Author Topic: Help needed: pump operation/theory question (Read 4711 times)

v8volvo · « **on:** August 17, 2004, 04:22:40 am »

Hello all,

I have a couple questions that you, the Bosch pump experts, seem to be probably the most able to answer.

These regard my ever-continuing and frustrating attempts to figure out why my car smokes the way it does. I forget if I posted here about this before, but basically the problem is that, when warm, it smokes badly, a blue-silver-colered smoke that is present at idle, cruise, and acceleration/hill climbing. It is accompanied by significant oil consumption. It has fresh injectors, timing belt, oil change, fuel filter, and I have verified pump and cam timing umpteen times. There is no air in the fuel lines, and the pump does not leak. I believe almost to certainty that the compression is very good, as it starts immediately even if I do not use the glow-plugs! It was supposedly rebuilt 90,000 miles ago.

Of late my main goal has been to try to establish if it is engine oil or improperly-burned diesel fuel that is causing the smoke. To that end I performed a test wherein I descended a hill coasting in 2nd gear (clutch engaged) at about 25 mph and my dad drove another car behind me, looking for smoke. Apparently it puts out a considerable amount of blue smoke even then. So, the question: does that definitely mean that that's oil burning in there, or is the pump injecting enough fuel under zero-throttle elevated-RPM conditions to create smoke? I'm not familiar enough with the operation of the fuel governor to know the answer to this, but it seems most people say there IS fuel going in, as opposed to the new TDI motors, whose brains recognize a negative-load situation and totally cut fuel injection off. What is the truth, and could it affect my problem? :?

Other question: there has been some debate as to whether or not oil burned in a diesel engine's cylinders will show up as blue smoke at the tailpipe. Since it does use more oil than I would think it should, and the issue only shows up after the engine has had a chance to warm up some, lowering oil viscosity so that it could get into places thicker oil couldn't (like past valve guides or oil rings), I think it's oil, but to be sure (before I tear into the engine) I'd like to try as best as I can to determine for certain that it is NOT related to fuel. I plan to perform a compression test and to set the pump timing with a dial indicator in the next week or so.

Anything outside of rings and valve guides I should consider as a way oil might work its way into the combustion chamber?

Thanks in advance for any help.

QuickTD · « **Reply #1 on:** August 17, 2004, 06:44:22 am »

If it's using significant oil, and it smokes blue, I think that wraps it up. It's burning oil. Desels will smoke blue when consuming oil. It may have got a "quickie" rebuild when it was done 90000miles ago. Blue smoke caused by fueling issues tends to be worse when the engine is cold and improves greatly as the engine warms. Oil smoke is the opposite.

Greasemonkey · « **Reply #2 on:** August 17, 2004, 07:57:09 am »

Quote from: "v8volvo"

It was supposedly rebuilt 90,000 miles ago.

key word here is supposedly

Quote from: "v8volvo"

Anything outside of rings and valve guides I should consider as a way oil might work its way into the combustion chamber?

Thanks in advance for any help.

possibly head gasket, even a cracked head. A compression test and if necessary a leakdown test will reveal all. Like quick said though, all signs point to a general engine wear problem.

DieselsRcool · « **Reply #3 on:** August 17, 2004, 11:23:42 am »

Rings! They all need rings and a valve job.

If you just pull the head, drop the pan and do a quickie hone and rings it'll do for a little while. I've been down the quickie road a number of times. I'm at the point I won't mess with anything but a td and I won't do a quickie again. Just do it! Fix it right and you'll love the way it runs.

janb · « **Reply #4 on:** August 18, 2004, 05:24:25 pm »

agreed, most likely rings

when you do a compression check, you can add a SMALL amount of oil to Cyl, to seal the rings, that will indicate valves if compression does not improve

I too have done the 'in-frame' econo rebuild. But when you compare the power of the 'econo' vs, a full rebuild (to say nothing of the improved oil pressure when you replace intermediate shaft bearings) It is worth the trouble to do the 'full-meal-deal' (unless of course you are broke, like I usually am) Econo is ~$80 - $100 (without head work)
full = ~$250 (w/o pistons) + $250 for head

v8volvo · « **Reply #5 on:** August 19, 2004, 03:00:32 am »

Well, sounds like the consensus is...rings. Like I sorta expected.

Is it possible that 1. they never seated and need something to make them do it, like Bon-Ami treatment? or 2. they are stuck in a piston groove or engine caking/sludge or gum is otherwise causing the problem? I heard that cleaning up the engine's innards is sometimes pretty effective--is there an engine flush/cleanser that you guys recommend? Current plan is to keep driving it for awhile, use biodiesel and synthetic oil, probably run some ATF or SeaFoam or Marvel Mystery Oil or Restore or something in the crankcase for several thousand miles, and if things don't start to clean up, I will start planning for a re-ring. Or maybe do a TD swap while I have the chance.

Thanks for the help.

farkman · « **Reply #6 on:** August 19, 2004, 06:22:00 am »

v8volvo

For the engine cleaner, I've read a lot of good things about Auto RX. It's not some quickie engine flush, rather you leave it in the motor for about 1500 miles and it slowly cleans the engine. Then you change the oil and do a rinse phase on dino oil. I just ordered 4 bottles on Tuesday because of all the good things I've heard. You can read more about it at bobistheoilguy.com and auto-rx.com.

Peter