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Premium Member
1985 500 SEL and 1986 560 SL
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73 Posts
Discussion Starter · #1 ·
I was helping out a neighbor today with his 300se with a 103 engine.
It stopped running after he shut it off and came back a couple hours later it would not start. He had it towed to a local indy shop here in reno and it was diagnosed as having a bad fuel distributor. He authorized the part and got a call yesterday to have his car towed from the shop,as the shop did not like working on poorly maintained cars. Wow, what a concept huh? He came over with his tale of woe, seem's that the shop replaced the fuel distributor, car did not run, then they replaced the fuel pump and fuel filters, car did not run, then they replaced the distributor cap , rotor ,wires, and plugs ,still did not run,, then he got the call to come get his car so he had towed back home. After listening to all this< OI was a bit worried that maybe it had lost the fuel relay or regulator and parts were thrown at it under the fix by replacement repair method.
So I brought some tools over including Vac gauges and compression tester expecting the worse. I thought I would start with the easy things like ensuring spark, fuel, air,, had plenty of spark!! ran up one arm and jerked the other as I did not have the plug grounded,, great start I thought!! I was lit up at 7 am in the morning! Ok so we had spark,, so I thought I would check for fuel,, had fuel to the fuel distributor and the return lines so I firgure that the pressure regulator was ok and the fuel relay was working ( I did listen for that pump to kick on ) I then thought well I will crack a fuel line to see if we had fuel from the distributor,No fuel while cranking, not a drop and plugs were pulled and dry as a bone in the Nevada heat! hmmm ok it was a rebuilt fuel distributor,, it could be bad?? so I am standing there looking at vac lines
cold start valve and so on just looking while thinking deep and awful thoughts about this poor guy with a bum car,,,,, I had the firing order written down and thought well I will just check to make sure that the shop had put the wires on correctly as long as I was checking stuff,,
Bingo!!!! the spark plug wires were installed wrong! I took them off and matched the plug wire up with the cyl numbers on the cap and thought it can't be this easy ,but this would at least correct one problem before I started on the fuel issue.. Before I got started on the fuel issue I thought ,,well lets try it and see how it spins,, hit the key ,no gas , and cranked for 7-8 seconds and The car started!!!! Wow ,, my friend thought I was a wizard!! so now I am asking you guys ,why did this not show fuel to the injectors with the plugs miswired, is the computer smart enough to shut fuel off if the wiring is screwed up??? never seen this before ,,,comments would be appreciated and read even I am now wondering if some messed with his wiring on the plugs while he was in the store and the shop just assumed that it was correct when they replace all the wires? for me it was just a fluke that I even thought about checking the firing order
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
+1 on the aliens....

I can't think of a single reason that the fuel delivery would even be aware of spark. If fuel is going to the FD, then it oughtta be spritzing fuel into the cylinders. Could you maybe have bonked something (OVP?? FPR??) while scooting around in there plugging and playing spark plug relay?

Oh well, glad the car started... and he's got some new parts too! Maybe go back to the shop and grab that FD back-- Spare, or return to sender?
 

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so now I am asking you guys ,why did this not show fuel to the injectors with the plugs miswired, is the computer smart enough to shut fuel off if the wiring is screwed up??? never seen this before ,,,comments would be appreciated and read even I am now wondering if some messed with his wiring on the plugs while he was in the store and the shop just assumed that it was correct when they replace all the wires? for me it was just a fluke that I even thought about checking the firing order
Same thing happened when my buddy brought his '94 firebird over that had 206k on it. we tore it down to the block with new parts and i crossed up some ignition wires and 2 or 3 times it nearly started and eventually it was just cranking. My assumption is the cars fuel distributor maybe cuts off fuel once the engine has been flooded? Might be a pressure issue but i would be simply amazed if the computer stopped the fuel as that is a primitive fuel system. just my .02
 

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SuperModerator
1986/1990 W126
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17,669 Posts
My car came to me with 2 HT leads plugged in wrong. Ran it like that for ages before we realised. Never failed to start though.
 

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1983 300SD
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50 Posts
Did the shop charge him for all of these parts before blaming the car and booting it out of the shop?? If so, you might have a case of criminal fraud to report. If you get a sympathetic detective, they will investigate as well as report to your local BAR which has enforcement power up to padlocking their door. At least here in CA. It's not real hard to find a cop, (or anyone else), with hatred for crooked auto mechanics. :mad:
 

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Premium Member
1985 500 SEL and 1986 560 SL
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73 Posts
Discussion Starter · #7 ·
Well I did suggest to the owner that he might have some recourse from the shop, however he said. it was lesson and hes not going back or having anything to do with that shop again, he has enough high blood pressure. he's happy that we were able to figure the issues and is just leaving it, he did give me the 'old" fuel distributor though. Appreciate the comments from folks ,but I am still preplexed as to how miswired plugs could effect the fuel system, it is possible I guess that fiddling with the OVP and fuel relay may have had effect also. This is just a unexplained mystery in the benz world I guess,,,,,
 
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