Help with JF80 3FE ground points (1 Viewer)

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

Joined
Feb 3, 2015
Threads
8
Messages
472
Location
Madison, WI
Can anyone list out or have a diagram for where the ground points are on a 3FE? I just put in a new (used) motor and I think I have the grounds incorrectly placed. Specifically the neg battery terminal. Currently I have one going to the body (I think that one is correct) and the main lead going to the ground bolt on the block. I don't think that is correct.

I really could not find the ground location in my service manual!

Thanks,
Adam
 
Doesn't matter too much as long as the ground cables are in good shape. I have a negative going from my battery to the body and another going from the battery to the passenger engine mount. There is one that mounts on the back of the head that goes to the firewall, another one that comes from one of the starter mounting bolts to the frame, and another from the exhaust heat shield to the frame near the t-case on the passenger side. There is one ground in each kick panel up front and another one under the center console. Those are all factory-installed ground points. It definitely wouldn't be a bad idea to fabricate new grounds if any of the factory ones are missing or look a little crummy. Just make sure the body, frame, and engine are well grounded to each other and the battery. Clean metal, clean ground lugs, clean mounting bolts, and a nice slathering of dielectric grease over all to make sure they don't corrode too badly.
 
@lzeloz. Thank you for the rundown. This is a big help That! That is basically how I have it now. I am going to recheck each of the points you listed just to make sure they are clean and add in some dielectric grease.
 
@jonheld. I just did a motor swap and I have a hard start which means it cranks over around 6-8 times before starting and it idles rough with a misfire. Once over 1000rpm the misfire goes away ant it runs smoothly.

I was thinking it was not getting enough spark at lower rpm due to a bad ground. I think all the other ground wires are correct based on my deinstall pictures. Of course I did not get a pic of the main ground wire off the battery. 😡

There are a number of rough running only at idle threads for the 3fe that I am going to start with. I'll start with the easy stuff go down the list. The fsm also has a trouble shooting list to work off of.

There is a noticeable valve tap that I also need to clean up which could be it too.

Oh yea, the I put a new header back exhaust on the the shop did not install one of the O2 sensors. There is just the one. With a check engine light on. That might do it too.

Much to clean up!!
 
@jonheld. I just did a motor swap and I have a hard start which means it cranks over around 6-8 times before starting and it idles rough with a misfire. Once over 1000rpm the misfire goes away ant it runs smoothly.

I was thinking it was not getting enough spark at lower rpm due to a bad ground. I think all the other ground wires are correct based on my deinstall pictures. Of course I did not get a pic of the main ground wire off the battery. 😡

There are a number of rough running only at idle threads for the 3fe that I am going to start with. I'll start with the easy stuff go down the list. The fsm also has a trouble shooting list to work off of.

There is a noticeable valve tap that I also need to clean up which could be it too.

Oh yea, the I put a new header back exhaust on the the shop did not install one of the O2 sensors. There is just the one. With a check engine light on. That might do it too.

Much to clean up!!
This is a tractor motor. Always look at the simple things first.
If the engine runs well above idle, then stop looking at spark. You obviously have it.
In most cases, a rough idle is caused by unmetered air entering the system. The top half of the engine wants to be sealed. This is why you have gaskets on the oil fill cap, the oil dipstick, etc. Any unmetered air entering the system will play havoc with idle. PVC grommet, valve cover gasket and grommets, side cover gasket are all suspect.

Deal with the CEL or she'll never run right. The ECU is doing its best to make corrections based on missing parameters, but it has a very narrow window to work with. Remember, 1986 technology.

Yes, the main battery ground attaches to the engine block as that is the primary ground plane. Make sure it has good connectivity and is not corroded, or simply replace it.
 
Last edited:
@jonheld, Thank you for the sage advice and conformation! I have a engine gasket kit waiting for me to start a reseal job on the top end. Ill do that once get the O2 bung welded on and O2 sensor installed. I think I checked everything fairly well but it is possible I missed something. I did a preliminary check of the intake boots but I think I need to pulled it all off and do a close inspection as well as replace the PCV valve and grommet with the one I have sitting in my glove box :)

Ill post when I find the issue for others or I may be back scratching my head.

Thanks again!
 
I hope this isn't derailing your thread too much, but my '91 also cranks several times before it starts (if it's been sitting for a bit). I think my issue is the fuel pump. There is a small check valve inside the pump that is designed to hold pressure in the system. I think my check valve is weak or has failed, thus requiring a full re-pressurizing of the fuel system at each start. So far I have just lived with the issue, but one of these days I will replace the (AFAIK original) fuel pump with a new Denso. HTH.
 
Ahh. @Lzloz. That make a heap of sense. That is what it feels like it is doing. I am also going to inspect the fuel lines again to see if there is a small leak. This is a very crusty truck on the underside and I have not replaced all the fuel lines. I have and original FP as well. That will need to be replaced at some point.
Thank you for the added direction!
 

Users who are viewing this thread

Back
Top Bottom