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Discussion Starter · #1 ·
Ok... just went out to fire up the 7.3 and it started to crank right up, but then died after having caught (just about 1/2 second after I let go of the key.) I thought that very odd and went to start it up again... but this time the Wait to Start Light won't light up, My DP tuner switch does nothing (nothing on the display at all -- no power) and when I turn the key, it just turns the engine... oh and no RPMS show on the dash.

That last bit about no RPMs makes me want to say CPS, but I just had the recall done 6 months ago and the lack of power to the other items has me wondering... grabbing a different CPS right now to try out, but looking for ideas as I am very doubtful

Note -- nothing leading up to this... just happened without warning... only thing out of the ordinary is I have been driving on bumpy dirt roads more than normal lately...

Thanks in advance...
 

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check the fuses under the hood, specifically the #22 spot. a no wait to start light a on 7.3L usually means that fuse was blown.
 

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Discussion Starter · #3 ·
Fuses

Interestingly enough... #22 fuse was fine but # 4 was burned out... (yes looking at ones under hood and not in cab)

replaced #4, still nothing -- shouldn't matter anyhow though since I believe that #4 has to do with my towing lights (it blew out once before while launching a boat if I recall correctly)

I think step 1 is new CPS since I am not seeing any RPMS when cranking... but the no power to my DP tuner, nor a wait to start light have me concerned that I am barking up either the wrong tree or at the very least one that has more than one branch...
 

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Discussion Starter · #4 ·
2 hours daylight remaining - CPS not it

Ok, I have 2 hours of daylight or so remaining, replaced the CPS, no dice. Also tried removing the fuel bowl heater plug, still no dice...

I am not still not getting power to my DP tuner, nor getting a Wait to start light... batteries are strong and cranking well, but still no hint of starting...

Tried swapping relays 30 & 31 as I was wondering if my PCM relay was dead...still no dice

All fuses including in cab and under hood are checked with multimeter for continuity...

Running short on time, advice welcomed!!!
 

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Discussion Starter · #5 · (Edited)
Swapped Relay 30 for known good relay

Ok, I removed the fuel bowl heater plug... then swapped relay #30 out with a known good relay... still no wait to start light...

Now I am trying disconnecting the batteries for 5 minutes then reattaching... hoping to clear some memory... (EDIT this did not work)

Also downloaded the operators guide and checked EVERY SINGLE FUSE that had anything to do with the PCM...contacts and all (not just continuity test as done earlier)

I need to know how to check for voltage getting to this relay and to the PCM... where are my check points?
 

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Discussion Starter · #6 ·
Specific Question - Checking for Voltage to PCM

Ok... I tore my PCM out and checked the connection of my DP tuner... put it all back together... still nothing....

Thus I now have 2 conclusions:

A. Relay is not getting proper exciter voltage to kick on

or

B. My PCM is Fried!! (and I want to know WHY)

So how can I check for voltage getting to my PCM? (Essentially how do I check the output of that relay #30??)

Thanks
 

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Ok... I tore my PCM out and checked the connection of my DP tuner... put it all back together... still nothing....

Thus I now have 2 conclusions:

A. Relay is not getting proper exciter voltage to kick on

or

B. My PCM is Fried!! (and I want to know WHY)

So how can I check for voltage getting to my PCM? (Essentially how do I check the output of that relay #30??)

Thanks
im guessing this. . . have you checked the codes?
 

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Discussion Starter · #8 ·
Have not checked codes

cliford,

I was under the impression that if there were any codes, I would get an SES light... I don't... am I mistaken on that one?

Next, I was pretty sure that when the PCM fries, you cannot connect to pull codes... Correct?

If it is fried, could it have taken my DP tuner with it, or perhaps vise versa?

Again, how can I be sure its getting power? has to be something I can check for power to the PCM...
 

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Discussion Starter · #9 · (Edited)
Bad contact in fuse block - Problem Solved

Ok... so tonight I decided to step through the system one contact at a time.

Started with the relay #30... looking for B+ (battery) voltage against ground... check

Trigger voltage (KeyPWR) approximately 1.8 VDC... way below needed threshold voltage for tripping the relay.

KeyPWR voltage on the relay for the blower motor however was fine at 11.8VDC ... thus I was pretty certain it wasn't in my key/tumbler system.

