94 GMC Yukon 6.5L diesel, looking for advice/info on rebuilds, etc.

[snarl95]

Welcome

 

[Chefhusker]

So I had time this moring, fired the truck up. The exhaust smells like fuel. I'm not sure what the chronological order is in relation to fuel lines, but I'm actively searching now. For the moment, I'm enjoying a bit of relief that it isn't a blown head gasket as I initially thought. I guess it still could be, but I don't have clues towards it.
I was also able to locate the OBD1 port. Maybe I shouldn't have gone looking for it at night! If it were a snake, it'd had bit me...

 

[Will L.]

Better to smell diesel than coolant. So hopefully no major damage then.

So that you are aware for the future:
Head gasket go on these just like a 350.
Heads crack easier between the valves which is a coolant loss when engine off and compression into coolant when running scenario. It is sometimes repairable but better to replace heads if affordable if that ever happens. The cylinder walls crack to the coolant passage with same as above but almost always is block end of life for cost of repair.
But no coolant smell in the smoke means you should be ok, just keep an eye on coolant level.
Btw, 195 is normal 205 is ok. 210 be careful and 220 pull over. Heat is hands down #1 killer if this engine.

Get the fuel return line out the front of the ip replaced with clear line. It is 1/4” and about 5” long. Hardware stores sell clear line, get a couple screw style hose clamps at same time. Start truck and watch for bubbles flowing. Having one small bubble traped is ok. Otherwise should be nice and clear.

Warwagon mentioned the clear line and something else we need you to address- how cold is it where you are? I live near Las Vegas where diesel fuel never gels in the cold, hut most of the country gets cold enough to do it- and gelled fuel will make it run bad to not at all. DONT just buy any anti-gel and pour it in. A lot of that stuff is hard on these style diesels.

The pmd was possibly damaged in the rip out fuse issue and could cause what you are seeing. There is no testing a pmd, only “replace with known good”. Buy the pmd remote kit with heatsink and cable from Leroy sense it is lifetime warranty and a quality extension. Mount it and see if that clears it up. If so, great and buy a second pmd as a spare. Spare pmd is like a spare tire- you don’t really need one, if you dont mind walking. If that didn’t fix it then keep your old pmd as the backup and when the new lifetime warranty one dies, use the backup to verify that issue and drive on it while waiting for the replacement one. I suggest two heatsinks with pmd mounted and a dummy plug in the backup to keep it clean. Being mounted means if it dies on you mid drive, you just move the wire and are on your way. Much better than playing mechanic on the side of the road when you are in a hurry.

 

[jrsavoie]

Better to smell diesel than coolant. So hopefully no major damage then.

So that you are aware for the future:
Head gasket go on these just like a 350.
Heads crack easier between the valves which is a coolant loss when engine off and compression into coolant when running scenario. It is sometimes repairable but better to replace heads if affordable if that ever happens. The cylinder walls crack to the coolant passage with same as above but almost always is block end of life for cost of repair.
But no coolant smell in the smoke means you should be ok, just keep an eye on coolant level.
Btw, 195 is normal 205 is ok. 210 be careful and 220 pull over. Heat is hands down #1 killer if this engine.

Get the fuel return line out the front of the ip replaced with clear line. It is 1/4” and about 5” long. Hardware stores sell clear line, get a couple screw style hose clamps at same time. Start truck and watch for bubbles flowing. Having one small bubble traped is ok. Otherwise should be nice and clear.

Warwagon mentioned the clear line and something else we need you to address- how cold is it where you are? I live near Las Vegas where diesel fuel never gels in the cold, hut most of the country gets cold enough to do it- and gelled fuel will make it run bad to not at all. DONT just buy any anti-gel and pour it in. A lot of that stuff is hard on these style diesels.

The pmd was possibly damaged in the rip out fuse issue and could cause what you are seeing. There is no testing a pmd, only “replace with known good”. Buy the pmd remote kit with heatsink and cable from Leroy sense it is lifetime warranty and a quality extension. Mount it and see if that clears it up. If so, great and buy a second pmd as a spare. Spare pmd is like a spare tire- you don’t really need one, if you dont mind walking. If that didn’t fix it then keep your old pmd as the backup and when the new lifetime warranty one dies, use the backup to verify that issue and drive on it while waiting for the replacement one. I suggest two heatsinks with pmd mounted and a dummy plug in the backup to keep it clean. Being mounted means if it dies on you mid drive, you just move the wire and are on your way. Much better than playing mechanic on the side of the road when you are in a hurry.

I used to do the 2 PMD's and 1 cable. After a few years, I decided I din't like crawling around to switch the plug in the bumper. I just got an additional extension cable and run them both up under the hood. All I have to do is pop the hood and switch plugs.

And the wife doesn't say, "Oh that's nice." when we are going someplace and I had to swap the PMD cable in the bumper

 

[WarWagon]

Does it sound even when spinning over or does it zing past a low compression hole?

Does the smoke clear up when driving or warmed up?

228k miles ... What is the repair history on this?
Original engine?
Original injectors? (They got a 100K life. It's a gamble past 100K.)
Original timing chain?

 

[jrsavoie]

I concur on Doing the lift pump relay upgrade is a #1 thing to do after you sort out what you have going on. Either make your own - plug and play like leroydiesel.com or Quadstar. It's the same harness from Leroy, just a different vendor. Not sure who all else might sell it.

I would also install a permanent fuel pressure gauge. You won't have to check your lift pump. you will know at all times.

If you do not know the history of the injectors, I would pull them and have them tested. There should be a recommended place here on the forum to send them to get tested/rebuilt. I have been happy with a place I used out of Michigan.

Even if the injectors have been replaced, it might not be a bad Idea to pull them and have them tested as you probably do not know if good injectors were used.

Since this is a forever vehicle, I would also plan on a Fluidampr, Braided stainless engine oil cooler lines, Stainless 4" exhaust if you are in the rust belt

That is one nice looking Yukon

 

[Chefhusker]

Does it sound even when spinning over or does it zing past a low compression hole?

Does the smoke clear up when driving or warmed up?

228k miles ... What is the repair history on this?
Original engine?
Original injectors? (They got a 100K life. It's a gamble past 100K.)
Original timing chain?

I regret to say it, but I have no real info on any repairs/replacements. I inherited the truck, and while I always loved my grandparents, I didn't live close enough to them to really know any repair/replace things that might have been done. Let's just say it's all original. I'll post some under the hood pics soon, and you may spot something that looks newer or aftermarket, etc. I appreciate your help.
I am going to try to familiarize myself with the "zing past a compression hole" idea. Would this be like a systemic repetitive quick surge or something?

 

[Will L.]

Yes, for the "zing" imagine no sparkplug in one cylinder when starting a 350- loss of compression in one (or more) cylinders.
Diesel uses a higher gauge than gas for compression test, and don't do a "wet" test as the oil can become a fuel and ignite into the gauge. Normal recommendation is do dry test all cylinders, then leakdown test all cylinders.

 

[MrMarty51]

One of the parts stores might have a diesel compression test kit that You can throw down a deposit for, then, after the kit is returned they will refund You Your money. Oriellys over here is the tool rental store.
While the glow plugs are out You can also test them with a volt/ohms meter set on ohms.