6.9 Diesel Timing Questions - Experts Required.

I swapped the motor in my truck with one that was supposedly rebuilt (there is a diesel shops sticker on the injection pump).  The replacement motor did not have the timing gear cover with the RPM option.  So, I needed to swap it over from the other motor.  Prior to doing this I completed my research so I would not mess up the timing gear.  As I was going to be disturbing the timing by removing the pump, I wanted to know what the timing was before I touched anything.  So I purchased "INNOVA 3568 Digital Timing Light" and a "Gunson - 77089 Diesel Adapter For Timing Lights".  I was able to get a reading of about 6 btdc.  The light was not steady at the 2000 RPM that is required.  

I installed the new cover and aligned the static timing marks (mark on housing and pump).  Started the truck and set timing to about 9 btdc.  The timing light flashes were not consistent again (i tried it all, many different spots on the line, cleaning and cleaning the line, light coating of oil on the line, different pressures on the piezo clamp, etc).  So i contacted Gunson and after several emails they tell me the timing adapter is only good to 1700 RPM.  That's almost exactly when the light flashes stop working properly.  

I have seen many different opinions on the correct timing for this truck (5-12 btdc).  I use "Alliant Power ULTRAGUARD Diesel Fuel Treatment".  The truck starts right away and runs fine.  Have not driven it enough to determine the fuel mileage yet.  The startup smoke appears to be mostly gone now and black smoke under heavy acceleration is minimal.  

1. What is the best/perfect timing for this truck?  I have the factory service manuals but of course they used another method back then which required testing the diesel and it was the luminosity method using atdc...I believe (don't quote me on that method though).

2. Is there a lower RPM that I can use to set timing using the pulse method?  I read something about 1400 RPM but there were no details.

3.  I read something about with the better fuel quality these days (higher cetane rating) that the timing should be set more advanced then normal.  I also read the opposite.  Which is correct?

4.  I also read that you advance the timing until you hear the "power stroke rattle" then retard it until its gone".  There is a constant "rattle" at highway speed. Truck sounds a little louder then when the timing was set at 6 btdc.  Is this what they were talking about and should I back it off until it quiets down?

Going to be pulling the camper soon and want to make sure I don't damage the engine.  I don't want to take it to the diesel shop to check timing as that is why I purchased all the equipment to do it myself. So hoping the answers are here.... :)  Thanks in advance for any info that can be provided!

I'll state this right from the outset - I can just barely spell "diesel", and am fairly good at fueling them, but I've never worked on one.  Never.

That having been said, we do have a "Timing The 6.9/7.3L" how-to on here if that would help: Engines/IDI.

Ok, I haven't been through all this with a Ford 6.9L or the 7.3L with injection pump, have done a number of GM 5.7L and 6.5L all of which use the Rossamaster injection pump.

The luminosity method uses a transparent dummy glow plug in #1 cylinder, and the reason it is an ATDC setting is it is looking at the flame in the prechamber.

I went round and round with the Oldsmobile dealer after I bought a new 1978 Delta 88 Royale Diesel, smoked like a chimney and got about 10 mpg in town, 14 highway (worse than my 302 Torino wagon). I got ahold of a Rossamaster service manual and found where their internal TDC mark was, wedged the ring in that position and loaded the drive gears against the direction of rotation then put a punch mark where the reference line on the pump sat. Car ran great, 20-22 mpg in town 30 highway, light gray smoke under load, normal Diesel "clatter".

About a month later the service manager at the dealer called and said they had a service bulletin from GM regarding improperly marked pump adapters and to bring the car in. When he performed the procedure, he said that my punch mark was dead on the correct location.

On the side of the Rossamaster pumps, there is a small cover, either oval or possibly similar to a house silhouette, under this cover you will find the TDC marks for #1 cylinder, with the crank a bit before TDC, slowly turn it to TDC, if you are on #1 the scribed lines should match, if only one is visible, go around one more time on the crank.

My Alldata mentions that IHC and Ford set the timing differently, however, there is shown the same alignment marks that GM used, just remember, the pump rotates the same direction as the crank since IHC used gears for the cam drive.

Hello, I will weigh in on this later tonight. I am just headed out the door to my first day at a new job but I have some things to add and I want to have time to look up your equipment that you bought and read your post again carefully. Sorry I missed this post over the weekend. I guess I was wearing a bunny suite and hiding eggs ha ha.

Hello, apologies for the late response... hopefully I can shed some light on a couple of the issues around timing. Clearly you have done a lot of homework so I will try not to over-explain the basics.

As you mentioned, the book specification for dynamic timing is 8.5* BTDC. This was via luminosity probe method with magnetic pick-up on the damper rather than strobe, and assuming sea level air density, 1980’s diesel fuel and no turbocharger. You also hit the nail on the head with timing it yourself. Guys who actually know how to time these correctly are extremely few and far between... and most shops don’t have the timing equipment for them. Paying someone to time it for you is a big fat waste of money almost 100% of the time. Most are either winging it by ear, or are incompetent or both.

6.9-250 wrote

1. What is the best/perfect timing for this truck?  I have the factory service manuals but of course they used another method back then which required testing the diesel and it was the luminosity method using atdc...I believe (don't quote me on that method though).

