a FJ40 speedo cable.

http://www.downeyoff-road.com/EngineComponents/EngineConvElectronics.html

 

[RockDoc]

No problem, I don't have a great amount of experience yet, but I am good at digging through paper.

 

[Godwin]

I found little regarding the speed sensor in the 1988 FSM. Pages EC-19&20 describe how to inspect the SS but do not provide a fix if it is defective. These pages are under the Emission Control Systems - Air Injection System section. On the diagnostic page FI-25 (EFI System -Diagnosis System) code # 42 is thrown if the "SPD" signal is faulty. But aside from providing a diagnosis for the code there is no direction to any page for repair.

The speed sensor feeds off the speedometer. I've driven months with a broken speedo cable and no code was thrown. During my 3FE installation I may have circumvented the speed sensor in some manner such as the speed sensor signal is not being fed to the ECU, or the speed sensor is not grounded.

My impression is that the speed sensor is not critical to the EFI operation of the 3FE and is not causing the problems you're experiencing.

 

[mmw68]

Well, now Iam very confused... It's a $100 fix, so Iam going to go ahead and install a speed sensor, that way I can eliminate the problem. I wonder if having a auto vs 4 speed with the EFI is the difference?

I did find this info:
http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html

 

[mmw68]

Jim, I just noticed you have a FJ60 with a 3FE, so that would be the 4 or 5 speed. But on the FJ60, do you still have the sensor coming off the instrument cluster? So did you use a 3FE Harness? And if so - where did the Lead that would go from the ECU to a VSS go?

 

[RockDoc]

mmw, did you keep the emissions stuff on the engine? Is your fuel pressure regulator seeing a vacuum signal? The stock set-up has this vacuum signal run through a vacuum switching valve, which I assume is controlled as a result of the speed sensor signal. There was some discussion of this in regards to de-smogging a 3fe a couple of days ago, I'll see if I can find the thread (jist was bypassing the vacuum swicth <seeing vacuum all the time> was fine, blocking off the signal <atmospheric pressure> to the regulator was not fine).

 

[RockDoc]

https://forum.ih8mud.com/showthread.php?t=186893

Not sure if it helps, but wouldn't hurt to make sure the FPR is seeing vacuum, otherwise it will run rich.

 

[mmw68]

I just read thru the PDF on Speed Sensors, and I do feel this is my problem. The emissions stuff is still in place. I'll check the FPR, it's new, but Iam not sure of how good the vacuume valve hooked too the FPR is. I have several spare 3FE parts, I'll just swap that out. I also should figure out how to hook a Fuel pressure gague up.

 

[mmw68]

If I run rich...would I stall??

 

[RockDoc]

I'm really starting to stretch beyond my experience, but I would think if this is the area of your problem, it would be the signal to the VSV, and not the VSV itself that is suspect. Could be affecting the Air Injection (hmmm, you said back firing) and EGR behavior as well, as they are controlled by VSVs too. DO you have a 3fe manual to check the behavior of these systems?

 

[mmw68]

Yep - this is my third 3FE engine, and I also own a FJ62, so Iam have spare parts, and manuals. This FJ40/3FE project truck that I bought had so many problems when I received it, that it has been hard to track down any one problem, but Iam making progress.

I'll do the FSM check on all the little vacuum sensors so I can rule those out.

 

[RockDoc]

Well, the AI system section includes a check of the speed sensor (p. EC19 in my 89 manual), but I guess the more important issue is what effect the speed sensor has on systems upstream of the combustion chamber (fuel pressure, EGR?).

I wonder if some of the other 3fe swaps are desmogged, and bypass this issue.

But I should back off now and let those with more experience pipe up.