Crank no start after EGR cooler replacement

[estew]

I've got a head scratcher in the shop. An f-250 with a 6.0 comes in running very rough and blowing white smoke. We were unable to get it fired, so we pushed it in, replaced the EGR cooler and valve, crank no start, performed ICP test,pass. Checked IPR,14% when cranking, rpm is good. FICM syncs up. Changed glow plugs.

What gives? Could the screen in the IPR be plugged and still be able to get pressure to the ICP? Any help would be greatly appreciated.

[Shlep]

IPR @ 14% cranking? are you sure? and whats the ICP at exactly?

[Bruce Amacker]

And what's the ICPV KOEO and cranking? It should be .17-.24v KOEO and reach 1.5v cranking. Ask Jim why voltage is important.

 

 

 

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[Jim Warman]

Hi, Eric.... Like Shlep, I have to wonder about 14% IPR cranking.... This is the KOEO value - cranking I would expect to see something closer in the 40% to 65% range.

 

Like Bruce mentioned, I'd start with checking ICP sensor bias.... early builds have a KOEO range of 0.18 to 0.24 volts... late builds have an expanded range.... 0.15 to 0.35 volts KOEO. At the same time, it wont cost any extra to check sensor coherency - take a peek at MAP, BARO and EBP_A in PSI (more on PSI in a bit).... these should all read within about 12/2 PSI of each other...

 

Section 4 in the applicable PC/ED will have a list of what I call the "no start" PIDs... these are listed in section 10 of the hard start/no start diagnostic worksheet... I like to add SYNC, FICM_MPWR and V_REF. It isn't really necessary to watch IPR% as long as ICP builds normally.... some of my personal variations include higher cranking speed desired and higher voltages - some modules appear to "shut down" when voltage falls below 9 VDC.

 

All day I deal with techs that assure me that they have performed a test procedure accurately and that the test result was "good".... Often, I take some of these jobs over - I start from square one and find that something gets fudged or overlooked (that looks too hard to do - it can't be that important). I highly recommend reposting and substituting actual test measurements for "it was good" - I am honestly not trying to be a dink.... a little more info about the truck would help, too.

 

Now.... Bruce mentioned the importance of voltage readings when watching sensor data... Volt (and/or hertz) readings are "live" data - this is the information that the sensor is reporting to the PCM in it's raw form.... PSI (and vacuum readings) is a computed value. If the module decides that the information it is receiving from the sensor cannot be trusted (a little oversimplified), the module will substitute a default value - this value WILL be displayed on the scan tool.... Ergo - your ICP sensor could report near 0 volts but the scan tool could display 750 PSI of ICP - EVEN THOUGH ICP IS NEAR 0 PSI.

 

Just for shits and giggles, check out test question #2