91 Mercedes 350SDL will not start! Help Please?
 

we have had the car a few weeks and have had no problems with it at all. everything works and it starts right up and shuts down evertime like it is supposed to.
My wife was driving the car on empty (reserve light on) and she stopped at the mall, for about an hour. she went back out to come home, backed up a few feet, it died and it would not start. thinking it may be out of gas we had it towed it to the gas station across the street and filled the tank up; no change. Towed it home, and have tried swapping filters, getting new lines and new clamps. Even tried the injector purge/clean instructions i found on the internet, and it still would not start (with just the purge tank hooked up. completely bypassing the gas tank and all its lines!)

the only time it tries to start It just starts after sitting overnight for about 10 seconds and sputters and coughs to it's death. Verified all the vacuum lines are connected and the hoses are in great shape. No leaks from the bypass lines at all or any where else I can see. I bypassed the fuel thermostat thinking that would make the fuel too warm in the 107F heat. I tested the automatic primer pump and it seems to be pumping , although i connot get any reading of pressure from the pump when cranking the engine. i do get a little fuel at the injectors when i crack the lines open and crank the engine over.
Any ideas what to test next?

Sounds like you still have some air... mash the pedal as you crank it. The 603 doesnt have a manual pump so you have to turn it over several times to work the air out. You were probably close, but having opened it up again and again you were just reintroducing air.

Zack

ok. i have gotten all the lines and filters replaced. i see no bubbles anywhere in the clear lines and every time i have cracked a line i get fuel, no air bubbles.
however i have cranked, and cranked, about 50 times and still it will not start. it seems to almost start, but it sputters out in a few seconds.
i have also tried a little tiny bit of starter fluid sprayed in the vacuum hole below the intake manifold pressure sending unit. but all it did was bang pretty hard.
please note this is in arizona, and it is 107 today, so i cant imagine that the glow plugs would even be needed, but i have not tested them at all. the glow plug light does come on for about 5 seconds, and it seems to try harder to start, but doesnt really make any difference. i have also tried cycling the glow plug, 3 or 4 times, then trying to start it, but it made no difference.
also as some background the person i bought this from drove it for a while with a badly leaking turbo, so everything is full of oil in the intake system. the vehicle does not smoke since the turbo was replaced, and cleaned the initial oil out of the system. we drove it problem free for 600+ miles. then, it just died when the fuel tank was near empty, the low fuel light had just come on.
i have checked the tank screen, and also tried reversing the supply and return lines with no difference.
any suggestions? ideas?

Explain how you tested this pump. This engine has no primer pump. There is a main fuel pump down on the driver's side of the engine. The pump is between the primary and secondary filters.

BTW, don't do that. :eek:

i followed the instructions from the mercedes manual i have that tells me to measure the output of the pump into a container that i can measure. i did this and got just a little more than spec. i got 180cc/30seconds and the spec is 150cc/30seconds.
so it said i did not need to go on to test pressure.

as for the starting fluid. i used no more than 1/2 cc total. i have read it posted no less than 5 times to this forum, and many times in others to use just a tiny bit to kick the combustion up a bit.

since i have been cranking it for a week i figured it would not hurt once. i appreciate any input since this is our only car.

so what next can i do without starting fluid. :)

When you changed the secondary, did you fill it completely with fuel before securing the bolt?

yes. i also didnt tighten it all the way and cranked it until fuel started coming out of the rim of the filter and tightened the nut up.

Have you cracked the injector lines to make sure you are getting fuel to them?

What about hooking a fuel tank directly into the lift pump? This way everything is bypassed. Lift this tank pretty high to, let gravity work for you. If that doesn't start it I would start to think about internal IP issues or some sort of timing problem.

What about taking off the hard lines and cranking. A healthy IP should shoot fuel pretty high and make a bit of a mess. A not so healthy one may only trickle.

With temps that high forget about the glow plugs, even if every single one was stone dead the engine would start.

so the lift pump is what i have been calling a fuel pump?

i have read from a few places not to disconnect all of the injector lines at one time that it may mess with some timing or other and if it does that then you cannot shut it off until it blows up?
can i just crack one at a time and floor it while starting?

also with the idle control, is there any chance i could have messed up the IP by adjusting the idle by releasing the locking nut on the adjuster and turning the center bolt counter clockwise to adjust the idle speed up to about 750? it was just over 500 and if you floored it and then let all the way off it would die.
is there any way this could have caused my issue, as i did it just a few days before the car stopped starting.

thanks again for any help.

narftroz,

Its a fuel pump, it pressurizes the IP. A lift pump just lifts the fuel usually to a carburator, a non pressure operated device. The IP needs fuel pressure to push the fuel into the barrels.

U can disconnect all the injector lines at once. It won't affect the timimg and the engine won't run away. Each of the outlets of the IP should squirt fuel high enough to hit the hood. If they don't squirt, then that is your problem.

P E H

...........if the intake manifold wasn't in the way............;)

350 disaster
 

now dear old dad 20 mercedes diesels later would say you get what you deserve with a 350 worse engine mercedes ever built but thats just dad

I think he needs some help.
 

I think hes asking for some help not opinions on his motor.Have you ever run the tank that low before ? I am not sure if this applies,maybe Brian can help here,I remember a similar peoblem last week on a 300sd and it was a tank vent problem,he removed the fuel cap and was able to start the engine,again not sure if it applies to your engine,best of luck .

