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Mercedes 1972 280SE 4.5 wont start!

27K views 48 replies 16 participants last post by  MBGraham 
#1 · (Edited)
Ok, so I think this may or may not be the second time I have posted on this forum, non the less, I have purchased my second W108 body, this time I decided to be a bit adventurous and buy one that was sitting and did not run. The first thing I did was check for spark/ignition [check]. Went on to replace the spark plugs, changed out some misc vacuum hoses for the hell of it, then drained the fuel tank. The fuel tank screen has been cleaned, new battery installed, all fuses checked, car would crank and turn over but not start. A little observing and i realized that my fuel pump was not engaging, I was getting voltage to the pump, but no action. Worried that I needed a new fuel pump, I removed it from the car and disassembled, turns out it was just jammed from sitting, works like a charm now.

I have put a new fuel filter on, and changed out the fuel hoses. A friend of mine and I just spent the better of an hour trying to get it to start, spraying carb cleaner into the manifold [only thing I had laying around], engine catches but does not run. I pulled one of the new fuel hoses off the rail and I am definitely getting fuel up from the tank [albeit it may be some old gas from the lines as it is fairly brownish in color]. I guess my question is...is the car running its course and purging out the old gas with the new [5 gallons of fresh gas was put in of reg, not premium] or clogged injectors?

Another question which is unrelated is should all fuel hoses after the fuel pump be fuel injector hoses? I accidentally purchased reg fuel line hoses for the fuel rail, and the better majority of the hoses on the rail excluding the fuel injectors have been replaced with reg fuel line hoses.

I have trolled and trolled and trolled the forum, but am at a whits end, am I missing something? My next step tomorrow is to purchase an actual started fluid can and try it out, if still no go, I am tempted to pull the injectors for cleaning...

Any advise, criticism or pointers are greatly appreciated! Pics of the car are attached.

Thanks!

L
 

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#2 ·
Non fuel injected rated hoses means that the things are not supported with an inner mesh. At some point, you risk popping one of them and having a gas leak in the engine bay.

Bad gas will have a definate effect on how the car runs, but it would still start.

If the fuel injectors were bad, the engine would start but run poorly (unless each of them were all bad).

If you know for a fact your spark is good, and fuel is getting to the rails, you may have control issues. Look for good voltage to your ECU, which if missing, will cause the car to not run. Check all fuses first.

In my experience, carb cleaner doesn't act well as a fuel - try starting fluid or ether.
 
#3 ·
A few things.

Yes, all the hoses on this car should be fuel injection hoses. The only thing that is not at 45psi is the return to the tank from the regulator.

Are you getting fuel to the cylinders? if you pull a plug, is is wet from gasoline or is it dry. If dry, your injectors are not firing. Either they are gummed/plugged or your EFI brain is bad. You could also have a bad ground on the injectors (front right by the fire wall) which would keep them from firing.

Had similar issues with mine. It had been sitting for 13 years. I ended up making a new harness.
 
#4 ·
Thanks TZ_280SEL and Grubeguy for the responses! I def did not buy enough fuel injector hoses when i went to the store, which is why part of it has regular fuel hoses on the car, i'll swing by tonight and get the correct hose.

I did not think about pulling the plugs and checking to see if they are wet or dry. Sorry to sound ignorant, but when you guys refer to the ECU and EFI brain, i am assuming you both mean the same thing, and it is the box located up front on the passenger size [one with the fuel pump relay and such?

Another ignorant question is I would assume it should have 12V going to it? I'll try the grounds for the fuel injectors tonight as well. I'll keep ya posted!

Thanks!

L
 
#5 ·
ok, so an update on what happened tonight:

-replaced all fuel hoses with proper fuel injection hoses
-pulled off all ground wires near fire wall behind battery and cleaned them all up, also cleaned up the positive wires that are ganged up just in front of the battery near the alternator
-put a hose from the FPR to a bottle to make sure I am actually getting fuel up to the rail, check, primed the fuel pump about 5 times and filled up the water bottle about a 1/4 to a 1/3.

So...I tried to fire up the engine on its own before attempting to use any starter fluid and it ran twice for like a second, more promising then it has before. After many tries, it would not start, tried with starter fluid, just sputtered and shut off. I primed the pump again, let it sit for about 5 minutes, then tried it again with no starter fluid and it ran again for a second then shut off. My guess is dirty or bad fuel injectors? I totally forgot to check if a spark plug was wet, by the time i remembered it was too dark out to try it again and i had already pulled the battery back out. One thing i also noticed that when it ran for a couple times for a second, there was a knock, i am not sure if it was the exhaust hitting the body or the engine, didnt run long enough.

One thing I did notice which i am not sure if it is related is that one of the ceramic blocks is cracked and a wire is just barely hanging on, its connected to a module on the driver side next to the radiator but i dont remember what the module is, i wanna say its related to fuel injection or ignition but i do not remember. I am attaching photos as well.

On a totally unrelated note, I noticed that the forward spark plug wire connection [rubber portion] on the drivers side is resting on the heat sheild the manifold, is this an issue?

I guess my next starting point is to pull all the injectors out and try to clean them up and replace the seals, anything else I should be attempting?
 

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#7 ·
After some researching, it appears that it is .4 ohms, would any brand resistor work so long as its .4 ohms?
 
#9 ·
"Any" .4 ohm resistor will work, but it has to be rated to take the power. I recommend using the same resistor. BTW, resistors either work or don't.

OK, so fuel is there and works. Are you certain you have spark? That it, have you pulled a spark plug wire and held it close to the engine, to see if you have an arc? If so, then it's likely you have an issue with the ECU. Did you check input power to it? The ECU controls the opening/closing of the fuel injectors.

It's not likely that
 
#10 ·
Ok, new update, put a new Bert ballast resister on (.4 ohms blue) that I was able to find locally, cleaned more grounds on the ignition module and both resister wires. Tried to fire it up, and it just cranks, I have fuel coming up the rails, so I pulled a plug after cranking, and the look bone dry.... I had my fiancé crank the car while I pulled a injector plug off and held a volt meter to it, it only read .03-.06, is this normal? I wouldn't think so. How van I check if the ECU is bad?

I feel like the only thing I am missing on this car is getting fuel to the cylinders, I am soooo close!!!
 
#11 ·
Just to make sure, my car does have the d-jet, correct? I am researching this right now and mainly looking at d-jet stuff
 
#12 ·
Fuel
Spark
Air

Air is rarely a problem.
If you pour fuel in the throttle body (take off the air cleaner and pour fuel in, or spray carb cleaner) does it sound like it's sparking and about to start... until it runs out of fuel? If so, that means you are not getting fuel. D-jets have "trigger points" in the bottom of the distributor that with a signal from the ECU they tell the injectors to open up and spray fuel. Many people experience some going bad, but not all of them. They are fairly well protected, but if they are corroded the electric signal to open the injector might not be getting to the injector. The engine bay does look like it's seen some corrosion. Those are some thoughts on fuel since you are confident the fuel pump is getting fuel to the rails.

Then there is spark. If the behavior does not change when you pour combustible stuff in the intake, then spark is most likely your problem. It's unlikely that all eight of anything will have gone bad on you, so you can probably steer clear of individual plug wires and plugs. However, it will certainly be worth checking the electric and connections on the coil, coil wire, and other stuff... but only if you determine that fuel is not your problem first.

Here's some of the reading we have over in 107-land. http://www.benzworld.org/forums/r-c...rehensive-illustrated-djet-72-75-350-a-2.html
 
#13 ·
Ok, we had a nasty thunderstorm that knocked out our power Friday and have been without the Internet, so I haven't been able to pos any updates. What I have done since Friday is:

Pulled the ECU (has a Bosch remanufactured sticker on it) and pulled the panel with the relays, they were all corroded over with bluish green corrosion, cleaned up all the contacts and put it back together. The fuel pump works as it should so I would assume all relays are in workin order.

Pulled the cold start injector and cleaned it, put it in a bowl and fired the car up and it sprays and fills the bowl no problem. Now the car does have spark because it fires up on its own from time to time and always fires with starter fluid, that being said it only runs for a second. If the cold start is spraying, wouldn't you think the car would fire up all the time on its own? Even if it was for a second?

I pulled the distributor out and cleaned the trigger points, need to get the car to TDC before I completely reassemble, didn't think about it when I pulled it, will do this today.

I am also going to pull one row of injectors out connected to the fuel day and place them in a pan to see if they actually fire into the pan.

Will try and keep everyone posted, however it's kinda hard when the only Internet you have at the moment is your iPhone :p

Thanks!

L
 
#14 ·
Thanks for the w107 link Fonzi! Will try and read it today, I hope my Internet comes back soon!

L
 
#15 ·
Ok, new update, Set the top dead center and got the distributor lined up with TDC. Decided to take the injectors out and was goin to keep them wired up and hooked to the fuel line with a pan and have my fiancé crank it to see if they would spray, I then decided to just pull them all out...each injectors fuel hose was filled with black gunky gas, poured out like oil. My guess is this is what is robbing the engine of gas, as I know fuel fills the rail.

I guess my next question is, I have one brand new Bosch injector from my previous w108 and filled it with carb cleaner, when hooking this up, shouldn't it spray? It just seems to drip out.

I filled the injector hoses with carb cleaner to let them soak, hoping this will free them up, wondering if I should just buy all new injectors, thoughts?

Thanks!

L
 
#17 ·
Finally running! sort of...

Ok, new update:

So I finally got the car started! Took about 2-3 days cleaning out the injectors to get them all firing. The car started and ran for about 5 minutes before I turned it off. Ran the car again, and actually moved it and parked it in a different location. Came back to start the car and it just cranked and cranked and cranked and wouldnt start, after about 20 minutes of trying [not continuous], it finally fired up and ran and I was able to park it again, any clues as to why it wouldnt fire up again?

