2001 F150 SuperCrew 5.4 Auto Air etc. 136K
Historical knowledge, AllData and Snap On scanner.

Whats Wrong
Hard start warm
No temperature gauge indication

The Story
Great truck, used to start and run fine, hot or cold. I have only had it since November, 131K.

About a month ago I had trouble starting the truck after it had been off for about an hour. I finally figured out that if I held the throttle open I could get it running.
At roughly the same time I noticed that the temperature guage was not indicating.
There were no other apparent symptoms with the cooling system or otherwise. No codes, no CE light.
I have since seen my mileage take a dive. OUCH

My gut feeling is that the computer does not know that the engine is warm and continues to feed the fuel like it is cold. Maybe????

Troubleshooting and maintenance.
Where I've Been
I thought maybe the t-stat was stuck open and replaced that. I was not really encouraged when I got it out and found it closed but went ahead and replaced it anyway. No difference.
I also replaced the fuel filter after reading threads pointing to hard hot start issues. Still no difference.
Where I'm Going
Sensors - I am thinking bad sensor of some sort but there are multiple.
I'm not sure where to start and I can't find some on the engine.
CHT - Cylinder Head Temperature - I know where this is, but there are no indications that I have a problem with it.
ECT - Engine Coolant Temperature - I can't find this (there are no sensors on the runner in front between the banks). When observing with the scanner I observe this temperature go from ~47 to 65 degrees F as it warms. This seems bad considering that it was ~ 70 outside when I was observing. But, how does this explain the lack of indication on the gauge?
Temperature Sensor (Gauge) - AllData lists a seperate sensor for the gauge. If I could find this, I would ground the wire and see if it pegs the gauge. At least I would know if it is the sensor or not. Even if this fixed the gauge issue, I wouldn't expect it to fix the hard hot start.

As the sensors are relatively cheap, I would have no problem replacing themif I knew where they were.

So now my questions
1.) Anybody have any thoughts on how I am approaching this?
2.) Can anyone tell where the temperature related sensors are on my engine?

I would greatly appreciate any help I can get on this.

 

You don' have an ECT. It was eliminated/ the CHT took over the ECT's responsibilities.

Your problem is most likley fuel related, = Regulator or fuel filter.

Clean MAF / Change fuel filter and check pressures.

I would say the Regulator if I had to guess. When bad , they over pressurize the rail. Pressure has to bleed off before they'll start. That can take a little time = no start when warm.

Could be the wrong plugs as well.

 

jbrew

I had replaced the fuel filter and that didn't help.
I will clean the MAF. I thought I saw a cleaning procedure in a past thread but can't seem to find now. I will continue to look.
I will also check the fuel pressure.

Any thoughts on the cooling related issues? No temp gauge reading?

 

are there any codes? you could have a cht issue. you could use that snap on scanner and see what the temp reading is for the sensor.

 

I can't recall where the temp sender is on that. Maybe the CHT handles that as well. Does ALLData have anything on a Temp Sender ? I know I have one behind the alternator.

If your CHT is acting, it could be the wires. I had to re-wire the CHT harness on my model, -the wires chaffed, but I caught it before I had short problems.

 

Yea, I want a scanner that reads history/ mode 6/ channel 3

 

Matts ford,
No codes, which is a little surprising to me.

I was able to observe the resultant voltage signal from the CHT. I could see it vary somewhere from the 4 to 3 volt range as the engine warmed. As it was changing, I kind of dismissed this as a possibility. Maybe wrong? I will be rechecking this, got any specs. on what I should expect to see voltage and or degrees?

 

i think 99 was the only year for the pi 5.4 to still use a coolant temp sender.

i would inspect the wiring harness to the cht first. as far as degrees go it would depend on how long its been running.- the stock thermostats a 195* thermostat so i would think it'd be close to that when it opens. i dont know the resistance specs for your sensor so i dont know what the output voltage would be but it should have around 4.5-5v going to it.

edit: according to my chiltons manual on my truck the ect at 3.5v output is something like 50*f

 

jbrew,
AllData shows P/Ns for the following 3 sensors. (locations for the CHT only)

Coolant Temperature Sensor/Switch (For Computer)
Coolant Temp Sensor F5AZ12A648AB $29.04

Engine Temperature Sensor
CYL Head Temp Sensor F65Z6G004AB $21.65

Temperature Sensor (Gauge)
Temp Sending Unit F65Z10884AA $11.53

Ford parts department verified the part numbers but could only come up with a location for the CHT.
When he asked for help from the shop he got (1) "don't have a clue" and (1) blank stare.

On the CHT chafing, the problem was in that short section that you show in the picture, correct?
Also, I will look behind the alternator but if it is there it must be buried.

 

The CHT and ECT are just about identical in looks , -just a brass bulb, nothing special visually. The ECT's would corrode in time because in came in contact with coolant. CHT's are simply screwed into it's own empty SEALED chamber. - NEVER corrodes. That's right, as Matt posted, after 99 (last and only year of the aluminum PI manifold) they were eliminated in the 5fours. The 4six still had them for a time - to 2000 or 01 I believe.

_____________________


Yes that's where the problem was, the short section plugs into the main harness. In the pic, I have the old and the new made up right next to it. You can't see the damage/chaffing in that pic.

The knock sensor is there as well, -disregard that.

 

Thanks for the help to both.
I will study the problem more over the weekend.

 

Sorry for the delay in reporting, I wanted to drive it a little bit to verify results.

Cylinder head temperature sensor solved my problems.
Apparently it tells the computer how cold the engine is and also tells the dash gauge. (regardless of what AllData says)
The gauge now works and it starts great again, cold or warm. Haven't checked yet but am hoping that my milage returns (or better yet, improves)

I was able to replace the CHT myself and it only took about an hour. That included ermoving the alternator for clearance and custom bending time for an offset box end wrench that now reaches in under the intake.

I still have not cleaned the MAF but would like to. Do I just spray it off with cleaner?

Thank you all for the sounding boards.
I have learned a lot from this site.

 

Yep - CRC makes a MAF cleaner, just spray it. Don't touch the fine wire, you can break it.