190 Fuel Pump - How can I test it ? - Technical Info

[Jeremy Holder]

My 1988 Mercedes 190E has died on me.... the engine turns over but will not fire. I suspect it possibly the fuel pump -  no smell of petrol that occurs when a car is not firing. How can I test the pump and if that is the problem what is involved in changing it and how much is one likely to cost. Any help most welcome PLEASE.

 

[Andy]

190 Fuel Pump - How can I test it ?

Hi Jeremy

First try the fuel pump relay. Situated behind the battery. Behind the black plastic cover. You should be able to identify it by its shape.Black rectangular box.Should have printed on it,in white letters 4zyl as well as the part number.
Remove it,it may be a little stiff. On the under side you will see some numbers. The number 87&30 should be opposite each other. Bridge these across with a paper clip or wire and refit relay. If vehicle starts. Thats your problem. If not then the pump (possibly). The pump should be operating continuously. Get a genuine relay. And not a copy. I find them a little unreliable.

Good luck

Regards

Andy @ www.mercedesservicing.com

PS. Do not leave the relay in bridged out unless you want to burn the fuel pump out!!!!!!!!!!

 

[Matt Crooke]

190 Fuel Pump - How can I test it ?

One other thing, remember back to before this problem happened...when you used to turn the ignition on, you should have heard a buzz for a couple of seconds from the rear of the car, this would be the pump priming itself.

Does it still make the noise?

 

[JohnG]

190 Fuel Pump - How can I test it ?

I'm afraid I can't offer advice on testing a fuel pump. Although it must be possible, it doesn't seem to be routine.

I changed the fuel pump on my 190E about 12 months ago. The replacement cost about £160 and it is also advisable to change the fuel filter at the same time. The job itself was surprisingly fiddly, largely because the pump is supported bu flexible rubber supports with the result that it tends to move when you attempt to unfasten the pipe unions. It is important to use spanners of exactly the right size. If a spanner slips off and hits something creating a spark, that could be very bad news. It is necessary to think carefully about the fire risk and what you would do in the event of a fire. Some recommend having an extinguisher handy. You also need to think about how to collect fuel that inevitably leaks out.

John

 

[JohnG]

190 Fuel Pump - How can I test it ?

Something that has occurred to me since last writing. When you referred to 'testing'a fuel pump, I assumed that you meant checking that the pump was delivering fuel at the appropriate pressure. Checking that it is working at all is much simpler. The pump is situated under a plastic cover beneath the car on the passenger side rear. Remove the cover by undoing the four plastic nuts holding it in place. Switch on ignition etc and check that you can hear a humming sound. You can also feel the pump vibrate if you touch it when it is running. If it isn't running, it's easy enough the check the electrical supply by connecting a voltmeter across the pump terminals. Clearly, if there is no electrical supply, the problem isn't with the pump but the electrics.

John

 

[Jeremy Holder]

190 Fuel Pump - How can I test it ?

Brilliant......Thanks Andy for your advice, you were spot on with the relay test. I did as you said and it fired up straight away. So now I am in search of a relay.
Thanks to all who viewed and replied to my call for help. It is very much appreciated. - Jeremy

 

[merctonight]

Just wanted to say thanks, great advice and saved me a fortune.

I pulled out the relay and got some wd40 on it, popped it back in and my 230ce coupe fired up straight away.

Had I not seen your helpfull replies on this topic I wouldn't have even known where the relay is.

PS I am going to order a new relay!