W124 fuel pump relay help requested

[neilrr]

How much did he save buying a FPR he didn't need? Enough to get it diagnosed by someone who knows what they're doing?

 

[optimusprime]

Yes i know, And as for the FPR these items are something you dont buy every day . But items i was talking about are maintenance items and you do need a good HT system on the engine first to start with. Then you can forget them and look in other places like fuel system . For a start in my location we have 5 garages and no one knows how to sort them out .Those people bought up on the mercedes motors have all retired .The dealers will look at them and experiment on them at your peril and you pay the bill . So information and help we try to give others is a waste of time .. I said nothing about picking up a FPR . I did say get the HT system sorted first ..

 

[DaveDacombe]

Have you change the distributor top and the rotor along with ht leads and spark plugs . Check you fuses in the fuse box - give them a turn for now. Look at the wires on to the coil for corrosion .And look at all the vacuum pipes for splits .

Have replaced with new - crank posn sensor, plugs, leads, distributor cap, rotor and coil a couple of months ago when I decided to put car back on the road. It had been sat on driveway for approx 1 year and had only been started occasionally. Car was running after these changes but with irregular idle pulsing from about 500-1700 rpm and occasionally stalling. Fuses were all checked turned and continuity checked then, and i have repeated this week. Earth points and battery terminals taken apart cleaned reassembled. (Have also tried adding a jump lead direct from engine to battery negative to ensure good earth). All wires at coil were also cleaned when coil was changed.
I then moved onto the fuel system - changed (real dirty) fuel filter, checked both pumps were running, added a couple of gallons of super unleaded to freshen the fuel a little checked the k tronic filter which was spotlessly clean, cleaned and lubricated the throttle cable and linkages checked idle micro-switch was working. After this I had no start condition.
I don't have a vacuum gauge but have visually checked connections wherever I can see them. I have seen a post elsewhere suggesting I plug all the vacuum take off points to eliminate ancillary leaks. Note - no air con but car is an auto. Also it seemed illogical to me to disconnect vac to ezl.
Should I have started this as a new post as I have tagged onto a solved one? I was initially only curious about the source of the engine running signal.

 

[DaveDacombe]

How much did he save buying a FPR he didn't need? Enough to get it diagnosed by someone who knows what they're doing?

Sorry I wasn't totally clear, the old fpr had a couple of dodgy looking solder joints and it was replaced to eliminate this as the cause. When the car is running again I will switch back to the re-soldered original to confirm it is functional and pack the new item away as a spare or resell it. Cost of the relay wouldn't get anywhere near to minimum charge at any garage I know of anyway.
Is there a section on the site to guide people to good garage services by location when all else fails?
I Had hoped there might be some experienced home mechanics locally willing to pitch in but no joy thus far. The only guy that was helpful when I had issues on my previous mercs emigrated a few years ago. Would like to have borrowed a fuel pressure test kit but it looks like that might be going on the shopping list soon.

 

[GP801]

As you are in Hampshire have a chat to PCS in Horndean. They sort any issues on our 124 and know their stuff on older Mercedes. Price is very fair too.

 

[DaveDacombe]

As you are in Hampshire have a chat to PCS in Horndean. They sort any issues on our 124 and know their stuff on older Mercedes. Price is very fair too.

Thanks for the info - they are the only place that I do know of. Contacted them a couple of weeks ago and they had no space, waiting on price to get car transported to them should it prove necessary.
Dave

 

[optimusprime]

Dave do you have a manual ?. You said you had replaced the CPS was this fitted to the rear or to the front .Do you see this on the top of the engine [picture ] if so remove the item and clean it out with white spirits shake it or let it sit over night .After do check and make sure you fit the pipes back in the right place after you do this .2 bolts on the top and a plug on the rear to take it out .Picture to follow . It wont hurt to clean it out .

 

[optimusprime]

Picture of the idle air control valve to remove for cleaning .

 

[DaveDacombe]

Dave do you have a manual ?. You said you had replaced the CPS was this fitted to the rear or to the front .Do you see this on the top of the engine [picture ] if so remove the item and clean it out with white spirits shake it or let it sit over night .After do check and make sure you fit the pipes back in the right place after you do this .2 bolts on the top and a plug on the rear to take it out .Picture to follow . It wont hurt to clean it out .

I'm using an electronic copy of manual from a link posted on here IIRC. Mercedes Benz Model 124 - M103 Maintenance Manuals
Only one cps on this old motor right at the back behind the oilfilter.
Iddle valve very clean and instant movement when 12v across. Washed it through with carbclean anyway. Added 2 clips to ensure no leaks at the rubbers just in case.

 

[optimusprime]

Yes you do have another sensor on the front of the engine but not a CPS ,some people dont know that the one is not the same as the other just wanted to check if it was the right one -looks like it is .. ,i too have the M103 .Can you try a smoke test for leaks in the system .One more check when engine stops look at the rev counter see if it moves when you try to start the engine .And did you fit part number for part number -not close enough but the right number parts for the m103 . Bosch parts only or Beru for ht side.

 

[DaveDacombe]

Yes you do have another sensor on the front of the engine but not a CPS ,some people dont know that the one is not the same as the other just wanted to check if it was the right one -looks like it is .. ,i too have the M103 .Can you try a smoke test for leaks in the system .One more check when engine stops look at the rev counter see if it moves when you try to start the engine .And did you fit part number for part number -not close enough but the right number parts for the m103 . Bosch parts only or Beru for ht side.

