First drive and help needed on various issues

[yuza]

I did already a terminal to terminal measure on each gauge and they all are either within specs or slightly out of, not sure this means they are ok and just giving a slightly wrong measure or they are gone...?

[PossumJr]

In your picture that is the pressure switch. I forgot that you have the straight 6 engine which I'm not familiar with, so I'm not certain what you should and should not have, but I don't believe there would be a difference so there should still be a separate sender unit tee'd off of the same connection the switch is on.

If the coil resistance in each gauge checks out that's no guarantee they will work, but likely they will provided 12v and ground is going where it needs to.

[yuza]

I am neither familiar with...anything, this is my first jeep ever!
Anybody more expert with the 258 able to help? Also with regard to the carb I posted above
Here's a full view of the engine bay, if this helps

[tgreese]

The oil pressure sender is on the passenger side of the block, about 2/3 back about halfway between the oil pan and cylinder head IIRC. The sending unit looks like this: https://www.rockauto.com/en/moreinfo.ph ... 17&jsn=383 There will be a single wire coming from the connector and into the wiring harness.

NB these replacement senders need a different connector on the wire - that's just what's available.

If you can't find things, look at the wiring diagram in the TSM, locate the wire for what you are seeking in the bulkhead connector at the firewall and follow the wire to what you are looking for. It will help you a lot just to read the TSM. Just read it, without any purpose other than improving your understanding.

Also note that the gauges will not work if the cluster is not grounded to the chassis. Do not apply power to the gauges unless the cluster is grounded. The CVR is pulse-modulated .. on-off-on-off-on-off etc - and is will be on all the time without a ground connection. If stuck on for long enough, it will damage the gauges.

Follow the procedure in the TSM for testing the gauges. Test the sending units with a multimeter, and test the gauges by substituting fixed resistances for the senders.

[PossumJr]

Do not apply power to the gauges unless the cluster is grounded. The CVR is pulse-modulated .. on-off-on-off-on-off etc - and is will be on all the time without a ground connection. If stuck on for long enough, it will damage the gauges.

Only if sender inputs are connected as well, which means the gauge coils can see ballpark twice the normal current. Simply hooking up 12v input to the cluster with no path to chassis ground, either the cluster ground or indirectly through senders, means no current flow through the CVR or gauges so there's no harm.

[tgreese]

True - there has to be a circuit for current to flow. If you connect power and the sender, the ground will be through the sender and the CVR will not regulate. This is at a minimum risky. The danger is in tilting the cluster out of the dash (disconnecting the chassis ground) and applying power. On a CJ, this will release the magic smoke from the gauges - I have not tested it on a FSJ (knowing what I do about other's experiences with CJ gauges, which use the same type of CVR).

[yuza]

I am trying to follow the wiring to identify what is what but I can’t find what is supposed to be there on a 258!

1) besides the pressure switch I can’t see anything else

There’s a spare yellow wire with a plug on top but in wiring diagram the wire from the sending unit should be purple

2) I can’t find the temp sender, the only thing looking similar to it is located at the very back of the valve cover and there is a spare purple/white wire out of the harness (cut, no connector) that corresponds to what the diagram reports as the temp sensor wiring


Any idea?

[yuza]

Alright I think I have understood the one in the back of valve cover is actually the temp sensor
Tried to unscrew it and coolant was leaking out.
Given the original plug is gone, would this connection give a reliable input, or am I altering the resistance seen by the gauge?

[tgreese]

Can you find the engine oil dipstick? The OP sender is in the side of the block between it and the firewall.

The type of connector is irrelevant as long as it makes good electrical contact.

To test the sender, measure the resistance between the water temp sender post and the block when the engine is cold and when it's warmed up. The TSM will tell you what those should be.

There are instructions in the TSM that will tell you how to test these systems.

You should put the year, model and equipment of your Jeep in every post. You can do this automatically by editing your signature file ("sig") at your user control panel.

[yuza]

Thanks, I will add those data in my profile

In the oil dipstick area the only thing I see is a kind of a bolt coming out of the crankcase, see picture. It is just behind the stick as you suggested and it holds a bracket to which the dipstick is attached

[tgreese]

It's right there in the middle of the picture. Item 3.605-3. The usual water temperature sensor location is at 3.610-3.

