S3 Cold Start Problem - Alfa Romeo Bulletin Board & Forums
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post #1 of 6 (permalink) Old 05-03-2017, 11:12 AM Thread Starter
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S3 Cold Start Problem

My Spider has developed a "hard to start when cold" issue. After sitting parked for a few days, it takes about 3 minutes of repeated starter cranking before she finally catches.

If I cycle the ignition key on-off, on-off, on-off (3 or 4 times) before turning it to start, the car will start after a few seconds. Does that suggest the Fuel Pressure Regulator (FPR) is bad? Does the repeated ignition key cycling turn the fuel pumps on each time, override the FPR, and force a pressure build in the system?

If I go for a drive somewhere and turn her off for an hour, she will start right up.

When running, the idle is always smooth, right in the 950-1000 range, and the throttle response and power under load is great.

I think Iíve got a faulty Cold Start Valve, but new Bosch 0 280 170 031 units are running over $300, so Iíd like to be satisfied that thatís the problem before I bite the bullet. Would appreciate some input from the forumís experience and knowledge.

I made each of the following tests when the ambient temperature in my garage was under 55įF and the car was cold (hadnít run in over a day):

1. Resistance between the two terminals on the Coolant Temperature Sensor (CTS): 2891 ohms (within spec)
2. Resistance between the G terminal and ground on the Thermo Time Switch (TTS): 33.1 ohms (within spec)
3. Resistance between the W terminal and ground on the Thermo Time Switch (TTS): 0.3 ohms (spec is 0)
4. Resistance between the G terminal and the W terminal on the Thermo Time Switch (TTS): 33.1 ohms (within spec)
5. Unbolted the Cold Start Injector/Valve (CSI) from the plenum, plugged the plenum CSI hole, had my son crank motor whilst I held the CSI in a clear plastic bottle: no spray at all
6. Pulled the vacuum hose off the top of the Fuel Pressure Regulator (FPR) and examined both: no gasoline present
7. Clamped the return hose under the Fuel Pressure Regulator (FPR) and tried to start the car: it started up after about 5 seconds of cranking

I donít have a noid light so is there another way to verify if the CSI is getting voltage to fire? Can I pull the Bosch connector off the CSI, jumper the terminals to my voltage meter and check for voltage while cranking cold?

I donít have a fuel pressure gauge or T-fitting to check the fuel pressure at the rail, but should the fact that the cars starts and runs fine when warm eliminate the fuel pumps as a possible issue?

I havenít pulled the Auxiliary Air Valve (AAV) and checked that yet, but I cleaned it and it and tested itís operation (with freezer & oven) about 18 months ago and it was working fine.

In summary:
ē the car idles, starts and runs perfectly when warm
ē the CTS and TTS test within resistance specs
ē the FPR is not leaking fuel
ē clamping/blocking the FPR return line, or cycling the ignition switch on-off several times before trying to start when cold seems to help (increased pressure in fuel rail?)
ē the CSI does not spray at all during cranking

Am I correct in thinking my Cold Start Valve is most likely the culprit? Thanks in advance for any thoughts, comments, and suggestions.
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post #2 of 6 (permalink) Old 05-03-2017, 12:53 PM
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The cold start injector is a separate fuel injector that only gets power during cranking. Green/gray wire is the 12 volts feed. The thermo time switch controls the ground side of the injector circuit. If the block is cold the switch should be closed allowing the injector to spray. You could check to make sure you are getting the 12 volts to the Bosch connector during cranking by measuring voltage from the connector ( green/gray wire) to the engine.
Also confirm that the other pin has continuity to ground verifying that the thermo time switch is closed.
I don't know why cycling the key from off to on should help. Each time you do that you do turn on the fuel pumps but the fuel pressure regulator should continue to work regulating the pressure. What I don't like about doing that is you are also cycling the two ECUs on and off.
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post #3 of 6 (permalink) Old 05-03-2017, 01:35 PM
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If your fuel pressure is low, your cold start valve wont spray anyway. Is there any resting pressure? if not, I doubt if when it starts cranking, the pressure will build right away and spray.

I do this; crank for maybe 6sec. Let it sit for maybe 10mins. It may start right away, then. Mine does. I have no idea why my cold start is this way, or why my fuel pressure in the system gets that low in 24+ hours...
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post #4 of 6 (permalink) Old 05-03-2017, 01:40 PM
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Hi Edward,

"7. Clamped the return hose under the Fuel Pressure Regulator (FPR) and tried to start the car: it started up after about 5 seconds of cranking"

I'd suspect the FPR, even though she runs, as you say....

Anyway, if she starts when you clamp the return hose, what about clamping the hose and then testing the CSI for spray?

(edit: If it is the FPR, get a bosch unit and be careful removing it on the S3. Unlike the S4, the connection to the fuel rail is not very well designed...!)

saw a s/h tested CSI on ebay for 100....might be worth a punt if it is that which is gone bad?
[ebay # 190659589627]
my 2cents is on the FPR though.


Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 05-03-2017 at 02:37 PM.
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post #5 of 6 (permalink) Old 05-06-2017, 03:08 PM Thread Starter
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update - problem solved!

Many thanks to spidryell, John533i and spiderserie4 for the tips.

I am pleased to announce that by following the instructions in Step 3 The cold start and warm up system of Greg Gordon's and Eric Russell's wonderful L-Jetronic Troubleshooting Guide, I was able to diagnose and correct my cold start problem.

Pretty simple really. The fact that the CSI only opens if the TTS is operating properly and completes the ground to the CSI switch, was the key to the puzzle.

To begin with, I knew my CSI was not spraying when the car was cold, because I removed it from the plenum and held it in a clear bottle while my son cranked the starter with the ignition key. I also knew the TTS appeared to be OK, based on the fact that the resistance between each terminal and ground, and between both terminals, was within spec. Finally, following spidryell's advice, I verified that the blue wire going to the CSI had continuity to ground when the block was cold (meaning the TTS was properly in the closed position). I could have checked for +12 volts during cranking on the green/gray wire going to the CSI, but I didn't have a helper handy, so I took a chance and bought a new cold start valve.

I managed to find one (made in Spain by BWD) at my local O'Rielly's for $120. Interestingly enough, it had BOSCH and 0 280 170 031 stamped into the housing.

Anyway, since I still had the clear bottle handy, after I attached the new CSI to the fuel hose, I stuck the tip of the CSI into the bottle and asked my wife to turn over the engine. A nice spray of gas flowed out into the bottle.

I put everything back together, waited a day, then turned the key. Immediate catch and idle! And thanks to the terrific help from this forum, I only had to buy the one part I needed.

Life is good.
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Last edited by Norseman50; 05-06-2017 at 03:13 PM.
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post #6 of 6 (permalink) Old 05-06-2017, 03:45 PM
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Fantastic! Enjoy driving your car. I'm still waiting on suitable weather here in the Buffalo NY area.
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