Yeah, I know, it's not really Olds, but frankly, this group seems unusually level-headed and competent, and might provide better answers than some GM truck group.

For five years, I've had a 6.2 in a 1990 GMC 3/4 Ton, now with 280,000 miles.
The thing ran flawlessly for the first four years. Started instantly from 105°F down to -10°, ran smoothly, had the expected amount of power.
The "computer" failed, so I've got the glow plugs and cold-retard on a toggle switch (the glow plug timer is separate form the "computer," and works fine)

Beginning last year, I've had a cold-start problem, and I haven't messed with it because I don't want to screw it up even more.
When it gets below about 40°, the problem starts, and it gets worse with colder temperatures.
What it does is to start instantly, just like normal, run for 30 to 60 seconds, then die, and be un-restartable without WD-40 and ether (I know, that's bad to do).
I switch on the glow plugs, wait for them to switch off, press in the accelerator to the recommended amount (½-way above freezing, all the way below freezing), turn the key, and she roars to life.
I hold down the pedal enough to keep the revs up around 1,500, and it runs for 30 to 60 seconds, then the revs climb a little bit, then it dies (if I just let it idle without holding down the pedal, it dies, too, a bit sooner).
After that, it acts like the injectors are dry (and they may be), and requires a whole lot of cranking, along with liberal sprays of WD-40 and little puffs of ether, before it will fire again, at which point it acts like it wants to catch for a while before it actually does catch and roars again.
After that, it will run perfectly, and will restart fine, even if allowed to go cold. With dropping temperatures, the amount of time between "good starts" will decrease, in other words, at 40° I may be able to get a good start if it was last run several days or even a week before, but at 10°, even if it ran last night it may not start.

I'm assuming that there's a bad / leaky return hose somewhere that sucks air during cold starts (there are no fuel leaks), but as to which hose, I have no clue - there's a lot of stuff down in that valley.

Also, the lift pump seems to run off the "computer" - you can hear it turn on when you turn the key, and it will run for an additional 30 seconds or so after you turn the key off. No problems with running with the pedal floored up hills on the highway, so I don't think the lift pump is bad.

Any diesel mechanics out there???

- Eric

 

Never had a 6.2, but I've heard a word or two about the PMD being a weak point on some of those. Have you checked that? Supposedly where they are mounted from the factory they tend to get cooked prematurely. That or could be a weak lift pump relay?

 

PMD?

Sorry - I'm not up on diesel terminology .

- Eric

 

The PMD was on the 6.5 turbo starting in '94. I know about that POS the hard way. Ugh. I'd try running a tank with some sea foam or Lucas before I scratched my head too hard. Hopefully it's just dirty in there somewhere. Sea Foam can be a miracle drug if that's the case.

 

Yeah, I admit I haven't tried SeaFoam yet.

I have changed the fuel filter, and I know the tank is clean because I replaced it when I found holes in it.

The lift pump goes on when it should, and stays on, so I doubt it's the pump. It also works fine at full throttle for long periods.

The PMD isn't relavent, because the 6.2 is a completely mechanical motor, with no electronics, other than a "computer" that manages long-since-removed EGR equipment and turns on the independent glow plug timer and retards the injection when it's cold.

There's nothing to this motor except a mechanical pump, injectors, and a bunch of return hoses, so I'm sure this is something simple.

- Eric

 

have you tried to bleed the pump lately? might do it for kicks see what happens

 

Not lately, and remember that it runs great after it gets going, and that when it's not cold, it's got no problem, so I doubt that's it.
Also, the last time I bled the injectors, I ended up with leaks that were tough to stop, so I'm leery of it.

- Eric

 

I haven't had a 6.2 before, but I had a Ford 6.9 idi as my first vehicle three years ago. Sold it to buy my Cutlass, sad but had to do it. Same general engine, indirect injection, mechanical injection, DB2 injection pumps(or DB4 or DS4 I believe). It sounds to me like your getting air in the return lines. The rubber lines running between each injector. When the air reaches the injectors, the struck will stutter or die. As far as identifying which hose, don't worry about it. Just google "6.2 diesel injector return lines" or something like that. You can get a kit with all new lines and everything else needed for like $20-$30. Install those well, and that should fix the problem. Over time those rubber hoses start cracking and and sucking air, even if they don't look that bad. And yes, you have an electric lift pump. Consider yourself lucky someone installed that, otherwise the system wouldn't prime itself before started, and you would be under the truck checking for leaks. If that still doesn't solve your problems, Heath Diesel specializes in 6.2's and 6.5's, I'm sure they would be happy to answer questions over the phone.

 

not to dig up an old thread.but did you get the 6.2 fixed.if not.pull the return line fitting off the pump where the return hose attaches.there is a little glass ball inside there and if any and i mean any spec of crap gets in there it will shut you down.if you ever have a runaway 6.2 or even a 5.7 just pinch the return line shut and it will die.

 

Nope, not fixed - exactly the same.

When I want to run it in the cold, I plug in the block heater for a few hours, pull the air cleaner cover, get out the WD-40 and the ether, turn on the glow plugs, fire it up (it catches instantly), run around to the front, start spraying the WD-40 (giant fogging aerosol can), along with an ocasional blip of ether, then it dies anyway, and I load it up with WD-40, crank it for about 30 seconds, hit the WD-40 again, crank it again, do this about five more times, and she roars to life and runs fine all day.

I'll take a look at that glass ball when it's a bit warmer (expecting a couple of feet of snow tomorrow).

I know I just need to pull the pump and the intake and go through and replace every single piece of rubber hose I can find, but every year when it's warm enough to play with it, it runs great, so I never get around to it .

Thanks for the reply, zombie thread or not!

- Eric

 

i had a 5.7 diesel with the same symptons drive me a little crazy years ago.it turned out to be the rubber fuel line between the fuel pump and the frame had gotten hard and even tho it felt tight was sucking air.i ran it off a can and a new piece of hose to the pump before i found it.this does have a mechanical pump before the injector pump right?jc

 

Yep seen these symptoms with bad fuel lines, faulty check valves and even frozen water in the fuel lines.

 

sounds like air is getting in somewhere

 

I am a retired 40 year diesel mech, not much to these engines. Glow plugs and a glow plug controller at rear of engine. Probally you have one or more bad glow plugs. You can check them with a test light, very easy to check and change. If the glow plugs cycle fast it may be glow plug controller at rear of engine. I doubt you have any air in system or it wouldn't hardly start. Never use either, will blow heads off engine One glow plug will do this. my e mail kyzercd71@yahoo.com do you have block heater plug in. Most of 6.2,s had one around lower bumper on left side

 

Wow. I had forgotten about this thread.

I actually fixed this over the summer, after a 6-hour drive that ended with the final two hours at 45mph, because when I tried to go faster, the truck would bog down and blow smoke.

It was another of those things that makes me say, "It's always something simple."

I knew that it had to be in the lines leading to the injector pump, and that it was probably an air leak.

I knew that the line from the tank to the lift pump was good, as I had replaced the rusty steel line when I replaced the tank, so I found the front end of the line from the pump, and tested the lift pump as per the manual, and found it to be good.
While testing it, I noticed that the filter block got a little bit wet around the heater module while the lift pump was running.

I then pulled the filter and the aluminum filter base from the back of the intake, and cleaned off the filter base.
I followed the line from the filter block to the injection pump, and it was in good shape and not leaking.
I looked for other lines that could be introducing air, and there were none.

When I disassembled the filter block, I found that the heater module came out of it very easily because its O-ring was dried out.
I chipped the old O-ring off, went to the hardware store, and bought a new O-ring for 39¢.
The new O-ring held the heater in firmly.

I put it back together (with a new filter) and ran the lift pump again. The filter block no longer got wet near the heater module.

I've never had another problem with it - it now starts immediately every time, no matter the temperature, or how long it's been sitting, just like before.

So, it was a 39¢ O-ring that made me have to essentially bleed the entire injector system every time I started the truck in cold weather. The O-ring was allowing air to leak in, which allowed the column of fuel to drop in the line, being replaced by air, which was then sucked into the injector pump and pressure lines when the engine started, causing the same condition you would get if you ran the truck out of fuel.
Near the end (last summer), the O-ring got so bad that it allowed air to be sucked in while driving, reducing the injector pressure, leading to incomplete atomization, poor combustion, low power, and smoking.

So, Thank You, '49 Olds, and everyone else, and welcome to Classic Olds!

- Eric

 

For what it's worth. I had one of those in an 85 Chebby 3/4. What a dog. I had it for about a year and got rid of it. Diesel? No torque with a camper and as said glo plug problems. Not to mention the filters and draining everything. 4sp manual with 4.11's I would have to down shift on a moderate grade. 5000 lb camper loaded.

 

Yeah, it's a gutless wonder, but it'll pull 7,500 pounds if it has to, and get 13mpg doing it (20mpg at all other times), and is still just about the best $550 I ever spent.

- Eric

 

Best bang for the buck I think are the older dodge ram with the 12v cummins the old mechanical engines. I had one for years (red 94 ) and I regret selling it. I would tow My cutlass some times through smaller towns with stop n go traffic and it had no issues keeping up with normal commuters. I got mine cheat at 3k but they are getting expensive. The 5.7 , 6.2's , 6.5's are cheap since most diesel hot rodders dont want em same goes for the 7.3 fords. They are work horses but not much in the power dept. although the 7.3 is very capable in stock form.


Bought it for 3 k put a new bed on it painted it put new wheels and tires , and other mant. parts. got 1500 and a 2002 Saturn . All it needed was lower ball joints and brake lines. I made that kids day I bet .

 

Old fashioned diesels are about as tough as they come, Gardner diesels from the '50s British trucks are still pushing third world boats around.
No frills simplicity means they produce not much power more or less forever, a 39c part and Erics truck is good to go again.
Simple diesels probably shaped history, it helped the Red Army roll back the Wermacht all the way to Berlin with their T34 tanks, they kept on going when the technically superior Tigers broke down.


Roger.

 

go to your local fuel injector shop, they make a kit with all return lines. If you ever remove pump pull all lines off together as a spider or its the devil to put them in right order. I worked for water and sewage in Pensacola. We had a lot of 6.2,s 6.5.s (worthless engine) and a lot of ih in fords and old Cummings and new Cummings, liked old Cummings the best WE only had one 6.2 engine broke a valve spring, the other 20 ran until they were sold at auction. We did change a few inj pumps, when they started leaking.dang good eng

 

Just a heads-up for anyone
who owns and drives Chevy trucks.
silveradosierra.com is a great resource
for our trucks. Check it out.

 

Yup. And mine is the end result. Bare bones truck, started life as a fleet vehicle for a major contractor, was well maintained, but beat hard - I found handfuls of mud dust up under the dash when I pulled the cluster to change the light bulbs.
I don't know how many people owned it between then and me, but it's got 280K on it now and shows no sign of slowing down.


Looks cool. Thanks!

- Eric