Mercedes-Benz Forum banner

1 - 20 of 74 Posts

·
Registered
Joined
·
91 Posts
Discussion Starter #1
Hello All
I have just replaced the ignition lock assembly in full as the old one failed. The car now is hard to start and won't idle. I think I shoot myself in the foot when I had a brain fade. I was jump starting the wagon with my truck and almost hooked up the leads at the wagon backwards. Of course large spark and chest pain:). The car seemed OK though and the two 10 amp fuses on the top of the OVP relay were also
OK. Can the relay still be toast if these fuses are OK? The car does start but not easily like it used to and doesn't want to idle at all. Runs smooth at higher RPMs but I haven't driven anywhere as I am afraid of getting stranded.
Thanks for your help.
G:)
 

·
Registered
Joined
·
4,624 Posts
Replace the OVP. If member Sbaert is out there, I am sure he can explain well why this is the next best step.
 

·
Registered
Joined
·
91 Posts
Discussion Starter #3
Will do. Thanks for the help. I guess the OVP internals are not always protected by the two fuses on top?
 

·
W201 Moderator
Joined
·
2,168 Posts
Will do. Thanks for the help. I guess the OVP internals are not always protected by the two fuses on top?
Probably not when you reverse hook it even momentarily. The electronics in there (especially the Zener diodes) are not going to like being reverse connected.

I would buy a new one and replace it. If no change at least you have a spare for the future.

- Cheers!
 

·
Registered
Joined
·
91 Posts
Discussion Starter #6
I installed the new KAE OVP today. It started with some difficulty and won't idle below 1,000 RPM ( that's with me holding it there with the accelerator pedal). Won't hot start. What's your next suggestion or tip? I amgoing to try and test the old OVP to be sure its dead but that's for another day.
Thanks
RG:)
 

·
W201 Moderator
Joined
·
2,168 Posts
Does this car have a standard old school Bosch Jetronic with ECU? Or is it the later model fuel delivery system?
 

·
W201 Moderator
Joined
·
2,168 Posts
In that case, since your idle is shot, I would recommend starting to make some voltage measurements starting from the IACV.
As the car is idling see what the average voltage (in DC mode) is at the IACV connector with the car idling. Should be in the 4V-5V range.

If you do not have a voltmeter, as the car is idling, disconnect it. In an operational system the idle would shoot up to 1000-1100 RPM.
If you hot plug it during idling the engine would immediately stall.

See if you have this expected behavior.
 

·
Registered
Joined
·
91 Posts
Discussion Starter #11
In that case, since your idle is shot, I would recommend starting to make some voltage measurements starting from the IACV.
As the car is idling see what the average voltage (in DC mode) is at the IACV connector with the car idling. Should be in the 4V-5V range.

If you do not have a voltmeter, as the car is idling, disconnect it. In an operational system the idle would shoot up to 1000-1100 RPM.
If you hot plug it during idling the engine would immediately stall.

See if you have this expected behavior.
New site software and my earlier reply did not appear yet so I am replying again with same message.
I replaced the ICAV after testing the old one out of the car. The old one only worked intermittently so replaced with new Bosch Unit. No change to symptoms posted earlier in this thread,
Based on your help I think its the fuel pump relay.I learned that my car does not have a seperate fuel pump relay. It is part if the MAS engine control unit located behind the battery which is kind of expensive to replace. Any opinions on a rebuilt unit vs new and where to buy it?
Thanks
G:)
 

·
Premium Member
Joined
·
10,078 Posts
New site software and my earlier reply did not appear yet so I am replying again with same message.
I replaced the ICAV after testing the old one out of the car. The old one only worked intermittently so replaced with new Bosch Unit. No change to symptoms posted earlier in this thread,
Based on your help I think its the fuel pump relay.I learned that my car does not have a seperate fuel pump relay. It is part if the MAS engine control unit located behind the battery which is kind of expensive to replace. Any opinions on a rebuilt unit vs new and where to buy it?
Thanks
G:)
MAS units for these cars are pretty cheap on eBay....if you want to go that route. You could buy a couple and substitute. Chance that two would be bad is pretty low. Did this all start after you reversed the polarity?

