M998 No Fuel to Injectors (Rebuilt IP last year)

[wpy2080]

1994 M998, 6.2. Last spring had Stanadyne IP rebuilt by factory dealer. After new IP, ran great all last summer. This spring, ran no issues for a month or so until today. Driving for about 5 minutes and it completely shut off. Pulled over, started again with heavy white smoke, ran for 2 minutes and it died again. Towed it home and let it sit. Put in new fuel filter and bled with bleeder screw. cranked for a few minutes and it started, ran for 5 minutes at idle and then died again. Cranked with incoming fuel line off (To the filter) and getting strong fuel flow to the fuel filter and from the fuel filter. I connected a clear hose to the IP fuel return line and cranked. THe IP return line had a lot of bubbles and air and once the fuel reached the front (drain) side of the IP return line, the HMMWV started again for about 5 minutes and then died. Next i cracked a few Injectors and cranked and no fuel to the injectors... I'm all ears... .

Forum research has lift pump as a potential issue, maybe a bad IP, could GPC be an issue, better air bleed? I have the yellow banded KDS with black control box that has bright green KDS label (Seeminly common combo)... [Located near Traverse City, Michigan]

 

[1 Patriot-of-many]

delete

 

[1 Patriot-of-many]

You look in your valley? Between the heads?

 

[wpy2080]

Everything looked dry in the valley. Not losing coolant...

 

[1 Patriot-of-many]

If you have bubbles in the return line, you are sucking air from somewhere. I suggested looking there because I had a pretty good seal leak on the injector pump. You are sucking air from somewhere causing hard to no start.

 

[WillWagner]

OR an injector pintle stuck open. Pull the delivery lines and crank it, look for compression pushing back up through the nozzle.

 

[wpy2080]

Would one stuck injector pintle stop flow to other injectors? I pulled 3 lines (lines to the injectors) and cranked, with no fuel. So if I pull the actual injector (any of the and crank, I should be able to see possible back pressure?

How would I test the seal in the IP? To make sure no air moving through?

Additionally, now I’m getting just a blink in my glow plug wait light. Any way electrical box, or GPC would be shutting off my IP? Trying to figure out how to bypass and test but need to read more on that.

 

[wpy2080]

And much appreciated for the help... I’m just mechanical enough to get into trouble when I really start digging...

 

[WillWagner]

Compression pushes back past the pintle and goes back into the pump, it pushes the fuel backwards through the system and through the return, shows up as air. It has been a bit since I messed with a GM diesel or HMMWV but, IIRC, isn't there a shut off solenoid on the pump? See if there is battery voltage to the solenoid with ign on. Possibly low supply voltage, this could splain the wait lamp just flickering.

Patriot is referring to a fuel leak, when the pump starts leaking, fuel runs into the valley and down the rear of the engine, ends up on the floor.

 

[wpy2080]

Thanks. There is a fuel shut-off solenoid at the top of the IP. I will try to test that and a lot of people listen for clicks, but i'm hearing that isn't a super reliable test. Any idea how often the solenoids go bad and would that also be indicative of the bubbles and weak to no flow of fuel in the IP return line?

 

[Milcommoguy]

MY IP NOTES... Fuel cutoff solenoid, 25 Ohms +/- 5. Idle Up Solenoid 100 Ohms +/- 15. Nominal resistance checks. When energized voltage to coil, it will be battery supply. (varies with your batteries at rest or running / charging look for 23.5 VDC to 28.5 VDC again +/-. Anything wildly different check connections, meter or test procedure to verify your not chasing your tail. Know your equipment and abilities.

Be aware of all the issues of "bad grounds" and with bad grounds comes bad "hot leads". Need both to work, RIGHT ??

Clicking test is a "quickie" field test as long as cut-off system was assembled correctly.

See link > http://www.stanadyne.com/dealerportal/ssi/english/Service Bulletin/108.pdf < More info that needed, part numbers may work for Hummwv.

