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Ethanol Fuel Wreaking Havoc with my old 914's F.I.

Due to ethanol being used in today's fuel, my car recently developed a problem of stalling after startup and fast idle for about 20 sec. Aside from checking filter to see if it is clogged, fuel pressure (to see if pump is bad), what else can I check to solve the stall and non-revable problem. The car dies when I step on the gas.
Old 12-22-2007, 09:10 AM
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Interesting premise. I wouldn't have thought of blaming the fuel. Actually, I'll step out a little further on the limb and suggest it's not the fuel.

What is fast idle? 2000rpms when cold? And it drops to what when warm?
How is your tuneup status? (Points, dwell, timing, etc.) Need those baselines nailed first.

We need to know what FI system you have.... Djet? Ljet? Or which motor/year?
Old 12-23-2007, 03:29 PM
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The car is stock 1974-1.8 L-jet, recently ran fine in summer till late november. Had a bout of wet weather last few weeks where the car sat outside in the rain for time to get moisture into the system (fuel system). The car was started last week and it starts fine after a few cranks (to get system fuel lines filled up from sitting unused) and the idle is 2000 rpm steady and OK. After the requisite normal time of about 30 sec-1 min the idle drops to 900 rpm. Then when given gas to rev up engine the stall occurs. Restarts upon cranking the starter but doesn't rev-cuts out at any gas pedal depression. Hence I suspect the fuel injection (not ignition) as the culprit. Possible components to check is throttle position sensor in addition to fuel pressure, filter, etc, but aside from my previous first post what else can I check first?
Old 12-24-2007, 05:09 AM
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ignition is fine (I've replaced points with Pertronix igniter) and I'm sure there is spark and no moisture in distributor cap. Need advice from L-Jet person regarding how water and ethanol has rendered the fuel mixture too lean. I've turned the idle air screw max closed because I suspect the ethanol and moisture absorbed by fuel is causing the stalling problem when ever the gas pedal is pushed down.

Appreciate the suggestions and keep them coming

From Brad roberts (914Club)"Air flow meter. Pull the black plastic over off of it and be prepared to clean inside with contact cleaner/brake cleaner. The moisture has caused a build up on the electrical contacts. You will probably find that someone has been inside the cover before Seal it back on with clear Permatex."
Old 12-27-2007, 05:29 AM
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Thanks Brad,
I took off the meter air box to clean as you suggested. I noticed immediately that before I removed the 4 screws holding the front plate to the meter housing that the gasket on two edges were sticking out in the path of the air flow leaving no seal at the two edges. The gasket had warped severely and will need replacement before I attempt to open the meter and disturb the sealant. The inside of the AFM may be ok if the new gasket solves my stalling problem.

I'll post back after I get a new gasket and let you know what worked.
Old 12-27-2007, 05:30 AM
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I made my own gasket since Pelicanparts don't seem to have that listed in the diagram. Put the cleaned AFM back and started it up it idles better and was able to rev it up to redline. However, the response to throttle input is still very sluggish and erratic. I cleaned the throttle housing of accumulated grease and I see what looks like a bimetallic spring sticking out of the top. Assume this is the initial warmup fast idle position regulator. Does anyone know if that bimetallic spring can still be purchased if it breaks? Also by feeling around the F.I. Boot (NLA) there appears to be leaks at where I had torn it last year when I had the engine lowered to do a rear oil main seal. I had silicone glued the boot up and now it appears I need to get another one. Luckily I had been able to obtain a used good one for $45 from another 914 guy who had it on eBay! Will see if this solves the problem
Old 12-27-2007, 05:31 AM
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I am mostly a Djet guy in practice and experience, but I do know that in an Ljet any Vacuum leaks or leaks between the throttle butterfly and the AFM will lean it out. Poor response to throttling I would check the Throttle Position sensor (if it has one, I think it would have to)
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Old 12-27-2007, 05:50 AM
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Quote:
Originally Posted by hardflex View Post
I am mostly a Djet guy in practice and experience, but I do know that in an Ljet any Vacuum leaks or leaks between the throttle butterfly and the AFM will lean it out. Poor response to throttling I would check the Throttle Position sensor (if it has one, I think it would have to)
My money is on an air leak, allowing unmetered air in, causing the symptoms you describe. L jet is sensitive to this. You will probably need to go through the whole thing, injector seals(bad ones let air in around them, may make a whistling noise) to air cleaner. Good system when it was new, parts getting tough now. I think busdepot has stuff that is hard to find for stock FI, but have not looked lately.

