The hot start problems are easy to solve. Others opinions...may differ...and I have argued long with them...and care not to anymore......mainly because I have never found a single fuel injection system that I cannot solve ALL of the hot start issues with.
You have to understnd what happens with each part in the system...and not just what the VOM says...based upon what the factory says it should say.
Think about these things. And...don't kid yourself, if the engine basic mechanical state and its compression are not well...nothing will help you, because that affects the metering system.
For starting you need correct fule mixture. If your fuel ixture is not correct in the first place, meaning you are either rich or lean, you will have trouble starting because that condition will be magnified.
Hot starting is usually caused by one of several things. One of the primary causes, is a combination of the CHT being maxed out...and staying that way because it banks heat (this causes a lean condition)....AND couple that with a fuel pressure regulator that is leaking down too quickly. Add to that an auxiliary air regulator that may open back up too quickly (It cools off too quick). So you have air bypassing (lean). Fuel pressure may be low or not stable (lean) and CHT is maxed (still around 100 ohms or lower).
This is most prevalent on L-jet and digijet. It is less of a problem with digifant due to the fact that they have re-added the fuel pump "buzz" or pre-load pump-up, into that system...unlike L-jet...which must have air flowing past the flap in order for the fuel pump to start up and pressurize the system.
You need to check your fuel pressure both at idle with vacuum line connected and without. Also, when you rev it...if it drops more than 2 psi...you have a suspect pump (most likely)...or a suspect regulator ...or both. The regulator should maintain 15-18 psi for at least 30 minutes after shutting down...or its defective.
For the CHT...I recommend sending $2.75 at Freyes electronics...or $8 at radio shack and getting a 0-1000 ohm adjustble cermet resistor to plug in line. Give it about an extra 100 ohms to start with. it will run beter in all modes...and not un so lean in hot weather...and have less hot starting problems.
One of the other great causes of hot starting problems...is running rich. Check all of the injectors for leaks. If you have a single vacuum leak anywhere in the engine....it will run rich. "0" vacuum leaks are allowed.
It causes the fuel pressure regulator to run higher pressure. Also, leaks makes the metering unit flap sluggish. Than can make the lean condition listed above worse.
This is not an insult or a jab...please don't take it that way....but if you need to take your car/van to someone to work on the injection...then you have vacuum leaks...trust me....you don't know enough about where to look for them. there are quite a few place to look that are not obvious. As me and I will list them. The best way to check for vacuum leaks...is to take each part loose, chec the flexibility of the rubber part...or replace it. All hoses...period...must be clamped. Once you have gone through teh whole engine, write down the date in a log book..and replace a little bit of everything over a 3 year period (its cheap and easy that way)...and you will never ever have the problem again. Fuel lines must ALL be replaced every two years.
Also, make sure that your auxiliary air regulator does not re-open until ambient temps drop below 100F after its has been heated up, closed and then shut down. All but the original d-jet auxiliary air regs are easily adjustable.
Almost all stock systems have weak ignition. This makes that problem worse. Even the later vanagons wit electronic..though greatly improved had a weak train of ignition. Use a better coil...use teh best wires you can get. Since they have resistor tips..get rid of the resistor plugs. Clean the carbon from teh cap and rotor at each oil change. It makes a difference.
Yeah a carb has one wire ...but is actually more complex than FI...and less dependable...and has sloppier/slower throttle response...less HP and less torque....gets less gas milage...AND you have to synch the carbs. I have a carb synch tool...I use it as a wheel chock
. Oh...if you have solid lifters..adjust your valves...and check them hot to make sure they are symmetrical. This makes a huge difference on injected vehicles. Ray