W108 280SE - Reinstalled fuel pump, ran, died, won't re-start

[Palolo]

Hi all... 71 280, M130...

Help!

I reinstalled the leaky fuel pump after reading the how-to (http://www.sl113.org/wiki/Fuel/FuelPumpRebuildLater)...I found some viton orings to seal it up. See pic of leaky pump in this post: http://www.peachparts.com/shopforum/2869962-post17.html The car was running great with the leaky pump. Grrrrr.

It no longer leaks, and it pumps gas. I put fresh, non-ethanol gas, in the tank, about 3-4 gallons.

Started car, it ran fine for about 5 mins, then bogged and died. Fuel starvation, i am guessing.

I checked return line: key on, fuel comes back from up front. Enough that it appears to be pumping well and not blocked.

What's happening is that while cranking, it wants to catch but it doesn't. Seems like it is on the brink of catching and purring at idle, but it just doesn't catch and falls back on the starter. It seems to be firing briefly, then not.

Any ideas? does it need to be bled? Is there a giant air bubble in the injection pump? Or is it somehow not delivering as much fuel as before. I didn't measure it before, but I would guess that with the leaks, less fuel was getting to the IP.

I recall my BMW doing this after I replaced its fuel pressure regulator (air got in) but I wanted to just check if I did something wrong, like perhaps install the pump vane upside down. I read and followed the write up at SL113.org about the pump, and think I got it right... just no sure why it would die, then not re-start again. Gotta be something I did. Ugh. Two steps forward, one step back.

Cheers,

Pat

Thanks!

[Palolo]

I need to move the car on Sunday as it has lost its home, and I am giving it one.

If I can't get it to start with the recharged battery cranking it through what I think is an air bubble, I am tempted to pull the pump and diagnose/futz with is in the future, but try an airtex pump just to get it started and mobile: Airtex 110-E8094 - Airtex External Electric Fuel Pumps - Overview - SummitRacing.com

That'll buy me some time to get the original pump back in action.

Spec:


Free Flow Rate 50 gph
Maximum Pressure (psi) 17 psi
Inlet Size 5/16 in.
Inlet Quantity One
Inlet Attachment Hose barb
Outlet Size 5/16 in.
Outlet Quantity One
Outlet Attachment Hose barb
Quantity Sold individually.

[JiveTurkey]

Originally Posted by Palolo

I need to move the car on Sunday as it has lost its home, and I am giving it one.

If I can't get it to start with the recharged battery cranking it through what I think is an air bubble, I am tempted to pull the pump and diagnose/futz with is in the future, but try an airtex pump just to get it started and mobile: Airtex 110-E8094 - Airtex External Electric Fuel Pumps - Overview - SummitRacing.com

That'll buy me some time to get the original pump back in action.

I checked the specs on that airtex. Will 17psi be enough fuel pressure?

[Palolo]

From the thread where I describe the leaky pump:

Originally Posted by mercmad6.3

Actually any EFi pump will work. You just need 14 Psi at 1 liter per 30 seconds volume.
The MFi pumps are a different animal to EFi units being designed to deliver volume rather than pressure . A new Mfi short pump is many hundreds of dollars so rebuilding is the best option if 100% originality is important.
The Mfi on this engine pumps it's own pressure at the engine,200 to 680 Psi .

So I was thinking it would be enough. There's obviously something not right with the pump I put back in, but as I put it in late in the day, I didn't bench test it to figure out if it was flowing adequately, nor did I have a way of checking pressure. I was roughly using 2qts/min or 30gph as the rough flow requirement needed, so that Airtex ought to work.

(Some of the other offerings were 14psi, but their flow was much higher at 100+gph.)

[mercmad6.3]

The engine will only use as much as it needs. I run a pump Efi pump on my 6.3 off a 280E . A used one at that. The engine requires the pressure and the volume as minimums,there is no maximum.
Undo the cold start valve fuel line.
If you have pressure there you have enough fuel to run the engine. No pressure,no fuel= blockage =fuel filter.
Check that the pump is below the tank level. they have to be fed fuel by gravity.
they do not suck.
Is the pump wired correctly?
they can run in reverse but will not pump.

Check the injection pump rack for movement. Un the front end of the pump(fan end of engine) ,there is round thing with a 10mm hex head.
Undo that . Under it a 6mm shaft poking out . screw a 5mm bolt into the endo that shaft and very gently move the shaft out. it should return to position by itself. if it slow or will not move,the rack is stuck and you need to get the car towed .
The pump needs a rebuild in this case.
The fact you mention the car starts(albeit low on power) says the ignition maybe close enough to run but the engine is running on the cold run device in the pump then cutting out once the engine reaches temp and the pump leans the mixture out.

