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Help, I have a A1 itb chassis with a problem that is stumping us. The car is equiped with msd, fixed distributer with and advance control, cockpit mounted, rev limiter, 10 gallon cell, two low pressure pumps filling sump to high pressure pump. The vehicle runs fine until everything gets hot, 30 minutes into the race then its like an on and off switch, high rpms 5-7 engine shuts off for a second or two then comes right back on. This goes on for the duration of the race, in the pits it can not be duplicated without a load on the motor or electrics I think. Replaced both low pressure pumps, coil, moved exhaust to prevent vapor locking the fuel system, no low fuel pressure, MSD said that our unit either works or will not, no itermittent problems. Where do I look next, oh replaced alternator and wires to it. Help.
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I know some people have used MSDs on VWs w/o any problems, but I'm a big fan of the stock Bosch ingnition. It just flat out works. And while the MSD will either work, or not, if you've got bad connections, it could lead to intermittent problems (that holds true for any ignition system, not just an MSD).
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Sound like it could have something to do with the warmup regulator or fuel related. Due to the fact that it does it when it gets hot. Did you switch out the regulator and try that? Just an idea.......
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I would suspect the high pressure pump, sounds like a fuel delivery issue..
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If you are using the stock fuel pump relay to provide power to one or more of the pumps, check the wiring between the relay and the coil. That relay can get very hot, especially when the draw is highest under load, and that can lead to an intermittant condition. The interconnection VW designed will shut down the fuel pump if it does not sense power to the coil. BTDT
Another thought, what is triggering the MSD to fire? If it is the Hall sensor in the distributor, that sensor has been known to fail with the symptoms you describe. Again, BTDT
Dave Zaslow
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I thought I was having similiar issues with my street Cabby when it got hot. turned out to be electrical not fuel related.
Check that the computer isn't vibrating and that all of your connections are solid.
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Back in my A1 days I found that if the high pressure pump delivery rate is inadequate I would get vapor lock when everything got good and warm. Run a fuel pump output test as described in the Bentley.
My A2 IT car was cutting out intermittently a few years back, didn't figure it out until I was scored a lap down from where I should have been. A loose wire on the master switch was cutting power to the ignition--and the transponder!
Good luck.
PS: check your fuel pump relay if you're running one. The A1 relays are always overheating and the symptoms are similar to yours.
