FMTV engine won’t start ... engine oil pressure?

[xomegaiv]

I did an oil change on my M1088 and I can’t seem to get it to turn. Before, I always noticed that I needed to see the Engine Oil Pressure Light on before I would let me push start. After the oils change I can’t seem to get Engine Oil Pressure ... please help, what am I doing wrong?


Sent from my iPhone using Tapatalk

 

[wheelspinner]

You won't get oil pressure without the engine turning over, didn't before and won't now.

 

[NDT]

There is no auto shut down circuit on the FMTVs related to oil pressure. Oil pressure is not required to crank the engine.

 

[xomegaiv]

Call it a bad short or what but I had to disconnect and reconnect the oil sensor and it started right up. Not sure why it did what it did but thank guys for the help.


Sent from my iPhone using Tapatalk

 

[frank8003]

Call it a bad short or what but I had to disconnect and reconnect the oil sensor and it started right up. Not sure why it did what it did but thank guys for the help.

now that's some interesting poop

 

[Coffey1]

Glad you got it running.

 

[coachgeo]

Call it a bad short or what but I had to disconnect and reconnect the oil sensor and it started right up. Not sure why it did what it did but thank guys for the help.

Do you have an A0 (mechanical control 3116 engine) or an A1 (computer controlled engine? - 3126?, C7?)

 

[xomegaiv]

Glad you got it running.

Thanks for the help brother


Sent from my iPhone using Tapatalk

 

[xomegaiv]

Do you have an A0 (mechanical control 3116 engine) or an A1 (computer controlled engine? - 3126?, C7?)

I believe it’s a 3126


Sent from my iPhone using Tapatalk

 

[coachgeo]

HATE when folk post up a problem on a board and in the discussion is led to a fix....... BUT THEY NEVER REPORT THAT...... they just disappear on their merry way. So thank you for replying back.

It appears from several things have searched out and read just now the sensor on the 3126 does talk to the ECM and may cause a start issue. Stuck pressure sensors have happened. Your plug and unplug may have been a short/bad connection... or maybe it helped the sensor un stick itself?

anyway here is an intereting discussion...... that appears to be somewhat helpful on this topic.... but would be SHIAT LOAD MORE HELP if the idiot reported back into the thread the final diagnosis and solution.

http://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=23887

 

[Pope]

To shed some light on the oil pressure switch causing the no crank issue the switch opens with oil pressure opening the ground for the starter relay. The end of the ground wire is fastened to the ground on the generator. Typically the switches fail and prevent cranking. Jump the two pins on the harness to quickly determine if the switch is the problem if you find yourself in a no crank situation and you know your batteries are good.
Failure of the switches was pretty common, I have a jumper that I made from a plug off an old pressure switch that I carried with me to get the 3126 powered trucks to start when I worked for the FMS shop.

 

[WassawBound]

I think I'm having a similar issue. This is an old post. How's the engine doing now? Did you replace the sensor?

My light came on and the truck stopped right there. Now my M1078 A1 is stranded.

 

[Ronmar]

I think I'm having a similar issue. This is an old post. How's the engine doing now? Did you replace the sensor?

My light came on and the truck stopped right there. Now my M1078 A1 is stranded.

A bad 15PSI oil pressure switch circuit on an A0/A1 will cause a failure to crank, not a failure to run…

 

[WassawBound]

A bad 15PSI oil pressure switch circuit on an A0/A1 will cause a failure to crank, not a failure to run…

Thanks @Ronmar. One less thing for me to worry with. I found a leaky fuel line. Hopefully that solves my no start problem.