Now, onto my current issue, the car will no longer crank or anything, i turn the key and all i get is the buzzer. I did notice that even with the car in park while trying to start it the seat belt light comes on, i thought this only came on when the car was put in drive or reverse? Also, before i turned the car off last night, the brakes totally locked up on my, so hard that i could not move the car even by stepping on the gas, luckily the car was already where it needed to be. Could the totally locked brakes have something to do with this? My suspicion is that the starter got fried some how or bad connection from the battery? Even if the starter was bad, shouldnt i hear some sort of noise when i turn the key? I am totally lost, i checked all fuses and connections and everything seems to be good.

Any advise or criticism appreciated! Check out the video of it running at:

Mercedes 280SE 4.5 - YouTube

now only if i could even get it to crank again!

Thanks!

L
 
#19 ·
When i got off work today, decided to run out and try the car again, did not have time to get under the car to check the ground strap, I fiddled the selector lever from P to D and then through all the gears, the Seat Belt light would go out slightly, then finally went out after a few tries in the Reverse position.

Went through my Mercedes CD and found the diagram explaining the adjustment of Starter Lock and back up light [attached], will get under the car tomorrow and see whats up with that.

Still need to figure out why the car wont start up immediately, keeping in mind that the cold start injector works, as well as all injectors, any input or advice is much appreciated.

Thanks!

Lewis
 

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#20 ·
Make sure you adjust the set of points that are directly under the distributor cap, these are your ignition breaker points. They send a 'pop' of juice (indirectly) to the coil for it to boost to send to the spark plugs. The amount of time these points are closed is called the "dwell", and they should be closed for about 32 degrees of engine rotation. (look up "breaker points" and "dwell angle" in google for a full explanation)

If these points are not set correctly, or are dirty/corroded, they could cause poor running symptoms much like you describe. But this is only one possible problem, you might have others. It does sound like you have a neutral safety / starter lockout switch problem, although that could be a result of bad shifter linkage bushings. On some cars, like the 107's, they are notoriously difficult to change, but you might not have as bad a time on yours.

Kent Bergsma at Mercedessource.com has a lot of videos with tips and hints, including a howto on shifter bushings.

Just a few wild guesses and hopefully a little useful information,
Scott
 
#21 · (Edited)
Scott thanks for the info, I assuming the first one in the link below is what I would need for the bushing?

Mercedes Parts - Mercedes Benz Parts - Discount Prices - automatic transmission shift linkage bushing - 1972 Mercedes Benz 280SE Automatic Transmission Shift Linkage Bushing

I got under the car and the bushing is definitely missing, found part of it in the driveway.

Regarding the car starting, I finally just took off both fuel rails, and the t shaped rail that comes up in front of the engine from the fuel pump and soaked them in chemdip over night, they had so much crude in them! The next day I disconnected the fuel tank lines and poured chem dip in the main fuel line from the fuel pump and the return line and let it soak for a couple of hours, cleaned out the fuel pump (as it was clogged up with gummy gas) and installed a new fuel filter. Put everything back together and the car fired right up! The car ran good for almost two hours. Backed it out of my driveway (which is on an incline) and let it idle for about ten minutes then decided to drive it around the block, it made it about 3/4 the way until the car died. During this process, while hittin then gas the car was losing power, I thought I was running outnofngas so I filled it up some more with a 5 gallon gas tank....wasn't the case. The car started up, but didn't want to move much and would lose power or shut off when u hit the gas. After some inspection and pulling a fuel hose, turn out the fuel pump or new filter or both is clogged again, gas comes out extremely weak. There is enough juice to start the car but not enough to rev it. My guess is from backing it out of the incline that possibly some deposits in the tank cruded up the fuel pump...so that will have to come back out tomorrow.....will keep everyone posted!

Thanks,

L
 
#23 ·
I have not, I live in an townhome community, while I have a garage, but its full so I have to work on the car in the driveway, I don't think people would be too happy with me dropping the tank here, I did put a clear filter on between the tank and fuel pump as an extra preventative.

I have been trying to find the correct size and type of fuel hose for the tank to the pump, can anyone confirm that it is to be 14mm fuel injector hose? It is impossible to find! For now I have a fuel line hose on it, but the fuel pump causes the hose to collapse, so I put a spring inside the hose for now to keep it from collapsing, although im sure I'm restricting the flow. I did notice that when I started the car after putting the spring in it, the car started smoking like crazy out of the exhaust, not sure if that is burnt oil though leaking into my header from the valve cover
 
#24 ·
I did get the car running BTW for my wedding and restored.

Got it looking like this:


Then did this >:)


Wasnt too happy, so i did this :-D
 
#26 ·
use a stethoscope to see if injectors are clicking when cranking .also with ignition on , if you pump the gas pedal , you should hear some [ 4 ] injectors clicking . i ll bet the trigger pointes needs cleaning . if the ignition work , and plugs are clean , you should be able to run the engine on starting fluid . to diagnose this kind of system , you need a can of starting fluid , a stethoscope , and a KV reader [ this clamp on ignition wires and tell you how much power you have ] i would go on e bay or amazon and find a use manual on this early EFI system .vw bug used this system before MB . the introduction 1971 3.5 car manual had the diagnostic on this system .
 
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