Yet another 6.5 stalling issue

[polecat]

Long time lurker, first time poster. I'm making progress w/ my problem and I wouldn't be at this point with out the help from this forum. Thank you.

I have a 1995 GMC 3500 HD. 2WD dually. 6.5 TD. (former phone co. truck) New rings and rod bearings. Rebuilt heads. 500 miles ago.

I know this problem has been addressed countless times on this forum. I have searched and found lots of good advice. But I'm still having problems.

The problem started out with hard starting and a slight hiccup at 3000 RPM's. Then it would stall. It would restart no problem. Sometimes, if I could catch it in time, I could pump the throttle very fast and it would continue running. The stalling and hard starting got progressively worse until I was stranded on the side of the road. The only code I can find is 49.

First thing I did was the PMD from SS Diesel, no change. (great co. BTW, great service, fast shipping) Checked all grounds. Replaced some Battery cables. Had alt. checked. 13.8 volts. Good batteries.

2nd, about 1 gallon of 5w30 in the full fuel tank with fresh fuel. Maybe a slight improvement.

3rd, checked lift pump. Good. Changed fuel filter. No change.

4th, unplugged OPS and, believe it or not, it seemed to run a little better. It did not stall when I cracked the brass "T" valve.

5th, installed a paper clip in the end of the OPS harness. Lift pump runs. I keep driving it and once in a while crack the bleeder screw at the top of the fuel filter to let out air. No air seems to come out, just fuel.

It seems to be improving. It will run great until I go up a steep hill. It will briefly stall, but keeps running with out any input from me.

My next step is an OPS with a relay mod. I may invest in a new lift pump as well. I'm thinking I may need an IP. Any advice would be much appreciated.

[racer55]

Did you get a PMD resistor with the new PMD?

Where did you mount the PMD/resistor/heatsink combo-the intake as directed by SS Diesel?
If so that is the worst location possible no matter what SS Diesel says.
By a PMD extension harness and mount the combo outside the underhood area,most use behind/under the frt bumper or behind the grill.

Where is the PMD harness ground located now?On the PMD heatsink?
If so extend the ground wire with solder and heatshrink and get it back to the stock location on the IP.

Is the optical sensor electronic filter still installed in the OS harness?
If so remove it completely and plg the harness directly into the OS and try it out-some trucks require the filter but you need to test this for yourself based on how it runs.

SS Diesel does sell replacement filters if it is required or you can go to radio shack and buy 3 pieces of ferrite core to place on each of the OS harness wires as a substitute for the OS filter to cancel the electronic radio frequency noise generated by the OS,sort of like when you can hear the blower motor run on AM radio-that noise can induce signals into the ECM.