Got it. So disconnecting just the gauges lets the truck run but reconnecting them makes it stall.

Try disconnecting the single wire connector on the alternator and see what happens then. On the alt there are two plug in connectors, one that has 3 wire in it and one that has one. Unplug the single wire connector and see what happens when you start it with the dash plugged in.

 

With the plugs pulled, truck started. Once I plugged them back in, key off no power (I don't play with plugs while power is applied), it wouldn't start, pull plugs it started, plug back in, no start. Repeated it at least ten times, and multiples on each just to be sure, currently truck won't start either way as I'm looking into a fuel/pickup issue.

 

What about the fuel tank selector switch? Is that plugged in to the harness? I don't know for sure how that works without seeing a a schematic, but I DO know that the feed for the fuel gauge goes through the selector valve and the switch controls the valve, but I don't know for sure what the relationship is (if any) between the switch and the gauge. Is that switch plugged in?

 

Fuel tank selector switch is a separate connector. The gauge feed actually goes through the valve, not the switch. Thing is, if the selector valve is set to either front or rear, you should be able to disconnect the switch and the valve will stay set; it doesn't need a constant signal or feed from the switch.

I think we both hit on it earlier, with the alternator trigger. Or at least there's an easy way to test it, as we both described. But it sounds like the OP is entertaining another challenge, if there's a pickup problem in the "selected" tank.

 

That makes sense. I don't know why I said that when I knew that the switching valve made the gauges switch. I edited my post so there wouldn't be false info out there with my name on it.

What, if any, difference could it make if the OP doesn't have the little diesel light cluster connected? Is there anything in that cluster that is a part of any of the PCM's signal paths?

 

So drained the front tank, which is what it's been running on, rear tank is empty and getting replaced due to a dent. Pulled the pickup/sending unit and found the pickup filter laying on the bottom of the tank. Drained the fuel out, tank was FULL due to adding fuel until it couldn't fit any more.





There is about a 3" visbility factor with this stuff, murky to say the least. Stuck a piece of wood in the diesel and at 3" it just kind of disappears. Drained the tank and looked inside and there is a green film on the bottom and about 4" up the walls. The red tinge can be explained by dyed fuel (before my time) or ATF I had in the filter housing at one time (same dye). Tomorrows project is cleaning the tank and lines out, got a new filter today. Crap fuel still doesn't explain the dash tho, it did something, just not sure what yet. Will know more once I get this junk dealt with.

 

Ok, been fighting a complete no start for a while, haven't been able to work on it much. Completely drained, flushed, scrubbed the tank out, it had a residue that would come off if it was disturbed. Scrub brush on a welding wire did the trick. New filter, clean everything and... poppity poppity nothing. It would turn over, pop and fart but never catch and has been getting worse and tonight it was barely even trying to fire. Got online and found guys saying pull the ICP connector. No oil leakage but wouldn't you know... it cranked, popped and then lit up (dash out). shut it off and restarted to confirm, then plugged dash back in, fired up again.

It's quite sluggish to say the least, takes it's sweet time revving up, wasn't impressed with it before this all happened either tho. At the least it's running again, got a few ideas of where to go with it now but definitely looking for input to save me time.

 

Sounds like a bad ICP.need more data though to be sure.need to see IPR pressure and duty cycle while cranking.

 

The truck will run without the ICP connected, but it most certainly won't set any speed records. If you think you're having issues with the ICP, you will probably need to try another one.

 

Tonight, dash in (not sure that it matters anymore but it was an issue before), ICP unplugged. (this is one crank/start attempt, seconds listed are actual seconds starting at 1) 5-6 seconds cranking with no restults.... 7-10 seconds cranking while it tries to fire and speeds up while cranking, after 10 seconds it stays running. Shut truck off... notice alternator smoking, no smell, unhook alternator.

Plug ICP back in, cranks for about 3 seconds with no results then 4-5 seconds it lights up. Runs 645 rpm, kinda rough, sluggish acceleration, not nearly enough turbo noise as I would expect or like (downpipe is the whole exhaust sytem right now) previous running resulted in a LOT of turbo noise even while idling. Random glitches where it runs better for a half a second, can't find anything loose or wiggle anything to repeat results. The longer it runs, the better it runs, still not nearly what it was but indeed better. Acceleration is getting better (engine not truck) and while still nothing to be proud of, it is an improvement over when it first started. Shut truck off.