When you turned the idle screw in and out, what did it do? If it did not do much, you have an air leak somewhere.
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Old 12-27-2007, 06:18 AM
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New boot and new hoses everywhere rules out air leak as problem. The idle crew affects idle which is great and steady at 2000 rpm (when cold started). The problem now is cannot rev it pass 2000 rpm as any throttle input results in engine decelerating and stalling if gas pedal is not released. What now?
Old 12-29-2007, 02:42 PM
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again, I'm no Ljet expert, but it sounds from here like you're getting no signal from the Air Flow meter. I would think you could check that with a Ohmmeter. either that, or a bad wire to the brain.

I just found this site, it might be helpful

http://manuals.type4.org/ljet/troubleshooting/ljet03.htm
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Last edited by hardflex; 12-30-2007 at 06:02 AM..
Old 12-30-2007, 05:58 AM
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Don't run a gasket - mine had the carboard one and failed (multiple times) after wet weather.

Clean both metal pieces and use a silicone based sealant. Dirko (Gray or red), permatex's purplish-black tar stuff, Curil... It will alleviate the problem.

My air flow sensor had a cardboard gasket before. The box was rebuilt. After it rained the first time the gasket was soaked and fell apart - hello vacuum leak. Idle would jump all over, hit the gas and it stalls. Vacuum leaks on L-Jet are life and death.
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Old 12-30-2007, 10:39 AM
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Quote:
Originally Posted by tshih View Post
New boot and new hoses everywhere rules out air leak as problem.
That doesn't really follow. There are more places than just the boot and hoses that can leak. The previously-mentioned injector seals, the seal between the intake runners and the head, the plenum itself, the seal between the throttle body and the plenum, the throttle body and the boot... And, since the crankcase is plumbed to the intake through the PCV system, an air leak at the oil filler or the oil cap (!!) can also affect things.

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Old 12-30-2007, 03:45 PM
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Thanks Hardflex for the useful site. Before I go tear into the system I'm going to add some isopropanol and toluene into my gas tank to see if the fuel mixture can run better.
Old 01-01-2008, 04:44 PM
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Well the added isopropanol and toluene did not help. Then I decided to change the spark plugs and noticed that the engine was actually running very rich (opposite of what I thought) as all the plugs were carbon coated. So the engine was stalling out when the gas pedal goes down because the system got flooded with either a bad spray pattern of fuel or fuel sensor is not working properly?

How does the L-jet work when starting up cold? Is there an auxiliary air valve that lets in more air to burn up more fuel during a cold start and then closes after warm up?

Is there a cold start fuel enricher injector whose function should stop after warmup (that could be leaking extra fuel into the system)? The engine starts and idles at 2000-3000 rpm then when it returns to 1000 rpm any gas pedal input stalls the engine.
Old 01-07-2008, 09:20 AM
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There is an AAR which allows air to go from "upstream" of the throttle to "downstream" of it when the engine is cold. The air supply is still "metered air", in that it has gone through the air flow meter so the EFI knows about it.

There is a cold-start valve that adds more fuel when the engine is "cold enough" (somewhere near freezing). However, it only sprays while the starter is cranking!

Cold-engine enrichment is provided by the head temp sensor circuit.

--DD
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Old 01-08-2008, 12:05 AM
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It could be the cold start valve is leaking, as it always sees fuel pressure.
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Old 01-08-2008, 03:28 AM
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So to check if the cold start valve is leaking I can remove and plug the fuel line to it.

What values should the head temp sensor read when cold and when hot? 3Kohm when cold and <300 ohm hot?
Old 01-09-2008, 07:17 AM
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Yes, you could plug the line. in the 3rd post you say the system needs the fuel lines filled to run. That would be consistent with a leaky cold start valve.

BTW, I think the fuel pump powers on for a couple of seconds to charge the system as soon as you turn the key on. So, turning the key off and on a few times will make it start sooner without burning up the starter to do it.

Those Ohm measurements will work.
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Last edited by hardflex; 01-09-2008 at 07:41 AM..
Old 01-09-2008, 07:35 AM
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The L-jet does not have the ~1.5 second "buzz" of the fuel pump when the key first goes to "on". It only runs the pump when the starter is cranking, or when the flap in the air flow meter is open.

--DD
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Old 01-10-2008, 08:02 AM
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OK, I checked the fuel pressure today and it reads 25 psi when the engine is fast idling (at 3000 rpm) or at 1000 rpm after initial warmup idle. Does that seem low and how do I adjust the pressure upward if possible?
The engine backfires and stalls when given throttle.

I bought an LM1 but haven't learned how to use it. Is it pretty easy to use?
Old 01-19-2008, 08:40 AM
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