Kevin
 

·
Registered
Joined
·
1,776 Posts
If the car starts, and runs and 1000RPM, I cannot see how the problem could possible be the MAS relay. This sounds a lot like you fried an ECU or something. I would not throw parts at this to diagnose it....
 

·
Premium Member
Joined
·
10,078 Posts
That's why I asked if this all started when he did the reverse polarity thing....or if there were issues before. Trying a used MAS unit is hardly throwing parts at anything. It's ruling out the entire MAS system which contains the fuel pump relay.

Keviin
 

·
Registered
Joined
·
91 Posts
Discussion Starter #15
Kevin - Yes its all my fault, ie reverse polarity thing. I don't want to buy a used unit. I have had good luck with Autohaus in AZ and their price was lowest at $280 plus core charge of $62. If you know a used parts seller you trust I would consider them instead but open ebay purchases have not worked out for me in the past. benz MAS Control Unit 0115457932

Dude99- I know what you are saying but I don't have a lot of electrical knowledge or test stuff to do it right. I did check the old parts out of the car and they all seemed bad. The MAS I need to replace shows signs of damage at pins #13 and #15 (dark discoloring) if that means anything:). Thanks for the input and for what its worth I agree with you.

Gozody:)shot to me
 

·
W201 Moderator
Joined
·
2,168 Posts
I have not seen answers to the questions raised in post #10. Before buying additional parts, I would recommend those quick experiments/measurements. It may shed a light into what parts to go after later.

Basically, for idle control you have to start at the actuator that controls idle and work backwards. Measure what the ECU is trying (or not trying) to do at the IACV electrically. Before working your way backwards.

Just a suggestion from someone who had his share of idle problems in the past 2 years .....
 

·
Registered
Joined
·
91 Posts
Discussion Starter #17
I have not seen answers to the questions raised in post #10. Before buying additional parts, I would recommend those quick experiments/measurements. It may shed a light into what parts to go after later.

Basically, for idle control you have to start at the actuator that controls idle and work backwards. Measure what the ECU is trying (or not trying) to do at the IACV electrically. Before working your way backwards.

Just a suggestion from someone who had his share of idle problems in the past 2 years .....
I have not seen answers to the questions raised in post #10. Before buying additional parts, I would recommend those quick experiments/measurements. It may shed a light into what parts to go after later.

Basically, for idle control you have to start at the actuator that controls idle and work backwards. Measure what the ECU is trying (or not trying) to do at the IACV electrically. Before working your way backwards.

Just a suggestion from someone who had his share of idle problems in the past 2 years .....
I have not seen answers to the questions raised in post #10. Before buying additional parts, I would recommend those quick experiments/measurements. It may shed a light into what parts to go after later.

Basically, for idle control you have to start at the actuator that controls idle and work backwards. Measure what the ECU is trying (or not trying) to do at the IACV electrically. Before working your way backwards.

Just a suggestion from someone who had his share of idle problems in the past 2 years .....
I have not seen answers to the questions raised in post #10. Before buying additional parts, I would recommend those quick experiments/measurements. It may shed a light into what parts to go after later.

Basically, for idle control you have to start at the actuator that controls idle and work backwards. Measure what the ECU is trying (or not trying) to do at the IACV electrically. Before working your way backwards.

Just a suggestion from someone who had his share of idle problems in the past 2 years .....

Put in new rebuilt MAS engine control module from ProgRama by way of Autohaus and sorry to say no change to the conditions:(. I have not checked to fuel pumps directly because I can hear them run for a few seconds when the ignition is first turned on and the engine runs strong once I get it started. What know? All suggestions are welcome:cry: If next idea fails I will be donating the car to a charity and writing it off to experience. I am in the 10576 zip code if anyone wants to buy it as there are more than $5,000.00 of new parts on it. Any offer is better than nothing so don't be shy. I will wait a few days before i put it on the local Craig's list. Of course best case is one of your next ideas gets it running:) See list attached for what I have done in the last year:

1991 Mercedes 300TE 4matic progress list in alphabetical order 7/2019 thru 8/22/19
note: all work done by shade tree mechanic outside without a lift. Approx Date

