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Discussion Starter #1
Hi,

I am trying to help a friend with his Spider - which nobody in our rural area wants to touch. The engine has sparks only at first and fourth cylinders. While starting, it has some interminent sparks also at 2 and 3. The cars has some variation of Bosch Motronic, but I cannot find an ignition module. Can anyone help to locate, or give an advice where is the gremlin hidden.. Thanks a lot.
 

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I would leave your ecu alone. Focus on the distributor cap and rotor, as well as the coil.

Best Regards,
John M
 

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Discussion Starter #4
I have checked cap and rotor, no visible wear out, crack or any other tale-tell.
Is the ignition module integrated in the ECU??
 

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Yes it is. Behind passenger seat beneath the carpeted shelf.

Check your friend's firing order. 1-3-4-2 clockwise from TDC.

Seems like firing noted would rule out the ecu and the sensor. Especially since you noted fire to all cyls intermittently. The 1-4 firing then 3-2 firing may be pointing towards coil or distributor. Or the underlying problem could be something else altogether. I would encourage you to look at fuel sys as well as any intake pathway air leaks between the air flow meter and the intake.

The ignition timing source is a crank pulley sensor on the front of the motor. Might check the pulley ring gear, crank pulley, and sensor and harness for damage and make sure within spec for gap.

I would describe ECU failure on a motronic as being a very rare occurance. I believe I have heard of only one or maybe two ever. Now there are some relays back around the ecu that can be problematic.

Best Regards,
John M
 

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I have checked cap and rotor, no visible wear out, crack or any other tale-tell.
Is the ignition module integrated in the ECU??
I believe S4 spiders use Motronic ML4.1. AFAIK (I'm still new to spiders) the ECU controls the ignition by grounding one of the coil's primary winding terminal (the other terminal gets 12V power). There's no additional external ignition module.

Like others said, the likely problem could be the dist cap and/or rotor. Check the center spring loaded contact of the dist closely.

Any recent work done on the car? What kind of spark plugs and plug gaps does it has?

You might want to check the resistance of the primary and secondary windings of the coil. They might be typically 0.5 and 6K ohms respectively. Spark plug gap should be ~.025" - too large a gap would make it hard for sparks to jump. The car is a 15 years old car, so clean as many connectors as you can find including the ground wires to chassis.
 

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Discussion Starter #7
funny thing, I cannot find any sensor in the area of the fron pulley. Only RPM sensor I see is on the end of intake cam with 3 wires coming out. On some Italian web I found thjat ML41 has either 1, 2 or 3 crank position sensor, but no details...Does anyone have a wiring diagrma - the ignition part, and sensor location?
 

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The thing on the end of the intake cam is the solenoid for the VVT device.

The Motronic Spiders (90-94) have one sensor aimed at the crankshaft pulley. Our '84 has Bosch L-jetronic (two sensors at the flywheel) so I can't get you more info. Try the search function - there'e a lot of info available here. But I think you really need a shop manual...
 

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Welcome to the AlfaBB and you deserve credit for trying to help out a buddy.
First bit of advice: Go slow. Alfas aren't especially fragile but they don't respond well to being beaten on. A well thought out reasoned approach will eventually get you where you want to be.

Where are you located? Someone on the board might know of an Alfa mechanic reasonably close to you (you never know unless you ask)

There is a toothed wheel mounted on the crank shaft at the front of the engine. The timing sensor is mounted on the lower left front of the engine. Its possible, but I doubt this is the issue.

Do you know that the coil is good?
Have you put a timing light on the coil wire to see if its firing consistently?
Have you tested the plug wires?

I just recently fixed an intermittent miss by tracing the problem to a bad relay. This was after MUCH wasted effort and thrashing around trying all kinds of stuff.

Use a slow, methodical approach and ask lots of questions on this board. There are many very experienced and very helpful people who will provide you with all the help you need.

John
 

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I agree with those here who caution you to take a step-by-step approach to this situation. And I also commend you for helping your friend to such an extent!
My father always taught me to check the least costly and easiest things first when troubleshooting car problems, so that is what I suggest to you.

Before we go any further, I'll ask the ultimate stupid question! Are the spark plugs new or fairly new? Are they clean and gapped correctly?

1) Locate the main ignition sensor down at the front of the engine, next to the crankshaft pulley, under the car. Clean it with a degreaser. The wiring connection should be secure. Obviously, the sensor itself should not be loose but must be clamped tightly in place. The manual calls for a gap of 0.5mm to 1.5mm between the toothed wheel and the sensor.
2) If you see no problem with the sensor, then replace the distributor cap, unless it is nearly new. Do not try to check it visually, because cracks and defects in caps are extremely difficult to see with the eye. Also replace the rotor at the same time. Always go with a new cap, new rotor combination. BTW- the rotor has a release clip, so it's much easier to work on the distributor if you simply remove it from the side of the engine block (one 11mm bolt). While you're at it, replace the rubber o-ring seal on the distributor shaft- it's an oil leak waiting to happen.
3) Do not move the engine while the distributor is removed! Replace the distributor in EXACTLY the same position you removed it.
4) If there is no consistent spark after replacing the cap and rotor, check the coil 12 volt terminals for continuity with a volt-ohm meter. There must be continuity through the coil windings. If you suspect a problem, replace the coil.
4) If there is still a problem with weak spark, check the spark plug wires for continuity. They should all have fairly equal values. If not, replace them. The terminals that snap onto the top of the spark plugs must also be clean and secure, and must fit tightly.

If the problem persists after these steps, then let us know and we'll proceed on to other areas. BTW- please ask your friend if this problem developed over time, or if the car had been sitting without being driven for a while.
 

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Discussion Starter #11
gentlemen,
thank you for your thorough and generou help. Without it, Iwould be still in dark.. Thanks to "gnhl", I have found that this car is a "hybrid". Althouh the sticker on the door sill claims model 1992, the engine must have been replaced sometime in the past because it has two sensors at the flywheel are (so ii is pre-1985 model). The current owner of the car doesn't know anything about it.Only now I noticed that the wiring harness is not attached at all possible fastening points...etc.
I disconnested both flywheel sensors. One is giving me a reading between two adjacent prongs of approx. 1kΩ, while the other 38MΩ - which for a such device is almost infinite resistance. Sensors are made by Bosch.... I hope that it will solve this car problem.
 

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Discussion Starter #13
Thanks for a link, it helped right on with those sensor values...
Sorry for so many typos, it looks like I need a new keyboard.. it starts to require heavy typing like an old mechanical typewriter
 
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