Brian Mitchell Posted June 26, 2010 Report Share Posted June 26, 2010 I have the 'FuelLink' fuel only ECU on my 1967 VW Bug w/ T3 turbo. It was set up and tuned by a well regarded engine builder. But, I'm experiencing some problems and he is 3,000 miles away. The engine seems to have two problems. First it seems to misfire, stumble, bog down, around 4000 to 4500 RPM at wide open throttle...it belches blue smoke when doing this. Second, it seems to be running crazy rich. The spark plugs are fouled, exhaust smells like raw gas. When hooked up to the PCLink I click "Diagnostics" under Runtime Displays and get a MAX RPM reading which is unrealistically high; sometimes into the 10K range. The MAX RPM consistantly reads ~2500 to ~3500 over actual engine RPMs. I refered to the manual which indicates this is a classic indication of a "Trigger Glitch". However, the other Runtime Displays display the RPMs accurately. For example, in Digital, Gauges, Plotting the RPMs read accurately. And by accurate I mean those displays indicate the RPMs are the same as the VDO tacho in my dash. Why would it read RPMs correctly in the various Runtime Displays but "Diagnostics" indicate a trigger glitch? Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted June 29, 2010 Author Report Share Posted June 29, 2010 To clarify the issue...I want to know why Runtime Displays indicate actual engine RPMs, but the Diagnostic shows erroneous information. According to the manual it indicates a 'trigger glitch'. Wouldn't an actual trigger glitch effect Runtime Display reading also? And how do I go about fixing it? Quote Link to comment Share on other sites More sharing options...
Simon Posted June 30, 2010 Report Share Posted June 30, 2010 What is most likely happening is that the logging is at too slow of a rate to pick up the false RPM reading. How is the unit being triggered (getting its RPM reading) Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted June 30, 2010 Author Report Share Posted June 30, 2010 Trigger comes from an "RPM Converter"...a little black box with a "Link Engine Management" decal on it. And the RPM converter gets a signal from the (-)terminal on the coil. Quote Link to comment Share on other sites More sharing options...
Simon Posted July 1, 2010 Report Share Posted July 1, 2010 Think the issue might lie with the sensitivity of the RPM Converter! If you open this up I suspect you will find an adjustable trim pot. If this is there I would suggest adjusting it in either direction and see if the issue is improved. One direction might make it worse if this is the case head the other way. Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted July 1, 2010 Author Report Share Posted July 1, 2010 I'll give that a try. Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted July 4, 2010 Author Report Share Posted July 4, 2010 I tried adjusting the 'trim pot'. If I'm reading the markings correctly it's infinitely adjustable resistance between "1" to "3". I found it set in what seemed to be the max low postion, at "1". I moved it to various positions but didn't seem to make any difference. I couldn't hear any difference in the engine running. And it didn't do anything to help the MAX RPM in Diagnostic mode. And it didn't change the rpm reading in Runtime mode. One thing I noticed was the MAX RPM in Diagnostic mode was almost perfectly 2x the tachometer in the dash. Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted July 4, 2010 Author Report Share Posted July 4, 2010 Another thing I found odd in Diagnostic mode was the MAP readings; they don't seem realistic. It shows the intake pulled 101kPa on an engine run that didn't exceed 3000rpm. I can't imagine I was getting anywhere near 101kPa. And btw is it possible to reset the Diagnostic readings on the fly? I keep having to shut the engine off to get Diagnostic to start new readings. There is the 'UPDATE' button, but it doesn't reset anything. Quote Link to comment Share on other sites More sharing options...
Simon Posted July 14, 2010 Report Share Posted July 14, 2010 The 101Kpa is what the map would be reading at key on.( I.e. atmosphere) Only way to reset the diagnostics is to power the ECU down. What type of ignition system is the engine running? Likely to be looking for a source of electrical noise. Ht leads not resistively supressed type, A bad lead? Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted July 23, 2010 Author Report Share Posted July 23, 2010 For ignition the engine has a 009 distributor, Bosch wires, Bosch blue coil, NGK BR7ES plugs. I have shielding (grounded) around the trigger wire that goes from the RPM converter to the ECU. And I have all ground wires terminating on a dedicated grounding bus bar. The RPM converter gets it's signal from the (-) coil. And that wire has the appropriate resistor installed. In an effort to isolate things from potential electrical noise I've gone so far as to pull the ECU and rpm converter out of the car and powered it using a separate battery. I set up the ECU and RPM converter on a table and extended the wiring harness to the engine. Then I ran the engine on it's own battery with the alternator disconnected. So, ECU and engine had their own separate battery power, and no alternator putting power into the system. And even after isolating the ECU from the car, and running the car only on battery power I still get the problem. I also hooked up a vacuum/boost gauge and noticed that the engine stumbles when the manifold pressure begins to transtion from vacuum to boost. Its at those moments when the engine bogs down, stumbles, and belches blue smoke. Quote Link to comment Share on other sites More sharing options...
Brian Mitchell Posted July 23, 2010 Author Report Share Posted July 23, 2010 Can you be more specific regarding what you mean by "Ht leads not resistively supressed type, A bad lead?" I don't quite follow. Quote Link to comment Share on other sites More sharing options...
Simon Posted August 26, 2010 Report Share Posted August 26, 2010 Leads from the distributor to the spark plug. If these are non suppressed or copper core, or in poor condition this can be a cause of interference. Quote Link to comment Share on other sites More sharing options...
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