Help reading results from testing my EOT resistance

[Eco Taxi]

Hello
I have a 2001 7.3 with 134k miles
I bought this a few months ago and have been making up for the lack of maintenance of the previous owner

I've done alot of research and i think my problem with my cold start could be my EOT - so im trying to test it. I've printed off paperwork that tells me the resistance values i should receive in ohms and then the volts of the sensor corresponding to the temperature.

First I will say I replaced the EOT sensor with a new one. Problem still there. Thus i think its a ground or electrical issue.

I will be the first to say I'm not good with the electrical aspect of working on my truck. Learning curve.

I am going to try to attach a picture of my multimeter so when i state what setting i am using another individual can verify this or tell me I'm way off.

.......So after letting my truck sit over night to ensure the oil temperature will be the same as the outside temperature i went to check the resistance. As the instructions stated (on my print out off this forum or maybe a different powerstroke one ) i didn't have the key on. The temp outside was 40F so the K ohms value should be 64 and the volts should be 4.18.

when i tested this i had my setting on the 200k ohm section (gray section on my multimeter) and i got a value of 11.9-12. When i would change settings to 2k or 200 I would get no reading.

The instructions also said if i turn the key on i could test the volts. i did this at the 1.5 volts setting (green section) and got 0.8.

I dont understand what this is telling me except I assume i have a ground issue or possible bare spot in my wire or something. I am going to track the eot wire to the 42 pin harness and on the way to the pcm.

Thoughts, suggestions?
Thanks for any help

So far in these few months of owning this I've had to replace
-all 8 glow plugs
-glow plug relay
-starter
-starter selnoid
-alternator
-both batteries
-upper and lower ball joints on both sides

[klhansen]

When you checked the EOT sensor resistance, did you have it disconnected from the harness? If not, you were probably measuring the combined resistance of the sensor and the bridge circuit in the PCM (that decodes the EOT sensor resistance so the PCM can use it.)

[Eco Taxi]

it was disconnected - from the sensor

[klhansen]

So did you measure the resistance of the sensor or the resistance across the harness pins?

Should have been the sensor to match with the chart of resistances.

When you measure the voltage across the sensor it needs to be connected to the harness. The way to really do that is with a breakout box.

When your meter is set to resistance scales it's sending a small voltage out thru the probes and thru the item you're measuring.

When your meter is set to voltage, there's a really high resistance across the probes (like 20k ohms per volt) so that it's making a true voltage reading.

[Eco Taxi]

So I guess I checked the resistance across the harness pins

What's this breakout box?

There's two reasons I'm checking my EOT.....
1) my oil temp gauge always says its at like 2/3 temp - even when it sits overnight and I turn it on it'll say its at 2/3
Additionally....
2) I'm having cold start problems and I'm eliminating this out of the variable- my understanding is if my EOT is incorrectly reading the temperature it'll default to a reading of like 212f and incorrectly signal how long the glow plugs should be on and incorrectly tell the PCM how much fuel is needed

It's is my first diesel and I'm having a learning curve but love my powerstroke

Let me know if I'm correct in my understanding here because is my EOT is sending the wrong signal then my PCM is sending the wrong signal else where

Thanks

[woodnthings8]

You mention that you replaced the GPR. Have you verified it is working?

Yes, your EOT does contribute tot he PCM determining how long the GPR is turned on. If you measure voltage on the large post with the two smaller wires (Glow Plug Side), how long is there voltage available? If the truck is cold, it should be on for up to 120 seconds. Being 40 degrees, you can expect roughly 60-90 seconds, possibly more.


Take a look at my webiste for EOT Sensor Testing (scroll down to the EOT Sensor section). Sounds like you are partially on the right track.

A breakout box gets hooked up between the PCM and the connector. It has 104 banana plug connections (one for each wire to the PCM). It gets hooked up and allows you to check each wire while driving or running. It is a good diagnostic tool to have when troubleshooting.

