Author Topic: fuel issues  (Read 3276 times)

rumb

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fuel issues
« on: 23 October 2016, 02:32 PM »
I finally installed the new fuel hose/lines to and from the fuel distributor. Same time I cleaned the Aux Air Valve and such and reinstalled all of that.

When I tried starting, it would only run sort of if I held the air flap open some, but could not get above an idle and it would die if I closed it. At some point it backfired and I decided to check all the lines under the car and discovered I had left a hose clamp pinching the rubber lines back by the gas tank. I thought that would be the trick, but after that point it seemed I had low fuel preasure. Before if I pushed the air flap in there was strong resistance, ever since not very much.  I pretty much at that point decided I had flooded the engine so left overnight.

Today the car did start up and can be revved up, but with a big missfire and huge clouds of greyish smoke out the back.  The previous night I had noticed this leak under the car and at that time thought it was coolant because I did have a hose at the firewall loose when I first tried starting.

Today I looked at several cups of liquid that had accumulated in the small bucket I put under the drip and realized it was gasoline. The gas is dripping out of the 3/8" hole you see on the bottom rear of the block on the left/drivers side. all those bolts are around the oil pan. 

Where is this gas coming from?  I can see no gas leaks from topside.  I suspect the gas leak and the over rich smoking have something in common.  I disconnected the wire to the the cold start valve, but could it be a stuck injector, or did something go wrong with the fuel distributor?

But what would the path be for gas to end up dripping out of that hole on the bottom of the block?




« Last Edit: 23 October 2016, 02:46 PM by rumb »
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

rumb

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Re: fuel issues
« Reply #1 on: 23 October 2016, 02:35 PM »
Having a problem attaching so here is link

https://1drv.ms/i/s!AgQ9-BbdVO39p0c-nrspe2NHJCN4
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UTn_boy

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Re: fuel issues
« Reply #2 on: 23 October 2016, 04:09 PM »
You're leaking gas somewhere on the intake manifold, and it's running down into the "V" area of the block. On the rear left of the block "V" area there is a drain, and that is why you're seeing gas on the bottom of the engine.  Otherwise, you may be leaking from one of the fuel lines that go to or from the tank......they don't like being crimped off when they're old.  They crack and break. 
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Mr6.9

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Re: fuel issues
« Reply #3 on: 23 October 2016, 11:04 PM »
When you say new fuel lines, do you mean just the hoses or are the fittings new too? If the fittings are new, i'd take them off and compare to the originals.

rumb

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Re: fuel issues
« Reply #4 on: 24 October 2016, 06:15 AM »
The fuel lines I replaced are the 2 big ones that start under the car and end up going into the distributor.  the return line is a new MB part, the in line I had new hose and crimps ends installed on the original hard line. 

The hose I mentioned clamping off are the very short pieces of rubber hose clear back by the gas tank.  They are new rubber also.

While the new hose would seem the obvious place to look for leaks, there is no leak there. 

So I know I have two issues, one gas leaking somewhere that eventually flows into valley and then drips out drain hole on bottom of engine.

2nd is the horrible rich running condition, huge amounts of smoke and rough misfiring.

My plan of attack is to pull plugs and see which cylinder is missing, then pull injectors and test to see if stuck open.

As far a finding leak, I am still at a loss. 

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Alec300SD

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Re: fuel issues
« Reply #5 on: 24 October 2016, 02:50 PM »
I suspect you have a fuel leak at the fuel distributor, at either the inlet union or outlet union, when the fuel system is pressurized.

The copper crush washer between the fuel distributor and the counter-hold nipple fitting may have lost its seal during removal of the inlet or outlet hoses.

Also, the mating surfaces of the flared fitting may be failing to seal.  You might need a one time use conical washer to get a good seal.
http://www.gen-aircraft-hardware.com/template.asp?pagename=conseal

To search for the leak: make sure the top of the engine is completely dry and clean, re-pressurize your fuel system,  twist the corner of a paper towel or tissue tightly to make a wick, use the paper wick to probe the unions and undersides of all of the fuel carrying components that could leak onto the top of the engine. When the wick gets wet, you will have found your leak.

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Mr6.9

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Re: fuel issues
« Reply #6 on: 24 October 2016, 06:50 PM »
The fuel lines I replaced are the 2 big ones that start under the car and end up going into the distributor.  the return line is a new MB part, the in line I had new hose and crimps ends installed on the original hard line. 

The hose I mentioned clamping off are the very short pieces of rubber hose clear back by the gas tank.  They are new rubber also.

While the new hose would seem the obvious place to look for leaks, there is no leak there. 

So I know I have two issues, one gas leaking somewhere that eventually flows into valley and then drips out drain hole on bottom of engine.

2nd is the horrible rich running condition, huge amounts of smoke and rough misfiring.

