I'm on the run so this will be scattered / a bit incomplete.

I have lots of knowledge about engines / mechanical / electronic things in general. I do not have specific info for this particular motor however it follows general design practice. Having to do this remotely is more difficult.


The hand primer will get stiff if an external pump is used. ( Line pressure is not higher. ) The stock pump would be capable of over 50 PSI is dead headed. I'd run the engine with the tank pump removed. You will also need a 2x coarser pickup screen. MB cars that could have come with gas or diesel had different screens. However, even with a fine gas screen the engine should start.

Some diesel injection pumps ( Like the tried and true Stanadyne rotary and I think Bosch VE ) have an internal system to control timing based on case pressure. I don't know if your pump has such a device.

There is a check valve in the Jeep pump and some pumps are positive displacement making it difficult / impossible to suck fuel through them.

I'd run the engine from a can and bypass all of the Jeeps system for now.



I see you are following the AR " If there isn't a Paint drawing, it didn't happen. " What was your old system like? I'm wondering if you are overpressurizing the injector pumps case and that is somehow moving the fuel rack to shutoff. Again, use the injection pump as stock from a can and see what happens.

Let me make something ABUNDANTLY clear: I am not panicking And I am not swapping pumps left and right. I have tried everything I know of doing and everything I have done in the past on diesel engines to no avail.

I have tried running it in stock configuration. The last method I used was with the manual hand pump intact and the fuel supply and return from a five gallon can with all factory lines connected to the stock fuel filter housing. The engine would start and run for a few seconds and shut off in this configuration. I attempted bypassing the hand primer pump with the stock fuel pump from the jeep cherokee. Same situation. I did this on both pumps. So you see, I am not panicking and throwing parts around left and right. I have been very calculated with how I have gone about it and I am open to all suggestions.

My initial findings and emails back and forth with Goran made me believe there could possibly be something wrong with the DM pump. The reason I swapped back on the original pump is 1.) it ran the motor previously on a skid at the shop and 2.) if it runs again this points to an issue with the DM pump. Since swapping the IP's lead to the same issue I am believing there is something currently either inhibiting me from properly bleeding air from the system or with the electronic fuel pump it is too much pressure for the IP. I am posing questions here trying to find solutions as I am positive someone else will do this swap and have similar issues.

I have tried running it from a can feeding the supply and return. The ONLY thing I have not done is bypass the filter housing. For obvious reasons I would rather not pump unfiltered fuel into my IP. The filter housing is the only piece of the puzzle that I have not addressed. I noticed when priming the system it tries pushing fuel UP the return lines to the injectors. I know there is a small pin hole in the filter housing but It seems odd that fuel would be pushing up the returns to the injectors. Maybe this is normal. Thoughts?

Perhaps we're getting somewhere. When priming the system, you should be getting fuel running back to your temporary bucket through the return line. If you've pumped the air out, you should be getting a squirt every time you pump the primer handle. There should be no pressure in the return part of the system, any overflow from the pump, injectors, or filter housing should be coming out the return line.

How do you currently have the filter plumbed? Do you have any banjo bolts with check valves in them somewhere (you had it wrong before, only reason for asking). The only special bolt in the system is on the backside of the IP. All the rest of the banjo bolts are "normal" with no spring/ball bearing.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

" I noticed when priming the system it tries pushing fuel UP the return lines to the injectors."

This sounds like a serious problem, find out why it's doing it and correct it, see what happens next .

Many are watching your struggles here and hoping to learn .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Did you ever verify that you were getting fuel out of the return line when the engine was running?

__________________
617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Currently the only fitting with a valve is the one on the block side of the pump near the cylinder five outlet. All other banjos are plain old standard banjo fittings. I learned that mistake during the swap from the first motor to the second motor LOL.

Yeah I am hoping to figure that out as well. This happens regardless of what pump I use. Even the hand pump will pulse fuel up the return lines towards the injectors. That seems wrong to me but I am honestly not sure.

I cant keep the engine running long enough. I know I am getting fuel from the return when using the hand primer or the electric pump. Not sure about when its running. I have a friend helping me out tonight so we will see if we learn anything else.

I am headed to the hardware store shortly and I will be buying all new return lines for the injectors, new O rings for the center bolt, and a new fuel filter.

I think my in tank fuel pump is a problem for sure as well. I believe it puts out too much flow and too much pressure. I am going to go back to the fuel tank test and put the return and supply into the fuel can next to the jeep, make the couple changes and try to see if that helps at all.

Does anyone know if it is possible to damage a MW pump if the supply fuel pressure is too high?

I doubt it, they're pretty stout. Plus your XJ puts out what, 75psi max?

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

I don't think it's possible to over-pressurize the pump with the electric lift pump. Any excess pressure will be bled off through the overflow valve on the back of the IP. Even if you did somehow dead-head it, there's not going to be anything damaged, it's just metal pistons pumping in metal sleeves.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

The XJ fuel pump will put out around 30-50 PSI from what my manual says. It definitely MOVES fuel fast through the lines when its powered up. I was debating on getting an in line regulator to knock that pressure down but honestly I think I am going to eliminate the factory fuel pump and just use the lift pump on the side of the mercedes IP

IIRC, the factory regulator is in tank, but it's just a basic spring ball setup or something simple like that.

Last XJ tank I had out it looked super easy to convert to dip tube.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment