MAPs ECUs and paint dots

[Drew20]

Hi all,
My d-jet E9 has an overfuelling issue at idle, lumpy and rich. I think the fuelling is otherwise ok, in that the car pulls strongly without hesitation at full and part load. I've run through the basics, testing the ignition side of things (all seems fine except for some slight play in the dissy rotor, which can be fixed this coming winter with new bushes), and I've checked for vac leaks around the manifold (none, once I had tweaked the cold start valve waxstat). ECU and MAP both seem fine visually. MAP holds a vacuum fine and the coil resistances are in spec. The MAP is still virgin intacta, but does look to have been out of the car at some point, as one of the two bolts was missing where it fixes to its bracket.

Elsewhere in the d-jet system, both the air and coolant temp senders appear to be within range, and the loom connects well back to the ECU plug, and the TPS tests as fine electrically. I've tried anther good ECU in the car and it runs the same: fine under load, rubbish and rich at idle. Both ECUs were dialled back to max lean (anti-clockwise) on the twiddly knob.

So I've whipped the MAP out, to check it over in more detail and, as well as the missing bolt, I noted that it doesn't have a paint spot on it. The ECU has a red sticker on it, but I can't see the corresponding dot on the MAP. Given that the MAP has (I think) been removed at some point, I'm thinking it's perhaps not original to the car?

Can anyone help me understand this better:
At idle I am measuring 14"Hg in the manifold, which I think is lower than ideal, but I think this is in part down to the lumpy idle, which swings around 400-700rpm. And the play in the dissy may also be having an impact as the spark timing may not be as precise as needed. What is a good manifold vac at idle? 15" is ok, or still some more?

How sensitive are our d-jet cars to the colour dots on MAPs and ECUs? I have read that they need to be pair matched (red with red, blue with blue, etc.). But I have also read on the net that being colour matched is not vital.

What colour dots should my car have? My car is a 1972 city-pack CSL

Given that the MAP holds a vacuum fine, I understand that means the full-load diaphragm is leak free, however I don't think there is any way to test if the pair of aneroid bellows inside the MAP are intact without opening it all up. I think if one or both of the aneroids were leaking (not expanding under vacuum) then the MAP would be sending a part load signal to the ECU at idle. I have read that the aneroids (bellows) don't often fail though, so I'm not sure if this could be the issue or not. Has anyone come across a MAP with an intact full-load diaphragm but leaky aneroids?

Anything else I should be looking at? I've not looked at the injector triggers in the dissy, as I couldn't see a link to my symptoms there.

thanks

 

[TomHom]

Hi Drew,
did you check your fuel pressure? Should be at 2+0,2Bar. Maybe your fuel regulator is out of order, with the pressure being too high.
As a consequence too much fuel would be injected.
As I just learned Bosch stopped putting the dots on the MAPs, from which date onwards I don't know. So I wouldn't worry about the dots.
What do you mean by play in the "dissy"? Distributor? If yes this would be the first thing I would correct!
Regards
Thomas

 

[ScottAndrews]

First thing I'd look for are vacuum leaks, which are most noticeable at lower RPMs (i.e. idle).
Also, have you checked your cold start valve? If this is leaking you will get too much fuel, and again, depending on the scope of the leak, this will be most noticeable at idle. Disconnecting the CSV is not necessarily a good test, since the leak may not be caused by the solenoid. Instead pinch off the fuel hose to cut fuel to the unit.

 

[Drew20]

thanks Thomas, thanks Scott
yes, sorry should have mentioned the work-up I did on the fuel system last year. I put a fuel pressure gauge on the CSV line and that measured the FPR was running at 2.0bar on the nose. I also had the injectors cleaned and flow balanced (and replaced all the hoses and seals at the same time). Somewhat surprisingly, the original injectors (inc the CSV) came up good after a professional servicing, so I put them all back in again with new seals, and the correct collars on the short rubber hoses to the injectors. So I think the fuel system is all running factory fresh, give or take 50 years...

On vac leaks, I have checked the obvious places; being the brake servos, the dipstick and the MAP itself. They were all fine. I did note that the aux air valve (apols, as I called this the CSV valve in my post above) was passing slightly when warm, but that is now good after I nipped the waxstat bulb in the vice, to give it a headstart on closing up the AAV. Is there anything else I can check for vac leaks? I am not entirely happy with my idle manifold vac figure of 14"Hg, as (from looking around on posts here) I think that should be 15" at least, so there may still be a leak, but I'm buggered if I can find it! Any tips welcome!

Maybe I should rebush the distributor (dissy) and take it from there, as there is very slight but noticeable radial play, and a good deal of axial play. And look at the injector pick-up whilst I am there, as that's the last bit (other than the MAP) that I have not looked over.

Plus any knowledge of MAPs and how they go bad would be appreciated, thanks.

 

[sfdon]

Do the easy part first.

Adjust your valves

Adjust the idle screw at base of throttle body until idle is at 1000 rpm

14" is low enough to trigger the MPS to think it is at cruise.

 

[TomHom]

Did you check the idle position switch on your throttle valve yet?

Measure between the contacts 12/14 and 17.
In idle position the contact should be closed, about 0 Ohm.
Opening the throttle valve by only about 1° should open the contact.

 

[Drew20]

Will do Don, I was just under the oil filler cap checking my oiler bar (thanks for that heads-up also) and had the thought that it is a couple of years since I did the valve gaps. Will do that tomorrow. 1000rpm seems quite high, no? Well I have just checked spec and it is 850-1000rpm for a Euro E9, so that is another easy one as you say.
I know exactly what you mean, I do tend to get sucked into complex theories as to what is wrong (and my current obsession is with the MAP!) but it is indeed always best to start with the most basic basics and go from there. A top-tip good for all seasons.

Hi Thomas, I have done the TPS checks before, but I will do so again, as Don's general point to start with the easy stuff would seem to cover TPS operation also.

 

[sfdon]

The MPS is basically a 3 position vacuum switch

 

[TomHom]

There are two coils:

For the primary coil measure between pin 7 and pin 15, should be about 90 Ohm. Between pin 7 and ground should be infinite, otherwise there's a short circuit to ground.
For the secondary coil measure between pin 8 and pin 10, should be about 350 Ohm.
Between pin 8 and ground should be infinite, otherwise there's a short circuit to ground

 

[Drew20]

thanks Thomas, I did those resistance tests earlier today and got 93 Ohms and 353 Ohms, and no shorts, so coils are good. I also tested the vac and that was all good too. I see no easy way to test the pair of internal aneroids though. With a LCR meter it is possible (I understand) to measure the inductive coupling between the two coils at various applied vacuum levels, which indirectly measures the movement of the MAP armature, which is itself an indirect measure of the performance of the aneroids through the part load range. But I don't have an LCR meter....

But anyway, I'll be starting with a general tune up first (I have already replaced air filter and spark plugs, and did a compression test whilst the plugs were out - no.1 was a bit lower than the others being 185, compared to 200-210 across the other five).

The Manifold Pressure Sensor

D-Jetronic chapter 4: Intake manifold pressure (MPS) sensor - function and repair

Chapter 4 of D-Jetronic article series by Dr-DJet describes the second most important part of D-Jetronic, the intake manifold pressure (MAP) sensor. It indirect

jetronic.org

D-jetronic system repair for BMW 3.0 CSi

D-jetronic system repair for BMW 3.0 CSi

jetronic.org

 

[TomHom]

A great source of information on this forum, I really like it and just got me that test adapter!

 

[nashvillecat]

After 50 years, matching the colored dots seems aspirational and not critical. Dot adhesive lasts only so long and your MAP sensor may have been removed only to access other parts, rather than for repair or replacement.

Quite a bit can be determined from reading your spark plugs and checking the gaps. If your ignition system is capable, wider gaps may provide a smoother idle. Conversely, if your engine is already running rich, wider gaps are more prone to misfire. However, since you state that your vehicle is A-OK when accelerating or under a load, it is unlikely that a spark plug or the secondary ignition system is a culprit, but as noted by others, the standard copper or silver plugs seem to perform better than platinum or iridium plugs. (Numerous forum threads discuss conventional wisdom and preferences.) Also, while this would not be my first guess, spark plugs that are too cold a heat range, may have a tendency to foul (hint: at idle). Along the same lines, you mention your questionable distributor. Setting aside any specific timing specifications/recommendations, have you used a timing light to confirm a smooth and steady timing mark? If you have a jumping timing mark . . . maybe it is time to recheck your points plate, including the attached vacuum retard apparatus, centrifugal advance weights/springs, cap and rotor, let alone, distributor bushes.

I also concur with checking the running fuel pressure. Evidently, you have already confirmed a 2 bar pressure, but I wonder about the accuracy of your gauge and, for that matter, the stability of the “adjustable” fuel pressure regulator. (Recently observed a different Djet-equipped vehicle where tapping on the regulator affected the gauge reading.)

Focusing on too much fuel/over rich condition at idle, have you tried disconnecting the fuel source at the cold start valve? It might be not fully closing, due to a faulty valve or the related electrics. Just a few dribbles might affect the idle. Of course, if the cold start valve is removed from the equation, by plugging the source, the auxiliary air valve being stuck open or partially open would likely result in a lean condition - which is anathema to your symptoms.

SfDon’s suggestion re checking valve gap is always a good idea, although the fact that you observed your engine operating well when accelerating, and off idle, suggests this might not be a significant issue. Nevertheless, improper valve lash can certainly affect idle and/or other engine operation.

Re vacuum readings, "typically" at idle, the higher the better. It goes without saying that your throttle plate assembly should be snug and not worn. Retarded or over-advanced ignition timing can affect manifold vacuum.

Note readings indicating "possible" issues with valve and ignition timing.

 

[TomHom]

....and check false air at the throttle valve bearings

Post in thread 'Throttle shaft seal leaking'

Jun 25, 2023

You will find them as spare part for the Yamaha XJ650, e.g. here

Dichtung Drosselklappenwelle Vergaser, € 6,10

12x8x2,2 Einzellippe

parts4motorcycles.de

Got this info from Gerhard from the german forum
Thomas

• TomHom

• 

 

[Drew20]

well, I've been busy. I have reset the valves to 0.3mm. Looking back at my file of stuff, it's actually been 4 years since I was last there, and some were a bit off, closer to 0.35 maybe, esp on the exhaust side. Idle bleed screw adjusted, and the idle is now stable at ~900rpm which seems like good progress. Manifold vacuum is very low though, now sitting at 12"Hg at idle. Also a slight misfire at idle, though overall it is idling much better than it was.

Also checked the TPS operation, and that is good; a solid continuity signal as soon as the throttle closes. No play in the TPS spindle. I also had a go with the carb spray around the gaskets on the intake, the injector seals, valve cover etc.... no sign of vac leaks. Compression still good across all 6, and plugs look fine (though they've only done about 100 miles). Fuel pressure still reading 2.0 bar spot on, and no change when I ding the FPR. What else... I also stuck a camera inside the cylinders whilst the plugs were out, seem fine to me, visible honing marks, but it's very difficult to see anything on the rubbish £20 camera I bought!

So tomorrow I can take a look at the throttle spindle seals (thanks Thomas). I've not heard about those before.

And (too late) I thought I should have checked the camshaft timing whilst I had the lid off. I have buttoned it all back up again, but I may well dive back in again to ensure valve timing is as it should be. What is the easiest way to get the valve cover off and on again. Today I left the throttle body and distributor in place as I didn't want to disturb stuff I didn't need to, but getting the valve cover back on again was a bear.

Oh, and should the valve cover breather have a clip on it? Not one on my car, and I can't see one on realoem either. Obvious false air candidate?

 

[sfdon]

well, I've been busy. I have reset the valves to 0.3mm. Looking back at my file of stuff, it's actually been 4 years since I was last there, and some were a bit off, closer to 0.35 maybe, esp on the exhaust side. Idle bleed screw adjusted, and the idle is now stable at ~900rpm which seems like good progress. Manifold vacuum is very low though, now sitting at 12"Hg at idle. Also a slight misfire at idle, though overall it is idling much better than it was.

Also checked the TPS operation, and that is good; a solid continuity signal as soon as the throttle closes. No play in the TPS spindle. I also had a go with the carb spray around the gaskets on the intake, the injector seals, valve cover etc.... no sign of vac leaks. Compression still good across all 6, and plugs look fine (though they've only done about 100 miles). Fuel pressure still reading 2.0 bar spot on, and no change when I ding the FPR. What else... I also stuck a camera inside the cylinders whilst the plugs were out, seem fine to me, visible honing marks, but it's very difficult to see anything on the rubbish £20 camera I bought!

So tomorrow I can take a look at the throttle spindle seals (thanks Thomas). I've not heard about those before.

And (too late) I thought I should have checked the camshaft timing whilst I had the lid off. I have buttoned it all back up again, but I may well dive back in again to ensure valve timing is as it should be. What is the easiest way to get the valve cover off and on again. Today I left the throttle body and distributor in place as I didn't want to disturb stuff I didn't need to, but getting the valve cover back on again was a bear.

Oh, and should the valve cover breather have a clip on it? Not one on my car, and I can't see one on realoem either. Obvious false air candidate?

 

[sfdon]

No clamps on the valve cover hose

 

[sfdon]

I would hook up the vacuum gauge and set the timing using that for highest vacuum and then back it off a bit

Then check your timing with the timing light at the flywheel

 

[TomHom]

well, I've been busy. I have reset the valves to 0.3mm. Looking back at my file of stuff, it's actually been 4 years since I was last there, and some were a bit off, closer to 0.35 maybe, esp on the exhaust side. Idle bleed screw adjusted, and the idle is now stable at ~900rpm which seems like good progress. Manifold vacuum is very low though, now sitting at 12"Hg at idle. Also a slight misfire at idle, though overall it is idling much better than it was.

Also checked the TPS operation, and that is good; a solid continuity signal as soon as the throttle closes. No play in the TPS spindle. I also had a go with the carb spray around the gaskets on the intake, the injector seals, valve cover etc.... no sign of vac leaks. Compression still good across all 6, and plugs look fine (though they've only done about 100 miles). Fuel pressure still reading 2.0 bar spot on, and no change when I ding the FPR. What else... I also stuck a camera inside the cylinders whilst the plugs were out, seem fine to me, visible honing marks, but it's very difficult to see anything on the rubbish £20 camera I bought!

So tomorrow I can take a look at the throttle spindle seals (thanks Thomas). I've not heard about those before.

And (too late) I thought I should have checked the camshaft timing whilst I had the lid off. I have buttoned it all back up again, but I may well dive back in again to ensure valve timing is as it should be. What is the easiest way to get the valve cover off and on again. Today I left the throttle body and distributor in place as I didn't want to disturb stuff I didn't need to, but getting the valve cover back on again was a bear.

Oh, and should the valve cover breather have a clip on it? Not one on my car, and I can't see one on realoem either. Obvious false air candidate?

These are the seals

throttle seal BDC36/325

THROTTLE SEAL original Mikuni carburetor parts * Mikuni = BDC36/325for following models: * DR750 * DR800 * GS1000 since 80' * GS550 since 80' * GS750 since 80' * GS850 since 80' * GSX1100 year 84-86 * GSX1100F year 88-94 * GSX600F year 88-8

www.motorradbay.de

 

[Drew20]

update: I have reset the valve clearances a bit tighter, to 0.25mm and checked the cam timing, which was spot on, of course

and then reset the ignition timing, which may well have been the cause of my problems. I will check this again, to double check my readings, but the engine appears to have been running way way too advanced (circa 55 degs adv at 2500rpm), which is bizarre, as I can see my tipex marks from the last time I set it (to factory spec) and I've not noted any pinking. Oddly it now runs very happily now at 43 degs adv at 2500rpm. I need to check all of this, as 43 degs is way off spec, but vacuum was a healthy 18"Hg at this level of over-advance. I can't help but think some degree of human error has crept in here somewhere, so will check it all again after a run out later.

also noted:
my timing (dab of white paint) mark on the front crank pulley has a lot of movement to it, in that it is far from stable under a timing strobe. I would estimate 20% of the flashes showed a white mark in the wrong place.
the valve cover is a lot easier to refit when the distributor is not there!
no obvious vac leak at the throttle spindles

 

[TomHom]

Well,
Ignition timing should be checked at the rear end, at a speed of 1700rpm
Check breaker contacts and verify dwell angle before.

Something special are the contacts of the pulse generator. We use this tool for checking and adjusting the contact gaps.

You observed radial and axial play on the distributor. Shouldn't be there!
Maybe it's a good time now to consider the upgrade to a modern contactless ignition system.