• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Double check my diagnosis please: 95 K3500

GM Guy

Manual Trans. 2WD Enthusiast
Messages
4,838
Reaction score
846
Location
NW Kansas and SC Idaho
Hey all,

I drug home another one. :) 95 K3500 CCLB DRW 6.5L 5spd 4wd.


It has about 250K on it, story goes he was just driving along and it just shut off, never to start again. Owner claims to be a good mechanic and has had a few 6.5Ls over the years and claimed it has to be the IP

I cracked the drain plug, normal looking black oil, no coolant in oil. only about 1 gallon low on coolant, (sat 5 years roughly) oil cooler lines look good on block, minor seepage at crimp, and the motor was full of oil and rocked over by hand, and starter bolts and brace were intact, so I paid the guy and drug it home.

Now, its home and I'm trying to get the ol sow to fire, It would be nice to drive it off the truck, but not a requirement. :)

Battery cables are pretty junky, newer but undersized starter cable, clamp on terminals, etc. cleaned it up a little, and put a decent set of batteries in. (Still room for improvement here)

OPS is bad, so I have the LP relay temporarily bypassed with a wire, bleeds the filter fine and squirts out at the t-valve, even at the t-valve the diesel is pretty clean looking so I dont think the system is contaminated (came from northern CO, so condensation is minimal compared to the corn belt)

PMD is on a bracket above the LH valve cover and has an undersized heatsink, so I plugged in my known good Heath PMD kit. Heath kit has a resistor.

IP has a green tag under the one screw, and the FSO has a crisp looking label on it, when key is turned it will magnetize and pull a wrench (lightly) I removed FSO and when you hotwire LP it gushes out of the hole (also clean looking fuel) , plunger moves by hand (though to keep from getting the FSO dirty and me working alone I did not verify with key on, I probably need to do this still)

Will not pump fuel out of DS front injector line, and of course no smoke. Spins over fine. I have had working block heater plugged in this whole time. Wont even try. I squirted a little WD40 into the one middle intake hole, but working alone I cant fog it properly, so I didnt get too crazy, didnt seem to try at all.

Grounds are not great. chassis to engine is not on the intake stud, but is on a bellhousing bolt. I got a skimpy set of jumper cables and clamped one end to the intake stud, went over the fender and down to the chassis.

Harness grounds are intact and look good. I need to run another from the cab to the engine. This could be the issue, as the ECM grounds this way, correct?

All fuses check out fine. dash lights up and does the bulb check and glows run and everything seems fine in that regard.

I currently have CTS unplugged for max glow time.

I did unhook the CPS once and no change.

Any suggestions? I am leaning towards IP issues. With the non-OP LP thanks to bad OPS and presumed lack of fuel additive, I am thinking it was out of lube internally and finally seized something.IMG_20190424_094034_386.jpg
 
OK, pulled upper intake and unplugged OS and no change. verified FSO this time, out when unplugged, sucks right in when plugged in with key on.
 
Redo the grounds- gonna have to anyways.

Swap pmd cable- closely examine pins are not damaged/ bent.

Ecm ground. Possible ecm? Crazy rare but if you can play the swap Around game, it will eliminate it for free and isn’t way hard to do while cleaning that ground wire.

Pull the glowplugs so that you know you aren’t dealing with swell-o-matics. Do a comp test so you know where engine is really at and then do the cranking for fuel with them out. It’ll spin so much faster and easier, it will pickup and go better.

Oh yeah-duh! I forgot the filter. Pull the filter and make sure it’s ok. Dont bother with new yet unless it os toasty- fill the filter with atf- or 50/50 atf diesel. That lube can work wonders for unhappy pumps to get a refire going. If head/rotor wear is the concern- premix 50% diesel, 40%atf, and 10% new 40wt oil. The thickness will get it to prime the worn and gouged gaps easier to get spray out the glow holes.

Get that clear tube on their asap too.
 
Oh, if you do find the ip bad later, out the filter and the oil mixture. Atf mix wouldn’t hurt a new pump, but the thickened oil isn’t the way to break in a new ip.
 
Make sure there is no fuel leak.

Rodents can do wonder with all the rubber fuel hoses.
Make sure the hoses are not kinked.
Batteries are load tested even if it is new.
Also test the starter and alternator.
 
So what was the outcome of all your effort?


Nothing yet. :) back burner project ever since wheat harvest hit, I did get the 95 GMC K2500 back on the road (Genuine Bosch new injectors and AC Delco 60G glow plugs, new valley hoses, FTB, low mile GM8, and new batteries and ALL battery cables with the bolt mod, cranks sooo much better.