This looks like a much later engine, or maybe a 4.0L or 4.0L head, not a 258. Definitely different from the domestic 258s. The T-176 was also not available in 1979 in the USA. What is your VIN? What is the engine build code? Location of the build code is shown in figure 1B-3 of the 1979 TSM, free to download here: http://oljeep.com/edge_parts_man.html

The signature is part of the profile. Suggest you edit the signature.

[tgreese]

This is your water temperature sender. Also, this looks exactly like a 4.0L engine, not a 258. What's your VIN? What's the engine build code?

[yuza]

I still have to check it, the car is hosted in the garage of a friend

If that is the temp sensor, what is the one in the back of the head? When unscrewed coolant came out of it

The vin tag is missing but the number on the frame is J9126071.
It has a t176 trans, levi interiors

[tgreese]

Head bolt? Better picture.

The chassis number only contains the sequential serial number part of the VIN, which resets back to one every model year. Is that number from the registration or did you read it from the frame rail?

VIN tag missing is very suspicious, ie a stolen car or rebuilt from a wreck or from parts. Since the VIN is missing, I'd say it's not a '79. Equipment is wrong for that. Get the engine build code from the side of the block. The location is shown in the TSM I linked above.

[yuza]

Will do. But as far as I have read on various sources equipment should match a 1980 cherokee (t176 with np208 were fitted since then, right?) and the tan/levi interiors miss the levi logo on the buttons, which I think was the case in 79 and 80

Might it be a 1980MY built at the end of 1979?

The serial number is on the frame, in right front wheel arc. If it is serial it would mean >120k units built in '79, so maybe this matches the end of year production period

It was registered in Italy 20 years ago, no idea of its story but given lack of parts here the engine might have been rebuilt using parts from later models eg grand cherokee, which was officially imported

[yuza]

Assuming I have a 4.0 engine or engine's head at least, by reading in XJ forums it seems that the sensor on the thermostat housing is indeed a switch that activates the cooling fan, and should have a 3/8" thread

What if I replace it with a normal temp sensor and wire it to my temp gauge?
Would it work?

I also found comments regarding some early 4.0 engines having the sensor in the back of the head, same as mine, so I likely do not need to use a different one

[tgreese]

Re 1980 vs 1979, sure. At that time, the model year started in September of the previous year and ran through the following summer. Production shut down for retooling in the summer, and many vehicles were built before September, to supply the dealerships with the next model year. So a 1980 Jeep could have been built any time in the 12 months starting July of 1979.

Yes get the proper sensor and a bushing to adapt the 1/8" NPT thread to the 3/8" NPT hole. Connect the wire and you're ok.

Back of the engine location will be ok, but you need to match the type of sensor with the gauges. Unlikely the 4.0L sensor will be correct for your gauges.

The number includes all Jeep production (trucks, Cherokees, CJs, everything), so 120K does not tell you much about the date of production. There are date codes on the axles, if you can find them and decode them (not something I can help with). These dates would precede the build date for the Jeep by a month or two, typically. The engine has a date code, but it's not right for a 1980 either. There is very little difference between the 1979 and 1980 engine. Note that the 4.0L was originally fuel injected, and this engine has been fitted with an earlier intake manifold and a carburetor - assuming it's a 4.0L. The exhaust manifold is 100% 4.0L. The date code on the engine will tell you both the date of production and the engine type.

[Longjohn61]

This is a 4.0L engine i have the same setup and mine ia a 1980 4sp manual but some po swapped the engine for a 4.0L
one way you can see it is the connector on the thermostat housing and the other is the oil filter house its typical 4.0L

/Nils from sweden

[yuza]

Thanks, I am not alone then!
Might need you help for troubleshooting
I will check engine codes later today or in coming days to confirm the assumption
Said that it is no more stock (maybe this lowers its value), should I expect to have much higher power?
4.0 was rated 170hp vs 115 of the older 4.2, right?
Then carb vs FI and many horses might have gone, but still it should be stronger

[tgreese]

The 4.0L is definitely better for the highway. Your assessment is mostly correct. Jeeps typically are not thought of as collectible cars, so a different, better engine should make the value higher - at least in the USA. The missing VIN plate would be a much bigger issue here, affecting clear title and ability to insure.