Next course of action: injection timing or injectors? - PeachParts Mercedes-Benz Forum

bipolardave · #1 08-04-2011, 10:14 PM

Planning this month's car budget.

I'm still getting to know the car and am trying to remedy some hard starting/nailing/smoke issues. After a Diesel Purge, some slight nailing goes away after about a minute of idling when cold. Some minor shaking also disappears. Still have some white smoke at cold idle and black smoke when I floor it.

To date I've:

1. Adjusted the valves (and then again to double check that I did it correctly).

2. Performed two compression tests (either 320 or 290, all pistons, depending on which Harbor Freight quality gauge you trust).

3. Drained tank and checked mesh filter.

4. Diesel purge, remove muck from the secondary filter housing, replaced both filters. Car sounded and idled very, very smooth while on the Purge. Also had more power afterwards.

5. Have continuity across all glow plugs.

6. Not a real check from what I've read, but the timing chain/pedestal mark correspond to TDC on the balancer.

7. Maybe related to the root cause of my problem: primary filter only half full. 100% full while sucking from my Purge tank.

Anyway, the PO replaced the injectors with Bosch one year ago. So I'm thinking about going the cheaper route first and buying the drip tube and 90 degree wrench to check the injector timing first. That being said, why the marked improvement with Diesel Purge if the injectors are fairly new?

Diesel911 · #2 08-05-2011, 12:28 AM

[QUOTE=bipolardave;2764091]Planning this month's car budget.

I'm still getting to know the car and am trying to remedy some hard starting/nailing/smoke issues. After a Diesel Purge, some slight nailing goes away after about a minute of idling when cold. Some minor shaking also disappears. Still have some white smoke at cold idle and black smoke when I floor it.

To date I've:

1. Adjusted the valves (and then again to double check that I did it correctly).

2. Performed two compression tests (either 320 or 290, all pistons, depending on which Harbor Freight quality gauge you trust).

3. Drained tank and checked mesh filter.

4. Diesel purge, remove muck from the secondary filter housing, replaced both filters. Car sounded and idled very, very smooth while on the Purge. Also had more power afterwards.

5. Have continuity across all glow plugs.

6. Not a real check from what I've read, but the timing chain/pedestal mark correspond to TDC on the balancer.

7. Maybe related to the root cause of my problem: primary filter only half full. 100% full while sucking from my Purge tank.

Anyway, the PO replaced the injectors with Bosch one year ago. So I'm thinking about going the cheaper route first and buying the drip tube and 90 degree wrench to check the injector timing first. That being said, why the marked improvement with Diesel Purge if the injectors are fairly new?[/QUOTE]

The Made in India Bosch Nozzles that go into the rebuilt Injectors establish a good reputation.

Item #12 is the Pintel of the Injector and to the right side is a blown up pic of the Pintel (#12). The drilled passages #14 and #15 can become plugged with Carbon if the Fuel is not burning well or a regular Diesel Purge (this is my opinion).

Monark, Bosio and the Bosch Nozzles made for later model Diesels do not have the drilled passages feature.

So if your Purge cleaned out the drilled passages it should run better.

You need to identify which of the Gauges you used for the compression test is accurate.

Diesel911 · #3 08-05-2011, 12:41 AM

If the Fuel Supply/Lift Pump was having trouble pulling from the Fuel Tank due to wear it would have an easier time pulling the Diesel Purge in because it is closer and higher up than the lowest part of the Fuel Tank.

But, if you are getting Black smoke when you accelerate you must be getting enough Fuel when the Engine is revved up.

Also if your 74 240D has a Pneumatic Governor the Governor Diaphragm can get stiff or get holes in it and that changes how well it works.
A new Diaphragm is around $285 for a Bosch one (and you need to be real careful when you change it) so it is a good idea to eliminate all other possible before thinking about that.

bipolardave · #4 08-05-2011, 04:16 PM

Quote:

Originally Posted by Diesel911

If the Fuel Supply/Lift Pump was having trouble pulling from the Fuel Tank due to wear it would have an easier time pulling the Diesel Purge in because it is closer and higher up than the lowest part of the Fuel Tank.

