• 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!

1997.5 H1 Hummer 6.5TD Rough Idle & Blow by w/video Ideas?

M

mk1spyder

Member
Messages
51
Reaction score
35
Location
charlotte

Not sure if that is normal blow by or not but I would imagine not. Engine has about 160k on it, I did basic maintenance to it drove it for 6 months on weekends, then it sat for 7 years without being started and a couple weeks ago it cranked up fine. Then the injection pump ate shit from sitting for so long. Did the FTB mod with walbro lift pump, has a new injection pump, SS Diesel economy injectors that are 7 years old but only have 2,000 miles on them, glow plugs are the same story old but no miles. Engine ran fine when it was shut down 7 years ago. Also has a new water pump, crank sensor, boost solenoid, MAP sensor, #9 resistor on an old but low miles PMD remote mounted of course.

It runs rough at idle you can feel the shake in the whole truck though it doesn't look that bad in the video or sound that bad really. I have a tech2 so I did a cylinder balance test and it doesnt seem isolated to one specific cylinder as they all drop the RPM evenly. Entire fuel system is new, the switching valve and both tanks and pickups and filter and housing cleaned, fuel level sensors etc... All new. I tried the time set function on the tech2 and it is sitting around 9.4 degrees at idle, if you hit the button it drops towards zero, right around 4-5 degrees the noise and the shake disappears runs real smooth. Any ideas?
 
Also no codes and it seems to run fine at higher RPM's and under load, throttle response is good it passes the 3k rpm test, runs fine under boost too no smoke no overheating. Fires right up cold or hot no significant smoke. TDC Offset is at -0.44, has the original CDR valve on it don't know if that could matter.
 
Last edited:
Try unplugging the CPS (crankshaft position sensor) and starting. It will take quite a bit of extra cranking and will start in limp mode. If it runs smoothly then that tells you the CPS is bad. You can do the same thing with the optic sensor.
 
Highly doubt that is the issue as they are both brand new and it ran basically the same prior to both being replaced, is the blow by not an issue?
 
I'd be worried about a valve being stuck open or a hole in the piston if is a symptom that came on suddenly. Start with the cheap stuff first
 
It did start fairly suddenly, but just starting and stopping the truck never even really drove it so I don't see how I put enough load on it to blow a hole in a piston. Now a snapped valve spring I could see, but like I said I did the cylinder balance test and every cylinder responded the same so doesn't that rule out a 1x cylinder issue? Wondering if it is just down on compression worn rings. I can try the optical and CPS tomorrow.
 
When killing cylinders for load test on idi, I prefer to crack the injector nut and see the fuel leak and listen for the idle change. Cutting fuel electronically works, but the inherent load on the IP is less. With the load staying there while it cycles the fuel, the rpm change is greater. Do a comparison and you'll hear what I am saying.

With the engine sitting that long, expect stuck rings until you load the engine up and work it a bit. Also valve seals probably toast. Expect leaking main seals too.

SS Diesel caught a bad name for their instaheat plugs and those injectors reinforced by poor service over the issues. That low of miles I wouldnt expect them to be bad, but wouldn't bet against them shooting a laserbeam stream of fuel to put a 3mm hole in the piston top- seen it on 2 engines (1 was in my 99).

I would add a quart of atf to the engine oil and sandbag the rig, then work it moderately hard for 40-50 miles. The detergents will clean any settled carbon from sitting and the conditioners will soften and engorge the rubber seals.

Follow AK's advice on the sensor tests. If you cant get anything there, run a heavy mix of atf in the ffm so it douses the Ip and injectors to clean and lube after it's slumber. I would expect a bit of pitting in the IP
Plunger- any moisture that made its way to the IP would collect there and do its damage.

Compression and leakdown tests will tell you whats what with the blow by, but if the rings sre sticking any, the atf from both ends will help that quickly.
 
I had an IP that had a shake at idle. When I shut off the cylinders one at a time they all dropped the same amount, but after doing it several times I noticed that one cylinder took about two or three seconds to recover after I turned it back on while the other cylinders recovered instantly. I ran a bottle of ATF through the IP as Will said, and added a bottle of Diesel Fire to the tank and after a day or two of driving the shake went away.
 
I should clarify the new IP was installed AFTER it had been sitting forever, so it is fresh, only the injectors and glow plugs are old. The other thing to note is when it was first fired up from sitting forever on the old IP and stock lift pump it ran fine the first 4-5 times I started it and moved it around. Then the tank switching valve ate shit, which put air into the lines because it got stuck on the AUX tank which had no diesel in it, and subsequently I got a lot of IP failure symptoms after the fact. So I figured it was the IP, followed all the tests which showed it to be the IP, and replaced it. I got my power back but now I have this issue.

