I'm pretty confident that the timing is off on my new IP install. I've been looking at setting the timing, shops (nearest I would trust 1/2 hour away) are asking over $100 to touch it. Poking around I see K-M time-n-tach's for $250-300 with the optical and/or piezo, and the $60 piezo for the injector line. I have a timing light. Does anyone have the piezo set-up and if so does it work? Also do we have 6mm or 1/4 inch lines (although I would think they may be the same - pretty darn close). I'm having trouble biting off $300 for a diesel only tool when I have exactly 1 diesel, but I don't want to wast $60 on something that doesn't do the job.

1/4" = 6.3mm

Slip the corresponding open ended wrenches on and which ever fits is the line OD.

Way back when I owned a 6.2 (279k miles total), I found that I could feel when it was right simply by trying advanced, neutral, and retarded. They all felt different, and I picked the one that felt best. I never once "wished" that I had the tool(s).

The GM light duty diesel engines are the easiest to "ballpark" tune. If the IP is reasonably close to the factory timing marks, the engine will start and run reasonably well. The finite difference of exact timing will be negligible to most operators. When fine tuning for optimum mileage or power, small gains can be made but for most folks, the factory setting of lining up the timing marks or slightly advancing the mark on the pump toward the driver's side will suffice.

I've worked in dealership shops where the latest and greatest equipment was available, being spoon fed to us by the factory as part of an "essential tool order". The timing devices worked when new but quickly degraded with time. The luminosity probe units suffered frequent damage from techs who overtightened the probe, breaking the glass, leaving less than desirable results. Even gentle use sometimes resulted in "crazing" or "clouding" of the probes. The times I saw techs using the piezo sensor units, they were questionable at best. Some guys could get a good "read" and others never did. After numerous trys at electronic timing devices, I found setting it by using the marks to be sufficient in normal driving applications.

Poking around I see K-M time-n-tach's for $250-300 with the optical and/or piezo, and the $60 piezo for the injector line. I have a timing light. Does anyone have the piezo set-up and if so does it work? .

Yes, it works fine as long as you know how to use it. And, if you find out the timing is off, what do you plan to do to fix it?

There are two timing settings, not one. When you install the pump, and/or shuffle it back and forth on its mount - that adjusts only the static/initial timing. That determines timing when you are first starting the engine, and at low RPMs. It is supposed to change and advance a lot more as the engine revs up. Usually 12-14 engine degrees more, which equals 6-7 degrees at the pump.

What usually gets worn is the timing advance, which is separate. It acts by hydraulic pressure and RPMs. When it gets worn, it gets slow and the engine tends to skip, smoke, break up, etc. at higher RPMs.

When you use a magnetic pickup (microphone) to run a timing light, you need to know what timing figures to use. Diesel timing specs are different than gas - because a gas engine uses electricity that travels at the speed of light. A diesel relies on a flow of diesel fuel and enters the engine and causes ignition - so timing figures can be expressed many ways.

For example, sometimes timing is expressed AT the pump. When a pump injects fuel, it happens a bit before the actual time of ignition (called injection lag). Also, one degree of timing at the pump equals two degrees at the engine flywheel. Same with pump RPM, which is half of engine RPM.

General Motors often expresses timing for a 6.2 as engine degrees at time of ignition and NOT time of injection. That is different than what a piezo pickup will read. They can differ by 3-5 engine degrees. Timing at 4 degrees BTDC read with the Piezo tool and timing light will equal around zero degrees (TDC) with a luminosity probe that GM uses.

Also, as I asked previously, if you find out your pump timing is not advancing properly - what are you going to do about it? Some people simply loosen the pump and move it - and that changes all the timing. It's a band-aid that sometimes works to a degree, but is not a fix. The Stanadyne DB2 pumps tend to get a worn pump housing where the advance piston rides. That's what usually causes the advance to get weak.

Did many. was always able to time by feel/ear. Start with the marks lined up. Creep to drivers side till sounds slightly marbley was how I always did it.

ive done mine by ear as well, you get used to the 6.2 rattle and its pretty easy to figure out.

If you loose power, go the other way with the pump.

My problem is that I don't know if the static timing or fuel is off.
Even with the marks aligned it's very noisy under cold advance and 'pings' under light throttle even when off cold advance. What that tells me is that timng is way off (like a tooth on the gear.....) or I have a serious fuel issue with my new lift pump or the replacement (used off a good truck) IP. Right now I'm afraid to drive the truck because the pinging is so bad.
So what I'm looking for is some way to get a baseline reading of where I'm at and then to follow up with adjustments. If the static timing is set correctly and I get no advance then it's time to spend the $300 and get a resealed and calibrated pump. If the timing is way out but advances properly then I can fix that.
Tuning by ear is great, particularly if you have an ear tuned to your motor. Mine has never been right due to the worn out IP, so I don't 'know' what a 'good' 6.2 rattle is. All I know right now is that something is very wrong. And it's rapidly convincing me to go back to gas. For what I have in this thing for parts and time I could have built a real nice L6 and gotten almost the same MPG, and gas is $.30 cheaper....

My problem is that I don't know if the static timing or fuel is off.


Most injection pumps that have over 100K miles on them have worn-out or slow advance systems. It is the first part of the pump to wear. That causes retarded timing when driven at highway speeds. But, often, when a pump advance gets weak, someone "times by ear" by simply loosening the pump and moving it. That then brings back some advance at higher speeds, and too much advance at lower.

A very-general rule-of-thumb (to check timing a higher RPMs is this). Start the engine, and before it warms up, rev it up while in neutral. If it revs high without skipping, the timing is in the ball park. If it breaks up under no load while cold, but smooths out when acutally driven - or when warmed up - it's a bit too retarded.