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Re: [T3] 68 Fastback FI (?) Issues - Diagnostic Help Requested

On 26 Mar 2006 at 15:22, Mike Smith wrote:

> I just completed a diagnostic run with fuel pressure gauge and voltmeter
> from voltage regulator.
> I had my son in the right seat and watching the gauges - we took two loops
> of a 7-mile route - half surface streets, half highway.
> Throughout, the fuel pressure held steady at 28 psi and the voltage went
> from about 14.5V at idle up to about 16-17V at speed.

Okay, good. You've eliminated the fuel pressure as the culprit.  

How confident are you about the accuracy of your gauge? The voltage 
should never go higher than 14.5V, but you might be hooked to the 
wrong side of the VR. You should connect to the lead that goes to the 
battery; this is the regulated side. The generator side will be 
higher in voltage by a small amount.  

If you're really getting 16-17 V at speed on the battery side of the 
VR, then this is too high. Replace the VR with a Bosch 30-019. I have 
these in stock if you can't find them locally, but they should be 
easy to find, since 12V generator beetles use the same part.  

What color is your VR? If it is black, then it is a US-made 
aftermarket replacement, and I've not had good luck with them  

> There were a few times I felt the car bog a bit - most noticable from a dead
> stop during acceleration to street speed (~40mph).
> For reasons that may be due to the Heisenberg Uncertainty Principle - the
> car actually "felt" better than it had in awhile... the next true test would
> be to take it on the trip to work (24 miles one-way - mostly highway).


> Well - took the fastback on a cruise - about 70 miles round-trip - almost
> all highway.
> Throughout the trip - no evidence of the "bucking" or "bogging down"
> reported on my previous trips from work to home.
> It may, or may not, be related, but I did note that I could not keep the
> car at constant highway speed (65-70 mph) at (near as I could tell)
> constant pedal depress.
> I'd keep my foot steady against the tunnel once I'd get to about 70 mph,
> but then the car would start to slow down - settling down at around 55
> mph.
> If I kept blipping the gas pedal, the engine would rev and I'd be back up
> to 65-70 mph.

That still sounds like bogging down to me.

This sounds to me like the engine is running too lean and 
overheating. I'm not sure, but this MIGHT be caused by the charging 
system putting out too high a voltage. I KNOW that low voltage makes 
the FI system run too rich, but I don't know that high voltage makes 
it lean. It sure seems possible.

High system voltage is a rare problem. I've only heard of one other 
case like this and I've never seen one for myself.

> Would this be indicative of a problem with the throttle sensor?


Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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