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Wed Jan 21, 2004 7:42 pm

Have a 1979 S.B. Conv (with fuel injection) that I love dearly, but in the 2 yrs that I've owned it, it has never wanted to start up easily -- (ie, just turn the key and vrrroooom) - I've had it to a couple of different VW mechanics, with no real improvement. It seems no one in Richmond, VA knows much about how to diagnose and correct fuel injected beetle problems.

I've replaced many of the fuel injected parts: temp sensor, thermo-time switch, aux air valve, fuel pump, double-relay, fuel pressure regulator, and even the gas tank - without any noticeable improvement.

Fuel pressure has checked out ok and the car has been tuned-up with new spark plugs and valve adjustment. Still, the car will not fire right up without continuously turning the key and pumping the gas pedal - and slowly...the engine comes alive.

It idles fine and runs smooth once started, but I've noticed that it definitely lacks power when accelerating or going up hills -- so much so that it won't hold a speed of 65 mph on the longer inclines - and will begin to slow down, even with the pedal floored.

Any advice would be greatly appreciated!

Thu Jan 22, 2004 1:05 am

'79 SB used basically the same L-Jetronic FI used in the busses. The 2 parts you haven't mentioned are the cold start valve and cold start relay. The relay supplys power to the valve, the thermo-time switch controls how long the valve sprays fuel during start, but if the cold start valve itself is dead you get absolutely no fuel (or very little) during start. Sound familiar? It can be other things too, but this is really high on the list. A bad connection to either wire on this valve will obviously cause it too. The valve only gets power for a few seconds (max 20) due to the thermo-time switch, otherwise the engine floods.

Your second problem is something else. Starting and running are different FI systems. One suspect due to age is ANY or ALL of the rubber hoses. These systems are very susceptible to vacuum leaks. Use only the original style FI hoses to replace them, not just a universal rubber vacuum line. If the VW dealer doesn't have them, you can probably get bulk hose from a Mercedes or Porsche dealer. Here's a site for '78 busses that lists some of the different hoses used on the bus and where to get them. http://homepage.mac.com/ratwell/VacuumHoses.html
I used to have a '74 Volvo that ran fantastic after I just put new hose clamps on all the old FI hoses. Night and day difference.

Here's a Bosch manual with diagnostic diagrams. Especially pay attention to the diagrams on pages 5, 6, and 7. Instructions for checking the cold start valve are on the bottom of page 6. Good luck! They're great when they work!

http://www.conservatory.com/vw/manuals_nyx/L-Jetronic.html

There's good FI info in the Bentley manual too - do you have one? No excuse not to. They're pretty cheap @ $28 from Amazon with free shipping. http://www.amazon.com/exec/obidos/tg/detail/-/0837...ce&s=books

Oh - and check out this '79 vert site too. :wink: Sweet car!
http://www.californiaclassix.com/archive/79_VW_c142.html

Thu Jan 22, 2004 5:09 am

Forgot to mention it - but we also replaced the cold start valve. Not sure about the cold start relay?

Thu Jan 22, 2004 10:58 am

I was wondering if you replaced the fuel lines as well? I had a mechanic advise me to change the old fuel lines, both supply and return. His explanation was that as the lines age they constrict on the inner diameter. Thus when under full throttle the volume isn't there to give you the power you desire.

I'm sure you changed the fuel filter when replacing the pump, but if you haven't do so. When I bought my car the filter was nearly plugged and would barely climb up hills.

Thu Jan 22, 2004 11:39 am

PC - right on with the filter! Prime suspect for low power. Good call! And if you do replace the fuel lines be sure to use F.I. rated lines. It's time to replace them just due to possible fire hazard if nothing else. There's just something about 25 year old rubber and vinyl.

Sat Jan 24, 2004 7:08 am

Thanks for the advice guys -- I haven't replaced the fuel lines/hoses - though the fuel filter has been replaced.

I've attempted to improve the situation up to this point by following all of the suggestions in an actual VW Fuel Injection manual I bought off of EBAY. It has also been a big help with learning more about the fuel injection system, but my problem still remians.

At this point, I'm tempted to go ahead and replace the remaining original parts of the F.I. system: AIR FLOW METER and FUEL INJECTORS. And your suggestion of replacing the fuel lines/hoses makes sense.

I'll keep everyone posted.

THANKS

Sat Jan 24, 2004 12:57 pm

I know how frustrating FI is when it doesn't work! But it makes no sense to arbitrarily just replace parts, and gets pretty dang expensive too, besides the possibility of introducing new problems due to possible bad parts being installed. :(

The air flow meter and injectors rarely fail, and if the engine idles OK they should both be OK. Did you do the test of the cold start valve? Does it spray for 15-20 seconds like it should? There are really only 3 parts in the cold start system - relay, time switch, and valve. If you have power to the cold start valve for 15-20 seconds, then both the relay and the time switch are working properly. You've already replaced the time switch and valve so they should be good, but no guarantees. Even new parts fail. Do the checks.

Here's another online conversion of the manual - http://manuals.type4.org/ljet/ Follow the test charts, and 99% of the time it will lead you right to the problem.

Or http://www.forparts.com/techbosLjetronic.htm

And even Bentley has a manual http://www.bentleypublishers.com/product.htm?code=H160&subject=25 although I'm not familiar with this one.

If you can't find a good VW FI mechanic, then call around to other foreign shops. The Bosch L-Jetronic system was used on many cars including VW, Volvo, Porsche, Audi, Peugeot, BMW, and others. Even Datsun made a clone of the system under license from Bosch for the early 80's 280ZX's. All the principles are the same no matter what make. You just need to find a mechanic who's familiar with the system.

Sat Jan 31, 2004 11:46 am

Hi! Well it sounds like you have replaced practically everything that can go wrong with your Fuel Injection. There is a head temperature sensor that is located near the spark plug hole on the number 4 cylinder. It could be faulty and causing your mixture to be or lean. You shouldn't have to step on the throttle to start your fuel injected engine. As this does nothing but introduce air into the engine. But if you have to do this to start the car then you might be running too rich. I have the same problem in the summer time when it's hot outside. I take a short trip to the store and when I get back in it takes a few moments to get it to start. My engine is very high mileage and I'm convinced that the problem is low compression. Do you know how many miles are on your engine? Has it ever been rebuilt? If not you might consider doing a compression check. The problem may be mechanical and not related to the F.I system at all.

Good Luck!

Sat Jan 31, 2004 11:53 am

Listen to dstefun, it sounds like the cold start valve or relay.

jeffrey

Mon Feb 02, 2004 11:56 pm

I know this might sound too simple, but I've seen people clean the injectors (replace as a last resort) and solve these problems lots of times. Sometimes the solution is the best. 5 bucks worth of injector cleaner and being embarrassed by the smoke it makes might be worth it.

Tue Feb 03, 2004 5:58 pm

Have tried numerous injector cleaners without any improvement -- have recently ordered new injectors/seals to replace the old ones. They're 24 years old now (this "1979 model" was actually built in January 1980) so I figure replacements are a good idea anyway.

The cold start valve probably isn't the root of my problem, although I had thought of that originally and replaced it with a new one. The hard starts occur whether its hot or cold.

I appreciate everyone's advice and suggestions up to this point.

Thu Feb 12, 2004 6:44 pm

Check your vane air flow sensor for proper opperation. These do wear out frequently & is one of the main inputs into the computer. :evil: