Hey man, don't let the car get you down... this is all just normal maintenance items on these cars. Everything you are experiencing I have also replaced on my car.

As for the tension spring, I'll bet they forgot to install it when they replaced the serpentine belt... I can't see how it could break and fall out.

Take a look at this link from Diesel Giant about the glow plug relay fuse. This is something you could easily do yourself and have fun doing it if this is the problem.... See if any steps in the pictorial can help you at all.

http://dieselgiant.com/glowplugrepair.htm

Compression and cranking speed are significant variables when attempting to start without plugs. One engine may be good to go without plugs and another may fail to start without them.

BRILLIANT OBSERVATION AND TROUBLESHOOTING. Excellent point!



I got lambasted a while back for discussing theory and design of diesel cycle operation because I bruised a fragile ego, so here goes again.

In my 25 years of personal and professional experience, living in Minnesota, without operational glow plugs in the 60x series aluminum head/iron block engine family, THEY DO NOT START COLD without an operational glow system. Maybe at 50°F and previously run, but not cold. Sorry. My old GM 4.3 would go after several minutes of continuos cranking, the MB's rarely do.

In the 80's when this design was introduced, MB radically altered the pre-chamber design in this family, which resulted in a negative affect of requiring lots of heat to start, and that heat is fully functional glow plugs. At 50°-60°F and with half the plugs failed, the 60x will still start. It will buck and smoke and fart and miss, but it will go. Without any plugs, well, good luck. You might need an aircraft ground power unit to help, but the starter brushes will be toasted first.

Get the ship to a Benz guy! Quick!

Interesting. And, a definite possibility.

We'll see if Hattie's personal mechanic will be installing a starter this weekend............:D

Hey, thanks for the cheering up! I have been getting frustrated by these problems because I have this great car that is such a joy to drive - and with the combination of the GreaseCar system and my home WVO filtration system (and my home-delivered WVO!) it also has the potential to SAVE me a lot of money in fuel costs. I guess I just have to deal with this initial outlay before I get to enjoy sitting back and watching the dollars pile up in my bank account while I get free fuel. I'll just try to relax and take this stuff one step at a time. I've already learned so much on here that sometimes I AM more knowledgable than my mechanic - but I will be quick to admit that he has many years of practical experience and knowledge that makes mine pale in comparison.

I think you're likely right that the *other* mechanic who did some work on my car forgot to install the spring when he replaced the serpentine belt. That's the kind of crap I hate about mechanics! As a matter of fact, anytime someone does a half-a$$ job on anything, it pisses me off - especially if I've paid a lot of my hard-earned dollars for it.

Alright - tomorrow morning I'm going to get with my mechanic and check that fuse. Could someone here point me in the right direction to find it? Then on to the missing tensioner spring! Then on to the defective GreaseCar valve/switch! Then on to whatever pops up next!!!

Thanks for all your help - I'll post here again when progress is made!

The glow plug relay is a black box about 1.5 x 3 x 4 inches on the left inner fender. Pull off the black plastic cover to see a couple of connectors and the strip fuse. Maybe a big power cable also.

At the front of the engine there's a small shock absorber. A couple of inches to the driver side of the upper attach point of the shock absorber is the upper perch of the spring. The lower perch is about 8 inches directly below, at the end of a lever opposite the lower end of the shock absorber. Takes about 5 minutes to fit a new spring including the time it takes to open and close the hood.

Sixto
93 300SD

Again - many thanks Sixto! I'll take this info with me to my mechanic's tomorrow morning. I'm hoping to get this stuff cleared up quick so I can get back on the road.

Hey - if nothing else, at least I'm learning a lot! It has been a while since I learned this much about anything in this short a time! My brain is getting a good workout with each and every problem I have to confront - I just have to learn how to NOT let them stress me out when they pop up!!!:D

Rusty,I agree with Hatterasguy.At this point I would to take this car to someone who is familiar with it.You having to advise him what to look for does not fair well with his basic knowledge of your 350sd.You may have allready spent more money and lost driving time by using this shop.The tensioner on the 350sd is about as basic as it can get ,installed incorrectly it could lead to major major problems. Perhaps someone else here can recommend a good shop in Vegas that can get you back on the road again quickly. ( as you mentioned being a professional musician ,hands on is not an option on your part ) . As always Good Luck:)

Spring is there; there is no place for the strip fuse...
 

