W124 300-24 strangeness after complete renewal of fuel pump pack.

[ray_hennig]

This copied from another forum as I need all the input I can get!

This for the M104.980 engine.

Whining fuel pump and occasional cut-out (but not stall, except for once) prompted me to suspect a fuel pump on the way out. Otherwise, car was starting and running like new. In fact, several people commented on the new (half a million Kms?) car. So we decided to renew everything from tank strainer to the pipe that takes fuel up front.

Pierburg pumps, Bosch accumulator, MB filter and all new hoses from MB.




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After what you see here, we aligned all the hoses properly, switched ignition on and looked for leaks. None.

Then, engine on - a few attempts to start - then smooth running. No leaks.

So, job done.

BUT ....

From cold, the car needs 2 attempts to start. On the second attempt, it's exactly as previously, instantaneous.

Thereafter, performance as new. If anything, slightly quicker off the line than with old pumps.

What could be going on here?

Also, last year, I installed a new fuel pressure regulator and that restored the instant start. So, everything is new from tank to fuel distributor.

And the entire metering head/fuel distributor & injectors are all newer than 2017, 80K Kms ago.

Baffled!

Any brainy boys with some ideas?

As an aside, we renewed the tank strainer as we had one in stock. But this is the old one, 33 years old, before I cleaned it up:

RayH

 

[carat 3.6]

Cold start injector working? EHA out of adjustment?

 

[ray_hennig]

Cold start injector working? EHA out of adjustment?

Makes no sense. All was 100% perfect, aside from a failing pump. Now we have new pumps and all associated stuff and cold start require 2 tries.

Just remembered, we put in a new cold start injector a few months ago just because one was in stock. All working perfectly before the fuel pump pach change.

Thanks for responding.

R

 

[Dodipops]

You can over tighten the bolt/screw in the frame that mounts the pump/filter, which in turn restricts the pump from turning properly, maybe worth slackening it back a touch??

 

[grober]

POOR CONTACTS ON THE IGNITION SWITCH WHICH SENDS THE INITIAL START SIGNAL TO THE FUEL PUMP TO PRESSURISE THE SYSTEM BEFORE TURNING THE ENGINE OVER-THEN SWITCHING TO A ENGINE RUNNING SIGNAL [ORIGIN VARIES] CHECK THAT THE FUEL PUMP RELAY IS GETTING THESE ELECTRICAL SIGNALS EVERY TIME RELIABLY?
ON FIRST COLD START DO YOU HEAR THE PUMPS "PRIMING" THE SYSTEM FOR A
FEW SECONDS ON IGNITION SWIITCH ON-BEFORE TURNING THE ENGINE OVER. PEOPLE OFTEN BLAME THE FUEL PUMP RELAY - A COMMON CAUSE TRUE BUT EVEN A GOOD FPR NEEDS RELIABLE ELECTRICAL SIGNALS TO OPERATE? sorry for the caps!

 

[sautah]

I had a simialr cold start issue on a non MB car....... Leaking injector would drip fuel in to the engine overnight, emptying the fuel rail and then allowing air into the system.

First attempt to start was a fail but the second or third would work as the air had been purged.

 

[optimusprime]

I have the same problem , only on a M103 engine after new pumps were fitted .Once its been running it will start on the button , but after a few days it gets a little harder each day to get it up and running . I have a new fuel flter and accumulator ready to go on . If that wont get it to work first turn of the key, then i recon fuel is leaking down through the seal on the plunger in the fuel distributor..There is never enough fuel to do a first start after the car is parked up .

 

[ray_hennig]

Thanks all.

But the strange thing is that everything was working perfectly before the pump pack change. And I mean everything.

The sole resaon for the change was an occasional pump noise that signalled imminent failure.

Before the change, starts were instantaneous and running (aside from the cut-outs when the pump was whining) was absolutely 100%, with no issues whatsoever.

All your suggestions are relevant in general but I cannot see their relevance in my case as the entire system in now new, including the ignition switch.

Still baffled but grateful for your interest.

Still thinking.

RayH

 

[optimusprime]

Did you include your vin numbrer when you purchase the fuel pumps ? And the pumps dont look like original Mercedes .

 

[ray_hennig]

Did you include your vin numbrer when you purchase the fuel pumps ?