Looked over the fuse block again, both under hood and in cab... pulled all fuses related to the PCM... when I pulled Fuse 30 from in the cab I noticed some black oxidation on the contacts (not heavy -- just a dusting)... so I cleaned it off and put it back in -- still nothing... but that got me thinking about how the contacts in the fuse block must look... just for kicks I checked the resistance across the contacts on the fuse block itself... noticed that I had HIGH resistance... then I checked voltage drop with key on... had about 10VDC drop across the fuse... 10V + 1.8 V = 11.8V which is what I had on the trigger voltage for the other relay... so I cleaned the crap out of the contacts for the fuse... presto it works!! :happydance: guessing someone prior to me blew the fuse pretty bad and the resultant mess caused poor contact in the block itself... little bit of time, little bit of oxidation, little less voltage until one day there just wasn't enough to trip the relay... thus no power to the PCM or DP tuner

Thus closes my issue... hope it helps the other folks out there with similar problems...
 

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Looked over the fuse block again, both under hood and in cab... pulled all fuses related to the PCM... when I pulled Fuse 30 from in the cab I noticed some black oxidation on the contacts (not heavy -- just a dusting)... so I cleaned it off and put it back in -- still nothing... but that got me thinking about how the contacts in the fuse block must look... just for kicks I checked the resistance across the contacts on the fuse block itself... noticed that I had HIGH resistance... then I checked voltage drop with key on... had about 10VDC drop across the fuse... 10V + 1.8 V = 11.8V which is what I had on the trigger voltage for the other relay... so I cleaned the crap out of the contacts for the fuse... presto it works!! :happydance: guessing someone prior to me blew the fuse pretty bad and the resultant mess caused poor contact in the block itself... little bit of time, little bit of oxidation, little less voltage until one day there just wasn't enough to trip the relay... thus no power to the PCM or DP tuner
As a Ford dealer tech I would like to say KUDOS to you for solving your own problem. :thumb:

As one of my instructors used to say, "VOLTAGE DROPS, VOLTAGE DROPS, VOLTAGE DROPS" and "CHECK THE BASICS, CHECK THE BASICS, CHECK THE BASICS".
 

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Discussion Starter · #11 ·
Thanks

As a Ford dealer tech I would like to say KUDOS to you for solving your own problem. :thumb:
Thanks :)

As one of my instructors used to say, "VOLTAGE DROPS, VOLTAGE DROPS, VOLTAGE DROPS" and "CHECK THE BASICS, CHECK THE BASICS, CHECK THE BASICS".
Exactly... smart fellow there!!! :nod::thumb:
 

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Discussion Starter · #13 ·
ok im having a similar problem and just askin, but u just cleaned the contacts inside the panel?
2000PStrokeBlue,

Check fuse 30 under your dash... see if it is fried.... if so you likely have one of 2 problems - first see if there is any corrosion/oxidation on the fuse tabs or in the fuse block terminals that the fuse plugs into. If not, go under the hood and pull the fuel bowl heater plug off and leave it dangling, replace fuse 30 and see if that fixed it. If so, time to replace the fuel bowl heater element. I think I remember that meaning you have to buy the whole darn fuel bowl assembly, but someone else will need to chime in on that one.

FYI: Ford put the PCM and the fuel bowl heater on the same fuse... if your fuel bowl goes bad it takes the power for the pcm with it :doh:

If this does not work, before you go changing your pcm, check RELAY #30 under the hood, make sure it is getting both a battery voltage and its field coil voltage. Report back on what you find, even if the relay is good, knowing which terminals are not getting power will help in the diagnosis.

As to my problem, it was just a simple matter of someone had blown fuse 30 several times (guessing) in the past and it had left a lot of black oxide/soot and it was preventing a good contact for my fuse, got worse with warmer weather (increased resistance perhaps??) anyhow, I replaced it, cleaned the block, and life has since been good!:thumb:

If you have any more questions on this, feel free to post em and I will watch this thread tonight/tomorrow.
 

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ok so i read the above and i still need to check the relay, but i checked the fuse a very small bit of corrosion no more than other fuses, checked for power across with a lite, & no droppage across it, but did clean it before replacing, still no wait to start light and od lite still on, will post more when i know about the relay tommorow
 
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