"New" rear calipers installed upside down. Corrected & bled system. Ft & Rr Rotors/ Pads were new 7/18
Adjusted air/fuel mixture 7/18
Alarm system disconnected as non-original radio sets it off 10/18
Diagnosed and reattached vacuum line from intake manifold to transmission (driver side) 8/18
Filled gas tank to avoid condensation in the winter. 7/18
General cleaning of interior surfaces 7/18
Installed and secured LF headlight bulb 8/18
Installed missing aluminum crush washer on kickdown solenoid to stop slow ATF leak 11/18
Interior radio antennae installed on driver side front windshield. 6/19
New door bottom edge courtesy light and bulbs as needed 6/19
New 4matic valve control pressure accumulator at rt rear (not sls spheres) 5/19
New A/C air box drain tubes (2 in center console) 10/18
New A/C climate control unit above center console 10/18
New after market modern radio with USB port and flash drive inputs 10/18
New and lubed glove box light 6/19
New exhaust system including cat and O2 sensor 11/18
New fluids in ft and r differentials and Transfer Case 8/18
New fuses (all) with new ones and corrected wattage to reflect updates from MB 10/18
New gear shift linkage bushing 11/18
New headlight switch and knob 10/18
New ignition lock assembly including new ignition switch, lock barrel and key 8/19
New Interstate battery 10/18
New left front turn signal housing and lense 7/19
New left head light bezel 10/18
New oil and filter, air filter,and spark plugs (not fuel filter as appeared new) 8/18
New Over Voltage Protection unit 8/19
New parking brake shoes, L and Rt cables and springs 8/18
New passenger side remote mirror 10/18
New radiator cap, gas cap and oil fill cap 10/18
New radiator,new top and botton hoses, topped up antifreeze 10/18
New rear drive shaft center carrier, bearing, and boot 202,087 miles 7/19
New rt and left sun visor clip/contact for vanity mirror in visor 10/18
New serpentine belt 9/18
New Tandem power steering/ hydraulic pump and filter and fluid 9/18
New tires (5) 8/18
New Vacuum Modulator Control Valve for transmission 11/18
New wiper blades all around 10/18
New/ Rebuilt MAS engine control unit 8/19
Patched rust holes in spare tire well and left upper quarter panel with POR-15 and small plastic panels Various
POR-15 various rusted metal Various
Reattached and secured throttle cable to fuel injection linkage 7/18
Removed car phone and radar detector unit( ft and r) as well as associated wiring. 8/18
Removed car phone antennae from left rear glass 8/18
Repaired latches for rear seats so they would fold down flat 11/18
Repaired lip of plastic air intake that goes into air filter housing 9/18
Repaired or replaced various SLS and 4matic hydraulic lines so no leaks Various
Repaired passenger side lower molding by taping to front door 6/19
Repaired tailgate ground at upper left hinge. Third brake light, and rear wiper now work 5/19
Replaced missing tail light bulbs 7/18
Replaced third brake light bulb. 7/18
Spliced rusted parts of Transfer Case hydraulic lines from control valve to to TC near the TC 5/19
Tried to replace cabin filters only to learn Pelican Parts was wrong and this model year had none. 7/18
 

·
Registered
Joined
·
91 Posts
Discussion Starter #19
Try dolucasi's suggestion with the IACV.

Kevin
Thanks Kevin. I think I am over it. Sometimes you eat the bear and sometimes the bear eats you. It was fun trying though. That was the objective in the first place.
I forgot to include these two new items on my list:
New Meyle crankcase breather hose, valve cover to air filter housing 8/19
New oil and filter, air filter,and spark plugs (not fuel filter as appeared new) 8/19
 

·
Registered
Joined
·
1,776 Posts
I hate to say I told you so.... if the engine runs, it’s not the fuel pumps. Stop throwing parts at it.

X2 as above. Follow the source of the problem back. If you don’t know how to test it or use a meter, ask. No one here will flame you for asking a basic question, or wanting to trouble shoot properly.
 
1 - 20 of 74 Posts
About this Discussion
73 Replies
9 Participants
dolucasi
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top