New injector advice? What should I do? (91 350SD) - PeachParts Mercedes-Benz Forum

Blevinsax · #1 02-10-2007, 01:45 AM

Okay, the time has come to do something about my intermittently bouncing 350SD....

Sometimes it runs as smooth as silk - and sometimes it bounces up and down like a pimped out Lincoln (not really that bad - I exaggerate.) The only connection I can make is the bouncing starts when the engine warms up - but it does not do it all the time. It starts and runs super smooth in the morning when it is cool, but after it warms up it starts bouncing - but like I said, it is inconsistent. I can pull up to one stop light and it sits pretty still with only a *little* bounce - then it really starts hopping at the very next light! Pretty unpredictable and random - except there is one predictable element... it almost ALWAYS bounces when my wife (or another guest passenger) is in the car!! That's why it is time to do something about it! She told me to do whatever I need to do so it will stop bouncing while she's in the car!

I am running B20 (main tank) and WVO (GreaseCar system + VegTherm Mega) and although the bouncing happens on both fuels, it seems more common on B20 - but sometimes it runs perfectly smooth on B20, too!

So, where should I start? From what I have gathered here on the forum, most likely it seems to be injector related. Here are the injector options I have investigated:

1. Bosio nozzles - installed, balanced, and tested by a local diesel shop
2. New Bosch injectors from Mercedesshop.com at $67.37/each (x6)
3. VegJect (modified Bosch) injectors from Colorado Biodiesel (I spoke with Tom there and he said I'll have to wait until sometime later in March for availability... and now perhaps never since I can no longer find them on their site!)

Any other suggestions? My wife is demanding that I get it fixed because she doesn't like riding in my bouncing Benz, so..... what else am I to do?!?!?

Blevinsax · #2 02-10-2007, 12:35 PM

Bump...

I'm hoping to get this done next week, so some advice would be greatly appreciated!

Thanks!

TMAllison · #3 02-10-2007, 12:39 PM

Quote:

Originally Posted by Blevinsax

1. Bosio nozzles - installed, balanced, and tested by a local diesel shop
2. New Bosch injectors from Mercedesshop.com at $67.37/each (x6)
3. VegJect (modified Bosch) injectors from Colorado Biodiesel (I spoke with Tom there and he said I'll have to wait until sometime later in March for availability... and now perhaps never since I can no longer find them on their site!)

Any other suggestions?

0). Pull the OEM injectors and have them pop tested, re-balanced (as needed) and spray patterns checked at your local diesel shop.

There really is no need to replace nozzles or whole injectors unless you have a bad spray pattern that can't be corrected with new shims.

I'm sure you can find something else to spend $400 on.

Hatterasguy · #4 02-10-2007, 02:41 PM

Quote:

Originally Posted by TMAllison

0). Pull the OEM injectors and have them pop tested, re-balanced (as needed) and spray patterns checked at your local diesel shop.

There really is no need to replace nozzles or whole injectors unless you have a bad spray pattern that can't be corrected with new shims.

I'm sure you can find something else to spend $400 on.

I second this advice. A few are probably off, but not all six.

Blevinsax · #5 02-10-2007, 03:22 PM

Will do. I already had the online order form filled out for 6 Bosio's, but I'll put that on hold until I have the current ones checked. Thanks!

barry123400 · #6 02-10-2007, 03:54 PM

This car new enough to have codes? Nothing coming up? Not even a red engine trouble light? You are describing an intermittent injector condition. I was not aware they could be intermittent in themselves. More just either in good condition or bad. Anything is possible I imagine but what leads you to this? I know nothing at all about your newer series engine by the way. I might want a proffesional diagnosis before starting. Especially if the car has any kind of electronic engine management control system. Sounds pretty severe when the car starts its bouncing behaviour for it to be so obvious inside the cab.

Blevinsax · #7 02-18-2007, 12:42 PM

Quote:

Originally Posted by barry123400

This car new enough to have codes? Nothing coming up? Not even a red engine trouble light? You are describing an intermittent injector condition. I was not aware they could be intermittent in themselves. More just either in good condition or bad. Anything is possible I imagine but what leads you to this? I know nothing at all about your newer series engine by the way. I might want a proffesional diagnosis before starting. Especially if the car has any kind of electronic engine management control system. Sounds pretty severe when the car starts its bouncing behaviour for it to be so obvious inside the cab.

The 350SD is just a W126 with a 3.5L 603.970 motor - like the earlier 300SD - and has no red engine trouble lights. When I bought this car, I knew nearly nothing about diesels, and even less about Mercedes in particular. When I first encountered this problem, I seem to remember someone here on the forum say that a smooth cold idle but rough hot idle was indicative of injector problems. Mine is certainly intermittent, but I can say that it never idles rough when cold, only once it gets warm - and it seems to be worst when the motor is at its hottest.

TMAllison · #8 02-18-2007, 12:57 PM

Quote:

Originally Posted by Blevinsax

Mine is certainly intermittent, but I can say that it never idles rough when cold, only once it gets warm - and it seems to be worst when the motor is at its hottest.

Wow....that's an issue in the summer where you live.

I seem to remember some issues on the newer cars where the fuel thermo wouldnt close as the car warmed up and continued heating causing some issues like you describe. I think yours has one too.

I'd still test your original injectors before doing anything too drastic. You might run 2 cans of diesel purge through first to see if that cleared it up. Could be a WVO inj issue.....Is pretty easy to do and cheap enough you can feel good about doing it even if it doesnt help.

sixto · #9 02-18-2007, 01:09 PM

What does the tach register when it's loping? Maybe you have a bad connection between the EDS and the idle actuator (round thing at the back of the IP).

Sixto
93 300SD 3.0

Blevinsax · #10 02-18-2007, 01:31 PM

Quote:

Originally Posted by sixto

What does the tach register when it's loping? Maybe you have a bad connection between the EDS and the idle actuator (round thing at the back of the IP).

Sixto
93 300SD 3.0

I don't recall anything abnormal, but I'll pay closer attention to the tach when it happens - it only lopes at idle, so the tach is somewhere around 500-600 when it's happening.

sixto · #11 02-18-2007, 01:36 PM

I mean does the tach read lower when it's loping?

Sixto
93 300SD 3.0

Blevinsax · #12 02-18-2007, 07:56 PM

Quote:

Originally Posted by TMAllison

Wow....that's an issue in the summer where you live.

Actually, I was not talking about the weather temperature, just the engine temperature. The car runs really smooth with virtually no smoke when I start it in the morning, but as it runs throughout the day, the rough idle gets worse, especially as the engine temperature goes up. Fortunately it never really smokes much at all, though - except for the occasionaly Italian Tune-Up, and then the smoke is all white from the WVO. Also, it is not overheating, but it will sometimes reach the high 80's (C) in stop & go traffic, so I'm not concerned about the cooling system.

Quote:

Originally Posted by sixto

I mean does the tach read lower when it's loping?

Sixto
93 300SD 3.0

No, I paid attention to it today and there was nothing abnormal with the tach when it is loping - it idles at about 500 RPM as I think it should - and is very steady.