But, if you are getting Black smoke when you accelerate you must be getting enough Fuel when the Engine is revved up.

Also if your 74 240D has a Pneumatic Governor the Governor Diaphragm can get stiff or get holes in it and that changes how well it works.
A new Diaphragm is around $285 for a Bosch one (and you need to be real careful when you change it) so it is a good idea to eliminate all other possible before thinking about that.

Thanks for the advice.

However, I can't even get the bubble to collapse with the hand pump before I fire it off. It's been that way since I put everything back together. A bad lifter pump wouldn't maifest itself until after the car is running, no?

It was fine before I played "Adventures in Compression Testing". There was only a small bubble in the primary filter then.

For what it's worth, I had to replace the hand pump because it failed. That initial start up after the compression check was difficult because I couldn't bleed the lines.

As to the pnuematic governor...I have a clear plastic line running from the back of the IP to the breather. Would that be it? If so, how can one check for failure? I understand that it serves as the load line for the IP.

Jeremy5848 · #5 08-05-2011, 05:27 PM

The Diesel Purge may have helped based on what kind of fuel has been used since the injectors were new. Then again, Diesel Purge probably has a high cetane rating and will help just about any diesel sound like it is running better. Since it won't cost anything, you might consider taking the injectors apart and cleaning them. I started a thread on injector cleaning here. Your injectors will be different but all of the procedures should be the same.

Having the injectors balanced will cost you some money, either to buy or build a tester or to have a shop do the job for you. One of the forum members also offers this service and, I believe, has a good reputation.

Jeremy

tangofox007 · #6 08-05-2011, 05:45 PM

Quote:

Originally Posted by bipolardave

A bad lifter pump wouldn't maifest itself until after the car is running, no?

Not true.

Quote:

Originally Posted by bipolardave

For what it's worth, I had to replace the hand pump because it failed. That initial start up after the compression check was difficult because I couldn't bleed the lines.

The hand pump depends on the same suction and discharge valves as the engine-driven portion of the pump.

Diesel911 · #7 08-05-2011, 06:08 PM

Quote:

Originally Posted by bipolardave

Thanks for the advice.

However, I can't even get the bubble to collapse with the hand pump before I fire it off. It's been that way since I put everything back together. A bad lifter pump wouldn't maifest itself until after the car is running, no?

It was fine before I played "Adventures in Compression Testing". There was only a small bubble in the primary filter then.

For what it's worth, I had to replace the hand pump because it failed. That initial start up after the compression check was difficult because I couldn't bleed the lines.

As to the pnuematic governor...I have a clear plastic line running from the back of the IP to the breather. Would that be it? If so, how can one check for failure? I understand that it serves as the load line for the IP.

I PMed you some info on the Pneumatic Governor. I do not know how to trouble shoot them.

Actually if the Lift Pump Valves were leaking or the Pump Piston was worn (it does not happen very often that the Pump Piston gets worn unless dirt went thriough it; when that happens the sides of the Piston get scored up) it would be more noticable at idle speeds than at higer rpms.
Because Fuel has more time to leak past at idle speed and the Fuel Volume per minute is lower.

If you look at that info I sent there is some test proceedures for the Fuel Supply/Lift Pump; although not for your specific year.

junqueyardjim · #8 08-05-2011, 06:35 PM

Hey don't worry about a big or little bubble in the primary filter. They all have that! That is not a problem so just overlook it if it spooks you.

junqueyardjim · #9 08-05-2011, 06:40 PM

Also Dave, your compression shows at the lowest level of "good". If you did a "warm" compression test and gave it 7,8 or 9 strokes and all you got is 290/300, that is too low to really run good. Have you had that car on the road for 30 to 50 miles of hard running, I mean pouring the cobs to it, but don't get a ticket. It might do a lot for that engine.

bipolardave · #10 08-06-2011, 06:47 AM

Thanks for the many tips, folks.