XJ6 & XJ12 Series I, II & III 1968-1992

Out of the blue, startup/richness issues...

 
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Old 01-26-2019, 01:57 PM
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Default Out of the blue, startup/richness issues...

After two years of predictable starting/running from this car, we've suddenly got an issue with fuel mix especially at startup.

Before I get too far into that, let me say we've been converting the A/C down to manual control and have run into several vacuum leaks. We've got one now at the heater core blend door, but I don't *think* that's what is causing this issue.

Anyway, on startup now, you get slammed with this overwhelming raw fuel smell that slowly turns to that sickening half-burnt fuel smell. Both tailpipes eject whitish-gray smoke (but not all the time) and the exhaust reeks of raw/unburnt gasoline (but not antifreeze -- I don't think this is a head gasket issue). It's hard to get the car to start or idle. It coughs, sputters and dies a lot.

But once you get it to hold an idle for a couple of seconds, everything is perfect from an idling/driving standpoint. It holds idle, and runs down the road just fine. Accelerates fine, doesn't buck, doesn't throw smoke out the back. And more importantly, after a couple of minutes, you don't smell the gas smell nearly as bad.

Is this something as simple as ... a tune-up issue? Bad plugs or wires? The color of the smoke on cold start-up is worrisome, as it portends a head gasket or valve seal issue, but there is no evidence of water vapor in the exhaust, no mixing of water/oil anywhere in the engine or radiator, and no overheating from a the engine pressurizing the coolant flow.

Until now, for the last 2-3 years, here was my morning routine: Turn the ignition key and let the engine spin fruitlessly for about 10 seconds. Rotate the key off, then on again and it started instantly on the second try. EVERY SINGLE TIME. Regardless of outside temperature.

Now? The engine sounds like it's turning over/spinning at twice the speed. Sort of like when you replace a sour battery with a new one, how the starter seems to turn the engine more quickly. Except now, it takes 5-10 attempts to get it to start, catch and then idle. Once running, though, she's the same old car.

Jess
 
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Old 01-26-2019, 02:59 PM
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"Turn the ignition key and let the engine spin fruitlessly for about 10 seconds".

spin the engine or do you mean the fuel pump? otherwise, how do you do that?
 
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Old 01-26-2019, 03:09 PM
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Originally Posted by Jose View Post
"Turn the ignition key and let the engine spin fruitlessly for about 10 seconds".

spin the engine or do you mean the fuel pump? otherwise, how do you do that?
Engine. What used to happen on the first start of the day is you would rotate the key, and the engine would just spin and spin and spin. Didn't matter if you did it 5 seconds or until the battery expired. It refused to catch. All you had to do to make it catch, was turn the key off and back on again, and it would start instantly. Craziest thing I've ever seen. You just needed to make the first attempt last 5-10 seconds. It could be 100 degrees outside or -10. Rain or dry.

That doesn't work anymore, though, now that we've got this pig-rich situation on our hands.

Jess
 
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Old 01-26-2019, 03:17 PM
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Old 01-27-2019, 11:38 AM
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Remove the air cleaner and cranl...
 
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Old 01-27-2019, 12:48 PM
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Originally Posted by JagCad View Post
Remove the air cleaner and cranl...
We'll try it, although I forgot to mention someone had already converted this car to an open-box/cold air intake with K&N air filter.

I'm kind of eyeing that flexible fabric-looking hose that connects to the air filter. Can rips/tears in it cause this? What it's most acting like on startup is either a bad spark plug, or unmetered air getting into the system, but those problems shouldn't go away after it starts up.

We've recently replaced the cold-start injector relay and I *think* we replaced the coolant temp switch as well, but I'm not 100% certain on the latter.

Jess
 
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Old 01-27-2019, 06:51 PM
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Originally Posted by JessN16 View Post

I'm kind of eyeing that flexible fabric-looking hose that connects to the air filter. Can rips/tears in it cause this?
An air leak between the air filter and the Air Flow Meter won't change the way the engine runs. A leak between the Air Flow Meter and the throttle body will definitely cause a problem....but it would be problematic at all times

What it's most acting like on startup is either a bad spark plug, or unmetered air getting into the system, but those problems shouldn't go away after it starts up.
Personally I'd begin with checking the coolant temp sensor (the one for the fuel injection) and then do the capacitor mod

Cheers
DD
 
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