[Eco Taxi]

First thanks for all the info

I did investigate the GPR after installing it to verify it was sending 12.6 volts for a give time ( wether it be 60,90,120 seconds ) with the key turned on

Ill test it again in the morning

I can't wait to get a aeroforce gauge to monitor and scan my engine as well as getting other dedicated gauges ... Eventually ill get AE

Could my UVCH causes any problems like this - when I changed my glow plugs I noticed it was a little loose and I pushed it tight together .... I didn't do the 50 cent mod yet - I was kind of worried about the 50 cent mod and if the 50 cent piece could wiggle itself out and fall inside the valves or something

[woodnthings8]

What exactly is your cold start issue? I suppose a UVCH could cause hard cold starts, but so can a variety of other issues. Have you checked out the Hard/Cold Start thread in KLHansen's signature? Lots of great information in there!

[klhansen]

If your PCM is getting an EOT signal that's within normal range, but high, you'll have a hard time starting when the oil is cold. That's because the PCM uses the EOT signal to adjust injection timing to compensate for the cold thicker oil going to the injectors. If you pull the EOT connector off, the PCM will use defaut cold oil timing for every start, because it'll know that the EOT signal is out of range, and it will also throw a code.

[Eco Taxi]

Yes I have been utilizing klhansens's cold/no start thread - very useful

I checked the GPR this morning again - GPR is reading at 11.5/11.6 volts
I changed my glow plugs a couple of weeks ago and their resistance was fine then....
I'll check their resistance again tomorrow morning

This saturday I will be actually digging into my wiring to make sure i have no bare spots (from wires rubbing or something) that come from my EOT to my PCM and I'll check the wires around the 42 pin connector thats near the valve cover

The main reason I am looking at my wiring as an issue is my factory gauge for oil temp always reads at 2/3 temp - when i start my truck from sitting overnight or all day (in Iowa when its 30F outside) it'll say the engine oil temp is 2/3 .... and my engine block heater not being plugged in
This gauge problem started a few weeks ago ... actually around the time i changed my glow plugs

I don't have a scan gauge yet or AE and the local truck shop I've stopped by twice only have a generic scanner (i think)
I dont have any gauges .... which is my next to do ..... asap

I have a new ICP which I'll be changing this saturday and a new IPR

After I have all these changed out and I've checked the wires if im still having problems would i then look at a bad/faulty PCM? ...... because that'll mean i would have changed the IPR, ICP, EOT, start, both batteries, alternator, GPR, glow plugs and would have checked my wiring and UVCH

[klhansen]

Originally Posted by Eco Taxi

The main reason I am looking at my wiring as an issue is my factory gauge for oil temp always reads at 2/3 temp - when i start my truck from sitting overnight or all day (in Iowa when its 30F outside) it'll say the engine oil temp is 2/3 .... and my engine block heater not being plugged in
This gauge problem started a few weeks ago ... actually around the time i changed my glow plugs

That gauge on the dash is a coolant temp gauge, and on your truck it doesn't even connect to the PCM. The EOT sensor only reports to the PCM, but is not displayed anywhere. There's no oil temp gauge unless you put one in or are using one of the gizmoz that will display a bunch of different parameters. The coolant temp sender is mounted on top of the water pump. Maybe you mashed something when you were up there changing glow plugs.

[Eco Taxi]

Oook, as you can see I'm riding the learning curve. Ill check my coolant temperature sensor and wires. As I have been reading if my ICP sensor is oily then it's time to change .... Correct?
I'm trying to figure out why my truck starts rough when it gets really cold. As I stated I have a new ICP and IPR. After I post this ill be checking my resistance on my glow plugs.
Thanks for the help and eager to become a lifetime member and show the support.

[Eco Taxi]

I was incorrectly in stating which gauge it is that always reads 2/3 - it's my engine oil pressure gauge - thoughts?

[Dr. Snow]

2/3 when running? That is what mine reads 2/3 3/4 somewhere in there.

[klhansen]

Originally Posted by Eco Taxi

I was incorrectly in stating which gauge it is that always reads 2/3 - it's my engine oil pressure gauge - thoughts?

The oil pressure gauge on your truck is actually an idiot gauge. The sender is a pressure switch that closes when the pressure reaches 7 psi or so. When the switch closes, the gauge goes to the midrange position you're seeing. It never moves even though the oil pressure ranges normally from 10 psi to 75 psi or so.