My plan of attack is to pull plugs and see which cylinder is missing, then pull injectors and test to see if stuck open.

As far a finding leak, I am still at a loss.
have you checked the wur or pressure regulator? still new to the these cars, but I believe either one of those could potentially leak into the valley.

rumb

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Re: fuel issues
« Reply #7 on: 25 October 2016, 02:04 PM »
I started the car briefly and checked the right side spark plugs all were wet and black.

Started car again and it idles more or less, revving produces large smoke and increasing misfire.

I can find absolutely no leaks topside from any lines/fittings.  what ever is leaking is doing so at a fairly large rate. 2-3 minute of running will net several cups of gas.

I did find gas on the lower clamp on the bottom of the throttle body and gas liquid pools in the valley underneath, but cannot spot any actual gas flowing. Looking down air throat there is not gas in there and also below throttle plate in throttle body.

Still no idea about how it is getting into valley and also into the intake manifold thus making mixture overly rich.

The WUR was rebuilt and tested same time as fuel distributor, and car was running fine before these 2 changes.

Besides replacing the 2 fuel lines I swapped the AAV and hoses and fittings.  I took the AAV apart and cleaned-  perhaps messed that up?

Tomorrow I will first try swapping back in all the old AAV components. Will also check filter in WUR.

« Last Edit: 25 October 2016, 02:08 PM by rumb »
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Mr6.9

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Re: fuel issues
« Reply #8 on: 25 October 2016, 03:40 PM »
Are there any additives in the fuel? Try momentarily unplugging the relay while it's running and see if idle changes. If it improves, I'd check the injectors first.

Alec300SD

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Re: fuel issues
« Reply #9 on: 26 October 2016, 12:15 PM »
Rebuilt fuel distributor may be leaking, underneath where you can't see the drip.

The central control pressure rod seal is probably the culprit.

Sometimes the seals dry if the rebuilt has been in storage for a while.

You may be able to inspect the area, by loosening the mounting bolts for the air horn/fuel distributor assembly, and
lifting it up a bit (if you have enough play on the attached lines).
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Mr6.9

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Re: fuel issues
« Reply #10 on: 27 October 2016, 01:02 AM »
Rebuilt fuel distributor may be leaking, underneath where you can't see the drip.

The central control pressure rod seal is probably the culprit.

Sometimes the seals dry if the rebuilt has been in storage for a while.

You may be able to inspect the area, by loosening the mounting bolts for the air horn/fuel distributor assembly, and
lifting it up a bit (if you have enough play on the attached lines).
Agreed.  The lost resistance felt in air flap could be a sign the gasket failed. Thats what happened on a spare i pulled off a parts car that sat 20+ years. Made a nice sooty stain on the floor. To confirm my suspicions, I made a bench tester out of the upper intake from the same parts car. Pressurised and fuel poured out the bottom

rumb

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Re: fuel issues
« Reply #11 on: 27 October 2016, 06:55 AM »
Thanks for the great info.  The leaking fuel, did it flow inside the plenum?
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Mr6.9

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Re: fuel issues
« Reply #12 on: 28 October 2016, 02:26 AM »
Thanks for the great info.  The leaking fuel, did it flow inside the plenum?
I'm sure it did.  Enough flowed out the bench tester to quickly cover the table with gas

rumb

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Re: fuel issues
« Reply #13 on: 30 October 2016, 12:51 PM »
What does the fuel pressure damper that is at the back of the fuel distributor do?  where is the other end of the vacuum line that connects to it?


Inspection camera is arriving Monday to be able to see better in valley.

The clamp that holds the hose to top of throttle body gets damp, but looking further towards the rear on passenger side I can see some actual fuel flowing on casting.  Cant see far enough in the tell where it is coming from.

Back to the fuel damper, is gas supposes to come out of where the vacuum line connects?  I would think not, but there is.I can kind of see the vacuum line towards the front of engine that is also wet with fuel.Still not sure exactly where it connects to. but my guess would be at the back of the  throttle body.  Can someone confirm it's connection point?

Does this sound like a bad damper?

R

update, just went out to photograph the damper on my car, and tugged on the vac line going under the manifold.  it came out, and the far end is burnt and has a big hole in it!   will post shortly.

sounds like a new damper and vac line are needed.  I guess I will have to take a few parts off the top of engine to get to to it all, but at least I have something to work with now.



« Last Edit: 30 October 2016, 01:47 PM by rumb »
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

daantjie

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Re: fuel issues
« Reply #14 on: 30 October 2016, 02:14 PM »
Robert that is not a vacuum line but a leak line. If the diaphragm inside the damper ruptures then that leak line carries the leak fuel back to the intake by way of the breather hose on the RHS cylinder bank. Looks like that damper has said sayonara.
Daniel
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