Interval for changing injectors?
Hi!
I looked around for a similar post but couldn't find any.
Does anyone know if there is an interval for changing injectors (talking about a 300GE M103 engine), and are there any tell-tale signs that the injectors are on their way out (of action)?
Thanks in advance...
whats the milage of your truck, very rare for injectors to go but when they do they dump fuel in so it will flood on low revs, and you will notice it running rough and the fuel consumption will increase.
In case you haven’t fixed it yet. The injection system is quite straightforward; the mixture is richened and leaned by lowering and increasing the fuel pressure combined with extra air from the aux air valve. Anything that might affect the fuel pressure can cause problems: the fuel pump wearing out but also the fuel filter needing replacement. Make sure you change the filter at the proper intervals.
For cold start there is a cold start valve which is electrically operated and fires fuel for a period determined by the temperature. Any fault here can cause over richness of leanness. A simple test is to unplug it before a cold start and see what happens. It’s to be found on the inlet manifold with 2 wires plugged into it.
As said above its unlikely that the injectors will be you problem – if they are really worn they can cause rich mixture or if gummed up can stall out when hot at traffic lights. In that case a few bottles of injection cleaner will help.
As you say it is only at startup you may want to check the idle RPM as I had very similar problem to yours except it did stall after starting – I checked everything and was about to remove the aux air valve (a pig of a job) when I checked the idle RPM with an accurate strobe timing light – it was 250 RPM low - set it right problem solved.
If you really have an injection problem the best solution is to take it to a Bosch injection specialist – someone that understands these old mechanical injection systems.
Thanks for taking the time for a brief analysis. What puzzled me was that I changed the fuel filter, pump, and pressure accummulator all in the past 2 months, so from the fuel delivery side, I am pretty sure fuel is delivered to the injection system. The only thing I suspect there that has not been changed is the fuel pump relay, but I had an electrician open it and look inside, and he said he couldn't spot any poor welds or loose connections.
The reason for suspecting the relay: it used to (before changing pump) refuse to start when hot after a longish journey (engine turns but doesn't seem to get any fuel, no noise from fuel pump). This hasn't occured with the new pump, but once it cut off while I was driving, felt very strage, the engine dropped to idle speed and the accelerator did not respond, but only for a few moments, then everything went back to normal.
I have another issue that has come up in the past week, a loss of power!
When I floor it, it feels like the engine is only producing 3/4 total power, and this is reflected in the top speed (down to about 80-90mph) and acceleration. I have looked underneath the air cleaner and found the rubber grommet around the throttle cable end is disintegrating, maybe allowing for too much movement of the cable, but so far I (and the dealer) have failed to find a part or part number on his EPC or the online russian verion, very odd.
Lastly I will try disconnecting the cold start valve to see if it makes any difference.
Thanks for your time!
Taking a long time to start when hot is the fuel accumulator. It is designed to keep the fuel pressure up when the engine is turned off, when bad fuel leaks back hence the long cranking time before starting. I can take a very long time to start under these circumstances.
Bad or worn injectors can produce a poor spray pattern which can affect performance but you would not expect random cutting out. They can be tested but since you have to take them out and check each one replacing them is probably cheaper and is an easy job.
Cleaning the area under the air filter on the throttle body is a good idea – make sure the air meter flap is free to move without sticking
From the intermittent type of problem I would want to check the coil and EZL (sort of electronic ignition gizmo) after the usual plugs and leads route. I had one go bad on a 300e 124 merc caused al sorts of poor running – they are not cheap and its best to find a good one to swap with first. Also the coil could cause these problems as could a dodgy TDC position sensor. I don’t know if you have an over voltage protection relay on your truck but they go bad and cause problems.
Intermittent problems are a pain especially if you don’t want to throw stacks of money on a fishing expedition.
Some folks here have used Spilsby rd garage and independent old merc specialist on 01205 270241 nr Boston Lincs might be worth a call.
Good Luck
Thanks for all the great input! I have tried disconnection the cold start valve and the startup problem becomes a lot worse, so I guess at least the valve is functioning, as with it connected it takes a few turns of the engine, but eventually always starts.
A short while back all the plugs and leads have been changed, then I discovered (again last week!) that there was a light tapping sound from the engine, it turned out a plug had come loose and thus pressure in that cylinder was lost. I tightened them all with a torque wrench and refitted all the leads and now there is no more tapping.
The air meter flap works smoothly, but I will clean it as it seems a bit dirty. Maybe also wd-40 the throttle linkage part as it looks pretty dirty.
I have also removed the distributor cap and checked for cleanliness, and the rotor arm also looks fine.
You almost read my mind when talking of the coil and EZL, the coil is not that expensive, but as you mentioned, the EZL bit is about €1500 on the European MB parts site!
I now faintly recall, in the old days, our old 230GE once returned from an expensive service (this was when it was nearing 10yrs old), and they changed the EZL unit (from a bulky one to a flat transistorised one), and all the injectors. I couldn't figure the reason for that at the time, though the running became much more stable after that, from what little I remember.
That is the problem with intermittent problems, I guess when it becomes more "repeatable" then I will be able to do something about it, until then I will listen and observe carefully (the injectors are about £25 each at eurocarparts, so they can wait!).
Thanks for the number of the Spilsby Rd people, I might just call him and have him listen to it, perhaps he can share from his experience.
One last thing, as you seem to have experience with these engines, is an oil leak common from the front/side of the engine due to a leaking gasket, and is it a straightforward fix (i.e. new gasket?)
Many thanks for sharing your experience...I hope it gets sorted soon
One last thing, as you seem to have experience with these engines, is an oil leak common from the front/side of the engine due to a leaking gasket, and is it a straightforward fix (i.e. new gasket?)
In a word yes its common if you send me a PM with an email address I can send you the pages from the WIS on how to cure it.
Done! I will have to find a friendly mechanic with a strobe to check the idle speed, always start with the least expensive route!
Quick update on taking a long time to start, I replaced the Activated Charcoal Filter in the fuel tank venting system, and now it starts almost straight away. Amazing, that part needs changing every 5yrs/72,000 miles on the E-class according to some other forum, and it didn't look like it was ever changed (inside farside/right fender at the rear near fuel filler, a pain to access), and only about £21 from the dealer.
This is interesting. A lot of it sounds familiar.
I have same or similar symptoms on my Ambulance. (1983 280E with Auto) Hope this isn't recurrent to Gwagen 280E with auto I'm considering buying.
Not only is the idle sort of peculiar, (actually it's okay now; mechanic tuned it) it starts with a powerful roar, drops to somewhat high, maybe 1700 rpm and stays there.
Dig this though... When you poke it into Drive, idle goes RRRRrrr. Step on gas, engine will die immediately. BUT if you give just a tiny little gas, wait 1-2-3 seconds, then step on pedal, car goes like a rocket.
Another one.... Stop at red light, engine on. Maintain some throttle, brake with left foot. Release brake, car goes no prob.
Bizarre.
Any theories? Had an experienced mech tinker, cajole and fiddle with it. He just couldn't figure it out.
.
I think other members have faced similar problems recently, if you look under Technincal Forums>Petrol there are are a couple of posts by G-day dealing with his problems with the 280, might be some useful pointers in there.
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97k...i took 1 out and looked at it, didn't look dirty.
what made me suspicious: takes a few turns to start up, and on startup feels like it's about to die, but doesn't then everything is okay again. changed sparkplugs and leads, only things i can think of are coil and distributor (next up for inspection)!
thanks for your highly valued opinion :)