300SDL - What are the odds? - PeachParts Mercedes-Benz Forum

probear · #1 03-17-2009, 09:17 AM

My 86 SDL has a miss. It's obvious that it's running on 5 cylinders at least most of the time. I checked via the loosen injector fitting and found that the #6 cylinder was most likely the culprit. So, having a spare set of injectors, I R & R ed the injector and put in one of the others. (with a new washer).
It still misses. What are the odds of two bad injectors?? My next step is to either run a compression check or find a pressure gauge for the line.

Can an injector pump fail to generate fuel flow/pressure for just one cylinder?

Thanks !

pawoSD · #2 03-17-2009, 10:14 AM

Quote:

Originally Posted by probear

Can an injector pump fail to generate fuel flow/pressure for just one cylinder?

Thanks !

Yes. But I'd check all possibilities first. On my dad's SD we had the same issue....it kept missing and running on 4 cylinders....on the third spare injector it finally started running again. We replaced all the nozzles, and now it runs perfectly.

probear · #3 03-17-2009, 05:39 PM

It does not look good.

I have a spare set of injectors and injector lines, so I connected one of the injector lines to the pump, and the other to a spare injector. Started the engine and nothing from the injector. I switched to another injector and same results.

Looks like the IP is going south or has gone partially south.

Hip001 · #4 03-17-2009, 05:47 PM

Good question Probear! I'm waiting to hear the what they say about this too.

Diesel911 · #5 03-17-2009, 11:05 PM

I had to go find your other thread.
So this is a problem with 1 Element of the IP not putting out Fuel.

Is this an IP that you recently changed the Delivery Valve O-rings on?

If your IP has a Steel cover plate on the side I would remove that and take a peek inside.
If it is that type of pump that rack has pieces that when they adjust the Fuel on the test stand they slide them down the rack and tighten them down to hold them inplace. You will see screw heads on them 1 per cylinder (do not move the screws).
The reason I mention it is that on other types of IPs that use the same system I have seen where one of the screws loosens and allows that piece that adjust the fuel to move around. So you will be looking to make sure you cannot move those pieces.
Next get a Flash Light with a strong light and look inside of the IP while someone cranks the Engine (you do not need to start the Engine). Watch the action of the Plungers and the return springs as they go up and down. You are looking for a broken Return Spring or a Plunger that is stuck all the way UP and will not come down.
Also compare the working one to the one that is not working and look for anything that is out of the ordinary.

Diesel911 · #6 03-17-2009, 11:32 PM

Quote:

Originally Posted by Diesel911

I had to go find your other thread.
So this is a problem with 1 Element of the IP not putting out Fuel.

Is this an IP that you recently changed the Delivery Valve O-rings on?

If your IP has a Steel cover plate on the side I would remove that and take a peek inside.
If it is that type of pump that rack has pieces that when they adjust the Fuel on the test stand they slide them down the rack and tighten them down to hold them inplace. You will see screw heads on them 1 per cylinder (do not move the screws).
The reason I mention it is that on other types of IPs that use the same system I have seen where one of the screws loosens and allows that piece that adjust the fuel to move around. So you will be looking to make sure you cannot move those pieces.
Next get a Flash Light with a strong light and look inside of the IP while someone cranks the Engine (you do not need to start the Engine). Watch the action of the Plungers and the return springs as they go up and down. You are looking for a broken Return Spring or a Plunger that is stuck all the way UP and will not come down.
Also compare the working one to the one that is not working and look for anything that is out of the ordinary.

I barrowed the below pic. I think the Square pieces that adjust the fuel have been move in this pic as someone has taken part of the IP apart but you will get the idea. The square pieces are are supposed to be tightened to the Rack.

probear · #7 03-18-2009, 03:46 PM

OK. I opened up the side of the injector pump and took a look. All the 'slides' were tight and would not move. I verified that the bar attached to all the slides moved freely, which it did, and then spun the engine over several times to verify that each little 'piston' was indeed moving. I specifically looked for broken springs, and found none. The piston for the #6 was moving just like the rest.

I put it back together and fired her up just, well, just in case. Still missing on #6 and obvious difference when the flare nut is cracked at the injector. #6 kinda oozes whereas the others squirt.

Realistically, this engine has always has a slight miss, but I put it off as needing to rebuild the injectors but as time and mileage went on, it got worse.

Any more ideas?
Thanks.....

Diesel911 · #8 03-19-2009, 07:04 PM

If you have the special Socket to remove the Delivery Valve Holder. Remove the Delivery Valve Holder but do not disturb anything else and see if the Delivery Valve Spring is Broken or the Delivery Valve is not closing for some reason.
Also inspect the Crush Washer to see if it is in 1 piece and not erodded through.

When you do the above you are supposed to replace the Crush Washer and the O-ring; but if you do not find anything wrong up there I would just put it back together the way it is.

Diesel911 · #9 03-19-2009, 07:20 PM

Quote:

Originally Posted by Diesel911

If you have the special Socket to remove the Delivery Valve Holder. Remove the Delivery Valve Holder but do not disturb anything else and see if the Delivery Valve Spring is Broken or the Delivery Valve is not closing for some reason.
Also inspect the Crush Washer to see if it is in 1 piece and not erodded through.

When you do the above you are supposed to replace the Crush Washer and the O-ring; but if you do not find anything wrong up there I would just put it back together the way it is.

If you do not find a broken Delivery Valve Spring or any other problem you might want to check the following and carefully remove the Delivery Valve lower Body and use a Magnet coverec with thin cloth to pull out the Steel Barrel inside of the IP to see if the feed hole is obstructed.
These are barrowed pics from another thread- the 1st pic shows the fuel feed hole on the side of the barrel.
The 2nd pic shows the the slot in the barrel that lines the Barrel to a Pin inside of the IP housing.
The last pic shows the Pin in the IP housing; that pin has to go into the slot that is on the Barrel.
Before trying to slide the Barrel over the plunger dip the Barrel in clean Diesel fuel and do not force it onto the plunger; be very gentle inserting it.

probear · #10 03-20-2009, 07:07 PM

THANKS !!

I totally disassembled the barrel and plunger, cleaned it and reassembled it. It took a while since it's hard to see the #6 up under the manifold, but finally found it. Cleaned with bio-diesel, and after several minutes of 'bleeding' the system, she cranked.
Initially, it still missed...

but then, I looked and found I had forgotten to tighten one of the injector lines

(loosened all to quickly bleed the system). When I tightened it up, she was idling smooth, and the 'loosen to find miss' showed all cylinders firing...

YEAH !!!

Diesel911 · #11 03-21-2009, 01:42 AM

Quote:

Originally Posted by probear

THANKS !!

I totally disassembled the barrel and plunger, cleaned it and reassembled it. It took a while since it's hard to see the #6 up under the manifold, but finally found it. Cleaned with bio-diesel, and after several minutes of 'bleeding' the system, she cranked.
Initially, it still missed...

but then, I looked and found I had forgotten to tighten one of the injector lines

(loosened all to quickly bleed the system). When I tightened it up, she was idling smooth, and the 'loosen to find miss' showed all cylinders firing...

YEAH !!!

The above was a good thing to forget as it was an aid to bleeding out the air.

Do you think it was something plugging the feed hole in the Barrel?

probear · #12 03-21-2009, 02:39 PM

If there was something clogging it, I could not find it. Regardless, I sprayed through all holes and then soaked in bio-diesel.

I am assuming it was a clog since it gradually got worse.