After replacing and adjusting several components of the 1.8 L-jet system (TS2, AFS, injectors) the engine still runs less strong hot than cold. Quite the opposite of what one would expect.

I now suspect the fuel pump is the problem, because hot starting is difficult, and idle drops when hot. This can not sufficiently be corrected with idle adj., CO adj., or an extra serial resistance of say 300 Ohm with TS2. Also, there seems to be some fuel leakage from the fuel pump.

Any suggestions how to approach this problem? Simply replacing the fuel pump will be expensive and there is no guarantee that all will is well afterwards.

Will fuel pressure measurements be helpful?

Perhaps some L-jet experts care to comment.

hope i can help a fellow 1.8er.... you can check the fuel pressure easily, just attach a gauge to the small port on the drivers side (IIRC) fuel rail (metal piece that fuel injectors are attached to). 1.8 pressure is not adjustable like D-jet is. also check the cylinder head temperature sensor, i've heard that is a big factor in the FI system. now the adding the 300 ohm resistor puzzles me.... i've heard of adding it with D-jet but not L-jet. is that where you got the idea? i think cylinder head temp resistance should be zero when at operating temp (but i may be wrong).

Type47, I will try to find a gauge and check fuel pressure, but the manuals I have read describe the procedure during starting of the engine, ie., after removal of the the air filter.

The trick with the serial resistance is adapted from the D-jet guys; L-jet function depends heavily on it too (besides the input signal from the air flow sensor or AFS). Actually, I used a 1 kOhm potentiometer and tried various resistance values. The cylinder head temp. sensor (TS2) has a negative temperature coefficient (NTC); hotter head > lower resistance > leaner mixture. The idea behind it is that the typical resistance of TS2 decreases with age and that some extra resistance would correct this...

How does your 1.8 run when it is hot?

Anton,

I installed a fuel pressure gauge inside the engine compartment using a "T" in the rubber line.

Check out these sites, hopefully they help:

L-Jet Trouble shooting

L-Jet Manual

Mueller, thanks for the links. They are very illustrative...