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IP or electrical problem?

If you decide to go that route the process while fairly simple needs to be done with accuracy and then double check your idle fuel rate.
 
Sounds like an OS, but if your pump is original you might consider upgrading it. Also changing an OS your self can cause all sorts of problems if you don't do it correctly. There is a reason the OS is bench calibrated on a DS4 by the pump builder.

#67-63-04: HARD START, NO START, START STALL, ROUGH IDLE - (Oct 30, 1996)
SUBJECT: HARD START, NO START, START STALL, ROUGH IDLE, STUMBLE AND LACK OF POWER (NEW OPTICAL SENSOR AND CERAMIC ROLLERS)
MODELS: 1994-96 CHEVROLET AND GMC C/K TRUCKS WITH 6.5L DIESEL ENGINE ( VINS F, S, P--RPOS L65, L56, L49)
CONDITION:
Some owners may comment on the following concerns: Hard/No Start, Start Stall, Rough Idle, And Engine Stumbling when operationg under high temperatures and load conditions. RELATED DTCS: (1996: P0251, P0370, P1216, P1217), (1994-95: Codes 17, 18, 35, 36).
CAUSE:
A distressed Optical Sensor board may cay cause NO OR IMPROPER CAM SIGNALS which affects pump timing. Also, low lubricity fuel may result in worn injection pump cam rollers causing low fuel output.
An enhanced fuel injection pump was released eginning with the 1997 model year that contains an improved OPTICAL SENSOR. In addition, new ceramic rollers are also released which will help prevent roller wear due to low lubricity fuels.Service procedures as with any comment, the condition must be duplicated before attempting to do any repairs and a thorough investigation done to determine the primary cause of the concern. If DTC's are present, refer to section 6E of Volume 2 of the Service Manual to troubleshoot any/all DTCs. For other Driveability symptoms, use the same manual. 1994-96 Model Year Service Injection Pump 1. 1996 model year 0-12 months, 50,000 miles. Will be serviced using a new replacement pump, part number 1558156- Model No.5288 to replace part number 10225930 injection pump (Reference Bulletin 57-63-04A for 1996 injection pump exchange program policy). 2. Part number 10225930, Model No. 5067 injection pump will be rebuilt by the Stanadyne Dealer and identified by stamping Model S5288 and part number 12558156 on the manufacturers plate. In addition a "Green" tag will be attached to the front of the pump. 3. Part number 10225929, Model No. (5068). Injection pump will be rebuilt by the Stanadyne Dealer using new Optical Sensor and ceramic rollers. The pump will NOT be identified with a new model number but will have a "green" tag on the front of the injection pump and stamped (S5068) on the nomenclature label. 4. Any new injection pump (part number 10225930) will be superseded to the new part number 12558156. HOWEVER, if a new pump part number 10225929 is ordered it will be an updated model 5068 with the "green" tag hung from the front of the injection pump. Warranty information for vehicles repaired under warranty, use: Labor Labor Operation Description Time J5955 Pump, fuel injection use published labor time (diesel) replace plus 0.2 hours for administration time
 
If I go for a new pump, which sounds like the safest bet, are there any difference between these ones or which one should I get.

57692
 
I would try to avoid reman pumps.
If you are going to spend the cash, get a brand new one.
To many stories of problems with reman pumps out there.
Your housing and rotor may be in better condition than the used one you are buying.

You have to do the computer nonsense wether doing OS or IP, so don’t let that be your determination.
 
Unless you are allowed to do a change from ds4 to a db2. That is a lot more involved, but best way to go imo.
Eliminate the computer needs all together. There is more than one reason that all the 6.2/6.5 in the military does not use ds4...
More reliable,More power,More mpg,Less emissions

But the problem you might have is how your emission laws are in your location.
 
Contact a stanadyne dealer for pumps. I used Columbus Diesel here in Ohio. I would never get an injection pump from a major parts place like rockauto or auto zone. Your asking for trouble if you do.
 
So I ended up getting a used pump cheap and took the optical sensor out of that and stuck it into the pump in the truck and all codes disappeared except the 16. Have just under 6mm2 of idle fuel and it runs perfect now.

Took the optical sensor from my pump and checked it, the electronics housing on it was full of diesel, not sure if it was supposed to be like that or not as there was a whole in the cover that looked original. Drained the diesel from it and threw everything in the ultrasonic cleaner (should have tested it first to have a reference but didnt think of that until it was too late) blew all the liquid out of the electronics and had contact cleaner on it. then I put 5 volts and a multimeter on it to test. The temp sensor worked as it should, and both the cam reference and high resolution output showed 20.6mV open and 16.2mV with the optical sensor blocked. Dont know what the values are but it is registering. Also tried to check for Hz and it registers that also but I didnt have a setup to check that better than movin apiece of paper out and in to the slot. Might have to make s slotted wheel and run it with a known rpm to check.
 
After the OS change everything has been going fine, truck runs good no codes or problem.
But, there is always a but, my idle fuel is at 4, should I try a bump to get it a little higher? what are the consequences of leaving it as is?

Thanks
 
If I runs fine as is you shouldn't have any issues. Usually you end up with a touchy throttle. I believe you are in the range of a successful optic bump which used to be something that guys did for performance. Anymore it's not considered worth doing. IIRC the normal idle fuel rate is 7-10
 
I'm no DS4 expert but IIRC pulse width on the fuel solenoid needs to be between 1.2-2.5 or it's out of range and a 35 or 36 code will eventually set.
 
Have been going for nearly 6 months now with no problem, only hing is the idle fuel rate is a bit low according to what it should be. But no problems with the truck and all the codes I kept getting before I changed the OS is now gone.
 
I was thinking pulse width not fuel rate when I read your comment. 🤦‍♂️

Yeah fuel rate I believe is around 7mm3. What's your TDCO at?
 
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