What brand of injectors do you recommend since these SS diesel ones seem to be suspect at best? Is it possible to see the cylinders through a bore scope through the glow plug or injector holes?
 
Also I did the CPS and optical disconnects runs slightly worse and starts like shit, those are not my issue. Threw a quart of ATF in the oil, see my previous question on the bore scope. Can a normal gas engine compression tester be used on a diesel? I'm thinking not right, has to be alot higher psi.
 
mk1spyder said:

Not sure if that is normal blow by or not but I would imagine not. Engine has about 160k on it, I did basic maintenance to it drove it for 6 months on weekends, then it sat for 7 years without being started and a couple weeks ago it cranked up fine. Then the injection pump ate shit from sitting for so long. Did the FTB mod with walbro lift pump, has a new injection pump, SS Diesel economy injectors that are 7 years old but only have 2,000 miles on them, glow plugs are the same story old but no miles. Engine ran fine when it was shut down 7 years ago. Also has a new water pump, crank sensor, boost solenoid, MAP sensor, #9 resistor on an old but low miles PMD remote mounted of course.

It runs rough at idle you can feel the shake in the whole truck though it doesn't look that bad in the video or sound that bad really. I have a tech2 so I did a cylinder balance test and it doesnt seem isolated to one specific cylinder as they all drop the RPM evenly. Entire fuel system is new, the switching valve and both tanks and pickups and filter and housing cleaned, fuel level sensors etc... All new. I tried the time set function on the tech2 and it is sitting around 9.4 degrees at idle, if you hit the button it drops towards zero, right around 4-5 degrees the noise and the shake disappears runs real smooth. Any ideas?
Click to expand...

Get rid of those SS Diesel injectors. They are right from the era that sucked.
 
On a good day "New parts do not mean good parts." Keep this in mind always. Split an oring on install sucking air, bad IP, or continue down the replace parts flowchart. Before we get ahead of ourselves: have we put a clear return line on the IP and checked for air? You have PSI at the IP inlet? (In this case the fuel filter water drain is NOT the complete picture.) The clear return line will show "air" (diesel vapor lock) if you have a restriction between the filter and the IP rotary pump so the water drain for PSI readings works in combo.

You got an eyeball on the air filter to see if mice made a clogging nest?

Sounds like bugs in fuel and the SS, Super Shitty, injectors, the brand that is given away NEW as cores on here, were certainly damaged by the fuel system eating whatever. As it ruined the IP all the wear debris, corrosion, corrosive fuel, water, went through the injectors. The injectors are probably sticking open. Been There Replaced The injection System: from the tank to the injectors. So even if you did get a good set they are very suspect depending on what was in the fuel system. Corrosive bugs in fuel as I describe is one way to kill them.

The site vendor Leroy Diesel sells injectors. A set of 8 is CHEAP vs. a modern HPCR injector set. SS injectors even new are not worth the trouble to put in and haul back out. Let alone engine damage risk.

The blowby looks "normal". Only way to get rid of that is a ring job and using gapless rings. If the blowby is chugging from one cracked or burned through piston you would get a big puff among the background blowby.

Compression readings are in the 400+ PSI range. Mr. Diesel himself was nearly killed when the compression gauge he had exploded. Use the correct tool...
 
Get the injectors from Leroy- same Leroy on the hummer site.

If you can take the time and spend a little extra, take the new injectors to a shop near you and have them balance the injectors to within 25 psi of each other. Not necessary, but sure smooths the engine and helps power/mpg a tad.

Good to hear the IP swap was after the slumber period. Swap the injectors and skip the atf fuel treatment is better move with that info.

You need compression tester for diesel, not gas. Auto parts stores usually rent for free after returning.

The blowby-vent your cdr to the air for now, just no water fording- haha. See how much that affects blowby oil.
 
You guys are awesome, I bought a set of Bosch injectors and Bosch glow plugs fresh return hoses and valve cover gaskets. I'm going to take the valve covers off while I've got the injectors out and take a peak in there just to feel better about the valve springs. I went ahead and dumped a quart of ATF in I'll run it for a bit and change the oil later.

Hopefully the injectors fix the issue, I bought them back before people had really built a widespread opinion of SS diesel on the Hummer side of the world.

On a side note I found that a couple local scrap yards have new take out drivetrains from HMMWVs that have like 2,000 miles on new TD GEP 6.5s with 4L80E trans and 242 t-case for like $2500 lol. I'm going to buy as many as possible.
 
Holy find batman! If you end up with an extra tcase- mine took a dive years ago and has the small jeep planetary in it and did the 2wd conversion at the same time. I would be mighty intersted in a used one for some parts...

And if definitely gep take out engines, those are optimizers!
 
how many are there? Are they in Charlotte NC? I am not that far away............please say they are on the other side of the universe....don't need to be tempted to by more stuff right now.
 
You must log in or register to reply here.
Back
Top