CDI Glow Plugs - PeachParts Mercedes-Benz Forum

DieselPaul · #1 12-10-2015, 09:27 AM

Well the CDI failed the start the first couple of tries on a cold morning, and when it does start it clearly is starting on somewhere between 3 and 5 cylinders. No CELs but this sounds like glow plugs to me as it's entirely temp dependent. Car will start fine the rest of the day.

So, CDI glow plugs! Someone line vendors say cars were either Beru, or Bosch. I admittedly have not pulled a plug out to look. Pelican however does not make a brand distinction.

I called the dealer with my VIN and they told me to get 001 159 7401 which according to online vendors is the Beru number.

However the Bosch *looks* the same and is half the price.

So are all glow plugs the same, or are there Beru cars and Bosch cars?

This pelican review of the Bosch plugs on Pelican is interesting

Quote:

DO NOT BUY THE BOSCH for W211 USA e320 CDI
The Bosch glow plugs are 11.5v, not the correct 5v for your USA spec 05'-06' e320 cdi! They have worked fine for me but do not heat near as quickly and will be replaced shortly with the correct Beru/OEM Plugs. They carry same part number BUT ARE NOT THE SAME AS STOCK!

shertex · #2 12-10-2015, 10:57 AM

Sounds like the Beru is the one you want.

FWIW after years of using Bosch, I'm done...they burn out too early. On my cars that can take either I will spend the extra money and get Beru.

DieselPaul · #3 12-10-2015, 11:04 AM

I'll pull the engine cover after work and see if I can't easily do a quick multi-meter test to see if any of the plugs come up bad that way, then I'll call the dealer back and get some coming.

ILUVMILS · #4 12-10-2015, 11:55 AM

I'd check the low pressure fuel circuit before you replace the glow plugs. FWIW, I've never seen a faulty CDI glow plug or relay that didn't turn the CEL on......

GregMN · #5 12-10-2015, 12:05 PM

Quote:

Originally Posted by ILUVMILS

I've never seen a faulty CDI glow plug or relay that didn't turn the CEL on......

X2

Check your fuel system.

How old is your fuel filter?
Check your injectors for an open return fuel circuit.

A $69.99 UltraGauge will let you see the fuel pressure in the fuel rail. You can see what the pressure is during the start sequence. It has to be about 3500psi for the injectors to fire.
One injector with an open or weak return fuel valve can bleed off enough pressure to prevent a cold start, but work find the rest of the day.

DieselPaul · #6 12-10-2015, 12:26 PM

No CELs. I assumed I would get a glow plug CEL, aren't even 606 cars capable of throwing a GP code?

I did the fuel filter about 5,000 miles ago with a unit from the dealer.

I have an eBay Mercedes Carsoft scan tool like this:

Mercedes Benz Sprinter Diagnostic Scanner Tool SRS ABS Engine Icarsoft Mbii I980 | eBay

I'll see if I can get a look at rail pressure with it.

Glad I posted, I'll see what data I can come up with and post back. I appreciate your insights Greg and Iluvmils. Not as much good info out there on the CDIs yet, looking forward to learning more and more about them.

GregMN · #7 12-10-2015, 01:11 PM

The way to check for a leaking return circuit on an injector, or to find which one(s) is the bad one :
You will need a 6" piece of clear tubing that fits on the return fuel nipple for each injector.
Remove the return fuel connectors and replace each with a clear tube standing straight up.

During the start cycle, there should be no fuel returned, so all the tubes should be empty. If you have a leaker, that one is the problem.

When the engine is running, all the return tubes should fill at the same rate. If any are returning fuel faster then the others, those are candidates for replacement.

This test is so easy to do, but so many bad things can go seriously wrong. The parts are so fragile that if you are not careful you can make the problem you are looking for seem trivial compared to having to replace parts that were perfectly good before you started messing around with them. Find out how all the connectors you will try to disconnect work before you get started. Many times they are "clear only if known", like the fuel connector locks on the 606.

DieselPaul · #8 12-10-2015, 01:45 PM

Cool, sounds like a straightforward enough test, I'll try first to see if I can get a reading on the rail pressure with my scan tool.

Anyone rebuilding injectors yet for the CDI or am I stuck dropping like $390/injector or whatever I saw online if one turns up bad.

GregMN · #9 12-10-2015, 02:22 PM

Quote:

Originally Posted by DieselPaul

I'll try first to see if I can get a reading on the rail pressure with my scan tool.

Do that first.

It looks like that tool will everything except put away the dishes once they are clean.

If the problem is fuel rail pressure, then test to find the leaking injector.

GregMN · #10 12-10-2015, 04:47 PM

Quote:

Originally Posted by Diesel911

Out here in CA they don't sell the PVC that is rated for Hot Water

Just get the really cheap, clear, soft, tubing. It will not be handling hot fuel or any pressure.

Watch this video: OM 642 Injector leak test on 1 bank

That is what you are going to do if you need to test the injector leak down. That video is on one bank (3) of the injectors on 642, the 648 has the same injection system. I used a vice-grips to gently pinch off the return fuel line from the injectors sense it tee's into the 60psi fuel source line before the filter.

engatwork · #11 12-10-2015, 05:22 PM

Quote:

I've never seen a faulty CDI glow plug or relay that didn't turn the CEL on......

Same here.

big d · #12 12-10-2015, 09:06 PM

My 2006 CDI light turned on when glow plug went bad.There are Beru 5 volts plugs and Bosh 12 volts.You need Beru.

Skid Row Joe · #13 12-10-2015, 09:13 PM

Quote:

Originally Posted by ILUVMILS

I'd check the low pressure fuel circuit before you replace the glow plugs. FWIW, I've never seen a faulty CDI glow plug or relay that didn't turn the CEL on......

Quote:

Originally Posted by GregMN

X2

X3

Quote:

Originally Posted by engatwork

Same here.

Every time.....

Quote:

Originally Posted by big d

My 2006 CDI light turned on when glow plug went bad.There are Beru 5 volts plugs and Bosh 12 volts.You need Beru.

Same here.

hangit · #14 12-10-2015, 09:17 PM

You should search on this forum. Much more info on the modern MB vehicles.

W211 E-Class - Mercedes-Benz Forum

John

DieselPaul · #15 12-10-2015, 10:36 PM

Quote:

Originally Posted by Skid Row Joe

X3

Every time.....

Same here.

For all that repair work you've done on a car you've put 6,000 miles on and don't service yourself. Thanks for the insights brah.

On a serious note when I started the car with the scan tool when I left work I got a reading of 5,511psi for the rail pressure. But I got 0 until the car started. I need to play with it again and if I can get a reading with the car keyed on but not running.