IP timing questions

[Matt1031]

I've been reading around on adjusting pump timing and saw somewhere that the mil-spec 6.2's supposedly run less static advance than the civvy 6.2's. Any truth to that, or just a rumor?

There's no witness line stamped across my pump/timing cover which I thought was really strange. Anybody else come across this? I know where to look, what it looks like, and where it *should* be, but I swear there's nothing there - no line. I know I can scribe my own, just thought it was really odd that there's not even faint evidence of a timing mark. On a junkyard 6.2 I was checking out for comparison the mark was clear as can be.

Anyone try bumping the advance a smidge? Supposedly it makes for easier starts and a little more bottom end pep. I don't have a diesel timing light, so I'm going to have to go by the "if it's knocking at idle, you went to far" guideline. I'm not talking a lot - just a couple degrees to see if it's any improvement.

 

[jdemaris]

I've been reading around on adjusting pump timing and saw somewhere that the mil-spec 6.2's supposedly run less static advance than the civvy 6.2's. Any truth to that, or just a rumor?

.

Timing isn't really any different between civilian and military. Timing properly can be very confusing on any diesel.

With a gas engine, spark travels at the speed of light. So, time of spark at the distributor is the same as at the plug wire, and at the spark plug.

A diesel must send liquid fuel from the pump, through a long steel line, and then through an injector. That results in "injection lag." Timing AT the pump is different then timing AT an injector line, or AT the injector, or IN the combustion chamber. So, when you read any diesel timing specs, you have to know WHERE they are for. Some are timing the pump itself in degrees. Some are for injection midway through a line and some are for actual time of combustion inside the engine.

GM civilian 6.2s have different specs for different uses and pumps and the military specs also vary.

Generally, GM civilian 6.2, when timed AT the pump, is static timed to
TDC. Military is a range of .75 BTDC to 1.25 ATDC. So, basically the same setting. Timing specs vary by fuel cetane and altitude.

More important is where the timing is when the engine is actually running. That is controlled by an automatic advance that can advance timing by as much as 20 degrees. If it's not working, adjusting static timing isn't going to fix it. But if a little worn, bumping up the static timing can help. By doing so, you get timing at cranking a little too advance, but get more in the ball-park when running.

If it sounds complicated - that's because it is. Your crank pulley is marked in degrees. Put #1 cylinder on TDC of the compression stroke and the two lines inside the timing window of your pump should be lined up - or close. That is the static setting to get you started. The military often gives air-timing specs. Air timing tells you when the pump is at "inject" position . It's an alternative to using the two timing lines.

If you start a cold 6.2 and rev it high under no-load it should run smooth. If it breaks up a bit until warm, it's running too retarded. By "cold" I mean 40F or higher. At colder temps, it's always going to skip and smoke a bit until warm.

 

[allenhillview]

Which direction is advance if you're sitting in driver seat of the truck?
Also should I advance if only after turning up fuel a 1/16 of an inch, and which direction does that allen head go if looking at it from drivers fender?

 

[jdeoliveira74]

currently my truck sounds like it is two far advanced. With that i retarded the timing a bit. It sounds better it does miss alittle at idle. I believe my Ip pump is going bad. I pulled the check valve and cleaned it as it was full of junk. If the Ip is going bad would that make it hard to time??

 

[jdemaris]

Which direction is advance if you're sitting in driver seat of the truck?
Also should I advance if only after turning up fuel a 1/16 of an inch, and which direction does that allen head go if looking at it from drivers fender?

Top of pump gets pushed towards the driver's side of the vehicle to advance.

To turn up fuel, you have to tigthen the screw -which is clockwise.

 

[jdemaris]

currently my truck sounds like it is two far advanced. With that i retarded the timing a bit. It sounds better it does miss alittle at idle. I believe my Ip pump is going bad. I pulled the check valve and cleaned it as it was full of junk. If the Ip is going bad would that make it hard to time??

What kind of junk was in that regulator valve? If you found tiny little pieces of black rubber, you've got a broken weight retainer ring. They were only use in pumps from 1982 to early 1986. After that, the plastic was eliminated.

As far as a "bad" pump making an engine hard to time? That depends on what is wrong with the pump. Pre 1986 pumps often get the first failure due to a broken plastic weight retainer ring. Pumps made after mid-1986 often die slowly from the timing advances getting weak and finally failing. Happens even faster on military rigs run on JP8 fuel.

 

[jimm1009]

What regulator are you speaking of on the injection pump?

Do you have a reference for theis "screw" for turnng up the fuel?

I have the TMs and will research but if someone has the figure / item number that would be great for me (us).

jimm1009

 

[cucv1833]

What regulator are you speaking of on the injection pump?

Do you have a reference for theis "screw" for turnng up the fuel?

I have the TMs and will research but if someone has the figure / item number that would be great for me (us).

jimm1009

Here you go Jimm

Look through these
To crank up the fuel Click here
http://www.steelsoldiers.com/cucv/61045-fuel.html?highlight=injection+pump+fuel+screw

 

[jimm1009]

Thanks for the link but my pump was actually overhauled and set to military fuel pressure at that time.

I have advance my pump about two widths of the line and the smoke is mostly gone now.
I will drive it for a day or two locally and then see how it is overall.

I really need to find someone with a lumninocity meter now to tweak it into perfection.

jimm1009