Timing and Cold Advance

[njdevi11]

When I got my 6.2 in my jeep it had a hard time starting, I advanced the timing about 1/16th of an inch and it starts pretty easily now.

When I noticed that my cold timing advance switch is broken and stays on no matter how warm the engine is. The engine runs fine (aside from some surging when I push it hard). I was told that if I disconnect the cold advance circuit when the engine is warm this will go away. However, even if the engine is warm and I disconnect this circuit, the engine will begin to sputter and stall.

Do I need to advance my timing more?

[Robyn]

First off

Welcome to TDP :D:D:D:D:D
Good to have you with us. :)

Looking at the pix I am suspect that the IP may be a high miler. With the tendency to stall even after warm tells me there may be issues within the IP.

The Cold advance switch in the head should shut off the advance and the fast idle after about 5 minutes or so of running.

Check the fuel return line to be sure its flowing fuel back to the tank.

At this poit we need a bit more info about your engine such as age miles ect.

Be sure the fuel filter is clean and flows free. Also be sure the lift pump is working good and supplying pelnty of fuel up to the IP while cranking and running.

Also make sure you are not getting air into the system. This can be done with a clear plastic hose connected to the fuel return off the top of the IP.
Submerge the hose in a jar of clean fuel and run the engine at idle. There should be no air bubbles coming out of the clear tube. If you have bubble find out where the air is getting in and fix it.

Good luck and let us know :)

Robyn

[twaddle]

Check that the external lever going down the side of the pump body is not sticking at its pivot point. This may, if I'm not mistaken and Robyn can correct me if I'm wrong, cause similar symptoms.

Good luck

Jim

[njdevi11]

When I got the engine I was told it had 85000 Miles on it, It looks like the injection pump was either replaced with a rebuild or rebuilt because it has paint over some of the screws that the use to see if you've taken it apart.

As far as I know the injectors are original. I have been over the fuel system a few times and cannot find any air leaks. I already have a clear line installed on the return (the line at the bottom of the engine) and do not see any bubbles.

The original fuel filter/heater setup has been replaced with a generic inline filter. The lift pump is an electric putting out 7 psi, its wired directly to a switch. I know an obstructed return path will cause timing to retard more, as far as I can tell the return paths are pretty clean and I've ran a tank or so of sea foam though it. (sea foam is the reason I had to replace my rear seal, I put it in the crank case and it cleaned up the crap that was keeping it from leaking)

Is advancing the timing any more going to be seriously bad? Can I try it and if that doesn't help move it back?

The engine runs and sounds like it should with the advance circuit energized. I feel like I should also mention that this weekend I was replacing my rear main seal and found my timing chain to have a little more slack in it then I think it should, maybe .5"-.75" deflection. Now my opinion in this is completely worthless because I have no idea how tight a timing chain is supposed to be to begin with.

I think i'll try getting my hands on a higher flow filter or possibly put back the filter heater and see how that works.

[njdevi11]

Check that the external lever going down the side of the pump body is not sticking at its pivot point. This may, if I'm not mistaken and Robyn can correct me if I'm wrong, cause similar symptoms.

Good luck

Jim

I'm not sure what lever you are talking about... The throttle? I know there is a TPS on one side and the throttle linkage on the other which side is this lever and when does it move that it would stick?

Robyn: I forgot to mention in my previous post: I am aware that the cold advance switch is not functioning and am manually "simulating" its function by deenergizing the circuit when the engine gets warm.

Could this be an improperly set fast or slow idle?

[twaddle]

Hi there,
If you look down the side of the injection pump (on the passenger side of the vehicle) there is an external lever which pivots at the point where it is connected to the pump body, right down at the bottom of the pump body it pushes a spring loaded plunger which if my memory serves me right adjusts the pump timing as required. (been away from my old 6.2 M1008 pick up for a while as I've been using my 96 6.5 Suburban so I'm not up to speed on the 6.2 as I used to be).
The lever can jam at the pivot point which could mean that the pump is not operating or adjusting itself to the correct timing.

Sometimes this plunger right at the bottom of the pump body can also stick as crud can gather inside the lower parts of the pump and cause it to stick in one position instead of move freely as the external lever moves.
It might help to use a torch or light to see what I am talking about.

As for timing chain wear, I seem to remember that if you hold it side on and try to move it sideways there should be no more than .5 of an inch of play, anymore than this means the links, rollers and pins are worn.
Might be the time to change to gear drive.

Regards

Jim
PS. Yes you should be careful about taking the pump timing too far out of spec as this can cause severe overheating of the engine due to the timing of fuel injection being way out.

[wthif]

The original fuel filter/heater setup has been replaced with a generic inline filter.

Not good. You need a water separator / fuel filter with diesel fuel. IIRC the clearance inside the IP will not like the water and water doesn't combust easily ;). There are other reasons to keep the water out too. Though I doubt this is your problem, but fix this quickly.

[Robyn]

I am still suspect that there is an issue with the IP.
The unit definately needs a good filter/water seperator.
I have a Racor 230R2 on my dually now.
Water entering the IP will very quickly rust the finely machined parts and cause serious damage if let go.
The Racor I mentioned has a see through bowl and a drain.

The IP can pass water but as has been mentioned it does not burn well :eek: and the damage it can do is serious :(

The only real way to know whats going on is to get the IP tested at a reputable pump shop along with the injectors.

If there are issues this is outside the pervue of most of us.

Let the IP guys do that stuff.

If any amount of crud has entered the IP and been let sit the pump could have serious issues.

The timing chain when new is snug. I have found that a new chain is usually all thats needed to bring things back up to snuff.
I have seen rigs with 200K and the chain was sloppy and the sprockets were fine with virtually no wear and a new chain was all they needed.

With what you are describing I would yank the IP and get it checked.


Good luck

Robyn

[njdevi11]

Next step is to find an IP guy around here, diesels are not to popular around where I live and anybody who does it is real expensive.

I waited a little longer and got the engine temp up a little higher last night and when I disconnected the advance the engine stayed on and worked well. I think the other times it just wasn't warm enough yet.

I think I got a little water in the fuel system last night and i'm going to go bleed it out to see if I can clean it out. I sunk the jeep up to the top of the engine last night and it was a little weak on the way home...