[Palolo]

Hmmmm. Still stumped. Here's the latest:

Sat night, I charged the battery, which had run down a bit from cranking (when I thought I had to crank out an air bubble or to prime it).

Today, I brought back the battery, plus more fuel. There was a concern that the pump was drawing from the tank pot and running it dry.

I also took out the three-way hoses on the fuel return and went to a direct-to-tank return, blocking off the fuel pump "return input" with a spare idle adjustment screw from my Fiat 500L. Grazie!

After adding 5 gals to the 3 that were in the tank, I got it to catch. Yay! It ran for about 5 of the longest seconds. Then died and would not start again. So off for more gas I went. Three more times adding 2.5 gals at a time. The gas station people were looking at me funny.

After the 8 or so gallons were added, the car started and caught, and settled down at idle! Yeeee hah!! I decided to pack up my tools, moved my other car out of the way, and then...it died!

I was able to restart it, but only after (yes, I know, I shouldn't have) stepping on the gas. It caught, but was running rough (missing) and I could hear the odd pop-pop-pop backfire through the air cleaner. After some backfires, with the gas feathered to keep it running, it would die.

Sometimes would restart (but only with gas pedal half down) sometimes not.

I guess the fuel level is over the tank pot rim, since there is now 3/4 tank, so supply to the pump should be good.

Return is feeding straight back to the tank.

Cold start line had gas at the plenum fitting.

I was thinking maybe vapor lock in the fuel injection hard lines. They were hot. There's a water hose that crosses the engine from the throttle body, and heats up part of the IP. I thought maybe that was heating up the fuel too.

I am amazed that all this happened after I tried to sort out that leaky pump. When it was oozing gas like a waterfall, the car ran just great. I will try to source an aftermarket pump to see if it is indeed just the pump that has changed in the equation. Timing hasn't moved, nothing else adjusted or messed with, gas is over the flower pot rim, so... I am thinking it must be the pump.

Thanks all who have chimed in and PM'd. Your insights and ideas have been helpful, and validating my own logic.

Cheers,

Pat.

PS: hopefully some good news soon! Ever the optimist.

[JiveTurkey]

Originally Posted by Palolo

Hmmmm. Still stumped. Here's the latest:

Sat night, I charged the battery, which had run down a bit from cranking (when I thought I had to crank out an air bubble or to prime it).

Today, I brought back the battery, plus more fuel. There was a concern that the pump was drawing from the tank pot and running it dry.

I also took out the three-way hoses on the fuel return and went to a direct-to-tank return, blocking off the fuel pump "return input" with a spare idle adjustment screw from my Fiat 500L. Grazie!

After adding 5 gals to the 3 that were in the tank, I got it to catch. Yay! It ran for about 5 of the longest seconds. Then died and would not start again. So off for more gas I went. Three more times adding 2.5 gals at a time. The gas station people were looking at me funny.

After the 8 or so gallons were added, the car started and caught, and settled down at idle! Yeeee hah!! I decided to pack up my tools, moved my other car out of the way, and then...it died!

I was able to restart it, but only after (yes, I know, I shouldn't have) stepping on the gas. It caught, but was running rough (missing) and I could hear the odd pop-pop-pop backfire through the air cleaner. After some backfires, with the gas feathered to keep it running, it would die.

Sometimes would restart (but only with gas pedal half down) sometimes not.

I guess the fuel level is over the tank pot rim, since there is now 3/4 tank, so supply to the pump should be good.

Return is feeding straight back to the tank.

Cold start line had gas at the plenum fitting.

I was thinking maybe vapor lock in the fuel injection hard lines. They were hot. There's a water hose that crosses the engine from the throttle body, and heats up part of the IP. I thought maybe that was heating up the fuel too.

I am amazed that all this happened after I tried to sort out that leaky pump. When it was oozing gas like a waterfall, the car ran just great. I will try to source an aftermarket pump to see if it is indeed just the pump that has changed in the equation. Timing hasn't moved, nothing else adjusted or messed with, gas is over the flower pot rim, so... I am thinking it must be the pump.

Thanks all who have chimed in and PM'd. Your insights and ideas have been helpful, and validating my own logic.

Cheers,

Pat.

PS: hopefully some good news soon! Ever the optimist.

I know how you feel. Wilmas fuel pump and fuel pump relay died in march of last year. I only recently have gotten the last needed part (d jet relay) but she's still not running.

[sjefke]

Sounds like you have starvation. Here are a few things you may want to check/do:

1 - Add more gas. I chased a problem in my car over a year ago and threw up my hands only to realize that the gas was bad. You may have water in the tank and it's mixing with the fuel. I had gas coming out up front at my injector rail (at least it smelled like gas), but it was bad stuff. After I added 4 gallons, car sputtered and came back to life. Gas gauge should show at least quarter full.

