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Post Info TOPIC: BOSCH D-Jetronic Trigger Point problems & solutions


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BOSCH D-Jetronic Trigger Point problems & solutions


Hello folks,

 

Recently, my little M116, 3.5ltr V-8 started playing-up, & in typical MB fashion, stopped playing-up when you popped the bonnet to have a look at things ! The symptoms were very similar to what you may experience when you acquire a little bit of water in your fuel, & being winter here, that was my first thought. The typical result is very similar to what you may have experienced when an ignition-lead / wire goes faulty, & you're left with only what feels like 7&1/2 cylinders etc to run with.

Anyhow, the difference here was that the problem usually disappeared almost as soon as it started, but it's frequency was increasing from a glitch nearly once-a-week or so, to everyday, so I had to do something about this.

Being a MB mechanic, I was aware of the components that also live in the distributor of these models with D-Jetronic, & decided to inspect & clean the trigger-points, as this was the usual 1st-step in isolating the potential issue. After pulling the point-set out, I could see that they had been in there a long-time, & that maybe a replacement set was required rather than just a clean with CRC electrosolve.

The "Trigger Points" initiate the opening of the fuel injector solenoids when they're closed. Each point-set is paired to 2 x injectors, & they open in 4-groups of 2, leading the firing order of 1-5, 4-8, 6-3, 7-2.

I checked all the electrical poles at the point-set solder-joints & plug-socket to ensure continuity of the 40-year old wiring loom & found everything OK. Even the continuity across each of the 4-point-sets was fine, so I refitted the assembly to see how my baby would run now...

The results were much better running, but the problem still existed, so I decided to source a new set, as the other side to a point-set wearing out, is it's rubbing-block against the cam-lobe, not just electrical debrit from arcing. When the point-block wears out, you get rich mixtures at the affected cylinders.

Thankfully, Bosch still make a replacement point-set, however, you have to wire / solder the set into the wiring looms terminal block, that slides into the metal-cover, that's then screwed into place on your distributor. This can be quite tricky to do, as always with soldering, you could do with another pair-of-hands to hold things, but you do what you can LOL.

Sadly, the wiring looms terminal block, that's made of plastic had disintergrated with age on my vehicle, so a neat repair with silicone was needed to address this issue, as this perishable part is not available separately, & does not come with the repair-kit. The Bosch repair kit costs around $500:00, where a genuine MB part that included the loom was $2,500:00. Better to go the repair kit I think !!!

Anyhow, I've attached a few photos for you all to see what these points look like, & what you have to do to solder them in.

Remember to mark your distributor to the front cover, & the rotor-button to the housing before taking the unit out, to avoid the hassle of re-timing everything once you're done !

Cheers,

Rastus

IMG_1782.JPG

 

The above picture shows the removed & old point-set & the new point-set wired into it's repaired terminal bock. Remember to check your electrical connexions with a multi-meter once you're finished.

 

IMG_1782.JPG

 

It looks like you get this photo twice folks LOL ! I don't know what I did, but that's what you get sometimes....



-- Edited by Rastus on Monday 3rd of August 2015 11:31:44 PM

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Good Job! Looks like a tedious process. 

I don't quite understand how they justify the cost on such an older design, but as such is the way when it comes to Mercedes. were you not able to source one online for a better price? 

 



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Hey SELLC,

Nice to hear from you mate !!!

Though years ago now that I finished my apprenticeship at a MB dealership, one-of-the spare parts persons who I knew ( from back then ) advised me to go through a friend of his that operates a business known as "Access Parts". The ware-house in Oz for genuine MB parts is of limited capacity, & every-so-many-years, they sell-off the genuine MB parts to folks like "Access Parts", to make room for all the parts needed for new models.

With "Access Parts", Chris has all the passed-down-knowledge of the "who-what-&-where's" for bits & pieces that you can't get any more, & he's pretty quick too ! Put simply, if he can't source it, you have to wait around 2-weeks for an overseas order to come through. So he's my one-stop-shop, & I've stopped looking around, as over the years, he's proven himself both capable, honest, & competitive price-wise. His quotes always list MB prices, & then his price next to it. If there's something S/H to be found, he'll let you know too.

With cars this old, parts are still made for them, but it's possible to source both the genuine MB parts, & the OEM parts, that essentially come in a different box, & are about 1/2 the price or less....

As an example, a company called "FACET" in Italy, have pretty much taken over production of ignition parts ( & other components) for these older cars ( eg. points, dizzy-caps & rotor-buttons etc ). This is when you start to learn that cars such as FIAT, BMW, FERRARI & others actually use the exact same set-of-contact-points etc etc. So the print on the box doesn't matter to me, as I know it's still the genuine item, just packaged differently. So often you're paying a lot of money for a box that you throw away ! This also means that BOSCH themselves are not making their own OEM parts for these cars, & have passed the duties on.

As with yourself however, there's parts that you don't take chances with, & anything that has to do with internal engine & drive-line components, will be MB only parts.

These trigger-points ( or Pulse Generator Contacts ) came in a Bosch package, at 80% less cost than the MB part. I couldn't justify the extra cost for a wiring loom that was still working fine, though part of the plastic-plug at the distributor had perished. It still secured itself perfectly ( clipped-in ), it was only the out-side portion that had perished & got a lick-of-silicone to keep it all air-tight. - ( Water resistant ).

The bottom line however, was that I wasn't 100% sure about this component being the fault, & it seemed better to have made a $500:00 error that a $2,500:00 error LOL ! I was confident that this would fix it, but you're never 100% sure until it's fixed & running well again, which it is by-the-way !

Cheers,

Rastus


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Good call!

What's the exchange rate on 500:.00 vs USD? Because that has to be the most expensive set of points I've ever seen! I got sticker shock and it's not even my part! LOL



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Hey folks,

The exchange rate at the moment is that $1:00 AUD = $0.73 USD. It's been around this mark for a few months now.

This means that these trigger points would cost you folks in the US-of-A around $365:00 for the Bosch repair kit. ( What I soldered in ).- ( It's also made in Germany BTW ).

The MB part with the loom included would cost around $1825:00 USD & whatever taxes you may or may not have to pay.

Trade discounts I can't comment on, as they vary from place to place, & part to part, but here in Oz, you usually get a "special-price" + another 10%.

Much better to shop in the US-of-A at the moment LOL !!! 12-months ago however you were better off down here...The exchange rate was near identical, but the other way around !

Cheers,

Rastus


IMG_1785.JPG
-- Edited by Rastus on Wednesday 19th of August 2015 12:05:02 AM



-- Edited by Rastus on Wednesday 19th of August 2015 01:49:45 AM

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MANIFOLD PRESSURE SENSOR


Hello folks,

Rather than start a new thread, I thought I'd just continue on from here, & keep all the stuff "D-Jetronic" related...As the title states, this is about the Manifold Pressure Sensor, as found on all MB D-Jetronic fueled vehicles, typically from around 1968 to 1976, & how I went about discovering my fault, diagnosing, & repairing.

My little 350SLC developed an odd fault a few months ago, that typically got worse & worse, & time rolled on. And the biggest issue with the cars of this era, is that though computerized, no RAM was included in the design, so there was no codes available ( like now-days ) for your mechanic to check & rectify. This means that frequent & un-fruitful visits to the MB repair shop, left both the customer & mechanic scratching their heads as to what the problem actually was / is, & the usual & expensive 1st-step of Fuel-Pump & filter replacement to be initiated, so as to eliminate the most likely probable cause first. And then let the fun continue, & see what happens....

Even if plugged into the "Official" Bosch diagnostic equipment, if the electrical components had continuity, & read the correct readings ( usually in Ohms ), no fault could be sourced, even if one existed...

Anyhow, my problem began with the car basically cutting-out, & losing all power, forcing me to pull-over, shit my pants for a second or two, & then shut everything down to try for a start-up. The car would instantly fire-up, & continue on its happy way, with no more problems....

After about a month, the issue became more consistent, & I noticed that it happened only after a re-start when hot, after shopping at my supermarket...You'd start up, drive out, go around a corner, & then nothing...The motor would stall, leaving me high & dry on the side of the road, only to seconds later, fire-up, & run fine again, all the way home ( via freeway ).

Of course, when testing at home, everything worked, so there was nothing to check ! But I did go to the trouble of feeling my my fuel-pump whilst running, so as to determine that it was not noisy in operation, didn't vibrate irradicaly, & had a smooth transfer of fluid as it ran.

The next step was to then determine whether the trigger-points I'd fitted about a year earlier, hadn't developed a cold solder-joint, & found everything to be fine there.

After this, I tested the Manifold Pressure Sensor, & found all the electrical reading to be within spec, this being 90 & 350 Ohms, as measured from the two outside terminals, & the two inner terminals. I then removed the unit, & sucked on the pipe that reads the manifold pressure, & it seemed fine ! However, I bought myself a hand-held Vacuum-Pump a while ago, & when tested with this device, discovered that the Sensors diaphragm had a slow but constant leak. This meant that the car ran fine cold with lots of fuel circulating in the cylinders, fine out on the highway with constant & regenerating vacuum @ RPM's, but terrible when in town, warm engine, & brake applications. This basically would have caused the unit to obviously send the computer incorrect information, & an over-rich mixture caused it to cut-out.