Many other testing along the way. Lift pump fuel pressure while important (3 plus PSI minimum). I like to know input side vacuum. Can't draw fuel from tank, low flow is a bigger problem than pressure. (somewhat related)

Old truck sold at auction with fuel cap missing for who knows how long, spells > clogged / sand/ water / soda (I didn't say it) in fuel system? (see pictures all the time no cap, truck sat in Barstow sand storm for weeks / years)

Good comments here on SS. Look at it as an extension of the hobby, as a teachable / learning experience. No one "thats it fixed" with multiple components. Process of elimination to fix or hand over your wallet.

Mr. Good Wrench.

 

[wpy2080]

Thanks a lot for sharing!

 

[wpy2080]

Question about trying to figure out if an injector is stuck open... I pulled two fuel lines that run from the IP to the injectors and cranked. No fuel at all is coming out of the fuel lines at the injectors. If an injector is stuck open, would it prevent fuel from going to the other functioning injectors that i checked? Also, when I crank the engine, the fuel flow from the fuel filter to the IP seems strong. Can the mechanical lift pump be broken even though it is showing strong fuel flow from the fuel filter to the injector while cranking? I am next going to check all the voltages on the IP and set up a manual drain from a bucket directly into the IP to rule out everything in line before the pump...

 

[wpy2080]

Again, really appreciate the advice/assistance.
- Today i tested the return lines from the IP and blew air. There were no apparent obstructions and i could hear the air in the tank so I don't think the return is blocked - I again tested the fuel flow from the fuel filter to the IP with clear hose. Fuel flowed strong but there were some small bubbles. Not sure if this is significant. - I tested voltage at shut off solenoid. The TM says 5 Amps, but (Maybe user error) I didn't get 5 with my tester, only 2.0, but I got 24.5 Volts. I ran a bypass direct from the battery to the IP shut off soleoid and again got 24.5 volts but still not starting. I am not hearing the click i hear people talk about and my glow plug wait light is flashing once fast and not staying on but temp here is 75 degrees. This is something that the truck was't doint prior to strandig me on the side of the road.
- I pulled a intector line and cranked and saw some fuel, but didn't last time i looked. I pulled a glow plug and it was wet with fuel.
- I noticed my mech lift pump has fuel on it and there is a small dr0p at the bottom, but I can't tell where from. Tiny drop, but not dripping.
- After cranking for a bout 3 minutes it fired up and spit out a huge cloud of white smoke. After a few minutes the smoke went away and it idled for about 10 minuites and then died. couldn't re-start.

I guess what to do next is the question. mech lift pump, S3 smart box and some glow plugs? All wouldn't hurt to have anyway ($$$) but my concern is with the IP.. Should i buy the solenoid that i don't hear clicking, cleant the check valve?? It is like clockwork that this beast starts really hard, blows white smoke then dies after 10 minutes...... And it all started out of the blue.
-

 

[wpy2080]

This weekend I put in a new KDS Smart Start System PCB with matching TSU and new OEM glow plugs. The truck started, no more white smoke, ran for about 3 minutes and then just shut off. Then i put on a brand new fuel lift pump. Went to start and the truck would not even crank... Wait light comes on for right time and i turn switch to start and nothing. Starter not even engaging.. Could this lack of cranking be related to the truck shutting off at random in the first place? It failed to crank on a few occasions with the old PCB as well when troubleshooting fuel delivery. Batteries tested at 25 Volts. I charged them prior to installing the new Smart Start PCB...

Also, starter was strong when working. Do these just go dead, or do they get weak and then die? The lack of cranking has been on again, off again and appears at random. Do starters do that when going bad or is that more of an electrical issue?

Does low voltage prevent the truck from cranking or will it still crank but sound like a car battery right before it dies?

Another thought i had is with the fuel shutoff solenoid. If it's stuck off, will it prevent the truck from cranking? And would it ever exhibit the original symptoms i posted, running and then shutting off after a period of time?

