# getting and keeping it running



## cletis (Aug 29, 2009)

greetings all, 
i hope that i am posting in the correct catagory. i am currently on vacation in afghanistan courtesy of the us army. i have a 1981 4 door rabbit, fuel injected gas burner. it has been sitting for a while. i have replaced the gas, fuel filter, and fuel pump. all i can make it do is run for about 15 seconds. when it fires up, and i press the gas pedal it dies. i have been researching this car for about a year. i am thinking about installing a fuel cell and a simple wiring system i saw advertised in a rat rod mag. is there any thing else that i could do to try to make and keep this car running? thank you for your time.


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## where_2 (Jul 21, 2003)

*Re: getting and keeping it running (cletis)*

Obtain a copy of "Bosch Fuel Injection & Engine Management" by Robert Probst (published by Robert Bentley Publishing). The book will help you understand the workings of the system you have. It runs around $20 on Amazon.com 
From your short description, it sounds as if your fuel pump relay is not getting a signal from the ignition system. 
Let me explain (because I spent months studying the above described book): Early in the concept of fuel injection, there was concern that if a fuel injected vehicle was in an accident and the engine stopped running, a raging fire could be fueled by the fuel pump feeding gasoline a high pressure stream of gas. To avoid this problem, Bosch (the maker's of your Rabbit's fuel injection system) designed a fuel pump relay with a brain. About 15 seconds after the key is turned on, the fuel pump's brain starts looking for the engine tachometer signal to be present. If the relay senses that the engine is still turning over (running) then the pump continues pumping. If no signal is found, the relay opens to stop a potential fuel spill.
The Bosch continuous fuel injection system that you have in your rabbit is very simple. If adequate fuel pressure is present, and air is still lifting the air sensor plate (at the fuel distributor), then fuel continues to be released from the injectors. There is no cycling on or off of the injectors. Continuous injection systems spray fuel out all the injectors as long as the sensor plate is lifted. Air leaks after the sensor plate are a problem. The sensor plate is actually a well calibrated air flow sensor. Air being drawn into the engine lifts the sensor plate which meters a precise amount of fuel to be dumped out the injectors just above the valves. 
And that's the short course on continuous fuel injection theory, and the possible cause of your problem. The book described above is worth the investment. It's cheaper than almost anything you could possibly replace in the fuel injection system. 
Back in the early 1990's, I bought a 1980 Scirocco_S with Bosch Jetronic fuel injection (very similar to what your Rabbit has). The vehicle had a blown engine (rod out the front of the block) when I bought it, and had been sitting outside for quite some time in Northern Florida without a fuelcap on the fuel tank. As a result, the steel fuel tank was rusting from the inside out. After replacing the engine, I spent quite some time working the kinks out of the fuel injection system. In the process, I found that there is a little known very fine brass screen attached to the bottom of the fuel tank. When you remove the opening in the top of the fuel tank under the back seat, you can rotate the sender mount 1/4 turn to remove it. Peering down into the fuel tank, you may see a yellow/white colored 1-1/4" round thing at the bottom of the fuel tank. On top is a loop that you an hook with a sturdy wire hook to remove, if need be. Looking around the bottom of the tank, if there is fine rust or junk, you will probably be able to see it. The inside of the tank should be bare steel. 
As I mentioned, I spent quite some time working the kinks out of my rusty fuel tank feeding my fuel injection. I found that the first thing to get plugged was the filter inside the tank. If fine rust makes it past that then some will get stuck to the magnets in the fuel pump, since fuel is used to cool the pump and passes literally through the middle of the motor. After that, it will get caught in the fuel filter in the engine compartment. 
I recall at one point spending an afternoon with a hand pump drawing fuel out the top of my tank, running it through a coffee filter and funnel and draining it back into a gas can. Oh the joy and memories this brings back...








Need more suggestions, ask away. 



_Modified by where_2 at 8:19 PM 8-31-2009_


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