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Join Date: Apr 2006
Location: Texas
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L-Jet problems

Hi,

As some of you know, I just drove from LA to Corpus Christi
last weekend. The car gave me no major problems! It was
missing a bit but only around 3000 rpm. By the end, it would
not idle at all, but still ran okay.

Now that it is home, it won't start. It cranks and may fire
for a few seconds, and then die. I have checked the TPS, the
air flow sensor (appears okay). Fuel pump is running. Fuel filter
was changed last weekend. Some times it backfires a little in
the engine compartment. I'm getting frustrated!! It doesn't
help that 914club is down!

Oh yeah, there is a sensor(?) disconnected. It is not the one by
cylinder 3, it is one mounted on the rear of the engine into the
vertical aluminum plate under the throttle body. It has a heavy
whitish wire on it. Could this be related?

This is a '75 1.8 L-Jet.

I'd really love to get it running again. I have to get it regisitered!

Can anyone offer some suggestions of things to check?

Thanks,

Jeff
Old 05-15-2006, 12:18 PM
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Groucho Marxist
 
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That sounds like a bad vacuum hose. Have had same symptoms on other L-jet cars that straightened right out with having the vacuum lines hooked up.
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Old 05-15-2006, 12:22 PM
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All the lines are hooked up, but I can't guarantee how well!

I was going to start replacing all of the small ones
tomorrow, then the larger ones. Sigh....
Old 05-15-2006, 12:26 PM
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Any gaskets on the throttle body?

Are there any gaskets on the throttle body? I just tried starting
the car again with some help. The backfire is through the throttle
body to intake air distributor junction. This is with the throttle
partly open when trying to start the engine. I remember a
plastic ring that might have been in there before Iremoved the
throttle body.

I thought that was a spare part left over from a previous repair!!

Thanks,

Jeff
Old 05-15-2006, 01:18 PM
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There is a rubber gasket that goes between the throttle body and the plenum. If it is missing, you will get a bad air leak.
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Old 05-15-2006, 01:19 PM
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While you're at it, replace the TWO o-rings in the oil filler cap. They'll make it a non-starter. Get 2 of each, 'cause you'll be needing them again! The Cap'n
Old 05-15-2006, 02:27 PM
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Now this you gotta love....


Cap'n Crusty..... "Junior Member"....


LOL!!!!

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74 914 1.8L (Frodrick)
73 914 /6 4.0L 964 motor (Igor)
70 914 /6 Factory Six. (Elwood)
95 BMW 540i (Inga)
Old 05-15-2006, 02:44 PM
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I agree with Le cap'n. I love L-jet...without vacuum leaks. those vacuum rubber elbows leak when they harden. never hold teh gas pedal down when startign an L-Jet
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Old 05-15-2006, 03:42 PM
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Thanks to all.

I think I lost my gasket! I thought it was left over junk! It
seemed like hard plastic. I've got to find it or make a
new one. Pelican lists one for a 1.8 l still, hopefully they are still
available.

I don't like the way tubes go into the "s" shaped coupler from
the throttle body to the airflowsensor. How do you seal those??
One of mine is wrapped with tape to help seal it!

I'll also look for the oil filler seals. We never tried starting the
car at WOT, but that's a really good warning!!

Thanks again,

Jeff
Old 05-15-2006, 04:06 PM
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I too am suffering the "find vacuum leaks" problem.

Sounds to me like you either have an injector or two disconnected, or the Air Flow Sensor disconnected. Definitely a problem with metering air.

If that big rubber intake boot is cracked or splitting, it will be one major vacuum leak. L-Jet does not like these at all.
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Old 05-15-2006, 04:51 PM
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The boot has reliefs moulded into the holes for the vacuum ports. The parts that are inserted into the ports have a flange, which MUST "snap" into those grooves. Once that's done, a little judicious application of Black RTV, one of the most evil and misused products in the world, will fill any cracks in the area. Reinstall the boot after things have cured and stabilized. The boots are NLA, and used ones are gonna be real hard to find, so take care of the one ya got! The Cap'n
Old 05-15-2006, 05:06 PM
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I just got through some similar problems on my 74 1.8. Ditto everything mentioned and when I got most of my vacuum leaks fixed, I had another AFM go bad. Car ran great for 50 miles and then started backfiring through the intake, wouldn't idle, stalling while under load. Replaced the AFM and it runs like a new car again.
Old 05-15-2006, 05:13 PM
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Where do I get black RTV?? I've never seen that, although there
was a lot of it around on the tubes that are there! The big boot
looks okay so far. It is still flexible, but I hope I don't break it if
I have to take things apart too often!

I feel so ignorant with all this knowledge floating around here!

Thanks,

Jeff
Old 05-15-2006, 05:13 PM
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Black RTV can be had at any FLAPS
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Old 05-15-2006, 07:14 PM
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Anyone have a pic of the L jet boot for the 1.8? I ask because it might be pssible to use one for a Super Beetle or something
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Old 05-18-2006, 11:57 AM
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Quote:
Originally posted by Tobra
Anyone have a pic of the L jet boot for the 1.8? I ask because it might be pssible to use one for a Super Beetle or something
Perfect! Other than the length, the diameter, the configuration, and the ports for the push in lines, it'll work fine! Actually, there's no other boot I've ever seen that will work. At least there are some out there for 1.8 owners. Poor huys with 912Es are playing with a much smaller number of possible donor cars. The Cap'n
Old 05-18-2006, 02:37 PM
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[QUOTE]Originally posted by jd66921
[B]Where do I get black RTV?? I've never seen that, although there
was a lot of it around on the tubes that are there! The big boot
looks okay so far. It is still flexible, but I hope I don't break it if
I have to take things apart too often!

I feel so ignorant with all this knowledge floating around here!

Thanks,

Jeff

Me too!
Geoff
Old 05-18-2006, 02:47 PM
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Here's my 2 cents worth:

Based on your comments and mentioning that some things are "taped", etc...it sounds like the same L-jet problems I had when I first got my 914.

L-Jet is actually a very simple setup and my car runs consistantly well - as long as I don't have "any" vaccum leaks. L-Jet has one primary sensor that is critical to proper performance and that is the airflow sensor. It measures the amount of air entering the engine and adjusts the fuel mixture accordingly.

That being said, any additional air entered into the engine (i.e., via vaccum leaks) is "un-measured" air and the fuel injection system will not add any additional fuel because it is not measured by the airflow sensor.

Step one: fix all vaccum leaks. I reccomend that you replace every vaccum line whether it looks good or not. When I replaced my vaccum lines, it seamed like I gained 5hp with each new line.

Step two: replace gaskets. there are 4 gaskets (or hose things) on the intake tubes, a gasket at each head under the intake runners, fuel injector gaskets - one large and one small for each fuel injector, throttle body gasket, oil cap gasket & gasket under the oil breather, and lastly the boot should be in perfect shape. When inspecting the air boot, be sure to flex and look for tiny cracks - if there is any cracking, the boot should be replaced. Of course, nobody sells them but you can use one from a VW bus but they are slightly different.

Step 3: Head Temp Sensor. You can test it to see if it's good but there only $20 at Pelican so I would just get a new one.

Step 4: Only after all vaccum leaks are corrected, you can start tuning the fuel injection system. This requires specialized equipment but you may find out that your car starts running better with just new hoses.

If your car is old (and all 914's are) you should probably replace all of the fuel lines too.....no sense getting it running just to set it on fire.

Also, backfiring can be very harmful to the air flow meter. It dosent always cause problems but it can.

I reccomend a book called "914 tech tips". They sell it at Auto Atlanta (if you can stand them) and it's a very good book. I have solved virtually every problem with my car using this book and I knew nothing when I first got started.

Hope this helps a little.........................Vern
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Last edited by Tidybuoy; 05-18-2006 at 02:56 PM..
Old 05-18-2006, 02:52 PM
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What year bus boot will work for this application? Are they available new?
Old 05-18-2006, 06:50 PM
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Quote:
Originally posted by Ctrout
What year bus boot will work for this application? Are they available new?
None of the bus boots fit The Cap'n
Old 05-19-2006, 07:29 AM
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