Mercedes W124 M103 260E

[optimusprime]

I am in this hole right now , Car failed to start other than a hum from the fuel pumps .I have never had a noise like it so i thought fuel pumps gone. ,. Both pumps changed and right away engine started .Packed tools away jub well done so i thought ..So just now i go out to try the car,, and yes you guesed it it wont start ...only with starter fuid ,,removed ovp and fuel pump relays a put in a good used ones ..Still no start .So pulled the feed for the fuel injection distributor and put the pipe in to a container . Switched car on spun it over no fuel came out of the feed pipe .So problem must be in the rear end with the pump set up .I was thinking fuel filter but it is not that old .Any ideas ?

 

[optimusprime]

Bump need help with this one , i have done all i can think of but stull no fuel as pumps are not working ,,,will get under Friday and take another look .is there a joint under in the engine compartment . So i can check the power to the pumps

 

[Bellow]

Don't overlook the earths.

 

[optimusprime]

Bellow will the earth point be close by the pumps ?

 

[carat 3.6]

Remove the fuse box cover and move the fuse and relay panels to one side. Buried in the wiring under there is a black single pin round plug, that is the live feed to the pumps so you can test if your getting power to them.

 

[Bellow]

Bellow will the earth point be close by the pumps ?

I don't know but one of the following will prevail.
Either the pump is earthed via its hard mounting to the chassis (or with a jump lead - esp if rubber mounted) or, the electrical connector will have another terminal alongside the power-in one which connects to the loom and somewhere further upstream the loom has an earth point.
In the latter case, check for continuity (best done with a test lamp that 'loads' the wire but a multi-meter test is better than no test) at that connector terminal and some known to be good earth point. Or - if physically possible - try a jumper lead from the motor's earth connector or body to earth and see if that lets the pump run.

 

[optimusprime]

Looking a lot like an intermittent fault . Just been out and jumped the fpr at 7 and 8 still no start .Put relay back in, and pumped it with srarter fluid .It started up and i gave it gas and it is still running.. So now i am where i was after new pumps were fitted ... now the fuel accumulator or is my next swap outif it womnt start after its cooled down ,,,keep watching this space ..

 

[optimusprime]

carat 3.6 I can see on on the passengerrs side just off the battery, if i picture it could you tell if its the test point you talk about​

 

[optimusprime]

Thank you Bellow i will get the mobile mechanic to test earth points on the pump cradle ..wish i could get under and give it the works .

 

[Bellow]

Looking a lot like an intermittent fault . Just been out and jumped the fpr at 7 and 8 still no start .Put relay back in, and pumped it with srarter fluid .It started up and i gave it gas and it is still running..

I'm wondering if the current to the pump is higher with the engine not yet running (full prime pressure) vs when engine is running (fuel flow lowering pressure) and if so is catching out a poor connection somewhere on either feed or earths.

Smart fortwos could have transmission problems often as not due to broken wires. The wires were OK at lower currents but not at higher when they'd be overwhelmed. A diagnosis for this was when the problem occurred only on the 3rd to 4th and 4th to 3rd shifts. Those shifts required that two selector forks were moved simultaneously (other shifts moved only one) and the additional load on the motor and consequently higher current draw would push the broken wire to failure. This type of scenario is where continuity testing with an MM is inadequate. One strand in an otherwise broken wire will give a good reading on an MM but fail at its intended task with a higher current.

 

[carat 3.6]

carat 3.6 I can see on on the passengerrs side just off the battery, if i picture it could you tell if its the test point you talk about​

It's drivers side, under the fuseboard.

 

[carat 3.6]

My bet is a dodgy contact on the block that the fuel pump relay pushes into, unless it has an old alarm system tucked away behind the dashboard?

 

[carat 3.6]

I cant remember exactly where the pump earth point is, but I think it is visible if you remove the rear seat base. I seem to think it was a ring terminal to a stud on the car body, possibly under the central locking pump.

 

[optimusprime]

Thanks to every member that came to my help .All the hints and tip i will keep in mind by keeping this post in my favorites menue .Car engine has been running out side for 30 mins and as yet no problem ,so put air box on and i closed it down until engine was cold .Next start went fine . So i cancelled the call from the mobile mechanic ..i do know a fair bit about these W124s but without the ability to get out and get under to look at things then i am helpless..But whats strange ,i gave the mechanic a print out of what he needed to do to replace both the pumps .But i know he never opened the gas cap to let the vacuum out ..could that be the cause of the no run situation after it started up once .Dont think he listened to me i said clamp off the feed hose ..Reply was i will plug it with a bolt ,,,haha bolt came out and soaked his teeshirt ...If it car was running at the time i would have take it to my local garage, but it was a dead duck on the drive and i had no option but to go mobile.mechanic .Lets hope it starts Saturday lol .

 

[Bellow]

If the problem resurfaces....
I appreciate your difficulty working on the car but often when dealing with a suspected broken wire it's worth (with the circuit live) tracing the length of the wire wiggling and bending as you do (the wire - not you!). Sometimes contact will be made and the location of the failure can be established. Other times it will kill it stone dead breaking what continuity there was - which is a result of sorts also.

 

[optimusprime]

Thank you Bellow i will rember what you said .And next time it refuses i will call the mechanic back and tell him just what you said in the above post .

 

[Bellow]

Coincidentally, this >> RockAuto June Newsletter appeared today. There's a piece about fuel pumps that explains more thoroughly some of the things I touched on earlier.

 

[optimusprime]

Bellow i took a screen shot of the information section by section, that information is now in my folder so i can read later on, and also pass a printout to the mechanic ..Also joind Rockauto to have their emails .Thanks a lot .

 

[optimusprime]

Saterday the mobile thingimabob never cam ..Car started right up and i let it run for 30 mins it never stoped . As a test i let the car sit for 4 days its now Tuesday and i am about to give it a try .....back in a moment ...back--- she started right up ..So now its take the car out on the road .. got a recovery guy lined up just in case it goes tits up haha

 

[optimusprime]

Yesterday- Tuesday i went to stert the car up after 3 days ,and it started right away stumbled, and stopped.But started again right away .. Have a new fuel fiter on its way, it should come to-day. I will get that fitted along with the original accumulator i keep after i fitted a new one 5 years back at the same time the filter was fitted .Get earths checked at the same time . Keep looking in for further news .Mobile thingamabob will be here Thursday to do it.