New units are available from Mercedes Benz at $3,500:00 AUD.

Bosch Genuine replacement units were available up until 2002, & cost approx. $1,500:00 AUD.

Bosch offer a reconditioning service that will set you back around $750:00 with new parts fitted to your old unit. Turn-around time is not available however, & neither is the location of the nearest facility...

I found a good Second Hand unit for $350:00.

Anyway, the car is running fine again ! And I'm happy to have discovered this tricky fault by myself, though it did take a quality tool to confirm the fault, where I thought it was fine...My next step was to inspect & re-set the throttle-switch, but that was not necessary.

I hope this helps you folks out-there with MB cars fitted with Bosch "D-Jetronic" EFI. (I'll post some photos later).

Cheers,

Rastus

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Rastus wrote:


New units are available from Mercedes Benz at $3,500:00 AUD.

Bosch Genuine replacement units were available up until 2002, & cost approx. $1,500:00 AUD.

Bosch offer a reconditioning service that will set you back around $750:00 with new parts fitted to your old unit. Turn-around time is not available however, & neither is the location of the nearest facility...

I found a good Second Hand unit for $350:00.

Anyway, the car is running fine again ! And I'm happy to have discovered this tricky fault by myself, though it did take a quality tool to confirm the fault, where I thought it was fine...My next step was to inspect & re-set the throttle-switch, but that was not necessary.

I hope this helps you folks out-there with MB cars fitted with Bosch "D-Jetronic" EFI. (I'll post some photos later).

Cheers,

Rastus


 

I'm sure glad you were able to source one used! Some of these new parts from Mercedes are starting to get seriously expensive given the age of technology. Often times a used original equipment part will outlast a brand new aftermarket! I've seen it with my own eyes! Great information Rastus!



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Hi Folks,

Thanks SELLC, & you're quite right about OEM 2nd-hand parts often outlasting new after-market stuff.

It seems that Bosch too over the years, started to simplify replacement items for these older cars, by combining a 1-part suits all approach... This means that where once upon a time, there were specific Bosh made parts to suit your 280, 350 or 450, they've all been "compromised", & now a one-part-suits-all-engines formula has / had been devised across the board.

As an example, you can log-on to their web-site, punch-in your make & model vehicle specs, & find a list of their parts available, but with up-dated part numbers, where you then discover that the same part fits all the other engines, especially with fuel pumps. This also means that subtle modifications will need to be made...As for the fuel pump for eg., the part will fit my vehicle & work fine, but I'll need to extend the wiring loom approx.-8", & find a screw in plug for the high-pressure outlet with a 90-degree outlet nozzle. And that's fine too, but they don't offer the modified parts to make things work, so more running around is required...But that's life, at least you can get something new that's still relatively OEM, & I can understand why they've stream-lined the product range, to simplify their growing & already very vast range of available products...

Here's a list of current Bosh D-Jetronic parts & their Part No.s that are available pending your order, & them determining availability of stock, as of July 2016....

Fuel Pump = Part No. 0 580 464 125.

Manifold Pressure sensor = 0 280 100 018.

Throttle Switch = 0280 120 011.

Trigger Points ( Impulse Generator Sensor ) = F 026 T03 035.

Ignition Trigger Box = 0227 051 022.

There's also temperature-sensors, but they seem available everywhere still...


Here's a picture of my Manifold Pressure Sensor. It's essentially a spring-loaded shaft, with an armature attached mid-way, that moves through a coil of wire, via the movement of the diaphragm, that has manifold pressure sensed on the RHS, & atmospheric pressure on the LHS. The movement of the armature through the coil generates a variable voltage, depending on it's position, that's sent to the computer for processing.

IMG_1965.JPG

 They've broken the heads of the fasteners, so that you can't open-it-up without going to some trouble...There's no point for me to open it up, since I can't get any new parts to install...That's left to the Bosch specialists out-there somewhere, probably in Europe...

Cheers,

 

Rastus



-- Edited by Rastus on Friday 12th of August 2016 01:08:58 AM



-- Edited by Rastus on Friday 12th of August 2016 01:11:49 AM

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IMG_1969.JPGHello folks,

Well, my problem didn't go away for too long unfortunately, & though the car was running a lot better ( much better throttle response ), I still suffered from an intermittent cut-out, that seemed to only happen when warm, & in city traffic, & usually after using the brakes...

I fitted the new Fuel Pump with filter. This takes some modifications to fit, as the new "one-for-all" Bosch pump is basically too long, & you'll need to remove the one-way-valve ( not necessary on a MB ), & fit a suitable bolt with a banjo fitting for the discharge nozzle. Also, the suction pipe on the new pump is 5/8'' ( 16mm), where the standard size on the OEM pump is 1/2" ( 13mm ). Needless to say, a reducer is required & a small length of 5/8'' fuel hose with a couple of clamps. You'll find that the wiring will reach the poles without trouble, even though they are now at the discharge side of the pump.

As mentioned previously, a new fuel pump is often the first-step to rectifying faults with these older cars, as it eliminates the hardest working component in the system that's prone to failure, & after setting the fuel-pressure to the recommended 2.0 Bar pressure, you're now free to asses the remaining components, if problems persisted. And for me, they did....

Realizing that my fault occurred after using the brakes, I had to start looking again at the intake system, & for possible leaks. After attaching my vacuum pump to the distributor vacuum hose, I noted that the vacuum was sitting at a steady 15"hg, which is actually pretty good for these engines, as they are relatively "cammed" for top-end HP delivery, meaning that the usual expected reading of 17-22"hg was in the ball-park, as with your average stock carbed GM or Ford engines of yester-year.

A quick inspection & spray of CRC around the injector seals & manifold gaskets revealed no leaks, so the only parts left to inspect were with the PCV-assy, & the Auxilliary-Air-Valve assy. The removal of some rubber pipe-work revealed the PCV-valve to be clean, & in good shape. It also gave me access to spray contact-cleaner in the AAV assy, to remove any gunk / varnish that may cause this component, that's thermostatically controlled by a bellows & water temp, to stick in its movement of opening or closing ported excess air, so as to maintain sufficient idle RPM's, at all engine temperatures. After a good 2-3 sprays, & allowing it to dry-off, I then gave a squirt of regular CRC to lubricate the sliding piston assy.

I also noted a possible dodgy electrical connexion at a sensor on the thermostat housing, that I repaired, as it was likely a temp-feed for the computer, since my temp.gauge was still working when I disconnected it ( LOL ).

The car is now running fine again !!! I figure that it was the subtle combination of a few faults that appeared over time & with age, & I'll certainly monitor the state of operation of my AAV, & ensure it gets a clean & lube, at every major service. I've also been driving the beast far less than usual, & this doesn't help either. They need to be driven & enjoyed.

I hope this helps folks out who have issues with these older cars ! And I'll attach some pictures when I get some new batteries for my camera LOL.

Cheers,

Rastus

NB You can see the new long Bosch pump wired-up, resting above the rear axle, & the old pump with filter-assy laying in the spill-tray.



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I got a wonky computer side temp sensor in my 560 I need to fix, either that or a wonky thermos switch. Between a certain temp 60-80c when warming up it will sometimes run poorly. Be glad you only have the one pump, on mine it's a dual setup with twice the bologna! Looks nice and clean back there though and I cant tell you how many roached out Mercedes I have worked with over the years that have mushrooms crawling out of every banjo connections and fuel lines cracked from dry rot. There is an awful lot of "small" parts involved in rebuilding Mercedes Benz fuel pump assemblies of this era, even if you only have the single pump.

It takes a finesse to do what you have done, patience and also commitment. I have got to do a little fixing myself in the months ahead on my car. I've collected a great deal of new factory Mercedes parts over the years and I have to get them installed soon. Heck on Tuesday of this week my alternator went out on the smoke 560, luckily I had a few used ones kicking around but it took two tries to weed out the bad ones. Last time my alternator went out I had to change 3 of them on the side of the road before I found a good one! LOL talk about being cheap!  



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Thanks SELLC !

It's really annoying when you start spending money on your car to fix a problem, & the problem doesn't go away !!! But worse is the loss-of-confidence in the car, for not knowing if it will stop for no-reason... And of course, going about repairing a fault that doesn't show-up on tests...At least my fuel consumption should improve a little-bit now, with a good MPS fitted.

I'm sure you'll be repairing the 560 well-enough when the time is due, & being aware of the problem means it's already 1/2-fixed ! CISE is a different injection system again, with its own set of problems & solutions. The most common fault with the system here in Oz, has proven to be sticking plungers in fuel-dividers after many miles of usage. Usually a reconditioned change-over unit is the fix for everything from poor-starting, general running, & crap fuel consumption...

Alternators are amazing, in the sense they do so-much-work for such-a-long-time, & then one day out-of-the-blue for no reason, they'll take a big shit. I'm glad that you had plenty of spares to choose from to get you going again. Sometimes new bearings & brushes / regulator-pack aren't enough...I think that the brush-spring, when the brush is well-worn, will fick-out, & cause a short & other damage. Great when you can catch them before this, not so good when there's no warning.

Sometimes a film will form over the brushes & slip-rings causing a no-contact situation. I hope you still have these old alternators as the fix may be an easy one.

Cheers,

Rastus

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A vehicle not being driven and sitting a long period of time really can result in some pesky and expensive repairs. Working out the bugs of a vehicle sitting for a long time can also take some time as not to overspend replacing something when a simple cleaning could resolve the problem. That's not the case when it comes to dry rot though, lol... No fixing dry rot!

I'm going to post a thread soon about a leak I have in the W126, that's my first order of business in the repair saga of Goldilocks. I feel your pain, you fix one thing and on to the other dozen or so. lol 



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Hello folks,

Well, it seems I've come full-circle, & the issue of my car just dropping out has continued...

After re-inspecting the near-new Trigger-Point assembly I wired in around a year ago, I found everything OK, as in nice & clean, & no broken wires...I decided to spray the contacts with electrosolve anyway, & the inside of the distributor, & so-far, with around 300-k's & climbing, no cut outs...

I'll keep this thread up-dated if the issue continues, but I hope it's now been put to rest !


Rule number 1 with Bosch D-Jetronic cars, is never think that the Trigger Points are OK. Clean them anyway !!!


Cheers,

Rastus

PS. I have no regrets fitting the parts that I have so-far. The MPS was faulty, & with a 43-year-old car, its nice to know the fuel-pump is new, & should go for at least the next 5-10 years.

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Is it already 43 years old!?

Lets face it, you love to tinker with it! lol

With age like that you have to be on it all the time if it's not a garage queen, and what fun is that?

Glad you got things sorted and at cost like I have seen you better hold onto even you old parts that were bad, never know when you can salvage something off it.



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LOL,

You're right there SELLC, I don't mind tinkering around with it...In fact, I always expected to have to, to keep it going strong...But the strange thing is, is that for the 1st 3-years of ownership, all I had to do was regular servicing, & put fuel in it. And then the niggles started LOL...

Hopefully now, a spray of electro-solve every service for the trigger-points will keep her running sweet ! The main reason for not driving her as much was purely from a down-turn in work for me, so I altered the schedule from "want" to drive it to "have / need" to drive it...Plus the Hayabusa is a little more exciting too, & can return 19.1-km per litre of fuel, when compared to the SLC's 8.5-km...We pay around 30-40% more for fuel on average than you folks. At the moment fuel is cheap at $01:37 per litre of 9ctane Caltex.

I bought the Hayabusa in May, & have already managed to clock over 10,000-km through winter...Of course, now some work is coming in, I'll miss the summer riding as I'll likely be at sea. At least having some work means I can keep-up with the bills again, though I really don't know how much work will flow through my hands, as there's a lot of Sea-farers "on the beach" at the moment down this way, & have been for a long time. At least we didn't have to wait for your elections for something to happen down here LOL !

Cheers,

Rastus



-- Edited by Rastus on Sunday 4th of September 2016 07:41:09 PM

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Love to see some photos of that Hayabusa! How come you never mentioned it?

Glad to hear you're getting back to work, I know you were going a bit stir crazy there for awhile with all the extra time. Given the fact you work on the sea I'm starting to understand your increased interest in the Japan Nuke spills and ocean quality, it's because you probably get a first hand view of the real damage!



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Hey SELLC,

Check out the V-8 Cafe for some Hayabusa news.

Yes, getting back to work will be great ! But there's a lot of hurdles to overcome first...Mainly passing a whole heap of Medicals...Not as easy to do as you think after sitting on your ass for 18-months. Gaining weight = Higher Blood Pressure, & the authorities want you as fit as an 18-year old...

Yes the Jap-Nuke-Crisis plays on my mind for a great many reasons, working at sea being one-of-them. But the spread of the radioactive toxins is inevitable over time, ships ballasting & de-ballasting will spread the shit around, along with making the vessel now radio-active. I've been refusing to work anywhere in the North Pacific ocean, though most of my work seems to come from the Indian Ocean thankfully, off the North West shelf of Australia, which just so happens to be the place that the U.K. nuked for atomic testing in the 1950's LOL, so there's no avoiding the shit LOL.

What do you do ?....

Cheers,

Rastus

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I don't know, but I am drawing the line at growing a 3rd eye! If that happens, heads are going to roll! LOL



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