motronic 4.1 ts diffciult starting - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 7 (permalink) Old 04-29-2011, 05:05 AM Thread Starter
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motronic 4.1 ts diffciult starting

Hallo everybody,
I've transplanted on my 1988 carburetted spider a 75 ts engine with its electronic management (a full photo story on this pages in the next future)
Everything works fine except for a quite long cranking before engine fires up.
I checked fuel pressure and realized that the fuel regulator was leaking and fuel came back to tank, so that when egine was not running the pressure dropped quickly to zero.
Now I have replaced it, and the situation is a lot better, but I still need to insist for quite a few seconds (8-10) to get the engine started. The pressure seems to drop slowly to 2 bar and then stops. Fuel pump anti-reverse ball works correctly.

Do anybody know whether the punp is supposed to work shortly when ignition is switched on? In my car pump works only when cranckshaft is spinning.

Many thanks.
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post #2 of 7 (permalink) Old 04-30-2011, 11:12 PM
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Quote:
Originally Posted by d.albe72 View Post
In my car pump works only when cranckshaft is spinning.
Yes, this is normal.

The TS can take two or three turns of the engine before starting but 8 to 10 seconds is excessive.

Craig,
1988 75 TS, 1989 164
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post #3 of 7 (permalink) Old 05-01-2011, 12:57 AM Thread Starter
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Thanks Craig for your reply.
I know that the Motronic needs a couple of revolutions to "understand" that the engine is running and detect the crank/pistons position.
My engine seems to take quite a lot more time, but fuel pressure is ok, fuel pre-pump is new, like filter, hoses, pressure regulator, spark plugs, cables, distributors caps. Valve gaps and timing are correct, fuel pressure sets at 2,5 bar at idle to 3,2 bar at maximum engine loads. Engine rides beautifully and idles well, exhaust gas analizing show 0,5% CO and 100/110 ppm HC.
Hot starting is far more quick than cold attempts.
I was guessing if, like in the Weber IAW system on my Guzzi, the ECU should activate the pump shortly when key is turned. On my California I hear a "bzzzzzzzzt" for two o three seconds when ignition is on. On my spider not: is it correct?

Hope to have been clear enough, thanks in advance for any help.

Last edited by d.albe72; 05-01-2011 at 01:01 AM.
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post #4 of 7 (permalink) Old 05-01-2011, 01:29 AM
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Originally Posted by d.albe72 View Post
I was guessing if, like in the Weber IAW system on my Guzzi, the ECU should activate the pump shortly when key is turned.
It probably should but Bosch did not design it to do that.

Craig,
1988 75 TS, 1989 164
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post #5 of 7 (permalink) Old 05-01-2011, 01:38 AM Thread Starter
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Thanks Craig,
I'll check for fuel pump flow, it's the last thing to be looked at.

many thanks again
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post #6 of 7 (permalink) Old 05-01-2011, 01:15 PM
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check your connecctors

d.albe72- assuming you are using the original TS wiring harness, yes? If so, note that it is possible to mix up the electrical connectors for the coolant temp. sensor at the rear of the cyl. head w/ the connector for the idle air control valve on the intake plenum- or it was on my harness because the color-coded connector had been replaced previously w/ a generic one. At least that is the excuse I have continued to use to explain why my similar conversion had such problems w/ cold starts. Starts up just fine when you hook up the wires right!
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post #7 of 7 (permalink) Old 05-01-2011, 01:37 PM Thread Starter
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Thank you Capp,
yes I'm using te original 75/milano harness.
I will check this possible trouble, thanks again.
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75 ts, cranking problems, fuel pump, motronic, starting issues

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