Recently I purchased a new motor for 81 Vanagon. The new motor was built to OE spec, with a minor change to the valve size. I went with 42 intake and 36 exhaust, and hydraulic valve lifters. The previous motor had solid lifters.
When the new motor was put back and buttoned up, everything worked like a charm.
The following parts were replaced:
New Distributor Cap
New Fuel Filter
New Spark Plugs
New Spark Plug Wires
New Fuel Pump
New Upgraded Fuel Filter
New Fuel Pressure Regulator
New Fuel Lines
New Vacuum Hoses
Plenty of power to go around, timing was perfect, and everything was going great, until I have developed a serious case of intermittent bucking. The infamous vanagon syndrome, but it was not. The issue would clear-up after a while, and I could be driving again. There was no way to figure this out as the issue would clear-up during troubleshooting.
I've put about 500 miles on the new motor, and issue only resurfaced three times. Fast forward to a week ago, and the issue re-appeared when I topped off the gas tank, Thinking this could be related to vacuum in the gas tank, I drove another 30 miles, and topped the tank off again trying to replicate the problem. The problem did not re-occur. On Saturday the van started and run fine. On Sunday we took a nice 100 mile road trip. The van run great. On Monday, the van started right up, but run extremely poorly, and ever since the issue did not go away.
The engine would misfire, spit, and act like a kinked hose, smoking black and white and generally running rich on all cylinders. Perfect! This is the same issue I have been having when the van started to buck. Get the ohm meter, and go to town. I ohmed everything, upside, downside, sideways, forwards, backwards, you name it. Multiple times, on different days. Everything ohmed to AFC specs. Voltages checked out. Fuel FLOW - perfect and steady.. AFM.. bench tested good. Harness good! Grounds good.
Things I did not check: vacuum, and compression, because my friends were convinced it had to be good; new motor, reputable builder, etc etc etc. Well, hell, let's re check everything again, and little did I know...While I was getting ahead of myself, and not paying attention while measuring voltages on the third pass, I accidentally burned up the ECU by reconnecting the harness while the ignition key was in the ON position.
Which brings me to today; the damage is already done. There were only 3 things that I did not check: compression (/intake plenum/ and vacuum which could directly affect the fuel pressure), ignition switch, and ECU.
Today, I will do the rest of the diligence to inspect the compression, and intake manifolds to ensure there were no leaks that could have affected compression and vacuum; re-test the old and new FPR, and call it a day.
Tomorrow, I will be putting a short list of parts needed to go ahead and convert to MicroSquirt v3 FI. I will be retaining 50% of the Vanagon's system - fuel injectors, plumbing, throttle body, intake plenums, the rubber S-boot, fuel pressure regulator, fuel pump
This is a cheaper alternative to Dual Weber carbs or sourcing original parts. The learning curve may be a bit like:
but once everything is dialed in, and on-board diagnostic will make my life much easier, and the engine layout will be much more readily accessible for maintenance and repairs.