Help (SOS): blipping idle/stalls/won't start --REALLY NEED HELP - PeachParts Mercedes-Benz Forum

rastaman190e · #1 06-07-2003, 01:21 AM

Hello:

I am having a problem (or problems) with my 93 2.6. --yes, I started a thread but it got no response so I am starting again.

The symptoms are:
1) Idle surges to approx 1500 then drops to 500 *10
2) Shortly, thereafter, car dies and will not restart

Here is what has been done to diagnose problem:
1) presure test of fuel pumps. Tested fine/holds pressure
2) Spark plug test. Fine --spark when key is turned

Indie mechanic concludes the fuel delivery is fine and that we have power so things should work.

Here is what has been replaced in attempt to resolve problem:
1) Mass Air flow sensor
2) Distributor cap
3) Rotor
4) CIS-ECU (used)
5) OVP
6) Idle control valve cleaned until carb cleaner fluid ran clear out of it. Lubed with WD40 (DIY).

The problem persists. HELP! SOS!. He is at a loss and is now sugesting that I get a new CIS-ECU and/or take it to a dealer.

Anyone, and I mean, anyone out there with an inkling of what could be wrong and how to troubleshoot this problem please help me.

I am especially interested in finding out how to test, electronically, the CIS-ECU and Idle control valve, and anything else to rule them out as the culprit.

SOS! HELP! SOS!

Thanks for responding in advance.

BenzMatic · #2 06-07-2003, 02:10 AM

Are you getting the voltage on the ICV? Put the key in ON position and touch the ICV, does it feel like it is viberating or huming. If not next thing is to check Idle Control Unit. I am not sure what car you have but It is under passenger footboard in my car. If you are handy with soldering, you can resolder all the board, hopefully it would fix your problem. Keep us posted.

Thanks

J.HIDALGO · #3 06-07-2003, 07:24 AM

There is an article written by Steve Brotherton on evaluating electronic engine controls. That should help you!
Good luck!

rastaman190e · #4 06-11-2003, 08:14 AM

I have the car back and it drives fine. The mechanic lifted off the fuel distributor from the mixture whatamacallit, cleaned the oring and reinstalled it. Since then the ride runs and accelerates fine. I drove it around town yesterday and to work this morning and all is well ..so far. And I also dropped a bottle on techron on 1/2 tank a gas.

The only outstanding issue is with starting. It has yet to start on the first crank as it did prior to this problem. One workaround, however, is to crank w/o engaging engine X3, then fully crank. Engine starts up sluggishly then runs fine. Note: engine starts fine if restarted right after the initial start up.

Research here and on Mercedeshop.com suggests the following potential sources of this issue:
1) Fuel accumulator (sp)
2) Cold start valve (or starting valve/fifth injector)

With the two items above in mind, I have the following questions:
1) What is a nice short test to find out if the fuel accumulator is bad? Is the cranking but no engine start X3 the best test?
2) Is the cold start valve the same as the starting valve, mentioned in the service CD, and is this the same as the fifth injector?

Thanks,

rastaman190e · #5 06-11-2003, 08:16 AM

The issue that lead to the car stalling, etc turned out to be a vacuum leak coming fron under the fuel distributor hence its disassembly and re-assembly.

lata,

sbourg · #6 06-11-2003, 10:00 AM

"The issue that lead to the car stalling, etc turned out to be a vacuum leak coming fron under the fuel distributor hence its disassembly and re-assembly"

If you mean the airpath to the idle control valve was leaking, this is what caused occasional stalling and other problems in our 2.3

"With the two items above in mind, I have the following questions:
1) What is a nice short test to find out if the fuel accumulator is bad? Is the cranking but no engine start X3 the best test?
2) Is the cold start valve the same as the starting valve, mentioned in the service CD, and is this the same as the fifth injector?"

I would think leaving the ignition on a moment before starting would get around a leakdown , whether from leaky injector check valves, bad accumulator, or other. Our car always starts more smoothly if I do this - but it always starts anyway if I don't. I doubt if this is your starting problem. Even when I have depressurized the system and bled the injector lines (then reconnected all), the engine starts after just a few cranks of the first attempt.

Since you have 6 ports with injectors, I could see the cold-start valve being called the 'seventh' injector, but not fifth. Maybe it's a term left over from when most engines were 4's? Anyway, pull the plug on it and see if anything changes.

Steve

rastaman190e · #7 06-11-2003, 05:45 PM

The car ran like a champ during the drive to and fro work today. I, however, still have the problem of hard/rough cold starting.

A lot of researching led to a lot of usefull pointers but also conflicting information. Below i am outlining a test plan and I hope that you will comment on it.

Research leads to the following items as the [I]only [I] potential sources of my cold start problem:
1) fuel accumulator
2) leaky fuel injector
3) leaky fuel distributor

Test Plan:

1) to test the fuel accumulator, I am going to unplug the fuel line --a forum member called it the "small line" and stated that ".no fuel should flow out of it when the engine is running". I am suppossing that if fuel runs out of it then it is defective. Is this test correct and is my supposition correct?

2) To test the fuel injectors, I am going to disconnect them, leaving their connection the fuel distributor intact, and look for leaks/drops. If leaking then replace. If not leaking then look at fuel distributor

3) to test fuel distributor ...., no idea what to do but hope that one of the two above is the culprit. Process of elimination worked for the SAT so I am hoping it will work here.

Prior to commenting, note the followings:

1) vacuum leak mentioned in previous posts was found under the fuel distributor --sound like it was coming for the o-ring under the distributor.

2) i am also going to get a hold of a fuel pressure gauge to test, overnight if I have to, the fuel pressure to determine if there is a loss and how much this loss is

3) a succinct description of my start issue: will not start on the first, second, or third crank. Will stat, however, if the key is turned far enough to turn the dash lights on and start the fuel pumps x3 then crank all the way. Car slugishly roars to life, idles, ****, and runs fine. Smooth like butter after the hard cold start. Note starts up fine if turned off then started right after the initial start-up.

Thanks for reading and responding, in advance.

rastaman190e · #8 06-14-2003, 11:33 AM

Anyone?

psfred · #9 06-14-2003, 02:54 PM

Diagnostic for a bad accumulator. Pressure test will verify loss of pressure on standing, with the result that it won't start until you get fuel pressure from the pump running.

The 3x on but don't crank will buzz the fuel pump three times for about a second each, and should restore most of the system pressure, so you have enough to spray the cold start valve when you crank.

Accumulater is under the floor of the car, next to the fuel filter, I think.

Peter