TheSamba.com :: View topic - HELP!!!!!!!!!! 86 Cabroliet fuel problems?????????

Tue Jul 11, 2006 9:12 am

I just bought an 86 VW Cabroliet convertable. Both of the fuel pumps have been replaced. The car will start and run for 1-2 seconds and then shut off. I have LOTS of fuel pressure on the supply line. I'm not familiar with the CIS fuel systems. If I cycle the key after each time that it dies, it will start back up and run for 1-2 seconds. Any idea's or comment's would be most appreciated.

Tue Jul 11, 2006 9:29 am

Could be the "warm up regulator" which are known to get plugged up. It's that silver box bolted to the engine block by the oil filter with two fuel hoses running to it and one electrical plug. Could be elsewhere in the fuel system, like the fuel distributor - which itself can get gummed up, especially if the car sat for a while at some point in its life. Or poor injectors. (When it's the fuel distributor, usually if you can get the car to rev up to a high RPM a couple of times then it will overcome any gumminess in the system and allow it to run and idle OK.) Could have something to do with the fuel pump relay as well, it might be kicking on then off again, it's activated whenever there is a spark signal being generated to the coil. I had a intermittantly bad fuel pump relay in my 85 Golf that every now and then caused this problem, always on hot restarts, and took me a while to track down. Then there's also the frequency valve and oxygen sensor. Your best bet is to get the Bentley manual for troubleshooting this system. Since your FI system (except the dual fuel pump design in back) is identical to the 81-84 Rabbits you can use that manual for CIS troubleshooting if you find one cheaper than the 85-93 Cabrio/Scirocco book. You also need a proper fuel pressure gauge with a cutoff valve to properly troubleshoot CIS. "Plenty" of pressure isn't a good enough test.
-Andy

Thu Jul 13, 2006 9:57 am

Thanks for your response. Not knowing this type of system it was actually something very simple. I know you VW buffs who are familar with CIS (continuous injection system) will have a few good laugh at this. Anyhoo after reading a chapter in Bosh Fuel Injection & Engine Management I discovered what I was doing wrong. Ok here it goes, I left the air intake snorkel tube assembly off. I removed it so I could have better access to replace the leaky fuel lines. So no vaccum was being pulled on the sensor plate which engages the fuel flow to the injectors via the fuel distributer. When I reinstalled the tube it started! Well this car sat for a few yrs so I put trans fluid in the tank with some fresh fuel, the longer it runs the better it runs. However, it is still sluggish starting and taking off. Any ideas?

Thu Jul 13, 2006 1:54 pm

If it sat like you said, the fuel distributor will be gummy. Classic sympton - engine runs and idle better the longer it's run. I'd try some good fuel system cleaner, like Techron or Berryman, and hope things improve. The more you drive it the better it'll get, in my experience.
-Andy