can't get my pagoda to run - Page 2 - Mercedes-Benz Forum

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post #11 of 21 (permalink) Old 04-17-2008, 10:03 AM
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Am I the only one who thinks 200psi on a compression test is maybe a bit too high?
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post #12 of 21 (permalink) Old 04-17-2008, 12:27 PM
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Am I the only one who thinks 200psi on a compression test is maybe a bit too high?
Not if it had 13-1 compression ratio and use 120 octane gas.
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post #13 of 21 (permalink) Old 04-17-2008, 12:29 PM
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Depends...

on how accurate the compression tester was...

JR
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post #14 of 21 (permalink) Old 04-17-2008, 01:35 PM
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or how accurate the compression tester was...

JR
I was going to say that but thought it might be bad form for a first post.
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post #15 of 21 (permalink) Old 04-17-2008, 09:55 PM Thread Starter
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I agree, 200psi definitely seems too high. The compression tester is a new Craftsman model. The head is a rebuilt one. Can machining a head cause an increase in compression?
Dimitri
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post #16 of 21 (permalink) Old 04-18-2008, 07:02 AM
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I agree, 200psi definitely seems too high. The compression tester is a new Craftsman model. The head is a rebuilt one. Can machining a head cause an increase in compression?
Dimitri

Yes, but not usually that high. Your gauge just reads high likely.
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post #17 of 21 (permalink) Old 04-18-2008, 07:50 AM
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Yes, but not usually that high. Your gauge just reads high likely.
The head would have had to be REALLY milled down to raise the compression that much, and if so, I doubt it would make the minimum thickness specification [and yes with a Mercedes there is one...].

The basics are that if you have fuel, compression, air and spark, the car should run. Something is inferring with one of those four elements.

From your earlier posts, it sounds like spark is the culprit, and that is where I would put my efforts...

Good luck,

JR
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post #18 of 21 (permalink) Old 04-18-2008, 02:10 PM
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I would think fuel is the more likely culprit. The 1rst thing you found was a blown fuel pump fuse. Something other than a bad spark caused that. You never mention where you checked the fuel flow rate. Was it before or after the fuel filter? You've fiddled with the ignition system now so there may be other new problems but based on you 1rst post I would guess it's fuel related.
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post #19 of 21 (permalink) Old 04-20-2008, 09:02 AM Thread Starter
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I checked the fuel pressure and flow rate before the fuel filter where the line comes into the engine compartment. I also checked flow and rate at the fuel line where it hooks up to the cold start valve. The values were the same at both locations. I know that it is very strange that my original observation was a blown fuel pump fuse. The current draw on the pump is normal though. The car still would not start after replacing the fuel pump fuse even though the pump started working again. After changing cap, rotor, points, condensor, wires and plugs, I got the car to at least start. This would lead one tho believe that the problem is ignition related. The whole picture is very confusing.

Dimitri
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post #20 of 21 (permalink) Old 05-21-2008, 01:01 AM
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280SL won't start

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Hi all. I have a 71 280SL which I was driving home almost 2yrs ago when it just stalled out in front of my apartment complex. I pushed it into the garage and I have been unable to get it to run since then and now I'm at witts end. I have been back and forth on the pagoda forum which has been extremely helpful and through their expertise I have ruled out a lot of things. However, the problem persists and we have not been able to come up with a diagnosis. I'm hoping that someone here might have some insight.

Initially, I noticed that the fuel pump wasn't running, so I checked the fuse. It was burned out. I replaced it and the pump started working. I then checked the current draw at the fuel pump fuse terminals. It was drawing 3.2 amps which is within normal range. The car still would not start. I then checked the fuel pressure and volume. The pressure was 16 psi (normal) and the volume was 600-700cc/15 sec which is under the 1000cc required output. This should nevertheless be enough to get the car to idle and probably run just fine.

I then tackled the ignition system. I replaced points, condenser, cap, rotor, plugs, wires, coil, ballast resistors, set the dwell to 38 and the car started. It however would not run. The engine would run roughly for a few minutes, put out gray/white smoke (not vapor), backfire occasionally, and eventually stall once too much or too little throttle was given. The car has remained in ths condition ever since.

I then checked compression and all six cylinders were around 200 psi. 197-201.

I turned my attention back to the fuel system. I check the main fuel filter in the engine which was clean. I replaced it anyway. I checked the small filter screen in the electric fuel pump where the intake line from the tank hooks up. It was clean. I then peered into the tank from the top through the sender hole. The tank was clean with bright shiny metal surface on the inside. I also blew out the fuel return line where it originates from the injection pump. The line was clear. At this point I ruled out a fuel tank, fuel pump, fuel line issue. I checked the rack in the injection pump which moved freely and I checked the cold start valve which doesn't leak and sprays a nice mist when cranking the engine cold.

I messed around with the timing, turning the distributor from right to left but still no change.

I'm getting frustrated here. Everything checks out but the car still won't run properly. Any suggestions appreciated.

Dimitri
'71 280SL
Dimitri,

I bought a 300SE one time with a "bad engine" and found that someone had installed the wrong rotor in the distributor. It was a little too long and it struck one of the posts in the cap and that was the only one that had a spark!

Gummed up fuel injection is my thought. I believe you have the 6 piston mechanicl injection system. I have seen these with a frozen rack so that the injectors could not stroke any fuel. have you cracked the injector connector lines to see if they are discharging fuel? There is a small cap on the front of the injection unit that covers the tip of the rack that sets the fuel quanitity. take that cap off and you can verify that the rack moves when you open the throttle. As I recall the eraser end of a shortened pencil works well to "feel" if the rack is moving. With fresh fuel, once you get it moving a little bit, it will clean itself of the gummy deposits. it is over 20 years since I was up close and personal with this gas injection system but it may be that the end of the rack is threaded internally for a small (4mm?) bolt which can be used to exercise the rack.

just a couple of WAGs. Good luck!

Jim in Phoenix

Jim Friesen
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