priming pump question
 

Hey All,
Love the site. I've just bought my first benz 3 months ago. it's an '83 240D and am learning all about the world of diesel. This site has taught me a lot...but alas not enough.
Here's my problem. I got in my car after it had sat for about 3 hours. Started up with no problem and pulled onto the street. After about a minute, it had no power or throttle reponse. ran this way for about 30 seconds then died. would not restart. starter is fine, throttle linkage is fine.
the car is new to me and the fuel gauge said i had maybe a little less than an 1/8th of a tank. Did i run out of fuel it thought? well, i got about a gallon and a half of diesel into the tank and then look at my priming pump. i've never used it before. so...i loosened the large bolt on top of my fuel filter and tried to use the pump. here's my question. i turned the pumphandle counter clockwise a little and pushed on the pump. i don't know if it was working. i heard no air hissing. i did see some diesel leaking out of the rim of my screw on fuel filter. the pump handle only traveled about an inch. is that correct or did i not get it open enough? i tried locking it by turning it clock wise but go no discernable locking, or stopping of it turning.
what is the normal travel of the the primer pump? does it click when it locks or unlocks? do you think i was actually pumping fuel with it?
the car still doesn't start. i'm hoping i just didn't get the system primed right and that i don't have a failed injection pump. does anyone have any suggestions?

thanks,

Dale

priming pump
 

I have a 220d, not a 240d, but I assume the priming pump is similar. First make sure you have adequate fuel in the tank. When the pump is in normal locked position it is turned fully clock-wise until it's well seated. Turn CCW to unlock; it should take a number of turns. On the 220d the full travel of the pump is more than an inch. You don't need to turn the large nut on the fuel filter; just unscrew the bleeder screw a little. Pump til no air is coming from around the bleeder, then screw the pump knob down all the way until it is seated. If you ran the car out of fuel it is going to take a lot of pumping. However, before bleeding the filter you need to bleed the IP. If it's similar to the 220d there will be a bleeder screw on top of the pump. You need to bleed on the downstroke, then tighten, pull pump handle out again and then open the IP bleeder and bleed on the downstroke to avoid sucking air in and out of the IP.

Thanks for the reply Ralph,
I got out and did some more work on it in daylight, and found a leaking fuel return line. i assume that's what it is, it is braid covered hose that goes down the line connecting each injector together and then goes back to the fuel filter area. would this have caused any problems? i know diesel is a high pressure system and i assume a closed system. would that have caused problems? anyway, it didn't solve my problem, although the car does seem to want to almost start. i need to let the battery rest now.
i will look at the ip and see if it has a bleeder. i still cant's get the pump to lock though. i must have spun it clockwise a dozen times and it just keeps spinning. could this be a problem or source of leak into the system?
I appreciate anyone's time and 2 cents. I'm definetely fast becoming an enthusiast of this car and really enjoy this forum,

dale

The old style bleeder pump handle has to be in the full down position to be able to tighten it for driving. When in the up position it will spin forever.

finally running
 

Phew! she started yersterday after a LOT of turning the starter. first it just seemed like it wanted to start for about a second. almost catching. after about 10 minutes of cranking it got more and more sounding lijke it was gwtting fuel. i hooked the battery up to my truck to keep the juice flowing and finally got it to turn over and stay running. i'm still confused as to why it would have taken so much. i obviously had fuel all the way to the injectors. maybe a pocket of air caught somewhere around the ip. anyway, i'll never run below a 1/4 tank again! what a hassle.
i STILL can't get my hand pump to lock down. welll, that'll be for another day.
Thanks for all the help guys. i appreciate it.

dale

1983 240D "The Grey Goose"

When the engine is running,
 

Look at the primer pump, if it is moving, you need to shut off the car, and push down on the handle, turn clockwise.
You could get air in the system if it isn't locked down and moving.
Good Luck!

many of the old primer pumps leak. They can let fuel out and air in. A new replacement pump is less than $20, smaller, and doesn't need locking/unlocking. Just push to pump, release, repeat.

A good investment for you would be to purchase a new Bosch primer pump. The pump has been redesigned to make it much less likely to leak and at the same time easier to use. The new one doesn't require any turning to unscrew it from a locked position - you just push down and release when you need to pump priming fuel. Cost about $20.

Plenty of information to search through here.

The original OEM pump has a lot of plastic parts and the pump seal gets old, shrinks, and starts leaking. My personal rule of thumb on my old cars with the OEM pump is to never run out of fuel to the extent I actually need to use the primer pump. For example, when you change out the "spin-on" fuel filter, if you fill the new one up with fuel before you bolt it down, the car will start without priming.

Ken300D

braided return line
 

Yes, if the braided return line is leaking this would cause the fuel to drain back to the tank when it is shut off. Any air leak in the system will yield the same problem of fuel draining back to tank. First, fix all leaks. If and when you have the problem of fuel draining back, use the hand primer rather than the starter. The advice given by our other forum member to go with the high quality pump is right on; this is not a place to save money. The braided lines go bad with age and will seep fuel. If they are wet with diesel you know it's time to replace. Given the cheap price of the braided line it is advisable to put in new lines. Also, wherever there is non-steel line, replace them. It is less likely but also possible that the steel lines can corrode from outside to inside with just an initial pinhole leak so check for any wetness in the steel lines. Unrelated, but if you have a drain plug at the bottom of the fuel filter cannister, remove it and this will drain any water in bottom of cannister; actually, the better method is to take the cannister off and clean it thoroughly.

aha!
 

I MUST have the new style pump already on there then. Like i've said. it won't lock down no matter how much i spin it. Had to go to the Benz dealership here to get the right size hose for the return line. every other discount auto part store just had thick walled stuff that didn't fit snuggly or seat properly. The delaership charged me $17 for a meter length of it. ouch! my first benz part purchase.
Ok one last question. I only have a haynes manual (worthless) so can't figure out what i saw. On the top part of my IP towards the rear was a slotted screw with a lock nut. the lock nut was backed up and the screw was able to spin freely. it was on top of an area that was round when viewed from above and looked like it might have been some sort of diaphragm under there? the question is, with this loose screw do i have something completely out of whack that needs to be tuned? the car actually seems to be running fine now.

Thanks again guys,

Dale
1983 240D " The Grey Goose"

[QUOTE=Dale240D]The delaership charged me $17 for a meter length of it. ouch

Dale

That would have been about $6 or $8 from Fastlane.

I have never experienced air entering the fuel system from a leaky return line of a MB, (on a Cummins, yes).
Its good to replace them when they start leaking but I dont think that was your problem.
I sounds more like fuel filters or tank strainer trying to plug up. Have you changed your fuel filters?? Especially if you ran the tank down low on fuel.

Going to change the filters and oil this weekend. it'll give me some more practice at priming again!
Thanks,

Dale

Have you looked at your clear inline filter?
When you change your secondary filter, fill it with CLEAN diesel and that will save you some pumping, also changing the filters when the engines warm makes for easier starting.

Looking at the clear inline filter ("primary filter") isn't really a reliable way to tell if it needs replacement IMHO. Take it off and try blowing through it and compare with blowing through a new one. I've changed and cleaned plenty of them when they got full of black stuff freed from my tank and lines as I was using a blend of 90% WVO and 10% RUG. They cost only around $2.00. I fill them with clean fuel when I replace them, as I do with the secondary (spin-on) filter. Steve

If the engine is running to your liking, you may want to tighten the lock nut.