79 fuel injected starts but dies. . .arrgggg

[Lepersrepel]

Hi, my '79 fuel injected Super Beetle starts and dies. I cannot accelerate it to keep it alive. It dies, but it starts right up every time. The injectors are less than a year old and so is the fuel filter and the block sensor. Last year I was having issues with it stalling after it warmed up or dying after starting when I tried to accelerate. The issue was resolved with the block sensor. After that I also had an issue in which the Beetle labored a bit to restart after it is warm (like when I took a short trip to the store). When it is cold, it started right up, after it warmed up it took a little cranking to get it started. I was told that the vent in the air filter housing might be sticking. . . I bring it up because it might be related, but back to the the stalling out. . .
. . .I just replaced the floor pans and the wiring on the floor was messed with (I don't believe I screwed anything up). Under the rear seat there is a relay that looked to be disabled. There is a hole in it and the wire with a fuse might have been disconnected, not 100% certain. In any case, the inside of the fuse housing was supper corroded and I don't think the fuse was doing anything. Is that relay related to the injection or fuel pump? Or does it go to the starter? When I got under the car I believe that the starter relay was moved down there because it looks added, it's rigged with a zip tie.
I checked all the air hoses well. All the injection components had been gone over and the bug was working pretty well four weeks ago before I redid the pans, now the stalling. I have a notion that it is electrical in nature and that the mysterious relay under the back seat might have something to do with it. . .or not??
ideas??

[zoti]

How long does it run before it dies?

[busdaddy]

I can't think of a FI related relay under the back seat, but if the little brown ground wire for the double relay behind the back seat isn't attached to the negative battery post it'll act like you describe.
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[Lepersrepel]

[Lepersrepel]

[Lepersrepel]

[vwoldbug]

The brown wires at the battery are for the fuel pump double relay ,check the wire diagram.

[EVfun]

There is a contact set in the AFM that senses more or less any air flow through the box and signals the double relay system to keep the fuel pump on. It sounds like the starter motor signal is telling the double relay to turn the fuel pump on while cranking but the air flow meter switch is not telling the pump to run after it starts. I got rid of my L-jetronic stuff after selling my late convertible so I don't have the terminal numbers available. I must say, a good running L-jet Bug is a really nice ride. Smooth operation at any rpm and smooth power with any change in throttle position.
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[Lepersrepel]

[Lepersrepel]

[EVfun]

Sometimes they don't make contact after years of service or the contacts just get dirty. Other times the plug fails to make good contact, at either end. Most of these cars have not seen a good contact cleaning and are now over 40 years old. It is an analog fuel injection system so questionable connections cause real problems. I remember that after chasing electrical demons my '79 drove like a dream. I was inside the AFM at one point but I never had a problem with those contacts.

Watch those plugs closely. They have a lot of years of service in a hot engine compartment and typically getting a bit fragile.
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[Lepersrepel]

[PuddleRainbow]

My 76 came to me with the fuel pump wired keyed hot from the fuse block. I can't remember which fuse under the hood right now. A inline fuse was wired in as well.

Try that to get it running. It's a temp fix at best for safety reasons.

I'm in Linden NJ, if you get it running that way PM me.

Jeff

[PuddleRainbow]

[Lepersrepel]

[Lepersrepel]

[Pepperbilly]

Lepersrepel,
The relay and fuse holder you found is for the rear window defogger. Your fuel injected computer needs at least 9 to 9.5 volts to operate. There is a 12 wire white or clear connector that runs to the computer. It is located in the same area as the other wires you speak of under the rear seat. Since you just worked on floor pans maybe you jiggled some wires loose. This wire connector is also very prone to corrosion. I solved my running problem by cleaning all these wires of corrosion. Like magic I got 12 volts to the computer. Corrosion is a huge issue here and can cause all sorts of intermittent running problems.

[VW_Jimbo]

Sounds like a vacuum leak. Might want to do a Busdaddy smoke test!
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Jimbo

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[zoti]

Check the Air Flow meter to see that it is working correctly. If it isn't, the car will die after a few seconds as the computer is looking for a signal from the air flow meter to tell it that the engine is running (sucking air) and that it needs to give signal to the fuel pump to deliver fuel.

It's a safety feature.

[volksworld]

whew... ok just some basics here....the dual relay (pump/computer) is not under the seat...the relay under the seat on the drivers side is the rear defogger...the dual relay is mounted next to the computer in the right rear corner of the package area behind the rear seat...under the corner of the rear window...they were originally mounted "upside down" (wires coming out of the top) and leaking rear window rubbers can cause them to fill with water...the bentley book has an easy to follow procedure just using a test light to check the function of the relay...it gets its power directly from the battery so follow its harness down under the carpet to the battery...there is a hot lead and ground attached to the battery terminals that are easily knocked off say if you hook up jumper cables.. since its a dual relay yes it is possible for only one half of it to fail so the pump and cold start could work but power to the computer itself might not....what you're experiencing is the cold start valve is working so the car initially fires up, but the rest of the system is not working.... most likely is a big vacuum leak somewhere...hose blew off, crack in the intake boot back where you cant see it etc...the flap in the afm controls the fuel pump contact so if air enters the system from somewhere else it wont open the flap far enough to engage the pump...other stuff could be a bent or jammed afm flap from a backfire (but these usually cause the pump to run continuously so listen for it)....theres a white wire that hooks to the points side of the coil...its what triggers the injectors to fire...if it fell off car wont run...if wire to head temp sensor disconnected or ohm reading of sensor bad car wont run....so theres a couple places to look but usually vacuum leaks are the #1 problem with injected bugs