trouble with ecm, no spark, no fuel pump, no connection with scan tool.

[87k5]

Hello to all in the CK5 world.
Here the situation,
1997 GMC Suburban 2500, 350, 4x4, stock, 275k.
A few weeks ago I put the truck in reverse and it shut off on me (it's done this 3 times and it starts right back up) I can't get it to crank back up now.
I have put a scan tool on it,(2 different ones) and I cannot get the scan tool to communicate with the ecm, it says "cannot communicate with the scan tool." (The key is on.)
When I turn the key to "acc" I get no fuel pump. When I try to start it, I get no fuel pump, and no spark at the spark plug. I have checked the grounds to the best of my ability.
I suspect I have a bad ecm. (Where should I start my search for an ecm if the CK5 world suspects that is the problem?)

Thanks,
Charles.

 

[87k5]

Could someone here give me their opinion? This truck is my father in laws and I would really like to help him out with this as this is the truck he works out of.

Thanks,
Charles.

 

[diesel4me]

I'm not much good at EFI,but have you checked the basics,like the ECM fuse?..on some GM vehicles if the cigar lighter fuse blows,the scan tool gets no power,and wont read codes...devious inspection garages have been known to purposely pop the lighter fuse,then tell the customer it needs "further diagnosis" to make more $$$...

I dont think the fuel pump should run with the key on "ACC"..just in the "run" position only...and it'll only "run" a few seconds until the engine starts most likely,thats normal..

 

[dyeager535]

Most of us probably aren't real familiar with OBD2...I know I'm not.

Does the check engine light work properly in the first place? Dying like that but starting back up can often be traced to a bad connection/wire somewhere.

Is there a way to test the fuel pump for operation? Earlier trucks the fuel pump relay had a test terminal, but if there is a fuel pump relay you can get access too, jumping the batt 12V terminal to the pump 12V terminal on the connector will force it to run, assuming the wiring is good.

I always recommend stepping back from blaming the mysterious box that controls everything. Rarely are they the issue, although they do fail, I've seen figures stating that over 90% of the ECM's returned as cores have no issues. The best investment made for diagnostics on a vehicle is the factory service manual/wiring diagram. They run through the diagnostic steps, most of which don't require

 

[87k5]

diesel4me...
I did check the fuses and they were all in good shape. I have heard if what you are talking about with some shady garages doing the whole fuse thing so the code reader wont read... hearing that makes me want to punch someone in the face!! (that garage specifically!!)

I thought the fuel pump would run in the ACC position for a few seconds to purge the fuel system and to put some fuel in the intake. Maybe I'm wrong though?

dyeager535...
The check engine light does come on when the key is turned to ACC.
I do agree with you about not jumping to the mysterious "black box" BUT with the symptoms I have...
1. No fuel pump in ACC(for a few seconds)
2. No fuel pump while cranking
3. No spark while cranking
4. No connectivity with the reader

I will have to check the fuel pump relay and jump it like your talking about just to see it that makes a difference.

I do agree with you about the factory service manuals. I have purchased those manuals for every Chevrolet I've owned. I have them for a 1987, 1988 and a 1991 they are truly indispensable when it comes to troubleshooting. I found a set on ebay for $152.00.... wow. Do you or anyone you know have a line on a set. I just thought I'd ask as you did recommend them so you know the value of them.

Thanks for your time,

Charles.

 

[dyeager535]

At $157 I'd probably choke a bit. I'm cheap, $50 for a very good set would probably be my limit lol.

Again, the OBD2 is not what I'm familiar with. On the OBD1 GM setups, even if the relay failed the oil pressure switch took over, and the pump still worked, independent of the ECM. If the PCM in OBD2 took that function over, then I'd agree with you that it seems like a PCM issue, or a connector/wiring issue.

Then you've got the "weird" spark distribution with the Vortec setups that isn't the same as all previous GM setups, with a crank position sensor, which I assume can also trigger a no-spark condition? OBD1 setups used the ignition module to "tell" the ECM that the engine was turning over, close the fuel pump relay (thus no long/hard starts), maybe OBD2 uses the CPS for the same function? Wild guesses, because I just don't know OBD2 that well.

Quick search via google didn't result in any PDF manuals for the Vortec trucks...someone with Alldata should be able to help though.

Checked the local library? If tied into a larger network, it's amazing what they can get...I was able to find a specific Ford Ranger service manual through ours years back.