Okay - I just got back from my mechanic's shop and I looked myself for the things that have been mentioned here...

First - in the glow plug relay, there is no place for the strip fuse whatsoever. I took the photos from dieselgiant.com with me and sure enough, there is no place for it. There looks to be a little spot of silicone or some other rubbery material over a metal spot, but no strip plug whatsoever.

Second - the spring by the belt tensioner IS there, but it is very loose. Could it be broken inside the black plastic/rubber tube? The belt is still basically floppy loose, too - no ideas what could be wrong/broken/missing.

Any thoughts? Does anybody have an idea what is different about my glow plug relay? What about that spring by the tensioner? This is very perplexing, but I'm keeping myself together - no freaking out yet!:silly:

Also - about my mechanic - since it is Friday and I will get no progress made anywhere else by having it towed elsewhere today, I'm going to leave it with him for now. Although he may not be an expert on my particular car, he is honest - and that counts for a lot. I have been taking other cars to him for 5 years and he has saved a couple cars for me. He is willing to put some time into it to help me, so I'll give him the benefit of the doubt...

...but if he can't figure it out today, I'm having it towed somewhere else first thing Monday morning.

Could you post a picture of your missing glow plug strip fuse so we can be sure of what you are describing?

I'll do that - I'm going to run back over there to take a picture; he's only 5 minutes away, so I'll get it and post it here ASAP....

Photos
 

Here are some photos of the belt tensioner/spring on my 350SD. Notice that with the tensioner and spring it is still loose enough for me to pull it sideways wih my hand.

Does anyone see any problems right off hand?

Here are some photos of my GP relay - notice the missing strip fuse. My mechanic found another strip fuse further up in a line, but it was further back near the power steering fluid reservoir (I think - it was on the driver's side, closer to the windshield) and it was intact.

I just received this email from BilliBob here at the Forums. Can anyone else confirm this? (Not to cast doubt, I just wanted to see if anyone else recognizes this.)

From BillyBob@ShopForum:

Check the 603 FSM later glow plug relays (after 1989) do not have a fuse and are essentially equipted with an internal circuit breaker, it is not externally resetable but resets itself. If you have an short circuit at a GP or the wiring to these you would in theory keep tripping it. Alternately the circuit breaker could have failed or some other element inside the relay. This info is detailed in the FSM 15-705 to 711. The thing that you could do is to disconnect the GP harness fron the relay and then cycle the ignition key to reset the circuit, then you can use a multi-meter, a 12V bulb or LED to test if the relay is providing voltage to the GPs, attach one wire from the bulb to engine ground and the other lead to one of the 6 pins in the relay. Cycle the key and you should be able to measure 12V or the bulb should light up, check all six pins this way. If all six pins show good voltage its not the relay. You can then open the 6 pole connector shell on the GP harness, attach one of the six female sockest to the male pin in the relay box. Cycle the ignition key and check for voltage at the pin. Do this adding a single GP wire socket to a male pin in the relay cycling the ignition key each time. If one of the glow plugs or its wiring is at fault the relay will trip and you won't find voltage at the male pin. Once you isolate the individual GP or its wiring that is short circuiting you can replace or repair it.

The serpentine belt tensioner should be tight if properly configured, if the belt is not properly routed usually it seems too short but perhaps it is incorrectly routed and is loose. The spring is attached at its bottom to a pin on the tensioner and at its top to a pin in the black plastic cam block. With the tensioner bolt that holds the cam block in place romoved and the belt loosened you should be able to move and observe the entire tensioner arm/pulley and rock it from side to side for free movement. The spring could be broken inside its plastic sleeve. The cam block should pivot freely on its pin. I assume that you've checked each of the pulleys on the PS, Alternator, AC and water pump to assure that they are all freewheeling. I had my AC compressor seize and it smoked the belt and made a hell of a noise.

Any ideas? Sorry - I don't mean to obsess, but as you can imagine I'm hoping to get to the bottom of this as soon as I can. None of the other problems I have encountered so far have made the car completely inoperable like this, so this one is really hitting a sensitive nerve!

Thanks for all your help - everyone!