michaelwoosley

A few days ago, I installed a new Beck Arnley fuel pump on my friends CLK430 car. A couple months ago, I replaced the fuel filter as a part of routine maintenance.

The only reason I replaced the fuel pump was because we are trying to eliminate a particular problem... his engine takes a prolonged time to start (about 8 seconds or more). This statement is true when it has sat for a prolonged period of time (an hour or more or overnight), otherwise, the engine generally starts quickly. The only reliable data we could find lead us to a fuel pump replacement. Unfortunately, the replacement pump did nothing to help correct the problem.

For clarification purposes... Position 1 = Key inserted only, Position 2 = first click, power to instrument panel. Position 3 = power to fuel pump. Position 4 = Start position
Our diagnosis with the fuel pump pressure tester goes as follows: key on/key Pos 2 = 0psi,
key on/key Pos 3 = 57psi
Then we turn the key off to position one... key off/key Pos 1 = 0 psi (should the pressure of stayed at 57 or was it normal for it to fall back to 0?)
Now we started to the vehicle... key on/key Pos 2 = 0 psi
key on/key Pos 3 = 57psi
key on/key Pos 4 = 57psi (key returned naturally to position 4)
Shutdown the engine.... key off/key Pos 1 = 0 psi (again, my thought is that the pressure should have held, or am I wrong?)

Any thoughts on this please. The fuel pump is less than a week old and a major manufacturer.

Here is a video of the pressure and the drop that I'm talking about

What should I be seeing? Is what I'm seeing correct or should the fuel pressure be holding with the key off, meaning I have a faulty fuel pump or potentially something else faulty?

Thanks.

cindyclk

my quick reply would be that the pump is not compatible with car.

michaelwoosley

cindyclk, I won't dismiss your thought as a potential cause of my problem. Rockauto does a really good job with their eCcatalog in regards to identifying "which" pump fits a specific automotive configuration. I have emailed tech support at Beck Arnley, asking them to provide specs on the pump to include specs on car... 2001 Mercedes Benz CLK430. I asked them if the pump had a back pressure valve built in; that would keep the pressure from bleeding off.
Wish me luck.
Thanks.

Serndipity

A good amount of fuel pressure should remain whenever the vehicle has been parked.

The fuel pressure valve is integrated into the fuel filter.

You'll find the functional diagram of the fuel system, showing the various components and direction of fuel flow in this thread .

cindyclk

this might help...

https://mercedessource.com/store/102...mp-check-valve

michaelwoosley

Serndipity, thanks for your reply and for the link to the fuel system diagram. I agree that there should be a provision to keep pressure at the fuel rail to aid in starting the engine quickly... I thought my diagnostic readings told a pretty good story, haha. I have ordered a new fuel pump and once it comes in, I believe your link to the fuel system diagram will come in very handy in ascertaining the accuracy of the fuel line connections.

Have a wonderful day.

michaelwoosley

Thanks cindyclk. Very good to know information for other customers, just not for my current one. I certainly do keep your recommendations near by

michaelwoosley

Serndipity, I did replace the fuel filter and it did solve the fuel pressure problem. Thanks a million for the great advice!!
I will need to post ANOTHER thread however because it DID NOT fix my absolute original problem... a PROLONGED 5+ second start sequence. Initially, that is what lead me to the thought that fuel was draining away from the fuel rail (loss of pressure), which was confirmed. The diagnostics confirmed a pressure drop with the ignition key off and no pump activity. Your suggestion to replace the fuel filter validated the theory of the pressure regulation within the filter which allowed the pressure to maintain once replaced.

I'll leave this post here with hopes that some will chime in with a possible solution while posting a new thread regarding prolonged start cycles.

Thanks again Serndipity..