Funky timing issue.

So I retimed my 90 7.3 today. Again. For like the third time in a week

I timed it to 8.5 btdc. Truck ran like crap, got 16mpg. I've gotten 18.2 in the past on diesel

I also had an odd hesitation just off idle under load

So I thought something was off. Timing marks, meter issue, loose nut behind the timing light......

So since I marked it when I originally timed it by ear i set it back to where he marks were.

Ran it for a few days. Mpg and power are back. No hesitation.

So I checked the timing again. Where it was set by ear. Over 10 degrees btdc

So. I walk away. Come back to it again. Reset to 8.5. Same thing low power. And hesitation is back.

So tonite it's back to the 10.5.

I had no grey smoke at 8.5

So. Thoughts are:

Meter is off?
Marks are off ?
Pump has an issue under load?
Injectors have an issue under load?
Operator is a nut case?

If........ Injectors pump timing marks and meter are all in good working order what's the down side to 10.5 degrees before top dead center?

NTOLERANCE said:

...
So. Thoughts are:

Meter is off?
Marks are off ?
Pump has an issue under load?
Injectors have an issue under load?
Operator is a nut case?

If........ Injectors pump timing marks and meter are all in good working order what's the down side to 10.5 degrees before top dead center?

Click to expand...

IF all is true and as it should be, and IF all is performing without error, and IF operator is not a nut case, then the only problem which comes immediately to mind is that having the timing too far advanced can burn your glow plug. You might have to replace the glow plugs significantly more frequently than normal.

However, I suspect that one of the above mentioned conditions must be true. Something isn't right.

I agree something is out of whack. I'm leaning towards pump and or injectors

So why would a burn glow plugs? Would they just fail? High egt?

I'm not sure just why the advanced timing would burn glow plugs. I'm not absolutely sure it will. However, I seem to recall that it will. I'm pretty sure I've read it here on the forum.

You're going to have to wait for somebody else to give you a better answer than my "definite maybe."

Lets look at a few things to answer as there isn't enough info...

1st What are you using to TIME the engine?

2nd How old are injectors and or the IP?

3rd have the injectors ever been pop tested.

I'm thinking that maybe yer ok on timing but the pump and or injectors are long in tooth...

So answer those questions so we can get a better idea of what's up

JM2CW

Al

If the timing is changing then the pump is shot. Bad injectors or either working or not working. When the spring weakens they do not get stronger and pop at higher pressures. Are you burning number 2 diesel or a mix of other fuels. You do know the number 1 and 4 cylinders time the engine exactly the same. Might try either cylinder and see if the timing is different. The might tell you if those 2 injectors pop the same.

riotwarrior said:

Lets look at a few things to answer as there isn't enough info...

1st What are you using to TIME the engine? - Mac timing adaptor and light. Worked fine on my 92 and my friends first gen cummins

2nd How old are injectors and or the IP? Pump was a stanadyne rebuild. Unknown mileage

3rd have the injectors ever been pop tested. Nope.

I'm thinking that maybe yer ok on timing but the pump and or injectors are long in tooth...

So answer those questions so we can get a better idea of what's up

JM2CW

Al

Click to expand...

I'm on straight pump diesel till a figure this out
I think my pump and injectors are a mismatch. I have another set of used injectors.
I think the timing moving around is still the loose nut behind the meter.

as gary said, try on cyl 4. I fought long and hard with a truck recently. could not get to time. tried cyl 4, timed up no problem.

Timing can be done on any cylinder but only if you know that cylinder offset. I had it here once but seems to have grown a pair of legs and walked off. Or its hiding from me. Who knows. Funny thing is both 1 & 4 time the same. Well the same if the injectors pop the same pressures.

When you time the engine using #4 do you set it at zero?

nope. still the 20 degrees. number 1 and 4 are companion cyls

Ok. Where is 10 degrees on the tab? All I can find is zero.

I cannot get to number one on the van. Too muc crap in the way. So Im on #4 at it's at zero.

http://vid30.photobucket.com/albums...6-BF0D-489E-90E1-E20F0390FE31_zpstcis3mws.mp4

Video

If I advance my meter the yellow timing mark line up towards the center of the engine
I thought that rotating the ip top towards the pass side of the vehicle was advancing. If I do that it moves the timing mark down and away from the center line of the engine. I have myself confused

tho not directly timing issue your dealing with,,i can tell you from experience,,you advance it toooo far,,youll def burn gp's...been there..beru's....