Yes. It came up with the MB number. Then I cross-referred to Bosch and Peirburg equivalents. The Pierburgs are shrouded with a rubber sleeve. The Bosch ones are not. The specification is the same with 6+ Bar pressure.

Pretty certain of compatibility.

My son was here today with more reliable hearing than mine. I switched on the ignition and he confirmed that the pumps were doing their usual "priming" before start up. Then we churned for about 1.5 seconds and it started. Just not immediate like before.

And performance, once started, is 100%.

R

 

[optimusprime]

I messaged Bosch themselves over in Germany to make sure mine were the right ones .I had to fit my own protective rubber sleeves Bosch filters and pumps for some reason now dont come with them, even had to buy filtter copper washers none in the box .

 

[ray_hennig]

I messaged Bosch themselves over in Germany to make sure mine were the right ones .I had to fit my own protective rubber sleeves Bosch filters and pumps for some reason now dont come with them, even had to buy filtter copper washers none in the box .

I saw some posts about leaking Bosch pumps so that's why we tried Pierburg. No reason to assume they're not working as they should, I think???

More as it happens.

One suggestion is that some crap got into the feed to the front and has been lodged in the fuel distributor screen. I have a couple of old ones but I've ordered a new one. Should be here by next weekend.

More as it happens.

R

 

[sautah]

How about disconnecting the fuel supply to the rail. Then when you turn the car on / prime the system you should see fuel being pumped.

Or of course with a diagnostic tool you would be able to see the fuel rail pressure etc.

 

[carat 3.6]

Thanks all.

But the strange thing is that everything was working perfectly before the pump pack change. And I mean everything.

The sole resaon for the change was an occasional pump noise that signalled imminent failure.

Before the change, starts were instantaneous and running (aside from the cut-outs when the pump was whining) was absolutely 100%, with no issues whatsoever.

All your suggestions are relevant in general but I cannot see their relevance in my case as the entire system in now new, including the ignition switch.

Still baffled but grateful for your interest.

Still thinking.

RayH

I think you need to start looking at fuel pressure if you want to chase this further, perhaps the old Bosch pumps were able to flow more thereby creating more pressure in the system?

 

[sautah]

Put the old stuff back in. Swap for each new component at a time ….. elimination

 

[optimusprime]

Ray can you remember the part number for the new pumps ?

 

[ray_hennig]

Ray can you remember the part number for the new pumps ?

Yes,

A0030915301, Older alternative: A0020918801, Pierburg 7.21659.53.0

R

 

[optimusprime]

Should be fine Ray . Maybe now you have a good fuel presure could it be leaking in past the Metering head past the plunger valve seal .My post 7 i told you about my new pumps .And hard start the longer i let it sit. .Well we pulled the accumulator of and it holds vacuum on the tester so i can rull that out now ..And next thing is if the problem sis till with me after a few days of sitting on the drive ,Then i think i have plunger leaking down like i said ..fuel is not going rearward so leak down in to the throttle plate area is a possability .

 

[ray_hennig]

Should be fine Ray . Maybe now you have a good fuel presure could it be leaking in past the Metering head past the plunger valve seal .My post 7 i told you about my new pumps .And hard start the longer i let it sit. .Well we pulled the accumulator of and it holds vacuum on the tester so i can rull that out now ..And next thing is if the problem sis till with me after a few days of sitting on the drive ,Then i think i have plunger leaking down like i said ..fuel is not going rearward so leak down in to the throttle plate area is a possability .

My thoughts too.

The next step is to install the new fuel distributor filter on order now. This was suggested by a chap on a US board as a cheap and simple job.

The point he made to me is that the filter is not included with the distributor so when my new one went in, it's likely that the original 33 year old one was used.

After that, I'll need to measure fuel pressures but I don't have the gauge to do that.

As said, the pump pack installation was text book stuff. Yes, a faulty new component can't be ruled out but I'm being optimistic at the moment.

And the fact that perfomance is faultless once the engine's started.

The current logic is that some crap might have found its way to the filter and that is the last straw.

Watch this space!

R

 

[Pontoneer]

How about disconnecting the fuel supply to the rail. Then when you turn the car on / prime the system you should see fuel being pumped.

Or of course with a diagnostic tool you would be able to see the fuel rail pressure etc.

On a W124 you are looking at blink codes