Miss at Idle After IP Removal and Timing - PeachParts Mercedes-Benz Forum

npretnar · #1 02-07-2013, 09:20 PM

I got the IP timed today. Had a thread going on that earlier ...

IP Timing Issues

Now my car starts up real quick without any problems and through a normal glow cycle but idles rough and seems to miss. There is a lot of clanking and nailing going on too, whereas prior to pump removal the car ran fine and was nowhere NEAR as noisy as it is now.

I tried adjusting the rack damper but that didn't do anything. It sounds like the old Massey-Fergusson my grandpa used to have –– lots of clanking, injector noise. Should I just give it a diesel purge and see if that works?

What could be causing the miss?
I'll post a video tomorrow to show what it looks/sounds like.

barry12345 · #2 02-08-2013, 12:46 AM

Did you shift the injector timing much? Might account for some increased noise.

Just re read your other thread on this . You have to get the drip timing actually dripping or working still. Without that the timing is quite possibly not right and could easily make the engine sound noisey..

npretnar · #3 02-14-2013, 10:56 AM

I did a diesel purge and changed the filters: that helped a little. Rechecked the timing, and it's at 25-BTDC, whereas before pump removal the timing was at about 26 or 27. The diesel purge helped the rough idle along with adjustment of the new rack damper bolt (just a year old) but it still misses occasionally, especially at cold start up. I put my stethoscope to the injectors and have hard nailing on 3 and 4 even though the records I have from the previous owner show that an Indy shop replaced the injectors 20,000 miles ago.

I believe a bad injector (or two) could cause a random misfire and contribute to hard starting conditions. Can somebody confirm this?

cho · #4 02-14-2013, 11:35 AM

Quote:

Originally Posted by npretnar

I did a diesel purge and changed the filters: that helped a little. Rechecked the timing, and it's at 25-BTDC, whereas before pump removal the timing was at about 26 or 27. The diesel purge helped the rough idle along with adjustment of the new rack damper bolt (just a year old) but it still misses occasionally, especially at cold start up. I put my stethoscope to the injectors and have hard nailing on 3 and 4 even though the records I have from the previous owner show that an Indy shop replaced the injectors 20,000 miles ago.

I believe a bad injector (or two) could cause a random misfire and contribute to hard starting conditions. Can somebody confirm this?

yes 2 bad injectors can do that,... wrong adjusted valves too,air in lines also,did you re-check lines
after putting it all back?

you can loose a bit line on injector to see if nailing goes away...

it is symptomatic that you have those nailing's after IP removal

if I were you I would check 2 suspicious injectors (or better all of them)
and as a must, lines for air leak.

and what about putting IP back to 26 dg?

fourth option is rare but it has happened before - bad new fuel filter.

edit: post a video if possible

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npretnar · #5 02-14-2013, 01:25 PM

Not the fuel filter: it was banging before i replaced it ... but here's some further diagnosis ...

The car has A TON of power out of the gate even when cold. This morning, she started rough but shot out whenever I gave it power. Also, If i over rev in first gear or reverse or even neutral, it stalls out coming back down to idle occasionally. I'm thinking the timing may just be too far advanced, hence the extra power. I'm going to try retarding it one-degree and see if that changes anything.

whunter · #6 02-14-2013, 06:33 PM

Quote:

Originally Posted by npretnar

I did a diesel purge and changed the filters: that helped a little. Rechecked the timing, and it's at 25-BTDC, whereas before pump removal the timing was at about 26 or 27. The diesel purge helped the rough idle along with adjustment of the new rack damper bolt (just a year old) but it still misses occasionally, especially at cold start up. I put my stethoscope to the injectors and have hard nailing on 3 and 4 even though the records I have from the previous owner show that an Indy shop replaced the injectors 20,000 miles ago.

I believe a bad injector (or two) could cause a random misfire and contribute to hard starting conditions. Can somebody confirm this?

Injector issues can directly impact timing on a single cylinder = delayed or advanced timing.

With mechanical injectors:
* A single weak injector spring, with 300 PSI reduced pop pressure = loping miss, knocking, smoking.
* The injector can become obstructed, causing timing/spray pattern issues.
* Pintle damage wrecks the spray pattern = critical damage can result in some cases.
* The injector nozzle may leak, causing coking, timing, spray pattern issues, or a lack of combustion on X cylinder.

From your description; This could not apply, but has happened to others.
* A previous owner may have miss matched incompatible nozzles = Monark and Bosch can NOT be installed on the same engine.

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Diesel911 · #7 02-14-2013, 06:57 PM

In Hunters list "The injector can become obstructed, causing timing/spray pattern issues"; even thoug I tried to keep things clean I have had at least 2 incidents on the Job where I managed to get Drit into Fuel Injection System ending up in the Injectors.

If you look up and do the Injector Cut Out Test it will give you and idea if it is the Injectors or not.

npretnar · #8 02-14-2013, 07:32 PM

Quote:

Originally Posted by whunter

Injector issues can directly impact timing on a single cylinder = delayed or advanced timing.

From your description; This could not apply, but has happened to others.
* A previous owner may have miss matched incompatible nozzles = Monark and Bosch can NOT be installed on the same engine.

.

Actually, i think this is very well possible. My records show that an Indy shop replaced the injectors 20,000 miles ago in September of 2009. The total cost for "5 injectors + labor" not 'remanufactured' or 'rebuilt' was $165. That seems awfully low according to my research on how much reman injectors cost. I'm willing to bet the nailing/pinging 3 and 4 injectors are just old, and the PO's mechanic merely replaced his injectors with used ones that only had limited miles remaining on them.

npretnar · #9 02-14-2013, 07:38 PM

This afternoon I retarded the timing to 26 and it runs a little bit better, but still starts hard. I'm going to replace injectors next and see what happens. Probably start with a couple used ones and then consider replacing nozzles in the future.

npretnar · #10 02-14-2013, 11:58 PM

Check out WHunter's recent heads up on smoke issues:
http://www.peachparts.com/shopforum/diesel-discussion/334677-reading-exhaust-smoke-related-comments.html

My current situations, IP recently timed:

Symptoms related to aforementioned idle MISS problem:
- white smoke with HEAVY diesel stench
- timed at 25-BTDC
- injector nail on 3 and 4

Prior to IP timing adjustment:
- black smoke at high load
- timed to 27-BTDC
- hard start

Advancing the timing changed the smoking composition. I haven't checked chain stretch, though I feel it is probably a variable in regards to the timing specs.

whunter · #11 02-15-2013, 01:29 AM

Some members are curious about the Mercedes Benz injection pump service documents we refer to.

Please note:
When you get to the final PDF documents, this website will only function for me with InternetExplorer.
Untitled Document

Using InternetExplorer, here is the document MB# 07.1-110 "Checking injection timing (begin of delivery) (flow pressure method)".
http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/617/07_1-110.pdf

Using InternetExplorer, here is the document MB# 07.1-200 "Removal and installation of injection pump".
http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/617/07_1-200.pdf

Using InternetExplorer, here is the document MB# 07.1-201 "Installation of injection pump (with locking screw)".
http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/617/07_1-201.pdf

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