You may be right of course. On the otherhand the unburnt fuel if that injector is really late could average through the system and seem constant or somewhat so out the tailpipe.

He is smelling unburnt fuel and the injectors have been checked I think. I might even want to do a compression check on that cylinder before going on to checking it for proper load sharing. I just went back through the thread and see that compression was good and fairly even. So I would move on to check for load sharing by the third cylinder.

Cylinder 3 was the only one that seemed normal out of the 5. The other 4 had severe carbon build up on the heat shields. If running WMO was the cause, I would expect to see all 5 injector shields in the same condition. If the timing is retarded, I would also expect to see all 5 in the same condition as well. I think I should check the injection timing next. If the timing is too retarded, I would expect excess carbon build up and WMO would make it worse than usual.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

The lack of carbon in #3 heat shield could be attributed to it falling out during dissassembly.

I don't believe so. The others were coked up enough that it would not be possible without me noticing it in the prechamber. Also, number 3 had the typical carbon build up on the nozzle. The others left the carbon in the heat shield when removed.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

I might consider also removing and cleaning out the delivery valve. The worse senario is the element has become worn on the number three . This may be compensated somewhat unless it is severe.

My limited logic would be that the element is now having to move further up the bore to generate the pressure to open the injector. Hence the raw fuel smell because of the extremely delayed timing on the number three injector. . .
Also that does indicate that the number three element can still generate opening pressure. Just later. Quantity of fuel delivered once the element is corrected may be okay.

This does tend to sound like injection pump damage from the fuel used to some extent. Not the end of the world if a used injection pump may be ultimatly required. I suspect that cylinder can be put back on line by careful use of the milli volt method. One could do it by ear once it is proved to be the issue. By ear is not the best though as by the same token you do not want any given cylinder runing hotter than the others.

Some familiarity with the milli volt system is not a bad ideal anyways. It can save you both time and money down the road on many issues. Basically it just is a method of reading the burn temperatures of one cylinder compared to the others.

Plus if you are careful and take no shortcuts can enable you to rematch the cylinders burn temperature to the others. I suspect number three is cold compared to the cylinders showing the carbon buildup and this is reflected by less milli volts on the glow plug compared to the ones showing carbon deposits when engine is running. Only takes a little reading in the archives and almost any cheap digital voltmeter meter. Everyone should own a digital voltmeter anyways in my opinion. It will pay it's nominal cost off many,many times over a persons lifetime. Useful even around the house.

Actually almost anytime you have to do electrical troubleshooting. Even if just locating an open glow plug for example.

Thanks, Barry. I am very well aware of the millivolt method and I have used it in the past to locate bad injectors, etc. The one caveat in using the millivolt method is that all the glow plugs must of the same make and age to get an accurate reading. I just replaced all 5 glow plugs a few weeks ago with new Bosch plugs, so I might just check the numbers to be sure.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Millivolt and Ohm readings at operating temp at idle:

Ohm
1: 3.5
2: 3.3
3: 4.2
4: 4.3
5: 3.3

Millivolt
1: 8.3
2: 8.15
3: 10.0
4: 10.4
5: 8.3

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Well the readings are differant than I would have expected. Two milli volts is a large millivolt spread in reality. As you say I too suspect the glow plugs are new enough for your test.

Not certain but probable. You may want to swap the number two and three glow plugs to be certain though.

It almost looks like some cylinders 3&4 Are running somewhat hoter instead of cooler. This to me is not the source of the raw fuel supply smell in my opinion.

I will give this some thought as well. Glad to hear you have used the milli volt method before. The only thing now is I expect both the carbon build up and lack of it on some cylinders may be perhaps a lesser amount of base oil getting into some cylinders than others. Or the hotter cylinders are burning it off as it forms. They are running substantially hotter in my opinion. Still this does not hold water well as number four showed a lot of carbon.

On a careful check two milli volts is too high a differeance between cylinders at the same time. I would now be curious to see if someone timed the injection pump by ear as if advanced cylinders three and four are leading that much the engine should have knocked when setting the number one element properly by drip I suspect. This on diesel oil rather than wvo.

Then with those cylinders that retarded if timing was compensated by ear . This could be the unburnt fuel smell.

As you are well aware of the importanace of the glow plugs having simular charactaristics I believe it is worth the effort of swapping say the number two and three plugs to verify what you have found. Then proceed accordingly. Even at one volt at idle is a large amount of differance. Especially when the base values are in the 3-4 mil;li volt range. Actually representing a 25 percent differance.

I know on some engines showing only a fifteen percent differance have had issues. Usually knocking though. That is where only one cylinder had an elevated voltage reading. For other members that have never used the milli volt system used carefully and as intended it can indicate a a lot. Take short cuts and can be worthless.

What you said makes sense. My next course of action will be to swap GPs from 2 and 3. I'll also look up the drip timing method and the step after the GPs will be seeing what results I get with that.

Edit: I'm still seeing some white smoke at startup when cold but less when running at temp. The smell at temp is less rich but I can still smell some fuel. Power is OK, not great. Idle has always been shaky but maybe I just need to replace the motor mounts.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Sequential injection for the power strokes is off enough to effect the idle in my opinion. Or at least the power strokes are not equal enough. Thats if swapping the glow plugs verifys the last readings of course. You should land up with a much better running engine when you get this sorted out.

Three of the cylinders coming in very late would easily cause the fuel smell I would suspect. Hindsight is great. I also suspect fuel milage is being impacted as well.

I just hope other people see how the milli volt method can find and allow people to deal with issues as your thread progresses. The more common approaches would take far longer and consume perhaps a lot of money in trying parts. Perhaps with no eventual resolution other than changing the injection pump.

At idle yours is the largest millivot spread percentagewise I think I have even seen other than with a dead cylinder. I am and have been wondering why it is two cylinders right next to each other though. Cannot decide if that is signifigant or not. Currently think not but time will tell. I think you are perhaps going to get to the point of adjusting the number three element at some point. How the number four responds to that if at all will be the answer.

One other clue that something is going on is the actual overall low readings of the milli volts at idle. Usually 6-8 millivolts is present with hot normal burns. Still this can just be the charactaristics of the glow plugs you have or the meter is not really accurate. This meter accuracy in itself if there or not is of no consequence as we both know you are using the presented voltages for comparison to each other only. I would expect lower voltages perhaps on wvo as well in comparison to diesel fuel but not certain of that either.

Before I swap 2 and 3 plugs, I am going to take the car for a short drive, make sure it is at op temp and get a second reading of the plugs. I have been running straight D2 for the last few tanks, so the fuel should not be in question at this point. No additives have been put in the tank, either.

I am using a multimeter that cost me about $40. It's not the cheapie from HF but I have one I will use as a cross reference.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Even the cheapest of digital multimeters seem to do just fine as comparison devices. I assume you are reffering to the low actual milli volt readings being presented at idle. This can occur with overall retarded timing at idle is one possible explanation.

But other than comparing with a another meter to check the actual milli volts I see it as no particular concern. The functions and dropping prices of those meters have been amazing over the years.

The first one I aquired was 100 dollars when you could actually buy something for a hundred dollars. Today I buy meters with almost endless functions for well under half that. The simplest 3.00-5.00 digital meter today is easily a match for the hundred dollar one of years ago.

Same with a twin trace scope off of ebay maybe three years ago. Like new and reasonably usable for maybe 49.00 delivered and just like new. Equal to the techtronics scopes of years ago and a less problamatic brand. My crt or visable screen was going bad and that was a cheaper option.I no longer do electronics but still like a few things around even though their use is fairly infrequent. A meter still gets a good workout for the many things I still do though. I would not want to be without one.

As to wvo usage I have no issues with that unless an individual is incapable of diagnosing or repairing even the simplest of things and then compounds that by adding wvo burning into the mix as well.. This has not worked out well for many of them in my opinion unless they were seriously prepared to learn. You fortunatly seem to be an individual that does easily know enough to burn the stuff.

Just for clarification, I do not burn WVO in my engine. I burn WMO: waste motor oil. I'm not convinced that is the cause of my current problem, though. It may be a contributor due to lack of certain tertiary parameters not being met. WMO must be burnt with advanced timing to allow more complete combustion. We have already ruled out compression and injection quality. Advancing the timing a few degrees needs to occur independent of the outcome of my current timing.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

I have not swapped any glow plugs at this point. Ran engine hard and let idle for a while at op temp after a 15 mile drive home from work.

First multimeter: on 200m setting
1: 8.5
2: 8.0
3: 8.1
4: 9.0
5: 8.0

Second (HF) multimeter: 200m setting
1: 8.5
2: 8.2
3: 8.2
4: 9.2
5: 8.3

Second reading of first meter: 200m setting
1: 8.3
2: 8.1
3: 7.9
4: 9.1
5: 8.1

Temperature readings taken at various places with an infrared temp gun.

Lower radiator housing input: 107F
Upper radiator housing discharge: 181F
Block between 2 and 3 cylinders: 195F
Oil filter housing: 172F
Exhaust manifold - directly post turbo: 221F
Turbine housing: 221F
#1 exhaust manifold: 182F
Injector pump-side flare nut fittings 1-5:
1: 107F
2: 107F
3: 108.5F
4: 109.4F
5: 109.4F

End of exhaust pipe: 133.7F

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Take a look at the temperature difference between manifold exhaust port #1 and the turbine housing. I'm thinking that retarded timing is not burning all the fuel in the combustion chamber and allowing the fuel to continue burning in the exhaust; creating more heat outside the cylinder. In some situations that can be desirable but this, I do not believe, is one of those situations.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge