Intermittent stalling. Electrical Gremlin?

[bengal taiga]

Intermittent stalling. Electrical Gremlin?:x

Perhaps you folks might be kind enough to short cut my fault diagnosis.

I have an E9 with 90,000K and the original D-Jet setup. For the past fifteen years I have run a capacitive discharge ignition “Premature” that was borrowed from a 911. I also use a red bosch coil. Compression is 195 lbs./in2 in all six cylinders. Typically engine runs fine from initial startup to redline. The engine will cutout when you least expect it - cold or hot - high speed and at idle - and I had a record four cutouts over the course of the last eight hours.

For those of you who are patient, here is the more comprehensive version:

After the winter de-mothballing I pulled the car out of the garage this morning. She started immediately and ran for two minutes before shutting down. I tried cranking and cranking but not fire. I know there was plenty of fuel pressure by looking at the inline gauge which reads 29.5 psi. I can also hear the pump. I jiggle the primary wires near the coil and the car immediately fired and died again. Bridged the ballast resistor and still no difference. I removed the cd unit and swapped it for another unit. Car started drove it down driveway, left it idling and - - it died again. This time I swapped the coil and the condenser and examined the points and rotor and - - car ran. I drove car 80 miles at extremely high speeds without any problems whatsoever.

Parked car for four hours got back into car, started and after reaching normal operating temperature, headed down the interstate at high speed. Four or five miles into my trip the engine cut out at speed. I put car in neutral and turned key to off position. Engine started to run on and diesel and I think run backwards! The smoke from the air filter and the fact that the vacuum retard hose to the distributor was blown off is a strong indicator. I put car in gear and dumped clutch to shut the engine off. I waited approximately 4-5 minutes before pulling all wires to check for loose connections or shorts or bare wires - and found none. Put key in car. Car started immediately and I drove home. Three blocks from home, the engine again cut out again. Pushed car to side of road. Waited a few minutes and the vehicle started again and has been running ever since.

I have since tried to duplicate the cutting out - without success. I have even taken to spraying all the wiring with a garden hose to see if I can’t induce a short - but I can’t.

Had what may have been the same or similar problem years ago. I can’t recall why, but I suspected the coil. I changed the coil and hadn’t had the problem recur until today. At present, I am concerned since the old gal does not appear to be very dependable. Please consider that the problem has occurred when the engine is both cold and at operating temperature - so I do not think it heat related. Please consider also that I have replaced the CD unit, the coil, the condenser and rotor to eliminate those parts as likely candidates. It did not seem to make any difference. I even rerouted the wiring to eliminate the CD unit and run the engine on the stock points setup - but it made no difference so I reinstalled the CD unit.

I have removed and examined all of the fuel injection related wiring/contacts and they are all clean. I have a spare CPU and pressure sending unit, but find it hard to believe they are the problem.

As it stands right now, the car runs magnificently - except when it doesn’t! First time she ever gave me cause to curse.:evil:

Any decent ideas - are appreciated. :idea:

 

[Honolulu]

Gather the significant DATA

Apparently (based on your fuel pressure statement) you have some kind of injection, we know not wot.

Air/gas/spark - one has gone missing. Since you still have the problem, it's not in the things you replaced. What's left?

Air is pretty much always there and no susceptible to going AWOL.

Fuel appears to be present based on your fuel pressur statement, but are the injectors working? Can you verify this when the car quits?

Sudden quitting suggests an electrical issue.

Assuming this is a Djet CSi, the ignition trigger points have frequently been cause for problems. Remove diz, clean, reinstall, set timing.

Is/are the brain and motor properly grounded/connected to the battery negative? Is there another brain in your neighborhood that you could swap temporarily?

Is you distributor cap clean and without carbon tracking inside or out?

Recently had a crank-but-no-start on my CS that resulted from one little wire at the solenoid having been knocked off. Dunno about CSi wiring but check there also.

I expect you have a loose connection somewhere.

 

[bengal taiga]

Re: Gather the significant DATA

Apparently (based on your fuel pressure statement) you have some kind of injection, we know not wot.

Sure we do: "I have an E9 . . . and the original D-Jet setup."

I have driven the car twice since the last episode and have not experienced any problem. I agree with your assessment of an electrical issue and in particular - an ignition related issue. Wet plugs suggest fuel is not the issue. When running, I have pulled the wires to each injector and they are all firing. Of course, pulling the wires when the engine is not running is fairly meaningless, but I really doubt the injectors are causing the no-run situation. As noted also, you can clearly hear the pump and see the pressure on the underhood gauge.


"Assuming this is a Djet CSi, the ignition trigger points have frequently been cause for problems. Remove diz, clean, reinstall, set timing." Done


"Is/are the brain and motor properly grounded/connected to the battery negative? Is there another brain in your neighborhood that you could swap temporarily?" Relatively new grounding straps and clean metal contacts. Yes I have checked to make sure the grounds are snug too. As noted in the original post, I have a different CPU and pressure sensing unit- but the car has always started after a brief 5-7 minute respite and then continued running without issue. For example, today I ran the car for 1 hour in stop and go traffic. I am not sure what purpose replacing these items might serve.

"Is you distributor cap clean and without carbon tracking inside or out?" Nil and cap is virtually new.

"Recently had a crank-but-no-start on my CS that resulted from one little wire at the solenoid having been knocked off. Dunno about CSi wiring but check there also." Good idea! Have had this with an 02, but - wiring is solid, clean and firmly attached.

"I expect you have a loose connection somewhere."

As noted, I agree with your sentiments and appreciate the effort. Since the problem is intermittent it is doubly difficult to locate. It wouldn't be so bad if replacing one component fixed a no-start issue, or was obviously defective - yet, since waiting a while seems to also result in the system returning to normal, swapping components is close to a shot in the dark. For all I know, the issue won't reappear for years. The wiring harness seems to be this car's weakest link in that some of it (wiring nearest the engine and injectors) is somewhat brittle. It is not broken or exposed that I can see, and the ohmmeter suggests there is continuity without resistance - but the insulation seems a little stiffer than I would like. I would prefer to find the gremlin in the driveway rather than the open road.

As a final (for the moment) thought, if you have ever suffered with a coil that was bad or going bad, that is what this reminds me of. To satisfy my instinct, I did try swapping the present coil and even ran the other coil on another car - without experiencing any problems on either vehicle.


Thank you again.

 

[Malc]

related to the above
Assuming the engine cuts out "instantly" then that to me says electrical rather than fuel starvation.

There are two areas to worry about.
The ignition system so checks (again :roll: )

1.. Distributor cap, coil and plug leads
2.. supply fuses.
3.. ignition switch on the column (possible bad/ intermittent contact)
4.. Condensor (if fitted) failing
5.. Make sure your rotor arm is a good one. I have had 2 bad brand new ones on a car it seems the quality has gone down the toilet recently.
6.. points, any evidence of pitting, worn lobe etc

And on the injections side
If possible test/check the following
1.. Air temperature sensor in inlet manifold "log"
2.. Throttle position switch.
3.. ECU Coolant temperature sensors
4.. Air slide sensors.
5.. Fuel pump relay.
6.. vacuum sensor and hose to inlet manifold.
7.. Cold start relay
8.. injection trigger points

Other stuff
1.. Is the one way valve to the servo functioning? - any air leaks in the inlet ?
2.. Wiring actually corrodes and "rots". The copper goes black and or green inside the plastic cover.

Attached diagram may be helpful

HTH
Malc

 

[Malc]

More other stuff
A "dieseling" engine or one that runs backwards when cut off could be due to a combination of the following:
1.. fuel grade is too low or too old
2.. wrong grade of spark plug
3.. Compression ratio too high for the type of fuel, see 1
4.. Ignition timing too far advanced
5.. Ignition not "shut off" properly
6.. choke or cold start valve on/open
7.. Fuel pump running
8.. Engine running too hot

 

[bengal taiga]

Good tips, all.

Good tips, all. Since car has not exhibited the complained of symptoms after 2 days of additional driving, as might be expected, everything seems très bon when something may, in fact, be nicht gut.

I will probably look at things closer this coming weekend and readjust valves and - although probably not necessary, retune or check the tune.

As an aside, I have had few major problems with the DJet excepting a couple of bad manifold pressure sensors and maybe a stuck injector. The distributor "injection" points were clean and unpitted as were the spare set with which I replaced them. I don't think I have ever allowed my system to become too degraded, even on other Djetted vehicles, so now I am curious, what effect would a dirty set of injector points have on the system?


Merci tout encore!

 

[Malc]

Dirty injector points with an intermittent or weak signal back to the ECU would mean that the ECU would not "fire" the injectors at the correct time or at all. Results could be
rough running
not running
no power
horrible fuel consumption

 

[bengal taiga]

d-jet problems revisited

Dirty injector points with an intermittent or weak signal back to the ECU would mean that the ECU would not "fire" the injectors at the correct time or at all. Results could be rough running not running no power
horrible fuel consumption

It is bizarre that almost a year ago to the date, my engine started acting up as described by the year-old posts and then - they mysteriously disappeared. I have used the car as a rolling test bed for several months and have not had any issues to speak of and the car has been dependable.

This past week, the problem reappeared, without warning. I have had this happen after driving 15-20 minutes both at idle and at speed. At least when in traffic, there has been a little warning since the idle starts to hunt. My modulating the accelerator pedal I can overcome the hunting, but eventually you can hit the gas and its is as though the throttle switch is disconnected because the car seems strangled for fuel. The hunting idle suggests fuel injection rather than ignition. I have since replaced throttle switch, ignition trigger points, coolant temp switch (014) and tried running with and without air temp sensor connected to no avail. Both sensors were tested for resistance and fall within specs as described by FI test procedure. I have rechecked the grounds and voltage seems clean and available to all components. Engine runs fine until it doesn't. After engine dies, cranking the engine is useless. Let the engine sit for 5 minutes and it cranks over and runs as though nothing was wrong. This suggests something heat or time related.

One thing that struck me as odd is a clicking sound I think I heard coming either from the ECU or the relay next to it. I think this occurred when the engine started hunting and it may be normal. I have swapped the pump relay, but this doesn't seem to make any difference.

Is there something that is possibly heat or time related I am ignoring? Or is April just a cruel month to drive this car?:cry:

Thanks in advance.

 

[bengal taiga]

d-jet problems revisited

Dirty injector points with an intermittent or weak signal back to the ECU would mean that the ECU would not "fire" the injectors at the correct time or at all. Results could be rough running not running no power
horrible fuel consumption

It is bizarre that almost a year ago to the date, my engine started acting up as described by the year-old posts and then - they mysteriously disappeared. I have used the car as a rolling test bed for several months and have not had any issues to speak of and the car has been dependable.

This past week, the problem reappeared, without warning. I have had this happen after driving 15-20 minutes both at idle and at speed. At least when in traffic, there has been a little warning since the idle starts to hunt. My modulating the accelerator pedal I can overcome the hunting, but eventually you can hit the gas and its is as though the throttle switch is disconnected because the car seems strangled for fuel. The hunting idle suggests fuel injection rather than ignition. I have since replaced throttle switch, ignition trigger points, coolant temp switch (014) and tried running with and without air temp sensor connected to no avail. Both sensors were tested for resistance and fall within specs as described by FI test procedure. I have rechecked the grounds and voltage seems clean and available to all components. Engine runs fine until it doesn't. After engine dies, cranking the engine is useless. Let the engine sit for 5 minutes and it cranks over and runs as though nothing was wrong. This suggests something heat or time related.

One thing that struck me as odd is a clicking sound I think I heard coming either from the ECU or the relay next to it. I think this occurred when the engine started hunting and it may be normal. I have swapped the pump relay, but this doesn't seem to make any difference.

Is there something that is possibly heat or time related I am ignoring? Or is April just a cruel month to drive this car?:cry:

Thanks in advance.

 

[Malc]

Hunting suggests an air leak somewhere downstream of the throttle body
(Where the revs rise and fall) or lack of fuel
Check all your hoses, especially the one to the brake servo (Or servos if RHD)
Air bypass valve hoses - is the valve functioning correctly and check the connectors to the sensors near it
Air hose to the MAP sensor
Servo leaking air

Strangled of fuel...
Have you tried a flow test to make sure the pump is delivering what it should?
Changed the fuel filter recently?
Flushed the pipes
Check the fuel pick up in the tank
Check the tank for dirt and debris
Tank breathing OK
Wiring to pump.

Clicking sound could be the relay opening and closing - possible power supply issue rather than the relay itself - ignition key barrel OK?

 

[Malc]

Hunting suggests an air leak somewhere downstream of the throttle body
(Where the revs rise and fall) or lack of fuel
Check all your hoses, especially the one to the brake servo (Or servos if RHD)
Air bypass valve hoses - is the valve functioning correctly and check the connectors to the sensors near it
Air hose to the MAP sensor
Servo leaking air

Strangled of fuel...
Have you tried a flow test to make sure the pump is delivering what it should?
Changed the fuel filter recently?
Flushed the pipes
Check the fuel pick up in the tank
Check the tank for dirt and debris
Tank breathing OK
Wiring to pump.

Clicking sound could be the relay opening and closing - possible power supply issue rather than the relay itself - ignition key barrel OK?

 

[pamp]

Stall

Look just beneath the brake booster and you will find a relay. I bet money that this T.U. As I posted before, a V.W. unit will work, just carefully twist the center spade (#30/51) to fit the plug. This relay is very hard to see and often overlooked. It would take some digging, but I could come up with some numbers if you wish. P.M. me

 

[pamp]

Stall

Look just beneath the brake booster and you will find a relay. I bet money that this T.U. As I posted before, a V.W. unit will work, just carefully twist the center spade (#30/51) to fit the plug. This relay is very hard to see and often overlooked. It would take some digging, but I could come up with some numbers if you wish. P.M. me

 

[pamp]

Stalling

Here is how it goes,
As mentioned in my post. Naturally you checked the fuel pump relay located by the ECU under the right side rear seat. But it is not known that there is a secondary relay mounted to the side of the brake booster, inboard.
This falls under the term "proprietary knowledge" This little sucker is a bitch, very hard to see and replace. I have found that the shade tree fix is to by-pass this baby with a jumper. Here is some #'s Bosch #0 332 003 021
or V.W. #311 906 061 I cannot remember the # for the original part, no matter as it is "unobtainium" once you score the relay as per the aforementioned spec. twist terminal #30/51 to fit the BMW plug. I had this exact same problem as you describe. It took quite a bit of hours to trouble shoot. I am reasonably certain that this will be your fix.
Al in Comox
P.S. Let me know if I am correct... the price for this part is minimal.

 

[pamp]

Stalling

Here is how it goes,
As mentioned in my post. Naturally you checked the fuel pump relay located by the ECU under the right side rear seat. But it is not known that there is a secondary relay mounted to the side of the brake booster, inboard.
This falls under the term "proprietary knowledge" This little sucker is a bitch, very hard to see and replace. I have found that the shade tree fix is to by-pass this baby with a jumper. Here is some #'s Bosch #0 332 003 021
or V.W. #311 906 061 I cannot remember the # for the original part, no matter as it is "unobtainium" once you score the relay as per the aforementioned spec. twist terminal #30/51 to fit the BMW plug. I had this exact same problem as you describe. It took quite a bit of hours to trouble shoot. I am reasonably certain that this will be your fix.
Al in Comox
P.S. Let me know if I am correct... the price for this part is minimal.

 

[bengal taiga]

Update?