2 - Check the flow up front AFTER the fuel filter. Something may have loosened itself and clogged the fuel filter. Change fuel filter.

3 - I don't know MFI system pumps, but check whether the pump is running when the car is on contact. Keep it on contact and see how long the pump stays on. Typically, pump either works or doesn't, but it may run intermittently if it has bad ground or plus. Clean off the terminal connections to fuel pump.

4 - Check the fuse/relay connection. If this car also has a master relay like d-jet cars, power to the pump may be cut off if master relay has bad connection with battery.

5 - Also, I put a pump back together two weeks ago and it did not want to run reassembled. I loosened the screws, and the thing ran again. Retightened it in a cross pattern bit by bit and it was fine (now under my car). I figured I had accidentally squeezed a roller and it jammed the motor. So loosen your screws a bit and see what happens (let it leak a bit if needed).

6 - Where the pump rollers in good shape and was there any rubber debris in the ports?

Good luck,

Bert

[michaelbiegas]

My 280se acted the same way. It turned out that the points were barley opening, reset gap and ran like a champ. Could be the fuel problem is solved. I hve sometimes become blinded and quit looking for basics like spark plugs ect.. Maybe the pump is now fine, takes only a couple minutes to pull a plug and check points.
Mike

[Palolo]

Thanks Michael.

I pulled a plug and grounded it on top of the cam cover so I could see it while turning the key from inside. I saw spark.

This car also has an "Allison" (Crane?) ignition module attached, which I believe does away with the points. I haven't popped open the distributor yet to verify, but will take a look today.

Pretty sure my issue is with fuel volume and constant supply. I found a suggested Carter fuel pump locally (new) for $215, so I may pick that up and hope it solves the issue. If not, I have a spare fuel pump.

Thanks much for all the suggestions!

[Palolo]

Ok... Maybe playing hard to get was all that was needed.

The car was under a hard deadline to vacate the carport by Thursday, as the lease was up, and new tenants were moving in.

So I went back today with a wish, a prayer and a tow strap. And my 4 year old copilot. Not sure if he would drive the tow car or the Benz, but we would cross that bridge when we got to it.

I had a new fuel filter with me. And I thought I could just change it there, you know, with a pair of 13mm wrenches or at most a socket on the bottom of the canister. But nooooo... Looks like some special gizmo is needed. No matter, scratch that.

I pulled the kid's car seat out of the working car (knock on fake-trim-wood) and positioned him in the back of the 280. Told him that we would see if the car starts, and if it does--big if--then we were going to try to make it to an uncle's house a few blocks away, maybe a mile at most. I was wondering/calculating how long the car ran the other day before dying, and how far that would get me at partial throttle. Didn't want to give it too much gas and go quicker but risk starvation short of the intended driveway destination.

Car started, first go, and settled at a nice burbly MB M130 idle. Humming. The gods are looking down on us!

Popped it in reverse without disconnecting the shifter linkage. Rolled out of the carport, and engaged drive... We are rolling! Semi-rolled through a stop sign--easy touch on both pedals-- and then up over a hill. Down the backside to the new driveway.

We made it.

I am one happy Benz owner thanks to all of you. Or from my wife's perspective: "no thanks to y'all" as now I have a fantabulous project.

[Mike D]

Yeah, women are funny that way. They go all "gooey-eyed" when they have a child, which you spend the next 18-25 years cleaning, feeding, chasing, educating, and supporting to the tune of a gadzillion dollars but if their guy gets a car, well, we're just wasting our time, money and effort which we should be spending on her!

As the saying goes, "Men are from Mars, women are from Venus, get over it!"

[Palolo]

Sheesh... I thought I had the fuel pump leak licked, but gosh darnit, it is gushing again.

Hmmmm.

Anyone know of a short pump seal kit? I guess there are other seals to fix.

Anyway, it is home, and I have more leisure to pull it off and seal it up.

Thanks!

Pat

[sjefke]

Find out first were it is leaking. Wipe it dry and check where the leak starts. My bet is that there are four seals in your pump, like in mine. 1 -Big o-ring between housing and roller body (probably not leaking), 2 - triangular routed o-ring in roller body, 3 - another rubber o-ring or so between roller body and outlet body, and 4 - a small o-ring around the terminal block. Rings 2 and 3 are easy to get to. 1 and 4 are a pain, but the terminal ring was the one that failed on my car.

I had one pump with a broken o-ring between roller body and outlet body, and applied liquid copper gasket sealant. That pump has not leaked.

It looks like Bosch used the same motor and roller assembly and just changed the outlet body to get the variety needed, so you may just have to find some o-rings to fit. Post some pics.

Good luck,

Bert