FSD Didn't Fix IT

[CareyWeber]

All,

Well I swapped my FSD friday evening and Saturday it drove great never stalled or missed.

Today however on the way home from church it missed quit a bit at times then died and turned on the SES light.

I had the codes read and come up with:
P0251 Injection Pump Metering Control "A"

PCM 0606 PCM Processor Fault

Here are the things that I think might be the cause:
Ignition switch (I also need to replace the key unit as I can

[gmctd]

That's the main optical sensor timimg reference.
Could be low fuel or dirty fuel filter causing air bubbles. Lift pump, anything in fuel supply.

Could also be result of changing the FSD, where the inj pump harnesses and connectors were disturbed during the operations. Grounds?

The other one I don't even want to talk about yet, but it looks bad.
I'd try the ignition switch, first.

[CareyWeber]

Originally posted by gmctd:
That's the main optical sensor timimg reference.
Could be low fuel or dirty fuel filter causing air bubbles. Lift pump, anything in fuel supply.

Could also be result of changing the FSD, where the inj pump harnesses and connectors were disturbed during the operations. Grounds?

The other one I don't even want to talk about yet, but it looks bad.
I'd try the ignition switch, first. gmctd,

So P0251 is the main optical sensor timimg reference.

About a week ago I replaced the Lift pump and while I did the FSD I also replaced the Oil Pressure Switch.

Carey

[CareyWeber]

Here is some more history of my truck:

In 2001 @ 96K miles GM replaced the Injection pump under Warranty (had the stalling issue then too). They would not say what the issue with the old pump was only that it was the farthest out of wack of any 6.5 pump they'd seen.

I now have 173K miles on my truck and I'm suppose to take leave in May/June and drive to Montana. I really don't want to fight this on the trip.

Carey

Carey

[rjwest]

Appears you need to fix the Ign Sw. Might as
well do it to be sure PCM not " Glitching " ref
PCM Fault code.

[CareyWeber]

I found one site where a guy swapped out an Optical Sensor.

http://www.mamut.com/homepages/Norway/3/4/royh/newsdet9.htm

Has anyone else done it?

[DickWells]

Carey: Here's one for you, just in case. I changed out my remote mounted FSD, down in Florida two months ago. For nothing! Turned out to be a broken wire inside the rubber block under the plenum on the right side front. A short harness, that you should be able to dis-connect and work on. I understand that the block is an rf filter of some kind, but my Sub. runs fine with the little purple wire snipped off both sides and repaired by soldering in a new piece. I had the same symptoms as you. I should have known better than to replace the FSD before I had done a more thorough search for the problem. I found it by wiggling and pulling on all the injection related wires while the engine was idling. My engine shut right down when I pulled on that harness! I probed all six of the leads, and found the purple wire broken, and intermittent.
Sure hope it's something as simple for you.
Dick Wells

[CareyWeber]

Originally posted by Dick Wells:
Carey: Here's one for you, just in case. I changed out my remote mounted FSD, down in Florida two months ago. For nothing! Turned out to be a broken wire inside the rubber block under the plenum on the right side front. A short harness, that you should be able to dis-connect and work on. I understand that the block is an rf filter of some kind, but my Sub. runs fine with the little purple wire snipped off both sides and repaired by soldering in a new piece. I had the same symptoms as you. I should have known better than to replace the FSD before I had done a more thorough search for the problem. I found it by wiggling and pulling on all the injection related wires while the engine was idling. My engine shut right down when I pulled on that harness! I probed all six of the leads, and found the purple wire broken, and intermittent.
Sure hope it's something as simple for you.
Dick Wells Dick,

Does the last picture on the we site I posted show what you are talking about?

Carey

[CareyWeber]

Is there a way to test the Optical Sensor when it's off the pump?

[rjwest]

I would be more concerned with the PCM processor fault code. If it is screwing up, I would be suspect of all other codes.

Does the Processor fault code always occur when it dies.?

[DickWells]

Carey: I (think?) that the harness you have pictured is the one I referred to. My rig is a 95, and the rubber block seems to be wider and thinner than the later ones. Still, if you had the same problem (unlikely), then all you would have to do to prove it is to fool with all those wires while the engine idles.
To get a better description of that block, go to a thread called "Too much boost". I think that's the heading. It's back to page 3 or 4 on the 6.5 Forum by now. Read Dr. Lee's remarks on it, from a question I had previousely. Also, find mine, and other descriptions of remote mounting of the FSD. I have found that my unit runs MUCH cooler up in front of the left-hand battery. You might want to get rid of that cover, too. I know it looks cool, but it runs hot under there. Besides, when you have to work on a 6.5,(something we all have to do), then you don't have to fool with that cover.
Good luck.
Dick

[CareyWeber]

Originally posted by Dick Wells:
Carey: I (think?) that the harness you have pictured is the one I referred to. My rig is a 95, and the rubber block seems to be wider and thinner than the later ones. Still, if you had the same problem (unlikely), then all you would have to do to prove it is to fool with all those wires while the engine idles.
To get a better description of that block, go to a thread called "Too much boost". I think that's the heading. It's back to page 3 or 4 on the 6.5 Forum by now. Read Dr. Lee's remarks on it, from a question I had previousely. Also, find mine, and other descriptions of remote mounting of the FSD. I have found that my unit runs MUCH cooler up in front of the left-hand battery. You might want to get rid of that cover, too. I know it looks cool, but it runs hot under there. Besides, when you have to work on a 6.5,(something we all have to do), then you don't have to fool with that cover.
Good luck.
Dick Thanks Dick I have not had a diesel cover since 1999.