Read the OP issues carefully:

new info!
 

new info! i removed all the injector lines from the IP this morning and got just a dribble out of them. no squirting, no nothing. my wife was in the car and we tried it with both the pedal to the floor and not pressed at all.
i tested the fuel pump again and it jumped up and pegged my gauge immidietly. 14psi+.
is there anyway i broke the IP when i tried to adjust the idle speed manually?

by the way, i appreciate all the help. but no more "this car is the worst" blah blah blah. this is the car i have and this is the car i am going to keep, if i can get it running again. so if you arent going to help please post on another thread.

thank you.

You won't get any squirting out of the hard lines, the fuel volume is too low.

I'm not sure how long you attempted this procedure with your wife. Crank it with the hard lines off and your right foot on the floor for 15 seconds. Then repeat. Wait a minute or so and repeat. You should get a decent amount of fuel coming from all hard lines so that it makes a bit of a mess underhood.

Once you get that, then tighten all the hard lines and it will start.

You didn't break anything when you adjusted the idle speed.

AFAIK, that vehicle should not need a mechanical idle speed adjustment. It has a computer controlled idle speed and you adjust it via a dial the it right in front of the windshield, under the hood, on the driver's side. If you have it, it will have seven numbers on it..........you turn it to adjust the speed in small increments.

injector lines
 

i am confused. should i get a stream by disconnecting the fuel lines from the injectors or not?

one user says this -
"What about taking off the hard lines and cranking. A healthy IP should shoot fuel pretty high and make a bit of a mess. A not so healthy one may only trickle."

another one says this -
You won't get any squirting out of the hard lines, the fuel volume is too low.

let me do this; ask a new question.
what will i get if i loosen all the hard fuel lines at the injectors and crank the engine with the pedal to the floor?

i will also try it with the 15 second procedure that was mentioned in the last response and let you know what happens.

BTW: thank you for the idle tip, i will use that if i ever get it running again.

Paul was confusing the issue with the "shooting fuel pretty high" statement. If you removed the hard lines from the IP, you'll get the fuel to shoot directly out the top of the IP, but, it won't proceed down the hard lines with any velocity.

You'll get a decent amount of fuel to come out near the injectors if you plant your right foot on the floor when cranking. But, remember, the engine uses only about 10 ounces of fuel per minute at maximum rpm's and maximum power. At cranking speed, the fuel delivery with the rack fully open would be somewhere around 1.5 ounces per minute..........total for all six cylinders. It's not a lot of fuel.

ok, i understand. but with all the lines taken off at the injectors i get two or three drips out of them in 15 seconds of cranking with the pedal to the floor. so i get a total of 18 drops in 15 seconds. is that what i should be getting? or should there be more?
if so, and the fuel pump is working properly, where do i look next to see why the ip is not pumping enough fuel?

remember when i stated that the person before me replaced the seconday screw on filter and they left the plastic molding remains from the center seal on the screw on filter? could a small piece of this broken off and plugged something down line from the filter in the IP?
i did completely remove the secondary filter housing and blew and scrubbed it clean.
the only two lines i have not replaced are the two clear lines that go from the secondary housing to the IP. i have used a flashlight but have not seen anything foreign in the lines.

That's not enough fuel.

The reason the IP is not pumping enough fuel is because it's not getting the fuel.

There must be air in the secondary or in the lines to the IP..........but........without being in front of it..........I'm at a loss as to how it was introduced and why it won't purge.

What's the total cranking time been with your right foot on the floor and with the hard lines off the injectors?

If I can Help
 

Brian I am home today,I have my 350sd so if I can pull any line for a flow comparison let me know .Will be monitoring the post.Johnny:confused:

60 seconds cranking with them off.
15 seconds each time.
i know i get fuel at the secondary filter housing, could there be something plugged so that it is all going to the bypass and not to the IP?
could i have used the wrong fuel lines or wrong clamps when i replaced the lines? i see no bubbles in the clear fuel lines.

one other odd thing i have noticed, in the morning when it starts to start, a few days ago i opened the secondary fuel filter and it was only half full? i have not checked it in the last two days.

what should i do next??

This tells me that the secondary is not getting fuel from the fuel pump. However, the pump has sufficient pressure...........so.........you've got the possibility of a plugged line between the pump and the secondary filter.........I say "possibility" because it would be very unlikely for this to occur.

The problem with the secondary half full must be cured otherwise the engine will never start.

I don't know what you adjusted, but to adjust the idle on these cars you move the black plastic knob behind the fuse box. It is numbered 1-9 the computer controlls the idle. Sounds like you messed with the ALDA, but if it ran after this adjustment your are fine. What the ALDA does is for another thread.

The problem is with that secondary filter only being half full. Do you see air in the clear lines that attach to the IP? Sounds like an air leak.

Did you refill the filter to the top and did that change anything?

when i tested the pressure from the pump i did it by disconnecting the discharge line from the pump at the connection to the secondary filter housing and hooking my pressure gauge up.

remember i unscrewed the filter, just so it leaked, and fuel pushed out and filled the filter.

so should i continue testing pressure through the lines to the IP?
should i plug the overflow/discharge line?

Fixed!
 

thank you all for your help!
what it ended up being is one issue that was existing and one i created.
the existing condition was that there was a piece of broken plastic in the feed line to the IP. so when i took the lines off the secondary filter housing and cleaned it, i removed that piece, however when i replaced the lines i mixed up the two lines on the left. so basically i hook the return line from the IP to the input line from the secondary housing.
swapped them, bled the lines like i have done so many times over the last few days, and bang! instant start.
thank you again for all the help.

Good job.

We were out of options at this point.:o

The lack of fuel in the secondary was your clue to that debacle.

Excellant news
 

Wow ,thats good news on a holiday weekend.I think ya might wanna raise a toast to these guys,Johnny:beerchug:

Ahh everything makes sense now.

narftroz,

I admire your tenacity in finding your problem. That would have driven me crazy.

P E H.