1972 Mercedes Benz 280 SE 4.5 Vapor Lock Investigation & Checking Condition of Flexible Fuel Lines

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About a week ago, after a long drive on a warm day the car experienced great difficulty restarting after sitting for 15 minutes with the engine stopped. I think the engine was experiencing fuel starvation via vapor lock. About a year ago, I had checked fuel pressure at the fuel rails, and it was around 30 PSI at warm idle which is correct. However, fuel pressure dropped to 20 PSI after engine was stopped for 1 hour. I read an opinion that fuel pressure in the D-Jetronic system should hold and not drop by more than 2-3 PSI after stopping the engine for 30 minutes. This video documents that. I saw a Facebook post of a Mercedes Benz 280 SE 4.5 burning and became worried about the condition of the flexible fuel hoses and injector hoses and seals. I inspected those too and they were fine. Finally, I conclude that the fuel tank is not venting properly.

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27 июн 2023

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Комментарии : 16

@AMNAbidi Год назад

I love your videos. I just got my 280 sel 4.5 a couple of days ago and your videos are giving me a great idea of how to go about things. maybe I'll start posting my investigations too. Thank you!

@kensshowtell 9 месяцев назад

Thank you for watching and your lovely comment. Yes, please do.

@Keeferlgb Год назад

Another very healthy sounding engine! You don't see many w108/109's in such nice condition anymore. That thing would make me want to take a cross country roadtrip!😁

@kensshowtell Год назад

Thank you. The car has a significant history of being well taken care of from 1972 till around 1980 then its maintenance history stopped till 2013. I acquired it in 2019 after rescuing it from a heavy equipment machine shed located at a landscaping business. I've made many other videos of documenting the find, recommissioning for the road, and a long drive. Again, thank you very much for watching and taking your time to comment.

@Mercmad Год назад

I just bought a write off to scavenge parts from, a W114 280E coupe. The car had been purchased recently for $30,000(!) .the fuel injector hoses had been neglected and the car of course caught fire. It's so common that anyone who owns a djet car, whether it be a VW Type III or a Mercedes ,get the rubber replaced!. The most tragic one I worked on was a W111 3.5 cabrio. Modern fuel evaporates too easily which is why Mercedes started fitting fuel coolers in the early 1990's to the last of the W126 models. I can get Djet injectors rebuilt here by Bosch ,which is very unique and one last thing,the ignition trigger points were always a problem as the engines got older. 123 ignitions in Holland make a conversion distributor which eliminates them completely.We just converted yet another W114 to this system and the car even sounds different. Utterly smooth and with more power. PS You are missing the plastic cover on your distributor. It's there for a reason, to stop raw fuel hitting the distributor cap if a hose should break.

@kensshowtell Год назад

Thank you for watching and taking the time to comment. I've installed Pertonix II ignition under the distributor cap, the correct Pertronix ignition coil and the correct Pertronix ignition wire set and that solved an intermittent "missing" problem I had. I took out the distributor, checked for wear, and cleaned the trigger points at the bottom of the distributor. (I made a video documenting this.) I've not seen the black plastic distributor cover on any 4.5. I've seen in on 3.5 engines. I will see about locating one.

@austinado16 Год назад

That D-jet system is operating so nicely! I guess you could do a driveway test that recreates more of the conditions that had occurred when the car was difficult to/or wouldn't restart when hot. For example, go drive it, bring it back and park it in the sun, leave the hood closed, and come back after a hot-soak, see what the pressure gauge says, and try to start it, no matter what the pressure gauge says. On thing that your method of pressure testing doesn't rule out, is a leaking cold start injector, which would cause the engine to be flooded, during a hot soak. If it were mine, I'd wait until I was at half a tank of fuel, pour in a full can of SeaFoam, and then go drive for an hour or 2. During that drive, I'd find a route that included a long grade to climb, so that I could go up that grade with significantly more throttle opening (but not let the transmission shift down), in order to get the injectors to all spray more volume, and clean themselves. Then I'd bring it home, let it sit for an hour or so, and go for a similar, shorter, drive. I'd also try to prove that the cold start injector was, or wasn't, leaking.

@kensshowtell Год назад

All excellent ideas. I've used Seafoam before on my SU carburetors in my MGs. I have not done so in this car because I've been using Liqui Moly gasoline fuel injector cleaner. I've also considered just bypassing the cold start injector as the car has never had a problem starting when cold. I've got a spare one that is known to not leak but I've not switched them out as of yet. Even though I addressed the fuel tank ventilation system it seems to continue to build undue vacuum. Tomorrow, my wife and I are taking the car out for a drive that will entail some stop and go driving and most likely the use of the air conditioning system. Before we go, I'm going to remove the fuel filler cap gasket and see what happens. Ironically, the car has 1/2 tank of fuel so I will also dump a can of Seafoam in as you suggest. I did not say so in the video, but I'm suspicious that one of those trumpet shaped valves in the fuel tank ventilation system is not working. Thank you very much for watching and making constructive suggestions.

@austinado16 Год назад

@@kensshowtell It probably won't start well cold, without the enrichment of the cold start injector. The intake runners and volume of the 4.5L is just too large. I'd just leave 'er all bone stock, run a can of SeaFoam, and then see if you can recreate the issue without the stresses of being "broke down" with the wifey on board. I'm not familiar with the D-Jet on that car because I worked on so few of them, but does it have a fuel pressure test port, like a little stub of pipe that has a small 4mm hex head screw in it, somewhere on the fuel rail? Seems like most of the early Bosch systems did, so that mechanics could install the test gauge, with just a simple hose clamp, and lay the gauge on the engine and go drive. It allowed for real-time/real-condition testing. You could even use a really long hose, and tape the gauge to the windshield, so that you could monitor while driving.....that's how we used to do it where I worked.

@kensshowtell Год назад

@@austinado16 The D-Jets on the 4.5 do not have a test port. However, one can be installed using a "T" connection in the cold start valve hose with a Shrader valve. I've considered doing that as it is straight forward and does not interfere with anything. I've read about folks doing that and riding with the test gauge in the car beside them when the engine is having fuel starvation issues at speed or under acceleration. The car runs great at speed, under acceleration, and climbing hills. When the hot start issue occurred, I was able to get underway again after waiting 15 minutes, hood up, parked in the shade. I did not think of checking if the tank had significant vacuum until I got home, and it did. I also noticed that the new fuel pump had a loud screaming/whining sound that stopped after relieving the vacuum in the tank.

@austinado16 Год назад

@@kensshowtell The fuel tank venting definitely sounds like your problem!

@kensshowtell Год назад

@@austinado16 Yes indeed. We just returned from a 75-mile ride that involved two stops, some stop and go driving, running the AC, outside temperature around 80 degrees F (which is warm for us). Before we left, I removed the rubber seal from the fuel filler cap and dumped a can of Liqui Moly gasoline engine fuel injector cleaner into a 1/2 full tank of 89 octane gasoline. The car drove, cooled, and restarted (twice) like a champ. I checked the fuel filler cap twice (once upon return) and there were no gasoline smells and no vacuum. Wunderbar!