Rough Idle, Nailing Diagnostic Questions - PeachParts Mercedes-Benz Forum

shertex · #1 10-08-2012, 02:44 PM

Sixto and GSXR have given me some good advice via email....thought I'd see if others have thoughts....and perhaps this thread could help others with similar symptoms.

Newly acquired 1987 300TD has the following symptoms:

1. Rough idle, with rhythmic puff at tailpipe
2. Nailing under moderate load
3. Fuel leaking at top of IP
4. 4 of the 6 splined collars for delivery valves are missing

In another thread, Sixto indicated that the nailing and the rough idle could be explained solely in terms of the leak. BUT, I'm also fearing more costly possibilities, e.g. bad IP or injectors.

My working assumption is that, diagnostically, all I can really do at this point is replace the delivery valves seals and see what happens. Is there any other approach to take? Would be glad to hear anyone's experience or input.

Diesel911 · #2 10-08-2012, 08:57 PM

Quote:

Originally Posted by shertex

Sixto and GSXR have given me some good advice via email....thought I'd see if others have thoughts....and perhaps this thread could help others with similar symptoms.

Newly acquired 1987 300TD has the following symptoms:

1. Rough idle, with rhythmic puff at tailpipe
2. Nailing under moderate load
3. Fuel leaking at top of IP
4. 4 of the 6 splined collars for delivery valves are missing

In another thread, Sixto indicated that the nailing and the rough idle could be explained solely in terms of the leak. BUT, I'm also fearing more costly possibilities, e.g. bad IP or injectors.

My working assumption is that, diagnostically, all I can really do at this point is replace the delivery valves seals and see what happens. Is there any other approach to take? Would be glad to hear anyone's experience or input.

Well, leaking Delivey Valve Holder Seals has caused nailing for other Members.
Air leak/s into the Fuel Inlet can also cause nailing but would not cause the Delivery Valve Seals to leak.

Was this a recenely bought Car?

"splined collars for delivery valves are missing" likely indicates the prior owner was trying to fix something. Did this nailing start after you owned the Car for several years or is it just since you bought the Car.

The splined collars for delivery valves are called Shackles on the parts Bag when you buy them. They are around $3 each from the Dealer. If they are something that comes in a Gasket kit for rebuilding Pumps it is likely that the local Fuel Injection shop has a bunch of old ones. They could surely get you new ones and the Screws also.

The Shackles are there to lock the Delivery Valve Holder in place to keep it from rotating.

If you are doing it Yourself replacing the Delivery Valve Crush Washers and the Delivery Valve Holder O-rings is the cheapest route. It needs to be done reguardless of the other work that might possibly be needed.

shertex · #3 10-09-2012, 06:20 AM

Quote:

Originally Posted by Diesel911

Well, leaking Delivey Valve Holder Seals has caused nailing for other Members.
Air leak/s into the Fuel Inlet can also cause nailing but would not cause the Delivery Valve Seals to leak.

Was this a recenely bought Car?

"splined collars for delivery valves are missing" likely indicates the prior owner was trying to fix something. Did this nailing start after you owned the Car for several years or is it just since you bought the Car.

The splined collars for delivery valves are called Shackles on the parts Bag when you buy them. They are around $3 each from the Dealer. If they are something that comes in a Gasket kit for rebuilding Pumps it is likely that the local Fuel Injection shop has a bunch of old ones. They could surely get you new ones and the Screws also.

The Shackles are there to lock the Delivery Valve Holder in place to keep it from rotating.

If you are doing it Yourself replacing the Delivery Valve Crush Washers and the Delivery Valve Holder O-rings is the cheapest route. It needs to be done reguardless of the other work that might possibly be needed.

Yes, recently bought. Was doing this when I bought it. The PO only owned it for six months or so....don't think he did the IP work. Delivery valves probably done by whoever put in replacement engine. Botched job, regardless. I'll deal with DV seals then report back.

shertex · #4 10-09-2012, 08:43 AM

PO just confirmed that it always ran rough for him. So I'm hopeful it's due simply to a botched delivery valve seal job.

Diesel911 · #5 10-09-2012, 09:49 AM

After you remove the Fuel Injection Hard Lines from the Fuel Injection Pump put a Ruler or something reasonably straight a crossed the top of the Delivery Valve Holders.

You will be trying to see if any of them are higher than the other ones next to them.

If they are not all the same height it is possible that the previous owner managed to pull up one or more of the Element Barrels up and out of the slot that lines it up.

shertex · #6 10-09-2012, 10:26 AM

Quote:

Originally Posted by Diesel911

After you remove the Fuel Injection Hard Lines from the Fuel Injection Pump put a Ruler or something reasonably straight a crossed the top of the Delivery Valve Holders.

You will be trying to see if any of them are higher than the other ones next to them.

If they are not all the same height it is possible that the previous owner managed to pull up one or more of the Element Barrels up and out of the slot that lines it up.

Thanks....my hope is that all he did was a bad seal job and did not damage the pump.