Weird problem with CIS-E - Long post

[jimbbski]

I have been working on this 1988 16V Scirocco for way to long, trying to get the car preped for ITA. When I had the time I didn't have the money and the money with no time to work on it. Well this summer I had a running car and took it to a HPDE to get some track time prior to a W-to-W drivers school. The car make 2 laps and barley make it back to the pit lane on the second.

Determined the fuel pump wasn't running, checked the relay and a few other items. Tried starting the car and it fried right up. Drove it to pitlane to go back out and it dies when I give it some gas in second gear. Car will not restart. Check thing out and find no power to fuel pump. Load it on trailer and go home.

I check over the car over the following weeks trying to get it ready for the drivers school in mid July. One day I drive the car around the block and it drives fine until I get on the gas hard in 2nd gear. The car sputters & dies. After a few minutes it restarts. Now the problem may be there in 1st, 3rd, & 4th but I never got the chance to try it.

The last time this happened was on Friday the day I was to leave for the school. Needless to say I didn't go, so now I will have to wait until next year to attend a school.

Since then I have discovered a way to duplicate the problem but I'm not sure why.
There are 3 wires coming from the throttle body. They are from the "Full Throttle & Closed Throttle" switches. If I move them with the engine runnig it will stumble, move them some more and the engine dies. Turn the key off and try to restart and you hear no fuel pump relay click or pump run. Move the wires again and try to restart and it does. This is where I'm at. I'm not in a big hurry to dig into it but i think that it may be a broken wire or bad connection at the plug on the throttle body. I will be getting a parts car next week so i plan on cutting that part of the harnes from that car and splice it into mine. I have used 2 different relays and checked the keyed ignition switch and both check out fine. I also replaced the fuel pump before I found this out so it's not the problem either.

Anyone with CIS-E experience who can tell me why this happens? Or how the throttle switches effect the power to the fuel pump relay?

[Flyinglizard]

I usually disconnect the throttle switch harness. They run rich all hooked up. Some guys pull the full throttle pin off so that it idles better and still has no WOT signel. That harness should not affect the fuel pump drivers.
Wire the pump to it's own electric circuit to avoid the rev limit and relay failure. Check over the grounds real well also.
If you have a "Mitchel" schematics book, it shows it very well. The Bently book is a lot harder to read. HTH,
Check both of the pumps. Clean the pickup screen inside and check the very short connector hose that feeds the line from the low pressure pump. I take out the tank very once in a while to clean all the crap out of it. Wash it out with hot water and joy soap.
MM
Sorry I see it is a Rocc. There is a very small filter clipped to the edge of the tank. Change it also.

[joeg]

Mike--How about checking all grounds?

[jimbbski]

Thanks for the suggestions. The pumps are both new, as is the fuel tank and all of the filters. I have the Bentley repair manual and i agree the wiring diagrams are not easy to follow. Where can I get a better one?

[Flyinglizard]

Pick the fuel pump color out of the door sill wire group. Look at the fuel pump conection to get the color. Usually it is red/bk/, red /yell or so. Follow the wire in to the back of the fuse box.
Energize this wire, confirming the fuel pump circuit... Cut the wire about 4 in from the FB plug. Add a nice big manual switch to add power to this lead.
If you use a negative battery break master switch system. You can run the fuel pump ground wire to the master switch, with not too much hassle.
The bat isolator will now shut off the fuel pump and the bat, stopping the engine right now without a lot of diodes or extra engineering.

When you get all done. switch on the fuel pump. Than add a jumper wire to the fuel pump feed. If the pumpp increases in speed, you need a better switch and/ or a big ass relay. Switch loss. There is always some switch loss, but try to keep the loss small.
HTH, MM

[GTIspirit]

If you install a manual switch for the fuel pump the fuel pump will not automatically stop when the engine stops running, if for example you got into a wreck and couldn't get to the kill switch. Just something to consider before you pursue the route suggested above.

Since you have a Scirocco 16V I suspect that you have what is sometimes referred to as the KA-Jetronic, Bosch part number 0 280 800 042. Not all KE-Jetronic are created equal.
http://www.wowway.com/~clmoore3rd/engine.html (http://www.wowway.com/%7Eclmoore3rd/engine.html)
I am not as intimately familiar with that model as I am with what is sometimes referred to as the KE2.5-Jetronic, Bosch part number 0 280 800 180, that is in my PL engine GTI 16V.

The low idle and WOT switches are for idle control and open loop WOT enrichment. It sounds like a coincidence that they come and go with your problem. On my GTI 16V it is the pin 10 of the knock box that goes to the fuel pump relay, to turn it on and off when the engine is running or not. On this particular KE-Jetronic this is not how the fuel cut rev limiter is controlled.

You might want to check the connections between your ignition coil and the ECU/knock box, and everything in between. On my KE-Jetronic for example the knock box first acquires the engine rpm signal and then passes it to the KE-Jetronic on pin 25.
http://www.a2resource.com/electrical/management/kejetronic.html
It sounds to me like your engine running signal is erratic, causing the fuel pump to shutoff and your engine to stall.

[jimbbski]

Thanks again for the additional suggestions. Now that it's going to be what I would consider normal weather for August heer in the Midwest this week I will get back to work on the car.

I think if I add an oil pressure activated switch to the fuel pump power wiring I should avoid the problem of the fuel pump running with the engine stopped.

I my first race car build I added this type switch to the electric fuel pump. To start the car I turned on the power, and then pressed two momentary push button switches. One for the starter and one for the fuel pump. Once the engine built up oil pressure the pressure switch took over suppling power to the fuel pump through a relay. I think it took all of 12-15 lbs to activate it.