Spark plugs were same as were in the car when I got it about 5yrs ago NGK BP6EFS had no problems with them on gas or LPG. Dizzy & rotor I'm pretty sure were Beru (had dodgy GSF parts before that which were rubbish) When it was running better there wasn't any tracking visible. The cps (part no. 70610200) and coil I dont know but going by the prices not bosch. All the parts came from german supplier Partex Global GmbH. The rev counter is working fine (petrol Gauge is a bit jumpy at lower levels but had the same on one of my old 190e's sticky float?). I am pretty confident the ignition components are all ok - good strong sparks when cranking and it fires up every time.
Tomorrow I will clip the voltmeter across the idle control valve to see if that is getting voltage during cranking, Cold start injector is definitely getting a pulse as this is the only fuel that seems to be getting in.
Took out no.1 fuel injector yesterday to check - rubber seal looked ok but it was dry in the plastic tube and plastic tube was tight in manifold. I am thinking a quick remove grease replace on all 6 to ensure good seal I am guessing any reasonable grease would do the job.
When engine was cranked over no fuel came out from injector nozzle - not sure if that should be the case! Will need to read up on that. Maybe try with bridged fuel relay.
Dave

 

[optimusprime]

Take the return pipe of the fuel distributor.then put in a container to catch fuel ,, then spin her over and see if fuel is returning to the fuel tank if not the problem is in the fuel distributor . Just try putting fuel in the fuel distributor via the throttle plate see if she runs . As for the fuel gauge RED X cleared my fuel gauge and cleaned gum of and let it move up and down on the rail freely in the tank .But look in to this later on with a good tank full of fuel and 1/2 bottle of red x . Replaced the injectors few weeks back in mine and i replaced everything .. The rubber seals and o rings need replacing but the carriers wont because they dont wear as a rule .Smear of silicon grease is the rubber items before refitting .

 

[DaveDacombe]

Tea break over! 1 year on and have finally got back to looking at the 300E.
Fuel flow at return pipe with fpr bridged approx 1.5 litre / minute.
Now able to check pressures in fuel system so with gauge straight onto fuel supply line pumps kick out over 9 bar (130+ psi) with fpr bridged. When power is shut off pressure drops almost immediately to around 3 bar (40 psi) then will hold at this. Checked back after 45 mins still same.
Not sure if this is a problem with accumulator. Should the non return valve hold pressure higher than 40psi? Is the fuel pressure accumulator allowing it to drop back? Cannot find a figure for the pressure the accumulator should maintain with ignition off, unless this is "fuel holding pressure " in the test data which would be ok as its just over the 2.8 bar minimum.
Moving on - pressure at cold start injection port after initial pump "priming" is not registering, with fpr bridged it will climb very slowly to around 40psi and goes no higher no matter how long its left. Pressure not dropping off when pump stops, still 40 psi 20 mins later.
This does not look good to me! M103 system pressure should be 5.3/5.5 bar (around 75 psi) If I am reading test results correct in 07.3-1603.
Just thinking out loud could this possibly be an injector leaking?

 

[optimusprime]

You wont get a correct reading with the fuel pump relay bridged ..Why did you bridge the FPR after you fitted a new one . Fuel presure is upper chamber = 5.7 bar and lower chamber = 5 bar .

 

[optimusprime]

Check fuel pump delivery in 40 seconds to a set volume of 1 litre of fuel .
You need a glass jar big enough to hold 2 litres mark the jar with a line for one litre ,. .Remove the conection from the rear of fuel regulator,then fit a hose in place to the regulator with a good clip, you dont want it to leak. Put the hose or pipe what every you have that fits the regulator in to your glass jar . Now with a good fuel pressure realay in the car switch on so the pumps work for 40 seconds ,use your mobile phone to time the operation .by keeping your eye on the time and the line in the jar .The fuel delivery to the jar should be one litre in 40 seconds . Thats the fuel delivery test .

 

[optimusprime]

Dave this free manual might be helpful to you ,,most of us w124 owners have it . Google this > Model 124 Maintenance Manual Index <

 

[DaveDacombe]

Dave this free manual might be helpful to you ,,most of us w124 owners have it . Google this > Model 124 Maintenance Manual Index <

Hi, good to see you are still on here.
That is the manual I use, which is where I got the system pressure figs from. "M103 system pressure should be 5.3/5.5 bar" (around 75 psi) If I am reading test results correct in section 07.3-1603. of Model 124 Maintenance Manual

 

[DaveDacombe]

You wont get a correct reading with the fuel pump relay bridged ..Why did you bridge the FPR after you fitted a new one . Fuel presure is upper chamber = 5.7 bar and lower chamber = 5 bar .

Have to bridge the fpr to get any build up of pressure. The initial few seconds of pumping wont increase the pressure much above the 3 bar, fuel pump running continuously (fpr bridged) same 3 bar, which I assume is maintained by the accumulator when ignition is off. 3 bar seems to be the maximum pressure my fuel system will hold even though the pumps will push out 10 bar.
Fuel delivery is about right then if I got 1.5 litre in 1 minute thats 1 litre in 40 seconds.

 

[optimusprime]

Dave you have a problem starboard with both of the pumps , or the accumulator , or fuel pump check valves . If pump is running all the time to build the .pressure up And with the original fuel relay bridged this is the wrong way to check it . See the right way is the relay will only run for a few seconds to build up this pressure and its not doing that without the bridged wire your uesing . Dave only way to do this fuel pressure test right is to unbridge the fuel pump relay..and do it again . Reading back about your dirty fuel filter ,,,was it that bad ,i am asking you because if sediment could have worked its way down from the fuel tank and in to the pumps and then on down in to injection unit.