72 280se 4.5 no injector pulse after engine warms up - Mercedes-Benz Forum

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post #1 of 17 (permalink) Old 06-08-2015, 11:02 PM Thread Starter
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Unhappy 72 280se 4.5 no injector pulse after engine warms up

Hello everyone. I am needing any ideas or maybe someone has encountered this issue. One of my 280se 4.5 dies after warming up. If it cools down, it will start again and eventually dies after warming up. On cold start, i would say no more than 15 minutes before engine stops running and then i get a crank no start issue. During that time, there is no injector pulse. I have cleaned the ground points by the battery, checked continuity to ground pin on ECU, swapped ecu's from my other three w108, and it is still the same. After warm up, no pulse. I even replaced the trigger points and still no dice. Checked continuity from ecu to trigger points and it is good. Also the continuity from the injectors to ecu is good and the ground pins for the injectors have good continuity. Has anyone encountered a scenerio like mine?? By the way, after it warms up and shuts off, i swap the ecu from another one of my cars and it still wont start (fuel pump works). I leave the swapped ecu connected and after vehicle cools down, car will start and after it warms up, engine shuts down. Any ideas? I also replaced the thermotime switch and same issue. It probably is something simple and i am overlooking something or i am just frustrated that i havent been able to fix it. Thanks everyone! I really want to drive my car again, but i am limited to how far and how much time i can travel.

"The grass is greener...where you water it!"
1994 Geo Prizm (RIP 11/2013)
1987 560SL
1970 280SL (sold)
1972 280se 4.5 white w/ red leather
1972 280se 4.5 rust bucket baby blue
1978 Datsun 280Z "Black Pearl"
1978 Datsun 280Z (CLK430 swap)
1971 Datsun 240Z Series 1 final production
1974 VW Karmann Ghia coupe (under restoration)
1972 VW Karmann Ghia coupe autostick
2007 Honda Odyssey
2004 Toyota Corolla
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post #2 of 17 (permalink) Old 06-09-2015, 05:28 AM
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Coil?
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post #3 of 17 (permalink) Old 06-09-2015, 11:22 AM
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I had one that actually had a cold solder joint on the ground lead for the trigger points in the distributor. Got hot and went open.
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post #4 of 17 (permalink) Old 06-09-2015, 05:32 PM
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72 280se 4.5 no injector pulse after engine warms up

I once left my battery connection loose on my 73 450sl, and when I would hit a bump the car would stall out.

It sounds stupid but check the battery connection and the ground to the battery.

I think there may have been a separate positive wire from the battery to which may have been the actual culprit not the main battery positive terminal.

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post #5 of 17 (permalink) Old 06-10-2015, 10:31 PM Thread Starter
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Originally Posted by Bill A View Post
I had one that actually had a cold solder joint on the ground lead for the trigger points in the distributor. Got hot and went open.
Was your cold solder joint on the trigger points themselves or on the connector?? I had replaced the trigger points from my running (until i took parts out) rusted parts car. I would like more info on your problem. It sounds very logical. There was continuity, but maybe i am not checking where i need to check. Earlier they told me coil, but i have good spark. I can get it running if i pour a little gas down the intake throttle body after it shuts off after warming up. Once again, i am loosing injector pulse. On a side note, if you move the throttle linkage slowly to the WOT position, four injectors do pulse 20 times as you are getting to WOT. That makes me know that the ECU is working. I appreciate everyones help!!
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post #6 of 17 (permalink) Old 06-10-2015, 10:41 PM Thread Starter
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Originally Posted by Fonzi View Post
I once left my battery connection loose on my 73 450sl, and when I would hit a bump the car would stall out.

It sounds stupid but check the battery connection and the ground to the battery.

