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D-jet ghosts

Started by UTn_boy, 29 June 2016, 01:59 PM

UTn_boy

I need some input from the other D-jet fellas.  D-jet has never bothered me, nor has it ever stumped me.....until a few days ago.  I'll make this short.  Here is what it's doing......when cold and up to operating temperature, it runs great.  No  problems.  After operating temperature has been reached, it'll slowly start cutting out on one cylinder.  It can be felt at idle, both in park and in gear.  Upon taking off, it'll stumble about on 7 cylinders while intermittently picking up on the full 8 cylinders.  After a  bit, the damned things runs on 7 cylinders the whole time.  I've narrowed it down to number 5 cylinder. 

Here is what has been done to the car recently:  new manifold pressure sensor, new points, coil, ballast resistors, ignition wires, correct non resistor bosch plugs, new wires, new coolant temperature sensor, new distributor car and new rotor button, new vacuum box for ignition advance, new pressure regulator, new damper, new fuel filter.  The throttle switch potentiometer has been tested and is not faulty, continuity checks of all of the wiring between the ECU and the inputs/outputs. 

I've switched out injectors, ECU's, and fuel pumps with known working units.  Nothing changes this problem.  The only thing I have not renewed are the injectors and the trigger points.  I've ruled the injectors out since they all tested good hot and cold, and they've been cleaned, tested, and their filter screens have also been cleaned. None of them are leaking, either.  Compression test revealed 150-165 between all 8, and the test was performed hot and cold.  The difference wasn't worth mentioning.  The fuel pressure was a 35 psi, but I turned it up to about 40 to get rid of the vapor lock problem I was having. 

My question is such: is it possible for the trigger points to have a temperature related fault? I'm about to go mad.  I've never encountered this type of problem.  Am I missing something? 
1966 250se coupe`,black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3,papyrus white/dark red leather
1975 450se, pine green metallic/green leather
1973 300sel 4.5,silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Guillaume C

One faulty trigger point makes two non-operative cylinders. If there is only one non-operative cylinder, I think trigger points are OK.

Did you check and adjust valve clearance ?

Could it be a worn out cam ?

UTn_boy

Yeah, that makes sense.  And yes, the valve lash and camshaft lobes are in check, as is the point dwell and ignition timing. 
1966 250se coupe`,black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3,papyrus white/dark red leather
1975 450se, pine green metallic/green leather
1973 300sel 4.5,silver blue metallic/blue leather
1979 450sel 516 red/bamboo

rumb

I know you replaced it, but could it be a bad rotor?
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

UTn_boy

Well, I kind of ruled the cap and rotor out because I replaced those thinking it may take care of the problem.  Nothing changed after I renewed them.  However, you've given me an idea....I'm going to check the high tension lead to number 5 cylinder.  Maybe it'll be bad, but with my luck, it won't be. :/ 
1966 250se coupe`,black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3,papyrus white/dark red leather
1975 450se, pine green metallic/green leather
1973 300sel 4.5,silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Zaxxon

Quote from: UTn_boy on 29 June 2016, 11:42 PM
Well, I kind of ruled the cap and rotor out because I replaced those thinking it may take care of the problem.  Nothing changed after I renewed them.  However, you've given me an idea....I'm going to check the high tension lead to number 5 cylinder.  Maybe it'll be bad, but with my luck, it won't be. :/

If you haven't changed it yet, a spark plug I have seen before giving a temperature dependent issue where some internal break must have widened with thermal expansion of the materials or so. Not too familiar with D-Jet, more of a K and L Jetronic kind of guy when it comes to Bosch, but have you checked the injector on that cylinder with a Noid-light or something, just in case it's an injector wiring or related issue? Just trying to think of some random things...
---
Mercedes: '99 CL500, '86 500SEC, '96 SL500, '06 R500, '02 ML320, '78 450SEL
Porsche: '80 928S 5-Speed, '86.5 928S RogerBox '86.5 928S 5-Speed, '83 944
Others: '84 Callaway Alfa Romeo GTV6, '83 Tiara, '87 FZ

Peter

I had a similar problem with my 280SE and it ended up being the HT lead to cylinder number 6. After many years the lead was rubbing just slightly on the steel of the head and on the very bottom side of the HT lead it had worn away enough to be making intermittent contact with the steel of the head. Very difficult to spot and engine was usually ok at cold start and then would fire on only 5 cylinders. I did almost everything you have described and spotted this faulty lead last in the search. Good luck

UTn_boy

Well, I figured out what my problem was.  Before I go into what the problem was, I want to scold myself.  Why?  Because I always tell everyone to CHECK THE BASICS FIRST!  I didn't practice what I preach, and had I done so, I would have had the problem taken care of much sooner.  For some reason I instantly assumed that the D-Jet system was at fault when it was actually fine the whole time. 

Rumb gave me the idea about it possibly being an ignition issue.  The cap, rotor, points, ignition coil, and ballast resistors were all brand new. The plugs and wires had been renewed prior, but I couldn't remember when.  So I looked to see how long ago I had replaced the plugs and wires. Turned out to be about 3 years ago.   They definitely have some miles and age on them.  So I went to the cylinder that was dead while it was hot, removed the high tension lead and replaced it with a temporary lead and the problem went away.  I still don't know if the wire end or the wire itself is what is going open, but at this point I really don't care.  haha 

The wires I put on the car were BERU brand.  Bosch wires are total crap lately, so that's why I tried the BERU, and up until this problem, there were no issues.  I think that if a bad wire is the worst I've encountered in all these years of owning it and thousands of miles of driving, then I'm doing just fine.  I don't mind to replace a bad wire. 

So the moral here is to, as always, check the basics firsts....even if it makes no sense to do so....do it anyway.  ;)
1966 250se coupe`,black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3,papyrus white/dark red leather
1975 450se, pine green metallic/green leather
1973 300sel 4.5,silver blue metallic/blue leather
1979 450sel 516 red/bamboo

Zaxxon

#8
Quote from: UTn_boy on 03 July 2016, 12:58 AM
So the moral here is to, as always, check the basics firsts....even if it makes no sense to do so....do it anyway.  ;)

And I have been around cars as long as I can think, and have owned more cars than what makes sense in any way (and still own most of them) and I will forget about that basic rule still every so often and could smack myself whenever I do! ;) But yes, very much the rule to go by. I mean in the end, if you have the right air/fuel mixture, and you have spark, the stuff is going to explode, no matter what! So glad to hear you got it figured out!

--Zax
---
Mercedes: '99 CL500, '86 500SEC, '96 SL500, '06 R500, '02 ML320, '78 450SEL
Porsche: '80 928S 5-Speed, '86.5 928S RogerBox '86.5 928S 5-Speed, '83 944
Others: '84 Callaway Alfa Romeo GTV6, '83 Tiara, '87 FZ

slfan

1978 - 450SEL 6.9 - 3170
1978 - 450SEL 6.9 "Parts Car" - 2973