Clamping the return line is for diagnostic purposes only. You're messing with injection system pressure if you drive the car with the return line clamped.

The lift pump is on the side of the injection pump. Follow the supply line from the tank through the small fuel filter. It might lead to a fuel thermostat then to the lift pump or directly to the lift pump. Fuel from the lift pump goes to the big fuel filter by the power steering pump.

This picture shows the lift pump. It's the device attached to the injection pump with a fuel line coming in from the top and a blue cap over the fuel supply fitting -



This picture shows the hidden side of the injection pump. The pressure control valve is the device with the fuel line leading off towards 2 o'clock. It's more or less a bolt that goes through a banjo fitting on the fuel line -



Sixto
87 300D

whunter says you can use one from a 617 - bypass valve question

Hit the wrecking yards before you spend more time diagnosing.

Sixto
87 300D

Sixto,

Great pics and explanation Thanks!!

Update:
I have to say that I did remove the clamp from the return line once it started, i have since started the car several times without problems. I have let it sit appx 30 to 45 minutes between starts and everything seems normal. I will check the lift pump tomorrow as it seems easy enough to check and I am also going to change the fuel filter even though it seems like its brand new.

I also removed the voltage regulator and noticed the carbons were worn different. One has about 7/16 of an inch and the 1/8, so I am going to replace it tomorrow if I can find it locally. I will update as soon as I get it back together.

Regards,
EzBusiness

1987 190D 2.5L 5 Cyl
Phx Az

Here is the latest update:

Today I got a new voltage regulator, i installed it and tried starting the car after having fully charged the battery. The car cranked fine but it would not start. Again I checked to see if fuel was coming out of injector line #1 and there was no fuel. I looked for any obvious signs of leaks that would cause the fuel system to loose its prime but nothing. I clamped the return line and began cranking, just when it was about to start the starter gave out. GRRRRRR I checked the started and in fact it seems to be dead. I guess I will be looking for a starter tomorrow, before I can get back to why the car is losing it's prime.

I will update again as soon as I get a new starter in.

Regards
EzBusiness

1987 190D 2.5L 5cyl
Phx, Az

PS I have never removed a starter from this type of vehicle, it looks pretty tight to remove. If anyone has any tricks to making removal easier, I would appreciate it.

Turn the front wheels from side-to-side to find a position with the greatest clearance to drop the starter.

Sixto
87 300D

Did you acquit vacuum in the fuel tank?

Sixto
87 300D

Hey Sixto,

Sorry for not responding right away, I had something unexpected happen that kept me away from working on my car until last night.

I took apart the starter and noticed two of the brushes were unwelded I guess due to excessive cranking. I took it to a starter shop and they welded them and it cranked perfect after I installed it. I tried removing the gas cap and still wouldn't start. I pinched the return line and it eventually started again. After it started I noticed a tiny amount of diesel seeping from the small braided hose going from injector #1 to the fuel filter return line. I cut the damaged line and put it back on and it started right away.

That was last night, this morning it would not start again. It is definitely a priming issue, if I start it within a couple hrs it starts right up. If i leave it over night or a long time sitting it wont start. I don't know where to go from here. I know what is happening but I don't know where to start looking for leak or ?, cause the diesel to retrace and loose it's prime. Since my car doesn't have a prime pump I don't want to kill my starter again. I would appreciate any suggestions.

Regards,
EzBusiness

1987 190D 2.5l 5cyl
Phoenix, Az

sounds like it might also be a glow plug issue. Has trouble starting when it's cold, but after a couple of hours starts with no problem?

Also, have you bled the air out of the return lines? It was the return line that was leaking that you fixed. Have you bled the return lines after you fixed it. Air in the lines could give you plenty of grief and have you jumping around from one potential problem to another. Bleed it first, see if there's an improvement . . . may not have to clamp any return lines to start after that.

Let us know how it's going.

__________________
1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

Hello Piccolovic,

Actually as far as starting is concerned, it's the opposite: it is hard to start due to air in the lines after sitting for a long time. Once it starts it re starts fine for up to 4 hrs. It's only after it sits over night that I have to pinch the return line to get it to prime itself faster and start.

I just got back from a 1 hr drive on the freeway with my baby benz and it drove great, I figured if there was any air in the lines it should be flushed out after a 1 hr drive around 70 miles/hr. I will try and start it tomorrow morning to see if it gets air in the system again.

I will give an update tomorrow.

Thanks
EzBusiness

Update of what I have done so far:

1) Car not charging.
a) R&R Voltage Regulator from salvage yard. Charging perfect now.

2) Idiot light for charging not turning on.
b) Changed light bulb still would not turn on. Turned on as soon as the Voltage Regulator was replaced and began charging normal.

3) Car would not crank.
c) R&R Starter, determined brushed needed to be welded back in place. Took it to local starter re-builder and they welded the brushes for me. Starter if working fine now.

4) Car cranked strong but would not start.
d) Checked 1st injector no fuel, determined air in the system. Pinched return line to accelerate priming system. Noticed small leak on braided line going from 1st injector to fuel filter return line and fixed it. Car started rough for a few minutes. After a few minutes car became smooth but if left more than 4 hrs is requiring to re-prime system(basically by pinching return line until it starts.

Still trying to find reason for how air is getting into the lines after it sits for more than 4hrs. I can't find any visible leaks.

Any suggestions are greatly appreciated.

PS I will update tomorrow after I try restarting after sitting all night.

Regards
EzBusiness

Have you checked the o-rings at the injector line leading from the injector ,these will leak over time .Cheap part to fix ,expensive tool to fix it.

Hello chasinthesun,

I checked the base of all injectors and no evidence of any leaks. Although i found a little diesel seeping from the top of the fuel pump. Not quite sure where its coming from. No other evidence of any leaks.

EzBusiness

General Update:

This morning when I started the car it was a little hard to start but it did start. However, for a few minutes it made a loud tapping sound from the top end of the motor. I know what a rod sounds like and this wasn't it. It seemed to come from around the head area. After a few minutes it went away and motor ran smooth again.

At least this morning I didn't have to pinch the return line to get it to start. I think it must be a very small leak at this point.

EzBusiness

1987 190D 5cyl 2,5L

Phoenix,Az

It's probably sucking air from around a loose clamp which is probably tight enough to fool you into thinking its very tight, or look for a crack in the line by the clamp . . . on either side of the fuel filter. Also, inspect the clear filter for any cracks, buildup, etc.

the last cylinder should have a little plug where if there were another cylinder behind it, would be another return hose. Remove that cap, run the engine, and try to catch as much of the fuel with a cup as you can, untill it stops spitting air. Then put the cap back on. Then you can consider the system to have been property bled for air.

__________________
1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

Hello Piccolo,

Over the last few days the car seems to start a little easier than in days past. I checked every clamp and tightened just in case they could be loose, I also purged the system by removing the last bit of hose and replacing it when I got no more bubbles. I have noticed that the car runs a little rougher than it did before I had the starting problems. It also has a strong ticking noise coming from cyl #1 when it first starts up.

What would cause a rough idle? what can cause high pitched noise from cyl #1 when car first starts? I know it is not a rod knock or crank not for sure, it's definitely at the top end of the head.

Thanks
EzBusiness