I'm going to stick with my pump mounted driver for now cause I just swapped it out.

Carey

[rjwest]

I do not recall in forum that a "P0251" ever ocurred
for a FSD problem, Not saying it can't, just
don't recall seeing it....

Ussually no codes, or a coe, something to do with
solenoid driver pulse to short....

Just info....I would go with wiring, or ign.

Has codes repeated, Anyway, Spare FSD
is always nice to have on trip, even better
if remote mount is accesable....

[CareyWeber]

On thing I have noticed is it doesn't do unless I use my AC.

Someone else said to look at where the wires go into the cab under the radiator coolant overflow tank.

This evening I'm going to check the Optical Encoder wiring and the wiring where it goes into cab for the ECM.

Carey

[rjwest]

How old is your alternator? May be low voltage
when AC kicks in....

[CareyWeber]

rjwest,

My alternator is good after the factory alt died I bought a Napa life-time alt and it lasted about a year. The Napa in Houston, MO swapped it out for my wife while she was on a trip. In all over 2 years I had that alt warranted a total of 4 times. I had replaced all but one battery cable on my truck with 1 ga welding cable when I replaced the last one the positive cable from the passenger battery to the started this also included a 1 ga cable from the alt to that same positive battery post.

Now for Optical Encoder Sensor update I found 4 wires that were chaffed (on the aluminum AC line) where the wiring harness goes into the cab under the receiver drier I think that as the AC was working the condensation would cause a short across these 4 wires I won

[Kollin Syverson]

[quote]Originally posted by CareyWeber:
[b] rjwest,

My alternator is good after the factory alt died I bought a Napa life-time alt and it lasted about a year. The Napa in Houston, MO swapped it out for my wife while she was on a trip. In all over 2 years I had that alt warranted a total of 4 times. I had replaced all but one battery cable on my truck with 1 ga welding cable when I replaced the last one the positive cable from the passenger battery to the started this also included a 1 ga cable from the alt to that same positive battery post.

Now for Optical Encoder Sensor update I found 4 wires that were chaffed (on the aluminum AC line) where the wiring harness goes into the cab under the receiver drier I think that as the AC was working the condensation would cause a short across these 4 wires I won

[CareyWeber]

Originally posted by Kollin Syverson:
[Just for your reference, anything electrical from NAPA is pure junk. I learned this lesson after 3 alternators and 1 starter, and 2 OPS unit. Go with original GM electrical parts only or have your factory alternator rebuilt by a reputable company. [/QB]Kollin Syverson,

This last one has been great now since 2002 I know the problem was not the alternators but the bad battery cable.

I think that all to often we swap parts rather than find out what is causing the part to fail.

I know I'm guilty of this.

Carey

[rjwest]

Carey Weber: Good Luck, God Bless, Thanks for your service.....!!!!

[CareyWeber]

Originally posted by rjwest:
Carey Weber: Good Luck, God Bless, Thanks for your service.....!!!! Thank you rjwest!!!

I temporarily covered the 4 wires bare spots with silicone because I was out of liquid electrical tape. All day today (+93

[CareyWeber]

Well it has not missed a beat / died since fixing the wires.

Thats a fix I can deal with $$$ wise. :cool: :cool: :cool:

Carey

[rjwest]

Good Show..... Lots of Kuddo's for fix.

[CareyWeber]

Well everyone I just back from my first true shake down run since the four wires were found bare and rubbing on the AC line.

I went from Columbia , SC to Montana and back with out any issues, so I'd say its a confirmed fix!

ps I'm at 178,000 miles and no major engine wrench yet. The only major work is a warrenty pump replacement at 99,000 miles.

Carey

[Techwest]

Kerry tell me more about where the four wires that you gooped are. Mine is a 94 so the code I get is 17(high reolution cct fault) but sounds the same as your problem and the steps I have taken are similar to yours. ( my other post "moved the FSD now I get code 17"
Thanks

[CareyWeber]

Originally posted by Techwest:
Kerry tell me more about where the four wires that you gooped are. Mine is a 94 so the code I get is 17(high reolution cct fault) but sounds the same as your problem and the steps I have taken are similar to yours. ( my other post "moved the FSD now I get code 17"
Thanks Techwest,

They are located where the wiring harness goes into the cab on the passenger side of the engine bay. To see the wires I had to remove the air filter housing and the coolant overflow tank.

I hope that helps let me know if you need more info.

Carey

[Techwest]

Thanks for the info. I removed the coolant resevior and air intake and could see the wires entering the cab. I used a mirror to check the underside...it all looked good. I can see the potential for chafing on the ac line. I also added another ground at the drivers side fromt of the head to the frame.
Unfortunatly this didn't fix my problem and my "Precious" is in the Stanadyne shop right now.