Does't seem like there is oil film in overflow tank or sludge on oil cap. Some tiny bubbles in coolant overflow when starting but then they go away.

After spending 15 hours on the truck this holiday weekend, i would love some additional suggestions... Don't know if i'm chasing one issue or multiple at this point.

 

[cwajciec]

You can test the starter by checking for 24v while the switch is engaged in the start position. 24v means you have a bad srarter (doubtful).
Next Try to eliminate one cause of no-crank at a time. I’d start with the ignition switch since it could give you all the symptoms you are having. I’d disconnect it and hot wire it. I think it’s only 3 wires and you can look in the manual for the right wires. If you lose 24v to one of the ignition wires then you have a wiring problem.
next would be the neutral safety switch. Bypass that by connecting the wires together. (But that wouldn’t cause the truck to shut off. ) that should get it cranking.

 

[Action]

This weekend I put in a new KDS Smart Start System PCB with matching TSU and new OEM glow plugs. The truck started, no more white smoke, ran for about 3 minutes and then just shut off. Then i put on a brand new fuel lift pump. Went to start and the truck would not even crank... Wait light comes on for right time and i turn switch to start and nothing. Starter not even engaging.. Could this lack of cranking be related to the truck shutting off at random in the first place? It failed to crank on a few occasions with the old PCB as well when troubleshooting fuel delivery. Batteries tested at 25 Volts. I charged them prior to installing the new Smart Start PCB...

Also, starter was strong when working. Do these just go dead, or do they get weak and then die? The lack of cranking has been on again, off again and appears at random. Do starters do that when going bad or is that more of an electrical issue?

Does low voltage prevent the truck from cranking or will it still crank but sound like a car battery right before it dies?

Another thought i had is with the fuel shutoff solenoid. If it's stuck off, will it prevent the truck from cranking? And would it ever exhibit the original symptoms i posted, running and then shutting off after a period of time?

Does't seem like there is oil film in overflow tank or sludge on oil cap. Some tiny bubbles in coolant overflow when starting but then they go away.

After spending 15 hours on the truck this holiday weekend, i would love some additional suggestions... Don't know if i'm chasing one issue or multiple at this point.

Move your shifter around while the switch is held in the START position. It needs to be in N or P.

 

[Retiredwarhorses]

I’ve had a bad starter that did what yours is doing....I had replaced the ignition 3 lever switch and still no go, here was the kicker, it only did it on the first start of the day, never after that, you literally had to wait till the next day to test what you did from the day before.
Now, on your truck dieing, make sure you didn’t get the 2 connections plugged in wrong on the top of the injector Pump, one is for cold advance, the other is for fuel cut off....it will work backwards til the engine hits 120 degrees.
The cold advance connectors has ribs on it for easy identification.

 

[wpy2080]

Thanks for all the help. Next time i'm in Michigan and able to work on the truck I will report back...

 

[wpy2080]

Turns out the issues was the fuel lift pump and the PCB. I replaced the lift pump and the stall went away and when I upgraded to the KDS Smart Start System, the white smoke went away.

That was great, but here is the kicker... I needed a few days to calm down before posting. My passenger seat has 4 bolts protruding about a half of an inch below the seat. When I put the seat on (And it wasn't seated just right) one bolt found the positive terminal and the opposite bolt found a body ground on the passenger side of the battery compartment. I realized something was screwed when my auxiliary ground wire (The wire from the block to the PCB, bolt literally caught on fire) and burned to the wire.

My question is now what? What are the most probable points of failure after a major short? I am going to check continuity on wires but is the body or engine harness most vulnerable to this sort of major short? Do I just go through the TM on testing continuity on all electrical components? Am I chasing my tail if they test out good but became brittle? Should I replace the harnesses both body and engine?

The starter turns but no wait light at all and engine does not start. I'm about to make someone a **** of a deal on a used M998.