W124 fuel tank leak

[grumpyartman]

Was having surging idle and stalling problems so went to change fuel filter only to discover fuel leak from filler pipe to tank weld. Would this have affected the fuel pressure? Being before the pump I can't see how, does the pump rely on the tank being relatively airtight?

My manual doesn't have any details about removing the fuel tank ( W124 1993 E220 estate) which should be straightforward, any specific problems?

When off, if a weld is required would filling the tank with water be the best course of action?

Thanks.

 

[grumpyartman]

Apologies, i'm a typical lazy poster, found some answers on here re tank/weld/kapow and it should be just disconnect and four 13mm nuts.

but first question is still relevant.

Has anyone ever epoxied a rusted and leaking weld ( neck to tank) successfully?

 

[230K]

Hi

I had to weld the tank on the wifes 124 Diesel Estate. I drained the tank and although there was still some diesel in the tank i welded it stood on its end.

The good metal is thin and the rusted metal very thin so i needed to play about with the mig welder turning off the gas to get some build up to sink the heat before closing over the weld with the gas on again. If you can mig then you will know what i mean.

It has worked well since and that was maybe 3 years ago or so.

230K

 

[grumpyartman]

Thx for answer sorry should have said petrol.

As it is a weep only at the mo I suppose I should try the epoxy route but I don't like bodging. But I also don't like throwing cash at probs either.

I'm presuming a petrol tank has a strainer like a diesel one, if so thats coming out as it might be the culprit if its fuel starvation thats my prob.

and the plenum inlet, I do read others posts y'know, how do you clear that? without an endoscope !

 

[grumpyartman]

With regards to the tank having some vacuum/pressure within I found my own answer here.

It is not pressurized. A breather valve at the fuel tank allows fuel vapor to flow out of the tank and be stored in a charcoal canister until it is drawn into the intake of the engine. It also allows fresh air into the tank to prevent a vacuum. The fuel cap is not vented, all air moves through the breather valve. Technically it may, at times, be pressurized or have a vacuum. However, a properly functioning vapor system should limit that to a max of .725psi, or a vacuum of .45in. Hg.

 

[230K]

Hi

Do not attempt to weld a petrol tank!!!!

I wrongly assumed you were diesel.

Best to try some of the epoxy repair pastes

230K

 

[mattc]

you can epoxy it. Did the same job on an old 124 estate we had and that lasted for another 60K before it went to the scrappy. Just make sure you sand the rusty section back well so the epoxy/glass fibre strip adhere well

 

[grumpyartman]

thx. Will do that.

Got the strainer out and its clean as a whistle. left me wondering if the feed into the plenum might be blocked as the little fuel left there took ages to dribble out. Does anyone know if its a singular inlet or does it work diving bell fashion?

Didnt have a 22mm allen handy to drop the strainer so used a chisel end on with an adjustable spanner on the blade shaft, fitted and worked perfectly. Special tools my ****.

 

[grumpyartman]

The old lady is now sporting a bad filler job on the tank but it seems to have sorted the leak but the bad idle remains after the fuel filter and fresh fuel replacement.

Pulled the ovp and cleaned the pins , same with fuel relay, but no improvement.

Now i might have to cough for an ovp just to find out. My soldering skills ain't so hot( sorry)

If I read it right someone pulled the fuse from a live ovp and this apparently resets the ovp, with some obvious risk to the ecu I suppose.

 

[grumpyartman]

I'm finding quite a bit out about this problem and this guy's words lifted from elsewhere make so much sense i've copied them to here.

300e Fuel Pressure

problem I know I posted here several times before...I have replaced many parts to this car and still cant figure out why the car keeps flooding out on me. I am 100% sure it is flooding out after a few minutes of running. The car is fine on a cold start but cuts out after a few minutes. When the OVP relay is DCd the car runs o.k. when warmed up. I installed a new fuel pump relay, fuel pump check valves, fuel accumulator, fuel pressure regulator, the OVP relay is pretty new, cap , totor, plugs, wires, o2 sensor, catalyitc converter... The old cat had 2 precats on it, this one only has the one cat in the middle, doe sthis make any difference? I appreciate all the help, I am on a fixed income in school and need this car to run....-chuck, nj
The fuel pressure (= mixture) is primarily controlled by the fuel distributor. It works in a way that the air mass sensor (the moving plate under air filter) controls the position of a plunger inside the fuel distributor, which again determines the fuel pressure to the injectors. The mixture is adjusted by the screw inside the tube, which leads to the top of the air filter.

The pressure is then fine adjusted by the fuel pressure regulator (EHA) through the incection computer.

If overvoltage occurs, the fuse in the OVP relay will blow and thereby disconnect the power supply to the injection and ABS computers.

When the injection computer has no power, the injection system works without fine adjustment of the pressure. Taking out OVP relay will simply remove power supply likewise.

Since the engine runs fine without the OVP relay, you can conclude that the basic system works and has almost correct mixture.

Since you see a difference with the OVP relay in place, you can also conclude that something is changing the pressure. That has to be the injection computer, which again means that it does get power supply through the OVP relay (which is then not the fault).

But apparently it gradually increases the pressure until the engine finally drowns. This indicates to me that the computer does not get correct feedback from the oxygen sensor (it should indicate too rich mixture, whereby the computer should reduce the fuel pressure). So check again the oxygen sensor and its connections.

Other inputs to the computer are:

coolant temperature sensor
EGR temperature sensor (if fitted)
idle switch
start signal (crank)
speed
rpm
airflow (potentiometer mesuring the sensor plate position)
altitude correction (if fitted)
reference resistor (under sealed cap)
All these inputs are used to preset the fuel pressure fine adjustment. But at the end of the day the oxygen sensor will measure whether the combustion is correct and make the computer fine adjust accordingly.

Therefor the major suspect is the oxygen sensor measuring incorrectly or not being connected correctly. Alternatively it could be the fuel pressure regulator not acting correctly according to its control signals. Or the computer is failing.

Jens, Denmark

 

[kth286]

the above describes a car injection and ignition system that is completely different to yours.

His is mechanical

and your's is fully electronic.

 

[grumpyartman]

thanks for pointing that out, I wasn't sure about the drowning bit. Surely its not entirely irrelevant.

Today I pulled the FPR, OVP and ECU out. All meter checks for 12v and earth on the OVP socket were good, the ECU board appeared pristine and the ECU plug 12v/ earths were good, the FPR socket was bridged 6 to 8 and the engine held the revs without too much fluctuation or hesitation so that's the first swop out to do.

My car will not start with the OVP disconnected as some others do.

It remains to be seen if the FPR is faulty or if the 'bridge' just bypassed the recognition of a fault elsewhere.

Onwards and upwards.