I decided to check the timing on the 90' tonight, the last little while I've noticed a small drop in fuel mileage and it seems that the truck has been down on power a little bit. While the timing appeared to be right around 7-8 degrees of advance on average the mark seemed very inconsistent, that is the line jumps back and forth quite a lot. The timing light was flickering on and off as well as well, I'm guessing that this is a sign that the injector or pump is missing? I noticed this same behaviour last time I checked the timing, but it wasn't nearly as bad.


I'm guessing that this is a good indicator that the pump and injectors are starting to show there age, it would seem that the timing mark should read steady normally? I have no idea how old the fuel system is, but I know that the PO would not have changed them unless the truck died on the side of the road and I've put about 45000 km on it. I haven't tried running a filter of ATF but I do add a liberal dose of Stanadyne additive to each tank. Thoughts and opinions appreciated.

 

I've seen this happen too. I assumed it was a result of inconsistent injector opening pressure, although I suppose injection pump problems could cause this as well. I'm curious to see what others think of this.

 

Its likely the timing equipment is causing the fluctuation you're seeing.
Not knowing what method you're using, some of the issues could be a dirty lumy probe, or the thing that pickups the flash from the lumy probe. Using the pulse method, the spot where you are clamping the piezo sensor might not be clean enough, or clamped down properly.

 

^^ That. That's what came to mind while reading the OP.

 

^ +3...........

 

I've got a ferret meter that has only been used a few times and timing light that us the same age. I polished the injector line clean and smooth with steel wool where everything hooks up. I tried moving the clamp and restarting, it didn't seem to make a difference. Are variations like that normal with a ferret meter? I will try the timing light on a gasser if I get a chance to make sure it's all good.

 

no.not normal.it should read steady enough to read where the lines are easy enough......but not perfectly steady.
id suspect your light.figure out why it's turning off/on.it shouldn't do that.

2k rpm
8 BTDC (+/- 2)
injector #1 or #4

try to take a reading on #4 fuel line to see if you get the same results.

 

I have the same setup as you and sometimes it takes 3-4 tries of adjusting the clamp and ground to get a smooth reading. I always check both cylinders 1 and 4 to make sure I'm getting a good reading.

 

Okay, i'll go over it again when I get a chance and report back. Thanks all for the help.

 

I had the same problem. Emery clothed the line moved the clamp half a dozen times and used a different light. Still jumps 6ish degrees iradically. Did not do this on the backhoe we timed 2 minutes later to verify the adapter was working correctly, and we didnt even clean the line.

My power and mpg are down as well, also running smokey. I, like you (the OP), have decided the pump is just done.

 

I've been thinking a lot lately about inconsistent timing on my 6.9. It's been a year since I hooked up my ferret meter, but I notice some extreme timing variation while driving. One moment it'll go advanced with tons of power and clatter, another moment it'll be retarded with no clatter and little power.
Like you guys, I'm not sure exactly how old my pump is, and it seems clear that the issue is in the pump, though in my case it seems more prevalent when running alternative fuels.

Can you guys hear any timing variation whole driving, or do you only see it on the meter?

 

I dont notice it driving, does yours surge?

 

Haven't had a chance to recheck the timing or play with the timing light anymore, all my junk is at my parents house until the shop gets built. I can't say I've noticed any audible changes in timing while driving and it idles smooth. It doesn't like cold stars though even with an all new charging system, batteries, glow plugs and starter that is only a couple years old.

 

mine is VERY noticeable while driving. it goes from one extreme to the other, or at least thats how it feels. not usually a consistent surge, more random. it'll switch suddenly and unexpectedly between retarded, advanced, or somewhere in the middle.
i haven't had a chance to play with the timing light to document the issue that way, just driving it.