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Old 06-30-2019, 12:50 PM
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Join Date: Mar 2003
Location: Southern California
Posts: 2,097
Sometimes I call it the "Mercurial-Benz"

I love the way my '88 190E 2.6 special order five-speed drives, but these cars are very complicated, which means much to go wrong. During the 50K/4-year warranty (which arrived about simultaneously in early 1992) it seems that I was back at the dealer every couple of months with some new problem. Fortunately it settled down and has been reasonably reliable in the 35K miles it has accrued since the warranty expired.

In the latest episode it had been sitting for a couple of months, and I wanted to use it, but it wouldn't start... cranked fine, but not even a hint of one cylinder firing. So I used another car and waited for the weekend when a neighbor was available to help check for fuel an spark.

Prior to that I removed the battery and snap in electrical compartment cover to check the FPR and OVP. I also removed the long/narrow connector to the Jetronic "e-box" finding no evidence of corrosion or bent pins, so cycled the connector a couple of times and went on to remove the FPR. One pin had some slight discoloration that I easily dressed off with some fine steel wool, then blew off and cleaned all the pins and receptacles with electrical cleaner on a Q-tip.

The OVP didn't want to come out, but I was able to flip up the plastic cover, remove and check the single 10A fuse and it was okay. The relay is marked:

89 7162
Germany
12V
10A

Circa 1990 I had a crank, but no start situation leaving my office in the late afternoon. After several attempts it finally started, but I had to keep revs at 5000 for minute or so until it was warm enough to idle. I drove to the dealer and left it with them to check out.

The next day the said they replaced the fuel pump relay, which didn't make a lot of sense to me. All the cold start enhancements are in the "e-part" of the KE system, so the fact that it was hard to start, but finally did while having to maintain very high revs to prevent it from stalling indicated to me that it had something to do with the KE system, like maybe the OVP relay.

I just checked the RO dated 4/2/90, and it states they replaced the FPR with part number 000-545-017-05.

So back to yesterday I removed the fuel pump cover and had my neighbor cycled the ignition three times while I stuck my head under the car and listened for the fuel pumps to energize briefly with each cycle. The did! The accumulator is new as it was the cause of increasingly hard cold and hot hard starts a couple of years ago. (I started a thread on this issue including a destructive analysis or the accumulator that revealed cranks in the elastomeric diaphragm, which caused an internal leak that prevented proper fuel pressure buildup.)

Next step was to remove the #5 plug wire and connect it to a loose plug that I grounded to the battery negative post with a test lead, had the neighbor crank, and I observed spark. If fact, it sounded like it hit on a couple of cylinders, so I reconnected the plug wire, hopped in the car and it started right up quickly assuming a smooth 1100 rev fast idle, which is about right for the 75F ambient temperature.

So what was the problem... that slightly discolored pin on the FPR?

Here's where it gets weird. The part number of the installed relay is 003-545-00-05, which doesn't jibe with the part number on that 1990 RO. Given that the third field is 00 rather than 17, it appears my installed FPR is earlier than the 1990 version listed on the RO.

My understanding is that FPR and OVP relay part numbers changed over the years, and the new numbers were service replacement for earlier models. So back in 1990 did they really replace the OVP rather than the FPR? The symptoms of that no-start episode correlates better to a failed OVP rather than FPR.

Since I didn't find a definitive cause of this latest no-start condition I'm going to have to make some test drives that start and stop from my house so I don't get stuck somewhere in case the problem reoccurs, and maybe take the necessary tools to pull out the battery and cycle the FRP when I use it for a two way trip.

Thanks for reading my story. Any comments? I'm particularly interested in the part number history of the FPR and OVP to figure out what I've got.

Duke
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  #2  
Old 06-30-2019, 02:26 PM
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Join Date: Jan 2012
Posts: 7,160
Quote:
Originally Posted by Duke2.6 View Post
I love the way my '88 190E 2.6 special order five-speed drives, but these cars are very complicated, which means much to go wrong. During the 50K/4-year warranty (which arrived about simultaneously in early 1992) it seems that I was back at the dealer every couple of months with some new problem. Fortunately it settled down and has been reasonably reliable in the 35K miles it has accrued since the warranty expired.
I sure hope those that say " The 2000 + MB cars are not built as well as the pre 1990's cars, MB just too greedy and makes unreliable cars." read the above.

Quote:
Originally Posted by Duke2.6 View Post
Circa 1990 I had a crank, but no start situation leaving my office in the late afternoon. After several attempts it finally started, but I had to keep revs at 5000 for minute or so until it was warm enough to idle. I drove to the dealer and left it with them to check out.

The next day the said they replaced the fuel pump relay, which didn't make a lot of sense to me. All the cold start enhancements are in the "e-part" of the KE system, so the fact that it was hard to start, but finally did while having to maintain very high revs to prevent it from stalling indicated to me that it had something to do with the KE system, like maybe the OVP relay.
Take a look at the wiring diagram and see if the fuel pump relay receives a tachometer signal from the ignition system / ECM. VW of this era used a relay that looked at tach signal to shut off the fuel pump is the engine was not running but key was on and MB might have done the same. Capacitors on the VW units would leak and cause intermittent no start / fuel pump turning its self on randomly.

Quote:
Originally Posted by Duke2.6 View Post
I just checked the RO dated 4/2/90, and it states they replaced the FPR with part number 000-545-017-05.

. . . .
Here's where it gets weird. The part number of the installed relay is 003-545-00-05, which doesn't jibe with the part number on that 1990 RO. Given that the third field is 00 rather than 17, it appears my installed FPR is earlier than the 1990 version listed on the RO.
Could have been old stock / parts system was updated. When things are billed out, they likely went by what the computer says not what is printed on the box.

Quote:
Originally Posted by Duke2.6 View Post
My understanding is that FPR and OVP relay part numbers changed over the years, and the new numbers were service replacement for earlier models. So back in 1990 did they really replace the OVP rather than the FPR? The symptoms of that no-start episode correlates better to a failed OVP rather than FPR.
When diagnosing various electrical faults, I've added lights to systems so I would know what quit working. Universal marker lights are small and handy, be sure to get the old style with an incandescent bulb because LED lights will still illuminate pretty well at voltages below 12V.

Even some generic light sockets would do the trick.
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