Sticking Injector/Bad Timing??

[rdurh]

Though I think I know what the problem might be and I've done a search of past posts. However, I haven't worked on diesels that much so I'd like some input.

I'm trying to help my younger sister with her 1984 6.2L diesel Blazer. Two years ago we transplanted in a 6.2L out of a military CUCV that had a little over 12,000 on the engine. The engine ran rough at idle and while driving, and put out a lot of grey/white smoke with a strong diesel fuel smell. If you followed it you couldn't see that much of the truck. I didn't have a timing light at the time and she didn't have the money to take it to someone. I recently purchased a Snap On MT-480 timing light with the 6.2L/6.5L luminosity probe. When I checked the truck's timing it was around 15 degrees ATDC. I had also purchased a KD Tools diesel compression tester, and the guy I purchased the tester from said the adaptor would fit 5.7L, 6.2L and 6.5L engines. Turns out it only fits the 5.7L GM diesel so I need to find a new adaptor (anyone know where I can get one the information would be appreciated). I want to do a timing check on this engine, and this may not be related to the issue below. She stored this engine outside and though it had the air cleaner still on the engine it wasn't tarped or otherwise sealed from the weather. When we tried to turn the engine over by hand before installing you could turn it over 180 degrees and hit a stuck open valve, and then go back 180 and hit the same valve. An over night soaking in Marvel Mystery Oil freed up the stuck valve, but I've wondered since if she might have a pitted out cylinder bore. So I want to find an adaptor for my KD Tools compression checker and see what may or may not be an issue. Though the main issue is what I believe is a sticking injector.

The trucks EPA sticker doesn't have a timing setting and in doing a search I've found various timing settings for the 6.2L. Anywhere from 0.5 to 1.5 degrees ATDC, 1.5 to 2.5 ATDC and 3.5 to 4.5 ATDC. The manuals I purchased also have nothing for a timing setting. I set the truck at 2.5 ATDC. The smoking reduced considerably and most of the time you can't see any. However, I think the truck has a sticking injector for a couple of reasons. First, when setting the timing the needle on the MT-480 swings a good bit, going from 3.5 ATDC to 0.5 BTDC. It will steady down for a few seconds and then start wandering. (I did zero out the meters before testing) Also, the engine has a pretty good lope most of the time. Sometimes it will idle really smooth but most of the time it will lope enough to give the truck a good shake. Like a 350 gas engine with a hot camshaft. Finally when driving it acts like one of the cylinders has a miss. The truck is gutless when driving, the rather tired 6.2L we took out had more power than this newer engine. If this were a gas engine I'd be looking for a missing spark plug wire.

Any thoughts?

[john8662]

Good job on adjusting the timing.

From the sounds of things the timing was really retarded (high ATDC number) and that would explain the rather large amount of white smoking the engine was doing.

When adjusting the pump, how far over towards the passenger's side was the pump? It's possible that the pump was installed incorrectly, and not aligned with the timing mark on the front timing cover.

Engine sitting outside. That's unfortunate I must say, but sounds like you were at least able to get it going. I think in a situation like that, since the engine was sitting out of the truck, the best solution would have been to remove the cylinder heads and have a look-see.

Could have been a sticking valve (hung/rusted) open, or the cylinder could have had water in it, and was hydrolocking when rotated. I'll bet you removed the glowplugs for the insertion of the small amout of mystery oil though.

As far as an injector sticking. You can run the cylinders one by one with the engine running to disable an injector at a time until you identify which hole has the problem. All you need to do is loosen the injector nut for the line, it'll cause that cylinder to stop firing, becuase it doesn't have sufficient pressure any more to pop the injector. Sometimes this troubleshooting technique helps.

How much blow-by and oil consumption are you seeing with this rig now that the smoking has reduced?

If the blow-by is little to none you might not have a compression issue but rather an injector issue for the rough idle.

In all honesty, most 6.2's don't have stellar idle. If you turn up the idle speed screw till around 700 (since you have a timing meter you can determine the RPM) and it's still rough, you have a problem. Usually smooth out decent at that RPM.

But usually, rough idle = worn IP and worn injectors or a compression related issue.

I would figure that hte 5.7 compresor adapter would work. Have you tried to screw it into the hole, I think they're the same thread pitch. Lemme know either way there...

Hope this helps!

J

[rdurh]

...
When adjusting the pump, how far over towards the passenger's side was the pump? It's possible that the pump was installed incorrectly, and not aligned with the timing mark on the front timing cover.

The pump marks were lined up with the mark on the timing chain cover.


Could have been a sticking valve (hung/rusted) open, or the cylinder could have had water in it, and was hydrolocking when rotated. I'll bet you removed the glowplugs for the insertion of the small amount of mystery oil though.

I did remove the glowplugs to initially turn the engine over by hand and then poured the oil through the glow plug holes and also down the intake.


...
How much blow-by and oil consumption are you seeing with this rig now that the smoking has reduced?

If the blow-by is little to none you might not have a compression issue but rather an injector issue for the rough idle.

The crankcase pressure turned out to be a stuck closed CDR. Replaced the CDR with one that worked and no pressure.


...In all honesty, most 6.2's don't have stellar idle. If you turn up the idle speed screw till around 700 (since you have a timing meter you can determine the RPM) and it's still rough, you have a problem. Usually smooth out decent at that RPM.

The RPMs are around 650 to 675. If you increase the RPMs with the fuel pedal it will smooth out quite a bit but I don't know at what RPM it's hitting before it smoothes out. I'll see if I can set it with the MT-480.


...I would figure that the 5.7 compression adapter would work. Have you tried to screw it into the hole, I think they're the same thread pitch. Lemme know either way there...

You can almost get the adaptor to screw into the head. It has a threaded part and then past that is a smooth section the width of the glow plug above the heating tip. However, the smooth section is twice as long as the portion on the glow plug. I even tried on my Jimmy and it won't go into the head. Both engines have low miles, 12000+ on my sister's and 15000+ on my engine. I've run a probe down the glow plug hole in the head and I can't get any soot/carbon and I can feel a shoulder where the glow plug tip goes into the head. It is like the glow plug hole goes in so far and then narrows to a width slightly larger than the tip of the glow plug.

I bought a Harbor Freight diesel compression set, the one for $24.95, and the instructions only have information for the 5.7L and nothing for the 6.2L or 6.5L engines. There is a generic fitting that is used for some of the other adaptor combinations that will fit in the glow plug hole, but it is threaded all the way and may not bottom out where the glow plug tip goes into the head. I may try it this weekend and see what happens.

Thanks for the help.