Hey guy's
If you remember, I recently replaced head gasket (2nd time) and I'm wondering,
that since I also replaced the gauges with an aftermarket set Incl sensors, leaving the original plugs disconnected, and it now won't fire up. Battery spins starter fine.

Did I screw up something needed by the computer? Water temp and Oil pressure gauges replaced, (because of erratic operation) wired to sensors and 12V power. OEM plugs left hanging.
The only indication is from the water temp which registers 180 deg, the instant I turn the key first thing in the AM. Can't tell anything yet about oil pres., as engine won't start. I'm hoping the Water temp issue is simply a matter of resistance and I'll have to add a resistor to the circuit to lower the gauge reading...

I don't have any means of transportation without this truck. I'm in the boonies! with cataracts, and having eye surgery scheduled this week.
That's the mess -o- trouble

Thanks All!!

 

The computer will fuel/adjust timing based off coolant temp. If its unhooked that would mess with proper operation but I don't think it would cause a no start.

What is the truck information. Looks like a late 90s Dakota, probably a 4.7?

 

The truck, is a 2000 sport with the 3.9L magnum.

 

Actually, yeah, it would..... With an open circuit, the PCM sees -40 degrees C, and positively DUMPS fuel trying to get a burnable mixture. That will flood the engine in short order, and cause the no start.

 

Thanks Admin....
So, can I just jumper the plugs , or do they need to "see" a specific resistance?
if so do you have that info?

 

You WANT the PCM to see an accurate temp reading, otherwise, the engine will only run 'properly' in a very limited temp range..... You gauge in the dash also gets its clue from the PCM, (2000 model year? Right??) if it read erratic, probably be a good idea to plug in with a scanner, and see what the PCM is actually seeing.

 

Yeah, I don't have that ability No other transport available If I can just get it to run, no matter how poorly, I can then drive it to a shop.

 

Plug in the original temp sensor...... Might wanna pull a plug or two, and see if they are wet....

 

Ironically you can still get OEM water temp sensors and its possible to do pretty easy yourself. Odds are the brass corroded and its almost disintegrated. Relatively common on magnums. Pretty sure its galvanic corrosion from some sensors or something. When you go to install the new one make sure you put some thread tape or some other sealant and go pretty light on the torque. The cast aluminum will crack very easily.

 

YEP!! I touched the temp sensor, and the connector crumbled under my touch. I saw no way to repair it, so I decided to add an aftermarket set of 3... all electric, from Amazon, as I didn't want to mess with drilling a hole in the firewall, for the oil tube. I used an aircraft ribbon cable from my aircraft wiring days to connect them. and just wound up the unused wire for spares....



above photo with plenum removed during head gasket replacement, and oil pres.sensor raised for convenience. Teflon tape on All sensor joints.