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Discussion Starter #1
I now have a twinspark motor residing in my otherwise original '74 GTV and it has a definite cold start problem.
Conditions are: When first cranking, it will hit once on maybe one cyl., then after much grinding ( w/ rest for the poor starter) it will catch on two or three, then finally start to run raggedly. If/when it finally starts, it takes about 20-30 seconds till it accepts throttle inputs. After warm up, everything is great and runs like it should w/ no drivability issues whatsoever. Warm restarts require more cranking than I'd like-- about 2-3 seconds. Hot restarts just fine.
Fuel pressure meets spec. at idle and regulator passes the squeeze test. Good battery voltage present at ECU pwr. pickup point-- 12.7V. Have timed the distributor per instructions.
Questions: 1.) Do the ignition amplifiers inside the ECU become weak but not completely bad? Plugs removed and observed under cranking seem to have good first spark then weaker. When I recently installed new NGK BKR6E plugs gapped at .032", no fire at all. When I regapped to about .026", got some improvement and eventual restart. 2.) Does the operation of the timing variator greatly influence starting? No, I haven't yet checked for voltage at the solenoid on the variator w/ just key on.
Another possible influencing factor is the fact that it will only idle properly w/ a restrictor orifice (about .125") in the IAC supply line. I think the IAC is, practically speaking, irrelevant. I have two supposedly good used ECUs and have tried both w/ no discernable difference. Have no idea if either is completely good, but the car runs and idles as well as I can reasonably expect when warmed up. I'm stumped and tired of research and throwing parts at it-- EFI 101 is no longer being fun and/or instructive.:(
 

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G'Day Capp,

Questions: 1.) Do the ignition amplifiers inside the ECU become weak but not completely bad?
Ignition amplifiers are on the coils. Are you using original coils? The TS normally has a massive spark, check that you have caps on the coils or the spark can jump from the HT lead to ground.

2.) Does the operation of the timing variator greatly influence starting? No, I haven't yet checked for voltage at the solenoid on the variator w/ just key on.
Well it can cause stalling at low speed so I guess it could affect starting, check the voltage anyway.


Another possible influencing factor is the fact that it will only idle properly w/ a restrictor orifice (about .125") in the IAC supply line. I think the IAC is, practically speaking, irrelevant. I have two supposedly good used ECUs and have tried both w/ no discernable difference.
This I don't like, have you cleaned and checked the operation of the IAC?
Use carbi cleaner then apply 12V to the connector (polarity doesn't matter), it should snap open with each application of power.

Also check for induction side air leaks (I use a cheap stethoscope with the diaphragm removed). Don't forget to check at the injector seals and the IAC connection to the plenum.



I have had a similar issue but it went away before I really started thinking about it :eek:

Hard to start, needs some throttle to catch, rough idle - may stall in first 30 seconds, hesitant under load but free revving under no load, goes away when warmer.
 

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Discussion Starter #3
O.K., I'm confused now.
Printed material I have (not Alfa specific) describes the operation of Motronic 4.1 and claims the amplifiers are internal to the ECU. Also says this is a drawback w/ this particular design-- that the ECU must be replaced when the ignition function dies. Apparently not all Motronic 4.1 applications are the same in terms of ignition hardware. My original harness and components looks exactly like yours however, and now that I consider the wire sizes involved, it's obvious that amplification takes place at the coil/pwr. transistor "thingie".:eek: I have since replaced the original coils w/ MSD Blaster coils, a common generic replacement that others have run successfully. Result was no different-- it was still hard to start, but it did eventually crank and run well w/ these new coils so I don't think that's an issue.
I don't think the IAC is affecting this problem because it's new (rebuilt), works mechanically when energized, and have verified pwr. to it when it's in the system. I have completely removed the IAC and the motor idles fine w/ all the holes plugged up. All injector o-rings are new as are intake spigot hoses and other vacuum hoses. Have checked oil dip stick and oil filler cap seals. I don't think I have any serious vacuum leaks as indicated by the 17" vacuum I see at hot idle. Should it be better?
 

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O.K., I'm confused now.
Welcome to my world :)

Printed material I have (not Alfa specific) describes the operation of Motronic 4.1 and claims the amplifiers are internal to the ECU. Also says this is a drawback w/ this particular design-- that the ECU must be replaced when the ignition function dies.
Well, repaired would do but you're right, the TS is the odd one out. Bosch removed the amplifier, cut the connection to pin 19 and connected pin 19 to pin 1 (effectively) to trigger the two external amplifiers mounted on the coils.

Apparently not all Motronic 4.1 applications are the same in terms of ignition hardware. My original harness and components looks exactly like yours however, and now that I consider the wire sizes involved, it's obvious that amplification takes place at the coil/pwr. transistor "thingie".:eek: I have since replaced the original coils w/ MSD Blaster coils, a common generic replacement that others have run successfully. Result was no different-- it was still hard to start, but it did eventually crank and run well w/ these new coils so I don't think that's an issue.
I'm still concerned about your weak spark but it doesn't ring any bells yet.

I don't think the IAC is affecting this problem because it's new (rebuilt), works mechanically when energized, and have verified pwr. to it when it's in the system.
Ok, good we can ignore it.

I have completely removed the IAC and the motor idles fine w/ all the holes plugged up.
I'm not sure it's supposed to do that :confused:

However if you just remove the connector to the IAC it should idle at about 1200 rpm (limp home mode).

All injector o-rings are new as are intake spigot hoses and other vacuum hoses. Have checked oil dip stick and oil filler cap seals. I don't think I have any serious vacuum leaks as indicated by the 17" vacuum I see at hot idle. Should it be better?
I don't have a vacuum gauge but it sounds like you covered all the bases.


So we're left with the weak spark, the VVT and maybe injectors (but I doubt it).


I 'think' mine was electrical as the ability to rev with no load seemed to rule out fuel. The VVT I'm not sure but I have my doubts that it's it.
 

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Discussion Starter #5
O.K.--
after considerable grinding I've started the car with NO restrictor in the IAC valve. It initially idles about 1200-1300 rpm fairly well, but after warming up a bit it will begin to surge, or rise and fall from ? rpm to 1200rpm or so, up and down, up and down, ad infinitum. When the restrictor is replaced, it idles right down between 700 rpm to whatever, depending on the setting of the butterfly stop screw. If I adjust this screw as specified, i.e.; to the point that the butterfly is just barely held open and not as an idle speed device, then the hot idle speed is usually around 825-850 rpm, as indicated by the tach. Car runs beautifully and has dead reliable idle w/ pretty good hot restarts. Does this give any hints? TIA.
 

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It could be a poor starter dragging the voltage down. try powering the ECU from a seperate battery. Aslo try changing the motoronic relay. Mine fails to start when the battery is low !!
 

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Discussion Starter #7
fetch the Dunce cap!

Cold start problem solved, probably. Last night I realized after staring at the engine for awhile that I had reversed the harness connectors for the idle air control valve and coolant temp sensor!:eek::eek::eek: I verified this by comparing individual wire colors to each sensor against a very poorly reproduced wiring schematic I have.
In my defense, I obviously connected it this way because that's presently the only way it can be connected. The harness pigtail that should go to the IAC is too short as the harness is currently routed, therefore I have to remove the plenum and all the related hardware to correct this unless I want to splice some length to the pigtail-- not an easy task as sits. Thanks everyone for the help-- ignorance can be "fixed", stupidity is forever.
 

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G'Day Capp,

Good to hear. Those connectors are close together aren't they? I replaced the connector on mine with a blue (aqua?) one in the later style with the push clip.

As a temp fix, go to a DIY wreckers and find a Volvo (240,245 etc I think) as they have a male connector in the right hand side front of the engine bay which would allow you to make an extension. You can also use them to make a useful test lead.
 

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