?? How do I adjust diesel timing?

 

Fn74 What are you using as the CPS timing mark ? kinda hard to tell in the pic with that angle but it should be the pointy metal mount that sticks out over the damper and not the tit on the CPS itself. Look at # 1 in this pic.

Vet I think kwik is refering to the VW diesels he wrenches on as far as adjusting timing, you have to pull the motor and reset the teeth on the gears on the powerstrokes.

 

Did you follow the directions to the T? I always double doubt myself and I have no hair left. I want to know exactly what your AE says. How does the truck idle. Any shakes or is it just smooth? Will diesel take over its own design and run at 180 off just by firing on the fuel left. Can it be enouph degrees off to allow for some of the valves to work right? I think you would have ejected a valve if you were off something like an odd degree but 180 might work. Someone tell me Im wrong Im just throwing out ideas and talking aloud.

 

On the older mechanical diesels you loosen the pump and move it like a gasser distributor.

 

Dang, I forgot all about pulling the CPS and now it's evening. I'm going into work tomorrow for the day to do chores and fix my air horns. I'll add that to the list and post.

 

I might doubley double check myself. It does act like timing. Even though it was only 9 hp and 30 lb-ft on the dyno, my F5 3 and 5 are night and day differance in driving. And a lot of that is timing. But what I do know is that there was a distinct change in startup and low rpm boost right after I changed the head gaskets from the Cometic back to stock. At least until I turned up the power. There has never been a sudden change in the way it runs. The guy who built the motor has built a few hundred race engines before, but never a 7.3. He mentioned the timing was as easy as it gets. Not even a chain to worry about. And he never removed the gear from the crank or the cam. I am about ready to drive to Swamps in Tennessee to get this figured out. Although I might stop in Seattle first........

 

If you decide to do that, let me know so that I can schedule some time to devote to looking at your truck.
Sometimes I get slammed and each minute needs to be budgeted.

 

What is the thickness of the stocks vs the aftermarket head gaskets? I know that on our race engines the copper head gaskets came in diffferent thickness for the heads and blocks that we decked. Once again you would have ejected a valve through the hood if it were too close.
How about rods being too short? Lots of compressed air but a midget swinging a digging bar.
It has been known for unfamiliar guys to put the pistons in backwards.

Maybe I need to go back to the top and re-read everything that you had done. Would calling the engine rebuiler and alot of foul words help?

 

KennedyFord, I have to agree with you that the common denominator here is the new engine in all of FN74's troubles. It seems all the externals have been checked and/or replaced with zero effect, and now it's time to start looking at something flukey like cam timing or short rods or something like that.
The thing that really needs to be adressed is the the cause of the super quiet idle. Whatever is making that happen has to be the cause of the too-high egt's and the rest of the trouble.
Could it be that the programming is running in some sort of default mode for the first few seconds and then it realizes that something's amiss and it starts to compensate or something like that because the normal sounding engine returns? This is just a guess/theory that I am pulling out of my southern extremities.

 

So the engine and rods are stock.....but the pistons have been replaced. Ill make a phone call to good ol dad and see if my suspicions are correct about the pistons backwards. Is this your old block?

 

Since we seem to have narrowed this down to a possible timing issue, at the risk of sounding overly simple, might want to try another CPS just to eliminate that. Don't know if that could alter timing and still work but who knows? At $25 a piece now it might not be a bad idea.

Also, I seem to recall that there is a gap requirement and shimming for those when they act up according to the shop manual. May want to have a look at that too.

To summarize, timing is determined from CMP, if that is OK and injectors are firing (good contribution test #s) something is laying down when getting on it. CMP signal too weak, chip tuning not right, or it is defueling. Any idea what #s your map is seeing? What kind of HPO #s are you seeing when it falls off?

 

Dan- The super quiet idle is actually not near as prominent since I replaced the Head Gaskets. But I do know I have to wait for the glow plugs to cycle before it will start, even when it is 55 out, and it smokes a fair amount until warmed up. I KNOW for a fact that the Cometic head gaskets were leaking under load. Everytime I got into the throttle hard, it would pressurize my coolant system and push antifreeze out the refill bottle. But ONLY under heavy throttle. And it didn't do it in Denver, or high altitudes. So I replaced the stainless steel Cometic Head gaskets with stock ones. And it seemed to run better for a day and a half, although I never pushed it at all. My boost was without a doubt more responsive. So after a couple warm up periods, I got into it and nothing. There was no sudden change, but the truck just didn't respond. And now I have a lot of the same symptoms as before with the known leaking head gaskets.

However I know stock HG don't just ooze, they seal or they don't. The thing idles fine, drives good, doesn't miss, Rotational Velocity was basically 0 on all cylinders. Doesn't leak antifreeze anymore. Had I rebuilt a stock truck, one would never know anything is wrong.

Another thought that had crossed my mind was I know long block was rebuilt using Mahle Pistons which are apprently a little shorter to compensate for decking. But then if that was the case, my compression should show up low, not at 400 wouldn't it?

 

Your still compressing air, its just stopping short. If you go to compress, larger area has more air, not enouph fuel because alotted amount is sprayed and combustions occurs but there is not stroke left....basically the math involved with decking, shorter gaskets and shorter pistons its like you have destroked the truck. Boost is just the gassious reading of pressure. In my mind its like you have a giant air compressor. Am I making any sense or is it just my mind?

Mental pic...lil midget quick response no arm reach

 

Ok call back from dad says that this engine do not have the notched pistons that makes putting them in backward criticle like the idi engines.

He says you need to know what the piston height change is to calculate your compression ratio. He says that the 400s seems low when the older engine he rebuilt was in the 500s. He doesnt rebuild them now so he is not refreshed on this engine specs but it (comedy) sounds like its a good compressor.

Did you have a dino diesel smoke color? Blueish is what he said it may be right now with your problems and glow plug start only.

 

IIRC, there were several NLOC guys that had problems with the Cometics not sealing right due to different procedures required during installation. If you want I can try and find out what they did to get 'em to seal up.
I'm by far no expert, but it sounds like you may have pushed another head gasket. If thats the case you could find imperfections in the decking surfaces or casting in the block or head. Could be the cam timing, which will make the entire RPM range very soft. Also sounds like it could be tolerence stacking with your piston-deck height, or a low static compression ratio. As i'm sure you know, dropping compression will soften power throughtout the RPM range unless upping the boost considerably, IMHO allot more than 35 psi. I suppose in theory you could lower static compression without loosing much cranking compression, but you would have to change LSA of the cam to do it. I don't thing it could be done with just changing cam timing.