Series 3 Starting Issue

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Sep 14, 2018 | 08:07 PM

#41

Jag-o-nomic

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From: Melbourne, Australia

Hi Mike,

2.4kg on the bathroom scales.

I wish my weight was a bit closer to that, or at least by that much less!!

Hope that helps.

Cheers,

Nigel

Sep 16, 2018 | 02:50 PM

#42

benji808

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From: Des Moines, Iowa

Well, installed the trumpet and still no change in the start issue. When it’s cooler outside it actually seems to start a little better (the tach actually moves on the several cranks vs no movement) so I’m pretty sure the CSI is working...This is a weird one! I just keep my hammer and screwdriver in the drivers door and pull it out whenever I need to start lol

Sep 18, 2018 | 02:25 PM

#43

benji808

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From: Des Moines, Iowa

So, if the AFM only gives slight enrichment at startup, where does the rest come from?
Is it starter relay > main relay > ecu, and then a specific part of the ecu fires the injector while cranking? Does anyone know if it’s a specific pin or part of the ecu?

thanks in advance!
Benjamin

Sep 18, 2018 | 08:39 PM

#44

Doug

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From: Pacific Northwest USA

Quote:

Originally Posted by benji808

So, if the AFM only gives slight enrichment at startup, where does the rest come from?

"Cranking enrichment", regardless of engine temp, comes from the ECU. Pretty sure it's the 'cranking signal' on Pin 4 that does it. Voltage to pin 4 comes from the starter relay. It's a different branch of the same white/yellow wires that give voltage to the cold start injector. This small enrichment occurs only when cranking the engine.

"Cold enrichment" also come from the ECU based on signal from the CTS - Coolant Temperature Sensor. This enrichment tapers off as the engine warms up and is all done by the time the coolant reaches about 170ºF or so.

Quote:

Is it starter relay > main relay > ecu, and then a specific part of the ecu fires the injector while cranking? Does anyone know if it’s a specific pin or part of the ecu?

The 6 regular injectors are operated by the 'injector drivers' in the ECU.

The CSI - Cold Start Injector operates independently of the ECU. The ECU and CSI don't talk to each other.

Have you tried swapping ECUs ?

Cheers
DD

Sep 18, 2018 | 09:23 PM

#45

benji808

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From: Des Moines, Iowa

Thank you! Reading this, it sounds like either the ecu, the coolant temperature sensor (sitting for an hour might cool the coolant enough so it might be needed), or a connection in between could be at fault. Is that a fair assessment?

Sep 18, 2018 | 10:17 PM

#46

Doug

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From: Pacific Northwest USA

Quote:

Originally Posted by benji808

Heh, heh...this is a weird problem. I think the 'fair assessment' boat sailed a long time ago

Unplug the CTS and jump the terminal n the socket with a paper clip. This obviously eliminates the CTS signal and 'tells' the ECU that the engine is warm, regardless of actual temperature. Do this on a warm engine; a cold engine really won't like it. If the behavior changes with the CTS bypassed, you might be hitting paydirt.

Or, just replace the CTS and cross your fingers. Only about $20 and 10 minutes effort so it's not painful as guesses go.

Carefully examine the CTS socket and wires for anything suspicious.

Trying a different ECU would be a guess as well. My theory...ha ha....is that a fault in the ECU is preventing it from recognizing the AFM signal under certain conditions. Used ECUs are not too hard to find....and maybe $100 or so?

Cheers
DD

Sep 19, 2018 | 03:58 PM

#47

benji808

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From: Des Moines, Iowa

No change with bypassing the CTS...ECU will be up next, I suppose!

Sep 19, 2018 | 08:12 PM

#48

JagXK2007

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Joined: Apr 2017

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From: SW Colorado

Quote:

Originally Posted by Doug

Not leaking is fine.....but doesn't prove that the regulator is doing it's job !

I'd actually check fuel pressure and go from there. Or, replace the regulator if you have a mind to do so.

Cheers
DD

agreed. my fuel regulator was bad and actually leaking through the vacuum line. however, if it's not regulating properly she will not start good. Ours ran a bit rough if I recall.

Sep 23, 2018 | 11:33 AM

#49

benji808

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From: Des Moines, Iowa

What’s the procedure to test that the ecu is getting what to needs? Should the 4th pin connector show 12v when cranking?

Oct 8, 2018 | 08:05 AM

#50

benji808

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From: Des Moines, Iowa

Interesting observation...while testing the CTS (Coolant Temperature Sensor), I discovered that unplugging it has the same effect as sticking the hammer down the throat of the AFM. I assume that unplugging it sends a "bone-cold" signal to the ECU, causing excess fueling. Again, it starts, dies, then I plug it back in and she starts right up. The switch itself seems fine - the resistance reading are within spec at the 3-4 temperatures I've tested it at, but at least I don't have to unscrew intake components and use a hammer!

Got an ECU from David Boger (everydayxj.com), and will probably try that sometime this week.

Oct 9, 2018 | 09:44 PM

#51

benji808

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From: Des Moines, Iowa

Closing out this thread for now. I got a different ECU, and it did not correct the issue, so I have hot-wired (cold-wired?) the Cold Start Injector to a ground so it always fires when I crank, for as long as I crank, and that provides a solution that appears to work, for starts both hot and cold. Not a solution I was originally hoping for, but very functional and provides what I need until further inspiration strikes.

Huge thank you to everyone who has commented on the thread - I've learned so much about my Jag through troubleshooting this one issue, and am immensely grateful for all the insight this community has provided. Thank you!