The length of this thread makes me question not just my memory, but also my sanity. :roll:

The collective suggestions, are much appreciated. FWIW, since my last post the next bout of stalling occurred after some 45 min. of a variety of driving. I rechecked all ignition components and then each FI component, including each sensor, the Throttle position switch, the pump, the various relays (two on the column supporting the brake booster and the Fuel pump relay near the ECU), the injection points and even the ECU and PSU. The engine would start cold and felt as thought it could be driven anywhere, until, without warning - stall.

Out of frustration, on the side of a very busy roadway, with the engine turning over but refusing to start, I started examining the wiring under the dash and found a few questionable connections. I also discovered part of the forward wiring loom that feeds through the frame rail was exposed (without its protective sheathing). The effort was time consuming, dirty, messy, and uncomfortable. Using the most primitive of methods, I broke most of the wire connections, cleaned them and reconnected everything. Thereafter, the engine fired just fine, ran smoothly and I have driven the car without any further stalling. I would like to think that there was either a short or very minor disconnection somewhere in the wiring harness that caused the problem - rather that attributing this to the Month of April. Finger's crossed! :wink:

If you have read this far, I sincerely thank you for your patience. If you skipped to this part, thank you anyway!

___________________________

PS. I noticed a Mercedes board that offered some fairly good supplemental advice regarding D-Jet trouble shooting. http://www.benzworld.org/forums/w11...-d-jetronic-k-jetronic-troubleshooting-2.html

The following excerpts might prove helpful to those stalwart D-Jetters unable to locate their shop manuals. (If the administrators determine this to be a waste of bandwidth, feel free to excise it or even move or link it to the FAQ forum.)

“Temperature Sensor I
Temperature Sensor I is an ambient air temperature sensor. As the ambient air temperature decreases, the density of the air increases. As a result, the ECU must inject more fuel on a cold day than on a warm day.

Temperature Sensor I is a temperature sensitive resistor known as negative temperature coefficient thermistor (NTC). This sensor has a resistance of between 400 and 500 ohms at 50 degrees F. At 100 degrees F., the resistance is between 150 to 200 ohms.

Temperature Sensor I actually has little effect on the operation on most D Jetronic equipped vehicles. This is because most of these cars have tens of thousands of miles on the engine and are running very rich due to this wear. The troubleshooting consequence of this is that disconnecting the air temperature sensor during the diagnostic procedure may have little effect on the way the engine runs, and in some cases it may actually improve the way it runs.

Temperature Sensor II
Temperature Sensor II is the coolant temperature sensor on water cooled engines. Like temperature sensor I, it is a NTC thermistor. The temperature of the engine is important because the intake manifold design of fuel injected engine does not permit the use of an air restrictive choke. Additionally, restricting the air to enrich the engine during warm up would cause inaccurate readings from the manifold pressure sensor. The warm up choke function is therefore performed by Temperature Sensor II.

When the coolant temperature is about 50 degrees F., the resistance of Temperature Sensor II is between 3000 and 4500 ohms. As the temperature increases to more that 120 degrees, F., the resistance drops to less than 1000 ohms. Thus the sensors work is done once the engine is warmed up. Also it must be continuously reminding the ECU that the engine has warmed up. If damaged, Temperature Sensor II will not continue to function partially( such as the resistance values shifting). It will completely fail, creating an open short or ground.

An open circuit in Temperature Sensor II or the wiring leading to it will cause the engine to run extremely rich once warmed up. Symptoms would be dark smoke from the tailpipe (most noticeable at idle), rough idle and poor power. Keep in mind that engine compression problems and ignition could also cause these same symptoms.

Should the sensor become shorted or the wiring harness grounded, the effects may not be noticeable at all when the engine is warmed up. The symptoms would be more like a carburetor with the choke stuck open-rough or erratic idle, stalling or hesitation when the engine is cold and progressively running better as the engine warms up.

Throttle Switch
The throttle switch tells the ECU when the throttle is closed, when the throttle is wide open and when the throttle is moving toward the open position. The switch consists of twenty-two contacts, with a set of wiping contacts that move across them as the throttle progresses from the closed position to the wide-open position.

One wiping contact is used to inform the ECU that the throttle is closed. Another makes contact only when the throttle is wide open and a third makes and breaks contact twenty times as the throttle opens. The electrical pulses created by the making and breaking of the contacts signals the ECU to open the injectors more frequently, by that enriching the mixture for acceleration. This feature behaves much like an accelerator pump on a carburetor.

Symptoms associated with a defective throttle switch include a rich(smoky)idle and hesitation. An intermittent condition at cruise-which feels like you shut off the engine and immediately turned the key back on, can also be caused by the throttle switch.

To test the throttle switch, open the throttle with the key on but the engine not running. The injectors should open exactly twenty times, evidenced by twenty evenly spaced clicks.

Pressure Sensor
The D Jetronic pressure sensor is known as a linear variable displacement transducer (LVDT).It consist of a pair of coils, one with about 150 ohms of resistance and the other with about 85 ohms of resistance. An iron core attached to a diaphragm runs through the center of these coils. As changes in manifold pressure moves the diaphragm, the iron core moves inside the coils, causing ripples in the current flowing through these coils. The ECU uses this signal to monitor the relationship between barometric pressure and manifold pressure.

The most common symptom from a defective pressure sensor is a rich running condition. Of course several other defects can cause rich running as well.

Of all the sensors used on D Jetronic, this one both the easiest and the most difficult to test. Usually a simple resistance test of the coils is enough to determine if the unit is good or bad. On the other hand, the only way to be sure is to replace it with a known good unit.

Electronic Control Unit (ECU)
The ECU receives input signals from the pressure sensor, Temp Sensor I, Temp Sensor II and the throttle switch to decide how long to leave the injectors open. It is only able to respond to air-fuel ratio request from one sensor at a time. As a result, whenever a sensor fails, the tendency will be for the ECU to send the injectors a full rich supply of fuel.

The electronic unit has no serviceable components. In the event of a failure, they replace the ECU as a unit. Failures are extremely rare and usually result in a no start.

D Jetronic that have an adjustable air fuel ratio have a detent potentiometer on the side of the ECU.This potentiometer can be used to fine tune the air-fuel ratio during a tune up.

Pin # nineteen and 25 of the ECU are connected to the fuel pump relay. When the ignition switch is turned to the on position, the ECU energizes the fuel pump to ensure that the fuel system is filled for ease of starting. If the engine is not cranked, the ECU will shut off the fuel pump after one or two seconds. If the engine is started, the fuel pump runs continuously until the engine is shut off.

In Tank Filter
Located inside the fuel tank is a screen or filter designed to protect the fuel pump from rust, dirt and debris. Although seldom the cause of a driveability problem, the in tank filter should be high on the list of items to check. In many cases these filters have been ignored, even on well maintained vehicles.”

 

[Luis A.]

Hey Bengal,

Sorry if I'm bringing up a bad memory here but since I'm considering a CSi I'm reading over old posts trying to develop a feel for potential issues with the D-jetronic system.

Did you ever resolve this issue? What was it?

Thanks!

 

[bengal taiga]

Hey Bengal,

Sorry if I'm bringing up a bad memory here but since I'm considering a CSi I'm reading over old posts trying to develop a feel for potential issues with the D-jetronic system.
Did you ever resolve this issue? What was it?
Thanks!

I think my last post answers most of your questions. There is nothing particularly bad about the D-Jet system any more than using the tried and true breaker point ignition systems. It is very primitive by today's standards - as is any carburetor. The major weak point is probably the wiring harness. Appearances can be most deceiving since clean wiring may look great, but looks do not always disclose brittle wiring or questionable connections. Major components may fail, but with a little ingenuity and patience and sacrifice of purity, workarounds exist. Given enough heat, humidity or unexpected road hazards, any car might suffer from a loose connection or a poor ground. Unfortunately, older-unrestored cars are more apt to suffer from such maladies.

Because I replaced so miscellaneous used odds and ends it is difficult to point to any specific problem area. Slight bits of corrosion may have been the real culprit. In any event, the subject car gets driven quite often and aside from door dings and pelican poop, I have not experienced any real surprises lately.

hth :wink: