Ideas as to huge MPG drop since overheating? - Page 5 - PeachParts Mercedes-Benz Forum

ps2cho · #61 02-09-2011, 12:18 PM

Right. I need to read mA current....
With the meter in series, the circuit is open. I can tell because the engine note changes when disconnected and it does not return when the meter lies in series....that is why I am a little confused over this harness.

I swapped a used distributor in and it was worse, but it was a junkyard distributor so can't tell 100%...
I really don't want to touch my 300TE's distributor, but at this point I need to 100% eliminate the distributor so I may go ahead and swap them and hope I don't make 2 issues out of one.

How can I eliminate plugged up cats? I guess its a possibility since the engine got very hot for that week...

JamesDean · #62 02-09-2011, 12:51 PM

Random Question,

where did you get the gauge you used for checking the fuel pressure?

ps2cho · #63 02-09-2011, 12:56 PM

Quote:

Originally Posted by JamesDean

Random Question,

where did you get the gauge you used for checking the fuel pressure?

I'm using a Star Products TU-443 Deluxe Fuel Injection Pressure Test Set.
I got it super cheap off ebay used so keep your eyes open. It comes standard with CIS-E adapters.

If you want a real cheap brand new kit, the Harbor Freight fuel pressure kit comes with CIS-E adapters too:
http://www.harborfreight.com/master-fuel-injection-pressure-test-kit-97706.html

JamesDean · #64 02-09-2011, 12:58 PM

Quote:

I'm having trouble with this EHA Test Harness....I cannot seem to get a reading.
The EHA does not function with the harness plugged in because the engine note does not change and the system goes into open loop.

Any ideas what I could be doing wrong? If I can ensure that the EHA is not enrichening the mixture it will help a lot.

This might have been addressed already but you are connected to the harness incorrectly to measure current. My apologies if this has already been covered.

The meter shows zero because there is nothing on the harness drawing current. You need to connect up the EHA with the meter in series on one of the pins....

You need to hook your meter up the following way and have your meter set to measure something in the amps range (you had that part correct):

ps2cho · #65 02-09-2011, 08:01 PM

Thanks for the help...I feel silly with this one but, maybe I am just not understanding the harness as I still can't get a reading...
Here is a photo of the harness....

I understand the left female clip goes directly to the EHA male....but what is the correct orientation for the other two?

jt20 · #66 02-09-2011, 08:24 PM

The tester must be installed so that you complete the EHA circuit. Whatever is left over is the connection for your leads.

It looks like you had it correct.

Do you need to turn the ignition off while you arrange this, then once installed, turn the ignition to 'on'?

As for plugged up cats, I had a muffler shop once inspect my flow for free. They drill some holes and put in a probe.

JamesDean · #67 02-09-2011, 08:35 PM

Did you ever do a compression test?

hstuehmeyer2000 · #68 02-09-2011, 11:18 PM

Check for an intake or exhaust restriction. This will cause the o2 sensor to read rich because the poor air flow will cause the air/fuel mixture to be off. You will need an exhaust back pressure gauge.

JamesDean · #69 02-10-2011, 01:15 AM

Quote:

Originally Posted by ps2cho

Thanks for the help...I feel silly with this one but, maybe I am just not understanding the harness as I still can't get a reading...
Here is a photo of the harness....

I understand the left female clip goes directly to the EHA male....but what is the correct orientation for the other two?

Is that a factory harness from the car or something you bought per the FSM? It looks to me that the harness pictured is simply a Y connector

If I were you I would just hook it up as per my paint diagram. Get a piece of wire and hold it in place and place the meter as I indicated. This would give you the data you desire.

KJZ78701 · #70 02-11-2011, 09:55 AM

I have not seen that you have checked the IAT sensor. I also found it really helpful to check resistance and continuity at the computer's harness.

The best tool someone like you (long term owner of a CIS-E MB) can own is a wide band O2 sensor.

BTW, testing the idle microswitch is easy. I use a small piece of vacuum line wedged behind the lever arm. Stick it in there and drive the car a bit. Until I pulled and adjusted the fuel distributor, EHA and idle screw, the idle switch engagement took my 14.7 air fuel (AF) ratio (in gear at 1000 RPM) down to 9.1 (no change in RPM). Without idle switch, in P or N RPM went up to 2000 but AF went back to 14.7. I got 22 MPG with the idle switch out of the equation.

Since then I have adjusted the fuel distributor again. Going about 1/2 turn in on all six screws with corresponding adjustments to the EHA and idle screw brought the idle back down with the idle switch back in the loop. I need to adjust again since it still is not perfect. Once done I will update the CIS-E tuning thread I created here and added to your site.

Bottom line, without the wideband O2 sensor, I would have been guessing.

You can also pull your plug wires one by one with the motor running to verify that you are getting good spark and fuel at each cylinder.

ps2cho · #71 02-11-2011, 01:28 PM

Intake air temp sensor? If so, they didn't introduce that until 89+ so I don't have one.

Regarding the wide band o2 sensor...that is new to me although I understand "what" it does. Do you have any more information as to where to get one or which one to get? Does it require a new O2 sensor itself, or is it just an add-on? I'm all for owning what I need since I have two cars that may benefit from it.

I'll check plug wires although I'm sure it won't give any indication since the car is not misfiring.

----

The harness is a factory tool from MB. Part # 102 589 04 63 00

KJZ78701 · #72 02-11-2011, 04:05 PM

Do a search for " afx wideband " $260-$300

Completely stand alone. Connect to the battery, run the display into the passenger compartment and run the sensor into the tailpipe (the wires are long enough). If you plan to drive it that way, you will need to clip the lead to the tailpipe to keep the sensor from backing out. I used a hitch pin clip and some bailing wire. The sensor is heated so you will have to disconnect the sensor at the battery when done. When we add these to the race cars, we drill a second hole into the exhaust system, weld in the included bung and connect the wideband there.

Back to your issue. Can you define all of the sensors and devices that regulate the fuel? I can't tell from reading this if you have pulled the connector to the computer and checked the sensor readings there. I mention this because the wires' insulation may have suffered from the overheating causing a short in the harness. You will only find this if you look at the inputs the way the computer sees them.

Check with everything plugged in and then check again by unplugging everything one by one. My MB document recommends that you disconnect the battery before you unplug the computer from the connector and don't connect the battery again until the computer is back in line.

JamesDean · #73 02-11-2011, 04:16 PM

1) retest EHA as I have outlined for you, forget the add-on harness tool thing. just do it as my picture describes.

2) compression test?

KJZ78701 · #74 02-11-2011, 07:26 PM

On my car the EHA leans the mixture at idle. If you are already suffering a rich condition you can disconnect the EHA and see if you hear a difference. In my case, disconnecting the EHA on a warm motor causes the idle to go way rich and the car tries to die.

When I watch the lower pressure on the fuel distributor, I see a drop of a couple psi as I disconnect the EHA.

ps2cho · #75 02-14-2011, 02:46 PM

Almost got the distributor from my 300TE (leaving same EHA attached for consistency)....but I noticed after removing the disty from the 260E, there seems to be a lot of slightly "brown" colored gas coming out.

This is the first time I've removed it since completely cleaning that distributor out. Is that 'normal' or could I have a lot of dirt in my gas tank? Not that this is probably related to my issue, but just curious.

I'll post back real soon once distrib is in and I've given her a good drive.