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> 1.8 Ljet overfuels
davesprinkle
post Dec 30 2007, 09:09 PM
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My 1.8 Ljet left me stranded yesterday. I did the usual debug stuff. Turns out the ECU is overfueling the engine. Injector pulsewidths are 10ms to 15ms under cranking conditions. This is roughly 10x what I would expect at startup. Anybody have any suggestions for what might be causing this problem? The airflow sensor maybe?

Thanks for any suggestions you can offer.

-dave sprinkle
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Twystd1
post Dec 30 2007, 09:17 PM
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Check your grounds FIRST....!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

BROWN wires. LOOK in your manual for ALL the injector connection points.

Then just for shits and grins. Pinch off your cold start injector fuel line with a flat faced locking pliers (Vice Grip). Or pull the fuel line and plug it.
Just to keep that possibility out of the over fueling equation.

Clayton
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Katmanken
post Dec 31 2007, 09:11 AM
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If your fuel pressure regulator is sticking, then you will get a higher fuel pressure and squirt too much fuel during a normal injection time.

Check the pressure.

And the CHT.

Ken
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davesprinkle
post Dec 31 2007, 09:39 AM
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Thanks for your responses, guys. Ground are OK. Fuel pressure is 40psi.

Here's the fundamental problem -- the injector pulsewidths are 10ms when cranking. This is roughly 10 times larger than what would be valid for a starting condition. It ain't the pressure, and it ain't the cold-start valve. The ECU is commanding too much fuel.
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Cap'n Krusty
post Dec 31 2007, 09:58 AM
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FIRST thing to check on a 1.8 is the air flow meter. The Cap'n
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davesprinkle
post Dec 31 2007, 03:37 PM
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QUOTE(Cap'n Krusty @ Dec 31 2007, 07:58 AM) *

FIRST thing to check on a 1.8 is the air flow meter. The Cap'n


I'll do that this evening. Thanks, Cap'n.

-dave
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davesprinkle
post Mar 29 2008, 12:59 PM
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I've finally found the cause of my ljet fueling problem. A puncture in the pressure reg diaphragm was passing fuel through the vent line and was dumping it into the intake plenum. Note that the pressure reg was STILL MAINTAINING PRESSURE even while filling up the engine with raw fuel.

Why am I surprised? I should have inferred from the deterioration of my targa seal that rubber parts don't last 30 years...

Thanks to everyone who offered advice and spare parts.
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Cap'n Krusty
post Mar 29 2008, 04:05 PM
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That's not all that uncommon on Vanagons, BMWs, and Volvos, but it's the first 914 I've heard of with that failure. Glad to hear you found it! The Cap'n
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davesprinkle
post Mar 29 2008, 06:56 PM
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Yeah, thanks for the support, Cap'n. Wanna sell me a new reg? Cause I don't think I'm gonna trust the spare one I've got in my old parts bin.

QUOTE(Cap'n Krusty @ Mar 29 2008, 03:05 PM) *

That's not all that uncommon on Vanagons, BMWs, and Volvos, but it's the first 914 I've heard of with that failure. Glad to hear you found it! The Cap'n
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type47
post Mar 29 2008, 07:02 PM
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QUOTE(davesprinkle @ Mar 29 2008, 10:59 AM) *

A puncture in the pressure reg diaphragm


now how in the world did you find that? or think that was a possibility? you're GOOD! (IMG:style_emoticons/default/pray.gif)
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davesprinkle
post Mar 29 2008, 07:41 PM
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Thanks for the kind words, but I can't claim any brilliance on this one. It was a triumph of perseverance over lack of insight. I tried a new ECU, a new loom, a new sensor, but still had the same problem of too much fuel. Finally, today, with the injectors all removed from the engine, I STILL HAD FUEL GETTING INTO THE ENGINE. What the EFF? Is this engine MANUFACTURING gasoline??? The last remaining connection between the fuel system and the plenum was the reg vent line. I pulled it off, turned on the fuel pump, and sure enough, it pissed fuel into my face. Don't worry about me, I'll recover my eyesight soon.

So, no, I'm not good. I'm slow. It took me, what, 3 months to figure this out? Jeez...

QUOTE(type47 @ Mar 29 2008, 06:02 PM) *

QUOTE(davesprinkle @ Mar 29 2008, 10:59 AM) *

A puncture in the pressure reg diaphragm


now how in the world did you find that? or think that was a possibility? you're GOOD! (IMG:style_emoticons/default/pray.gif)
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jesiv
post Mar 29 2008, 10:38 PM
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I don't quite understand. However, this sounds totally awesome. Do you have pics of what you are describing. I have a 75 1.8 and I am trying to understand what is casuing it to run so rich.

Regards,

James
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davesprinkle
post Mar 30 2008, 12:10 AM
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Sorry, James, don't have any pics of the damaged pressure regulator diaphragm. The pressure reg is a crimped can, so I haven't seen the puncture. I'm just inferring it from the fact that I've got fuel coming out of the vent line -- the only way this could happen is if the diaphragm is damaged.

If your 1.8 is running rich, I would suggest checking out the airflow meter. It could have been damaged by a backfire, which is a common failure mode. It might also be a cold-start valve that isn't shutting off. You might also want to verify that your fuel pressure is OK.

Good luck.
-dave

QUOTE(jesiv @ Mar 29 2008, 09:38 PM) *

I don't quite understand. However, this sounds totally awesome. Do you have pics of what you are describing. I have a 75 1.8 and I am trying to understand what is casuing it to run so rich.

Regards,

James
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