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Discussion Starter #1 (Edited)
Hello Alfa Community!

I just has an ignition computer replaced 1yr. ago (I don't drive the car very much. Maybe 6-7 times within that yr after replacing). After I start the car for the first time of the day, drive for a while, park it (wait 15-20 min) and car wouldn't crank. I know the fuel computer works. So I took it to my mechanic they ran diagnostic and found something to the extent of the ignition computer. The car still drives but sometimes it will choose when it wants to crank or not. My mechanic says it goes into it's limp mode. He did say that you can still drive the car but when it acts as if it doesn't want to crank, put the plug out of the ignition computer (wait 10 sec) and plug it back in and car will start right up. Anyway, my mechanic seems to think it's a computer compatibility issue. I would think that if he's right, then why did it take this long to figure out if it was compatible or not. It was working for a while with the new computer in.
 

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Welcome to the BB. I am not aware that either computer (there are two - the one behind the seat is the fuel injection computer, the ignition computer is behind the right side panel) has any sort of 'limp home mode'. They do have a basic fuel/ignition map that they will use if the inputs are not valid - perhaps that is what he means? And, switching off the ignition should have the same effect as unplugging the wire harness connector.

Let's clarify some terms. When you say 'it won't crank' do you mean the starter motor turns the crankshaft but the engine won't start? Or do you mean you turn the key to the start position and nothing happens - the starter does not operate & the crankshaft does not turn?
 

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Engine won't start. Car makes noise. I understand your position about the two computers. Looks as though I had them backwards. I'm not even sure what he means by "limp mode" guess it was something he came up with( I don't know). Maybe just car not working.
 

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So I guess that would mean (when I said pull the plug out of the ignition computer) I mean "Pull the plug out the the fuel computer" since I had them backwards.
 

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Engine won't start. Car makes noise. I understand your position about the two computers. Looks as though I had them backwards. I'm not even sure what he means by "limp mode" guess it was something he came up with( I don't know). Maybe just car not working.
Modern cars sometimes have a "limp mode," so it is a thing. But I don't believe that the Bosch L-Jet system in your Spider has anything like that. (And I don't believe that there is any computer diagnostic system that can be run on the L-Jet computers). I'm concerned that your mechanic may be a bit over his head in dealing with the problem. There are many individual tests for the various sensors that are the inputs to the L-Jet system. Normally, the problem is not either of the computers, but rather, one or more of the sensors (or fuel pump, or relays, or something else). My suggestion would be to get the car back from the mechanic and step through the L-Jet diagnostics page here to see if you can diagnose the problem yourself.
 

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OK, removing & replacing the plug from the computer isn't doing anything. Well, it gives you something to do that makes you think you've done something...

Again, trying to be very clear, when you turn the key to 'start' does the engine make the normal R-R-R-R sound or does it sound abnormal? A known problem area is the ignition switch itself. When they get old the internal contacts are not able to reliably pass the electrons needed to activate the starter motor. At first it is an occasional problem (say 1 out of 10 starts) then before long it becomes 1 out of 3 starts. There are two ways to fix this. One is to replace the ignition switch. They are not cheap and the replacements may not be of the best quality. The other way is to add a relay such that the ignition switch only has to pass a tiny amount of electricity to trigger the relay. This canmake a dodgy ignition switch work fine for many years.

If you turn the key to 'start' and the starter motor is activated (R-R-R-R-R) but the engine will not start then there is another issue that needs to be addressed. Go through all the checks outlined in the Spider L-jet Diagnosis page (link in my signature). Things to pay particular attention to are system voltage (the computers need about 10.5V to wake up and send the make spark/squirt fuel signals). It can sound like it is cranking over fine but if system voltage is below that threshold it will not start. Dirty battery connections or a slightly weak battery could affect system voltage. There is a stand-alone Cold Start System (not under computer control). It is supposed to squirt a little extra fuel on cold start and NOT squirt extra fuel on warm start. It can fail either way, both ways, one way but not the other, etc. The fuel injectors require properly regulated fuel pressure. A failing Fuel Pressure Regulator can make it hard to start cold or hard to start hot.

One other thought. There were a couple of slightly different computers used during the run of the Series 3 Spiders ('82 - '89). They will physically interchange but they might not be totally compatible. Post the numbers on both of your computers and we'll see if we can figure out if they are the correct ones for your model year Spider.
 

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I don't understand what your mechanic means when he suggests it's a computer "compatability" issue. When one of the computers was changed out a year ago, was it not replaced with an identical model computer?

If the car starts up fine and idles nicely when it is cold, but when the engine is warm the starter motor turns but the car doesn't "catch" and idle, it sounds like a relatively simple "warm start" problem.

I agree with sloboy89's comment above, in that your mechanic needs to follow the L-Jetronic Diagnostic Guide that was put together by Greg Gordon and Eric Russell and is located here: https://www.hpsimotorsports.com/l-jetronic--spider-

Tell your mechanic to pay particular attention to Step 3 the cold start and warm up system because a warm start issue may be due to something as simple as a faulty TTS (which would make the CSI spray and flood the engine when warm) or an AAV that was stuck in the open position.

A more comprehensive study of the theory of operation, troubleshooting and service of your car's injection system is presented in Bosch Fuel Injection & Engine Management by Charles O. Probst ISBN 0-8376-0300-5. Your mechanic should have a copy of this book (or something better) or he may not be qualified.
 

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Discussion Starter #11
As ghni said "There were a couple of slightly different computers used during the run of the Series 3 Spiders ('82 - '89)"
 

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my experience with the S-3 here in SoCal is that the computers are very durable and almost anything else could be the problem. When you crank is there spark? If there is current at the coil but it is not "flashing" (hence no spark) the problem is one of the flywheel sensors or its connections, the check for them is resistance using a multi-meter. When you turn the key "on" do you here the drive relay "click"? Have you checked that both fuel pumps work (with the key off run a test hot lead to the hot (small) terminal on the main pump, that should cause both pumps to operate. There is an inline fuse next to the FI computer, does that have continuity? Another test is to unplug an injector and then crank with a "noid light" in the pigtail, does it flash? My gut feeling is you have a faulty drive relay, When you start cold it works and continues to work as you drive but gets hot, so when restarting it doesn't work, once cold, works again.
 

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Discussion Starter #13
This is the problem. I'm not understanding. Ypu sa "FI computer" (which to me means fuel ignition). The car has two computers which one is for fuel and other is for ignition.
 

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Ok. I'm sorry. Just getting frustrated about it. Just a lot of confusion.
Understood. The L-Jet system can be very frustrating because when one piece stops working, the whole thing stops working. And that makes it difficult to figure out which piece stopped working first.
 

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One more thought, if the car doesn't crank (the starter doesn't turn) when hot, it could be the starter and or ignition switch, but the most prudent option is to install a relay between the ignition switch and the starter in the engine compartment. You can find kits for $20 on ebay for BMW 1600-2 / 2002 that work just fine.
 
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