Hi All,

Long time lurker, first time poster. I’m having some real trouble with my 6.5 so I’ll cut right to the chase:

Truck Specs:
1996 C2500
396,000 miles (I’ve got full service records w/ excellent service history)
ULSD

What I’ve changed:
-Lift Pump
-Engine Stop Solenoid
-PMD (w/ relocate kit)
-4 glow plugs, the others tested good

What it does:

The truck turns over and fires for about a second or two and stalls right out. If I keep cranking, I keep getting smoke from the exhaust and it spits and sputters but no go.

Here’s the story:

A couple of years ago I had the hot stalling problem so I put a new PMD with a relocation kit on it. The truck then ran fine. Recently, I had intermittent stalling. Sometimes it would be when it was hot, sometimes it would be when it was cold but it would usually start right back up. I became suspicious of my PMD relocation harness because the male pins that went into the vehicle connector are about half as thick as those in the PMD. Also, if I’d unplug it and then plug it back in again, it would typically restart immediately. My initial remedy was to bend the pins so they would make better contact. Sometimes it would help, sometimes it wouldn’t. I pulled out the green connector seal and lo and behold one of the wires wasn’t crimped to a pin. I bought a new harness and to eliminate the connector problem, I cut off the vehicle connector and soldered on the new extension harness. The truck ran fine but still had the stalling issue. My next step was to check the fuel return line. I wouldn’t say it was clogged but after I blew it out it was easer to blow through than when I started. The truck ran but still had the same problem eventually getting to the point where it wouldn’t start. I then moved on to the engine stop solenoid. I hot wired it and while you could hear it click it was very faint and I wasn’t too sure about it. I removed it and then it wouldn’t work at all. I thought I figured it out so I bought a new one. Still no start. I then was on to the PMD. It was already remote located so I just ordered another one. I put it on a few days ago and the truck fired right up and seemed to run fine. Well, the very next day I went out to start it again and nothing. It was colder out than the day I ran it and the truck was always a little hard starting so I became suspicious of the glow plugs. I moved it into a heated garage and checked the plugs. 4 of them were corroded on the terminal so it probably wasn’t making contact. I bought 4 new ones (Autolite, they didn't have the 60G's in stock) and before I put them in I tested them and watched each of the 8 plugs get hot and glow so I know they’re all good now. Still no start. I checked for fuel at the injectors and it kinda squirts here and there. I metered the ground on the IP and it checks out. I also metered the PMD connector and the ground checks out as well as power. I had a crappy meter but when I checked for the 1.2V signal it was about 1.8V so I imagine that’s fine. I also checked between pins B and F and it was showing 1-2VAC. Again, crappy meter but it came up off of zero so I imagine that’s fine. The service engine soon light does light up upon key on but there are no codes. I have loads of fuel getting to the IP from the lift pump and through the filter. Still suspicious of anything, I hotwired the lift pump and the engine stop solenoid on and still the same symptoms. I tried cranking with the optical sensor disconnected. Instead of firing right away, it takes a bit and then spits and sputters like normal but won’t run. It fires for 1-2 sec after I hit the key then stalls. If I keep cranking it, smoke (a mixture of black/white) comes out of the exhaust so I have to imagine it’s getting some amount of fuel. I have no idea where to go next. Any thoughts?

 

Plug the OS back in and try with the CPS unplugged.

Also redo the Accurate Diesel no start tests with a good meter-the results have to be what it asks for or else no start.

 

I just tried with the CPS unplugged and if anything it seemed a bit worse. As expected, it then gave me the crankshaft sensor code. I'll see if I can round up a decent Fluke to re-measure.

 

Even though you haven't mentioned any OS codes,you might want to remove the OS electronic noise filter and toss it in the trash-plug the remaining harness directly into the OS.

 

im on the same boat as you. hope between us two we can get somewhere.

 

Have you drained the water from the filter housing lately?

I also question the quality of the glow plugs still in the engine-an ohm test tells you nothing about their ability to glow.

They may only glow at the tip rather than along their length-the tip is not enough.

Also,I hope you know to begin cranking thengine over as soon as the wait to start/glow plug light goes out the first time?
The remaining flashes of the glow light are meant to happen when the engine is already running and are "after glow".

A starter in very good condition is also required the gear reduction starter along with good batteries and cables is needed to spin the engine quite quickly to get started-any limited speed starter will not get the job done especially on a hot engine.

 

I don't think the filter harness is on there. I disconnected the plug and the wires seem to go directly into the IP.

I'd imagine if there was any water in the fuel bowl it would have drained out when I had cracked the T-Valve to check LP operation. It was straight fuel that came out of the hose. I never saw any water in it.

I didn't rely on just the Ohm test, I did have all 8 plugs removed when I tested them. The method I used for testing was to place each cylinder's wire onto each cylinders glow plug with the glow plug removed from the head. I then ran a jumper wire to ground one plug at a time and cycled the key. I did see each of the 8 plugs get hot and glow fairly quickly. Once the glow reached about 1/4 of the plug (well before the light timed out), I had my helper shut the key off because otherwise they'd be to hot to handle.

Got it. I wasn't sure why exactly they kept turning on but that is how I was handling it. After the light turned off the first time I hit the key.

I had replaced the starter in 2009. With my scan tool, while cranking I saw RPM's in the 150-250 range. When it would fire they would go as high as 700.

I did some more checking and here are the results:

I pulled out the engine stop solenoid, leaving it plugged in, and hit the key watching it work.

I removed one fuel line and placed my finger over it. After cranking for a while the fuel wouldn't push past my finger. When I'd remove my finger after cranking it would give a little spurt.

This morning I ran the lift pump and checked for air again. I got some air to come out of the fuel bowl using the black bleeder on top of it.

I used a Fluke 75 Series II to re-measure the PMD. I was getting a solid 12.2VDC from Pin D to Pin F with the key on. I was getting 1.2-1.6VDC from Pin A to Pin F. I was getting 0.8-2VAC from Pin B to Pin F. It seems as though when it starts cranking these values are within spec and then when it fires or begins to fire they read the higher amount. That seems reasonable to me, but is it?

Thanks for the help so far racer55!

 

OS filter looks like this:

 

Just checked, definitely don't have one.

 

No problem-better to know for sure.