I think there may have been a separate positive wire from the battery to which may have been the actual culprit not the main battery positive terminal.
Thanks Fonzi! I know the feeling. I onced used to own a 1984 Nissan 720 4x4 pickup that i purchased after I got rid of my 2003 Nissan 350z and i had moved to Mexico. I was living up in the mountains where you need a 4x4. My battery did not have any tiedowns and at times the ground would come loose and the majority of the time when i would hit a bump my battery would short on the hood and i would see sparks! That battery didnt last long. LOL

"The grass is greener...where you water it!"
1994 Geo Prizm (RIP 11/2013)
1987 560SL
1970 280SL (sold)
1972 280se 4.5 white w/ red leather
1972 280se 4.5 rust bucket baby blue
1978 Datsun 280Z "Black Pearl"
1978 Datsun 280Z (CLK430 swap)
1971 Datsun 240Z Series 1 final production
1974 VW Karmann Ghia coupe (under restoration)
1972 VW Karmann Ghia coupe autostick
2007 Honda Odyssey
2004 Toyota Corolla
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post #7 of 17 (permalink) Old 06-10-2015, 10:57 PM
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Quote:
Originally Posted by OzzyQ80 View Post
Thanks Fonzi! I know the feeling. I onced used to own a 1984 Nissan 720 4x4 pickup that i purchased after I got rid of my 2003 Nissan 350z and i had moved to Mexico. I was living up in the mountains where you need a 4x4. My battery did not have any tiedowns and at times the ground would come loose and the majority of the time when i would hit a bump my battery would short on the hood and i would see sparks! That battery didnt last long. LOL

Test with your d-jet system. You'd think the car would run with the battery disconnected, but my d-jet 450sl cars would not. If I tried to swap out the battery while the car was running, the car would stall.

I think you said the ECU is still working when the car won't run when hot though. Right?

.

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post #8 of 17 (permalink) Old 06-11-2015, 06:24 AM
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Originally Posted by OzzyQ80 View Post
Was your cold solder joint on the trigger points themselves or on the connector?? I had replaced the trigger points from my running (until i took parts out) rusted parts car. I would like more info on your problem. It sounds very logical. There was continuity, but maybe i am not checking where i need to check. Earlier they told me coil, but i have good spark. I can get it running if i pour a little gas down the intake throttle body after it shuts off after warming up. Once again, i am loosing injector pulse. On a side note, if you move the throttle linkage slowly to the WOT position, four injectors do pulse 20 times as you are getting to WOT. That makes me know that the ECU is working. I appreciate everyones help!!
The cold solder joint was in the trigger point assembly itself so a replacement was the cure. the extra positive lead at the B+ is the power supply for the injection system on some models.
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post #9 of 17 (permalink) Old 06-11-2015, 08:30 PM Thread Starter
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Bill A, is the B+ terminal that younare referring to on the alternator or the little connection block that is located underneath the winshield washer resevoir tank? I remember once the car was running and when i shut the hood the engine turned off. That is why i started checking the grounds for loose connections. It only happened once. It didnt want to start for days, only crank over. I know enough to fix the newer models, but not these old cars that i love!!

"The grass is greener...where you water it!"
1994 Geo Prizm (RIP 11/2013)
1987 560SL
1970 280SL (sold)
1972 280se 4.5 white w/ red leather
1972 280se 4.5 rust bucket baby blue
1978 Datsun 280Z "Black Pearl"
1978 Datsun 280Z (CLK430 swap)
1971 Datsun 240Z Series 1 final production
1974 VW Karmann Ghia coupe (under restoration)
1972 VW Karmann Ghia coupe autostick
2007 Honda Odyssey
2004 Toyota Corolla
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post #10 of 17 (permalink) Old 06-11-2015, 10:15 PM
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Quote:
Originally Posted by OzzyQ80 View Post
Bill A, is the B+ terminal that younare referring to on the alternator or the little connection block that is located underneath the winshield washer resevoir tank? I remember once the car was running and when i shut the hood the engine turned off. That is why i started checking the grounds for loose connections. It only happened once. It didnt want to start for days, only crank over. I know enough to fix the newer models, but not these old cars that i love!!
It was in a couple of different places in different models. It was on the battery connector to the battery on one and it was on a two pole connector beneath the battery if memory serves me. I still have a couple of books but I donated moat all of them to our library a while back. I think I may have posted a diagram here that should show the wire you are asking about but it would cause the entire engine to die. I had one quit in an intersection of two 4 lane roads in LA years back and I opened the hood and hunted it until I found it, I hated intermittent problems but that was my job. Anyway I'm almost sure I posted diagrams here somewhere. I will do a search to see if I can find it.
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