Repeats the 3 seconds of cranking leading to a start, much longer than I am happy with, by this time 15 minutes or so engine is making heat in the cooling system, it indeed runs but I am not happy at this point. If I had driveshafts I would call it "driveable" but it wouldn't be impressive or fun.

IPR was cleaned/o-ringed a while back, almost no run time on it. I know it still may not be right.

Fuel system freshly cleaned and new fuel/filter.

All new 4/0 battery cables with 31 series batteries on a basically new starter, installed a couple years back then never used it.

Fuel filter housing was resealed and cleaned with the IPR.

Only variable I can't shake is the old fuel. Noone can explain it's appearance, and of concern to me was the pickup rubber on the end of the sending unit seemed swelled as it didn't fit the pickup pipe and had fallen off the pipe.... has me worried about damage upstream.

Whatever the issue is (IMO) appears to be limiting fuel, judging by the slow acceleration.

 

Been trying to find a good test/diagnose writeup but everything I find seems to be newer trucks with a code scanner or whatever... any insight into this would be greatly appreciated.

 

I still think your problem centers around the high pressure oil system. If you still have the ICP disconnected or you're still running it with a questionable ICP then the acceleration will be really slow as the ICP is limited to 675 PSI or something. Instead of the HPO system ramping up the pressures to the 2600 or so PSI you would usually see, you're only playing with about a third of that. That effectively limits fueling since the injection system is driven from the pressure in the HPO system. Do you have an OBD II port in the cab from the PSD wiring harness? The only way you're going to really know what's going on is to connect a scanner to the PCM and see what it is seeing. I know it's not ideal, but when the engine is electronically controlled like the PSD is, it's really the only way to diagnose some of these kinds of issues. Another thing is that if you had the IPR apart and haven't driven the truck extensively since then you likely have a bunch of air in the HPO system and that WILL DEFINITELY make your starts longer than they should be. You have to DRIVE the truck, sometimes for quite a while, to get the air out of the system. If you haven't been able to do that as of yet then that may be a big part of your slow start issue.

If we don't get hard data to be able to troubleshoot this we're all just guessing and changing parts.

The only other thing I can suggest if you can't get a scanner on it would be to plumb a 3000 PSI liquid filled gauge into one of the HPO rails and have someone read pressures while you're trying to start the engine, and trying to run it.

 

Tonight's findings.

Plumb gauge into oil line into drivers head. Initial cranking of about half a second to register pressure, in one second it's at roughly 2200 and starts to fire, 1.5 seconds in it's running, didn't notice gauge reading after it lit, but pressure climbed for a half sec, then dropped to about 1000 psi.

Second start attempt, noting increased cranking time. about 2 seconds of no pressure, then ramps up quickly to the 2200 and starts to light, starts and flares to about 3800psi, then settles back down to roughly 900.

Third attempt, again about 2-3 seconds of crank with no pressure, climbs quickly to 2200, starts to fire, starts, flares to about 3800 again, then settles down to about 800, I leave it run for a couple minutes then play with the throttle.

Slam accelerater pedal down quickly each time. Builds fast to 1800, then settles back to 1600, rpm ranging from idle to about 1400. Continue attemps results the same. As engine warms up, idle pressure lowers throughout test to about 600psi.

Rev tests now to over 2000 rpm, at 2000 RPM pressure climbs from the 1600 to about 2300 psi.

More crank attempts show longer crank times. (3-4 seconds before pressure registers, once it does it ramps quickly)

Warming up showed lower idle pressure.

Tests show it's capable of 3800 psi.

While pressure builds rapidly, rpm increase is still slow.... 3-4 seconds of pedal on floor to get over 2000 rpm.

All connections in place except for alternator.

 

Truck has very little run time since the IPR redo and I've had that oil line to the head off... could just need more run time like has been said. Seems to improve the more I run it, but can't actually drive truck yet, so lotta playing around in garage I guess...