Need a KE - Jetronic expert
 

I'm having some issues with my 83 380sel.


Currently:
-Cold starts are harsh. Studders for a few seconds, bringing up the rpm's cures this after a second. (It's now below freezing here in Michigan)
-Noticing less-than-great economy.
-No top end (nothing over 95; hell - my diesel was better)
- Idle in park = 1200-1300rpm; idle in drive - 900rpm
-o2 sensor is new, ICC is clean and lubed, Idle control is rebuilt, OVP is re-soldered.


Before I starting ripping into it all at once, what should I mess with first? Warm up regulator? Cold start injector? Mixer adjustment?


Someone help me!!!

OK, first you have not warm up regulator. That's on plain K-Jet -- warmup fuel mixture is controlled by the computer.

Here's what I would do: Find the diagnostic socket (usually a round fitting with a screw cover). Open it up, and connect the positive lead of a VOM set for duty cycle to the #3 position, ground the black lead. This should read 20% or 50% with the key on, engine off (may be 80% on some California models). Should read a fixed duty cycle when you start the engine cold, then start to swing up and down and steady around 50% with continuous variation as the engine warms up.

And replace the OVP -- resoldering will not necessarily fix it.

Check the fuel pressure, and I would replace the fuel pump relay. You should get the current draw on the pumps checked, too.

Replace the fuel filter is not done recently.

Check for a bad tank screen (you are starving for fuel if it has no top end).

A proper diagnosis will require checking main fuel pressure, differential pressure between the upper and lower chambers on the fuel distributor, and the main pressure regulator.

You should also check the electro-hydraulic regulator on the side of the fuel distribultor -- if it's leaking, replace it ($$$) as you have no mixture control.

Peter

are you sure we're talking the same system?


It indeed has a mix control, a 3mm hex through the passage between the fuel ditro. and the flap...(so I'm told)

I have a DVM: which pins would I use on the diag. socket? Duty cycle?

well he said you have no warm up mixture adjustment, not normal mixture adjustment... just an observation

An '83 380 would have K-Jet. Why do you think it's KE-Jet?

And it sounds like the warm-up regulator, and possibly a mixture problem.

Suggest putting a gauge on it and see what control pressure you are getting when cold.

I thought the "E" referred to it having a lambda sensor - which some didnt?

No. The 1981-85 US 380's have what is sometimes called "K-Jet with Lambda" referring to the package of an oxygen sensor, an analog computer, and a frequency valve connected to the fuel distributor. This setup used a mechanical warm-up regulator for warm-up and enrichment.

In 1986, KE-Jet came along. Basically, it replaced the warm-up regulator with a computer that controls the mixture with through an actuator mounted on the fuel distributor. I guess the E stands for "electronic." In KE-Jet, the oxygen sensor is one of the computer's inputs.

hello ctaylor738, my car does not have a lambda sensor (no catalysator) do you know whether there is provision in the design of the ECU to simulate the Oxygen sensor?

Thanks in advance

best location for pressure test?

The 3mm key only adjusts the idle mixture. The off-idle mixture is adjusted via the control pressure. If you have a warm-up regulator, that sets the baseline pressure and the lambda valve bleeds some off to trim it. Lower control pressure gives a richer mixture.

I haven't had a K-jet system for a while and that was on a SAAB, but the systems are all quite similar. I recall something like 70psi for the line pressure (which can be measured at the filter) and about 40psi control pressure for a warmed-up engine (which can be measured at the top center connection on the fuel distributor). You will need to buy, borrow or make the adapters for the pressure gauge. I made some.

Anyone know offhand what would cause warm restart issues in the M104 CIS model from the 300SL?

You need to connect the gauge so that it measures pressure in the large line from the FD to the WUR. You can connect it at either end, but the choice will probably depend on the fittings that come with the gauge. You want the shut-off to be on the WUR side. You close it to measure system pressure, and open it for control pressure.

So connect the gauge. Unplug the electrical connector from the WUR, and remove the fuel pump relay and jumper pin 30 to pin 87. This will cause the fuel pump to run constantly. Let it run for a few seconds and close the shut-off on the gauge to get system pressure, then open it to get your control pressure. Reconnect the the electrical and you should see 3.4-3.8 bar in under 5 minutes.