This is a sticky question. The injector line pulse detection method is a proxy and there are extraneous variables that will affect the numerical reading. Don’t get too hung up on the actual number, because it isn’t accurate, it’s a reference point. Timing these is both a science and an art. Having a light to establish the reference point and keeping track of how many degrees you adjust is the science part. The trial and error of finding the sweet spot is the art. Even the factory specification of 8.5* might not be where it runs best for your set up and under your conditions. The sound/rattle of the engine may help you know which direction to experiment in, but is not a very accurate indicator of “right” timing. You really need to drive it and see how it acts. Start with whatever your light says is 8.5*. Advancing it typically will give you a harsher rattle, easier starting, and will push the power band lower in rpm’s. Retarding the timing will push the power bad towards the mid and top rpm’s, have a less harsh rattle, and too much can make for harder starting. (Hence the cold idle advance solenoid on the injection pump). This is why some give the advice to time it, and while at operating temperature apply 12v to the cold advance solenoid and you should hear the rattle change to a harsh Powerstroke-like sound. Retarding the timing will also make a HUGE difference in spooling a turbo if you have one. If you are struggling to spool or build boost, retard the timing. Just play around with it, keep notes and keep track of the position of the IP housing marks and find where you want to run it. Seems like most NA guys like somewhere between 6-9* Turbo guys favor the lower end. I’ve heard of people finding happiness as high as 14* and as low as 4*. But again, remember the numbers are just reference points, not absolute values. That’s just what their timing light output read.

2. Is there a lower RPM that I can use to set timing using the pulse method?  I read something about 1400 RPM but there were no details.

If your timing light gets erratic at 2,000 rpm then you obviously can’t use that. Spec is at 2,000 rpm for standardization, but should be consistent at 1,400 rpm also... just a different value. You are kind of throwing the numerical portion out the window anyway. Just use the same rpm each time you do it... wherever your light is stable. Some years back everyone used the Ferret pulse adapter, but evidently they are out of business. The Gunson looks to be about the same thing, but I’ve not heard many reviews on it. I was looking at the Kent Moore J33300 which uses an injection line pulse, but also a vibration damper magnetic pickup instead of a strobe. It was just expensive... and now appears to be unavailable. However I did see that a new meter (DTI Tech-Time 3300-S) is nearly identical and far  more affordable. I may pull the trigger on this before it too becomes unavailable (separate strobe is available if you want). According to the eBay ad this is what the military uses to time humvee.
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F291925919893
Here is a video showing the Kent Moore meter:
https://m.youtube.com/watch?v=7pZK5Pwe22g

3.  I read something about with the better fuel quality these days (higher cetane rating) that the timing should be set more advanced then normal.  I also read the opposite.  Which is correct?

Today’s fuel has a higher cetane value but is more lean than it used to be. You can’t get the same mpg that you could in the 80’s and it does not lubricate nearly as well. I have not heard of any need to correct the dynamic timing value, just tune for best power and efficiency. A pyrometer helps detect efficient burn.

4.  I also read that you advance the timing until you hear the "power stroke rattle" then retard it until its gone".  There is a constant "rattle" at highway speed. Truck sounds a little louder then when the timing was set at 6 btdc.  Is this what they were talking about and should I back it off until it quiets down?

Timing by ear can give you a clue, but don’t give too much credit to this or that subjective sound evaluation. I know there are guys out there who swear their ear is better than any meter. Experience counts for something, but these things can run far out of time and give you confusing results. The owner of R&D is very experienced with timing and tuning IDI’s. Yet a couple years ago he decided to do an off the cuff IP swap to a four plunger pump at the annual hunting for horsepower competition. He timed it to the best of his ability by ear and pulled a respectable dyno run with it. Back home he checked it with the light and it was at 23*.... almost 15 ahead of factory spec. That’s how inaccurate an experienced ear can be on a new install.

Going to be pulling the camper soon and want to make sure I don't damage the engine.

The IDI is extremely forgiving. The performance will suffer if the timing is way out, but it won’t hurt much. Ignition timing does affect peak cylinder pressure, and can contribute to head gasket failure if you are running a lot of boost. But you are well within the range of good timing already. Biggest thing for towing is watch coolant temps and make sure your fan clutch is kicking in if applicable. Also watch for excessive black smoke. NA engines are easier to over-fuel and can reach piston melting temperatures if run too hard for too long with too much fuel. I can tell from your post that you are a particular and attentive owner, and I’m sure you will be fine! Enjoy your trip!

Thanks for the replies!

Not having a turbo I did not consider getting a pyrometer, possibly look into though.  

I always keep an eye on the coolant temp.  The fan clutch is working for sure.  The first time I heard it last summer, it sounded like the motor was in the process of blowing up, lol.  

You are welcome, and I hope it helps you find a timing spot that you are happy with. Most NA guys don’t have a pyrometer. They are a bit on the expensive side, and usually you know there is a problem by the clouds of black smoke. And I agree that you can prevent engine damage without consulting one... but it can also be used as a tuning tool or a driving aid if you see it starting to spike. Unlike gas engines that run hotter when lean, adding air (turbo) lowers EGT’s and overall engine temperatures. It’s cranking up the fuel that makes things get hot. If you do a lot of heavy towing you might look into picking up an inexpensive used turbo kit. Not that it can’t do the job without one, but it will be a more enjoyable experience and will actually run cooler and have better fuel economy with one. And yes! It sounds like your fan clutch is working! When that sucker kicks on it’s like a tornado under the hood. It doesn’t mess around 🌪