Alan '79 928

My OB has gotten harder and harder to start when cold. First, it would catch on the first crank, then stall, then start on the next crank. Now it cranks and cranks then catches and stalls, then it might start the next time.

Sometimes I have to crank it for 10 seconds, stop and try to start it again. I almost killed my battery the other day starting it. Pressing the gas pedal doesn't help. It starts fine when hot. I have already replaced the fuel pump check valve with no improvement.

When it does start, the engine sometimes "cycles" up and down slightly. The RPMs don't really change but it makes a sort of surging sound, then struggles a little, then sounds strong again. This happens until it warms up and the RPMs come down.

So where do I start? Cold start injector? Maybe it is losing fuel pressure? I'm really not familiar with the CIS system and how it operates in cold start mode or how to test it. So I don't know what to check first. It runs and idles well once warm though.

Thanks

jpitman2

Cold start enrichment is controlled by warm up regulator - fitting on front of engine above thermostat. It has a fuel line in (vertical entry)from fuel distributor at rear, a fuel return line out (sideways out), at least one vacuum line, and an electrical connector. Its job is to reduce back pressure when cold, allowing mixture to richen, slowly reducing effect as it warms. These are a common cause of this type of problem, and it can be due to internal blockages, crud in the fine gauze filter under inlet , which are difficult to remove. The real test requires a pressure gauge set (~$55 from JC Whitney) to check pressures. Mine used to do the surging until I 'fixed' the extra air valve to work better cold. Do a search on WUR or warm up regulator. If you were really brave, try cracking open the inlet connection while cranking cold (WITH GREAT CARE AND RAGS TO CATCH spillage!!), and if it starts and runs, that would indicate the wur is holding cold pressure too high. The gauge test is safer and more reliable. Get a copy of Ben Watson, Tuning Bosch injection, Amazon, ~$15.
jp 83 Euro S AT 50k

Alan '79 928

Ok thanks - I did a search and found some info about the WUR.

I'm gonna order that book and see about borrowing a pressure gauge from my mechanic. The car sat for almost a year so maybe the regulator is gunked up.

macreel

Alan '79 928... Watson's book is good.

Also helpful is: "Complete Idiot's Guide to Your VW Rabbit" (John Muir Press)
This has one of the best writeups I've used for CIS. Maybe
a VW friend has one and will Loan IT.

G'luck.

jpitman2

Some with cars that have stood for long periods have been known add some cleaning agent to the tank, bridge fuel pump relay, and just let the pump circulate fuel for hours at a time to try to wash crud out of the system. CIS system do not like being left unused for long periods. I have a write up with pics of WUR internals- if you want a copy send me an email address. If you can remove it from car, and find a way to push a solvent through it, you may get some improvement - it helped mine for a while.
jp 83 Euro S AT 50k