Then I threw my back out, and have been behind on stuff since. :)
 
OK, back at it since farming is about done for the year.

I put a new positive cable (pass batt to starter) in, that helped a bunch. along with better batteries.

Now I am getting fuel to the injectors, seems to go in cycles, some times it smokes good, other times not so much.

Spraying a little WD in the intake center bolt hole does not seem to affect anything at all.

Unplugged CPS and got some sort of healthy backfire through the intake. plugged it back in.

Block heater on this whole time. LP jumpered whole time. i did notice LP is getting warm to the touch. LP seems to spurt out decent from the t-valve.

Jumping with another pickup to keep the cranking speed up.
 
Quit putting flammable items in the intake. A compression test will answer that question. Backfire may have a broken valve spring, popped head gasket, or Glows lit off the WD 40. If compression is good it ain't getting fuel.

You sure you have enough cranking RPM? By chance have you given it 1/2 to full throttle while cranking?

Fuel smell like gasoline?

Did you repair the grounds? Cranking amps do weird things to PMD's and ECMs if the battery grounds are bad.

Block heater work? Tried it after warming it up for a few hours?

Smoking... Is that with some glow plugs out to see if it's giving a fuel mist? It may need to be primed with some GP's removed.

I would suggest a compression test next.
 
OK, cleaned most of the grounds today, got the one unhooked from the bellhousing bolt and back up on the intake where it belongs. Got the frame grounds. need to clean the firewall ground.

Changed fuel filter, looked OK. last ditch screen gone, put a good used one in. Possible the IP inlet screen is plugged? I still better unhook the return and blow it back.

New Delco OPS, old one was bad. will now trigger LP properly when oil PSI is present.

jumpered LP bled filter easily.

Block heater plugged in all day, t-stat crossover warm to touch.

Not getting fuel to injectors any longer, not even a puff of smoke. I have the 4 drivers side injector lines loose.

Tried swapping PMDs around with no change.

Plan to get a buddy involved and have him crank while I check for pump rotation, curious if it has a sheared key.

I can't seem to find the chart for the PMD plug on proper values, anyone have a link here? I probably better check the resistance on the fuel solenoid if the fuel checks out.

I am curious, with the bad OPS, I am curious if he ran it out of fuel, and it sitting long enough the plungers are sticking. I am also wondering if a new, strong lift pump might help, current one definitely pumps OK, but its far from blasting the underside of the hood.
 
The voltage flowchart is in the DS4 cal resistor document here:

 
OK, pinout helps immensely, thanks guys!

I checked with the multi-meter set on the 200K Ohm scale, and got a reading of 30 or 300 on the main fuel solenoid (left two pins on end, red and black), and zero on a known running pickup

Pretty safe to say main fuel solenoid is shot and IP needs swapped, wouldnt you all agree?
 
OK, tested some more, probably going to pull the intake to inspect wiring, putting the multimeter across the two pins I get a relatively low reading (0.9 on the 200K scale) but going from battery ground to pin i get like 30 on the 200K scale. would this be more likely a wiring issue?

I am still leaning a little towards pump is roached due to the previous owner driving around with a bad OPS< and thererfore starving the pump, and the fuel solenoid having to work harder, but hopefully I am wrong and its wiring related.
 
OK, wrote down some actual values versus going off my Pendleton compromised mind (last nights New Years Eve party was good! :) )

Staring into the PMD connector, tab up, left to right. Left two pins being the Fuel Solenoid wires.

95 K2500, runs great, using it as the "control" 95 K3500 is the "patient"

K2500
Pin 1 to Pin 2 Ohm reading on 200K scale, Engine and Ignition off: 3.4
Battery ground to pin 1: 0.1
Battery ground to pin 2: 3.6

Pin voltage, Engine off Key On.
Pin 1: 0
Pin 2: 5
Pin 3: 11.93
Pin 4-6: 0


K3500 (Patient)
Pin 1 to Pin 2 Ohm reading on 200K scale, Engine and Ignition off: 3.5
Battery ground to pin 1: 19.1
Battery ground to pin 2: 16.3

Pin voltage, Engine off Key On.
Pin 1: 0.18 (Backfeeding?)
Pin 2: 5.2
Pin 3: 12.4
Pin 4-6: 0



So I am pretty lacking in electrical knowledge, but it looks to me that the actual solenoid is fine going off the matching ohm readings compared to the good one, but something is jacked in the wiring, and its likely limited to the individual pump harness, probably loose screws and overheated wire ends. Everyone agree?
 
Back
Top