83 300TD 300d Air Bubbles in fuel lines hand pump? no start - PeachParts Mercedes-Benz Forum

bmitchell510 · #1 12-26-2003, 09:48 PM

After sitting in a snow storm for 2 days my 83 300td will not start. Here are the symptoms \ what I have done....

In the past month my car has acted like it is out of gas when it has had a half tank in it. There have been some bubbles in the return line from the IP.
I have had problems getting it started on two occassions (took about 45 sec to start)
Freeway/hill performance is solid no smoke

Drove the car to grandma's house in Tahoe for x-mas and let it sit for two days in the snow.
The return line from IP is full of air
All the hand pumping in the world will not fill pre filter.
Tried to bleed it out at return line banjo on top of main filter got only air or froth when hand pumping.
Blew compressed air back up metal fuel line into tank to clear screen....still no love.
replaced all rubber fuel hoses between metal line and hand pump.
removed gas cap while cranking
All glow plugs are working
Blah blah blah I could go on I have tried everything and can not get this thing to start. Until I get rid of that air I know things are going to stay the same. There are two obvious culprits and I would love an opinion. Yeah I know replace the POS white hand pump with the new style pump and get back to you. The rubber lines between the tank and the metal lines may be cracked, but wouldn't I see a leak on the ground? Could a leaky hand pump cause the ran out of gas symtom?
This car has consistantly started for me in 5 seconds or less in sub freezing temps on straight veg oil (it is on diesel now and I have made no modifications to the fuel system or at all for that matter). Anything helps, thanks in advance.

Brian
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jim16671836 · #2 12-26-2003, 10:37 PM

If the engine is turning over like it should with a charged battery, I would try some kind of spray--ether or anything sold at auto stores...just enough to get it started and then it will run all right....Jim

coachgeo · #3 12-26-2003, 11:13 PM

Do a search in here on how to do ether use properly!!!! Done wrong it is said can be dammaging to your engine.

You can also temporarly add a $30 elec. fuel pump. Get the Purlater-Faucet pump. There are two. YOu want the one with the lowest PSI. Found at any cheapo auto parts store.

Mount anyway you can back by the fuel tank with a prefilter just before it. This will remove any vacuum sucking in air cause it will positive push fuel thru the lines instead of sucking it. Mount a switch to it under the dash so u can turn it off.

How and when you need to kick the elec. pump on will also help you get a clue to what your problems are. It might also show you were leaks are cause now where there was holes sucking air in you will get fuel dripping out when the pump is on. Infact they make a new stuff that you add to the fuel that glows under ultraviolet light. Turn the pump on and look for glow where the leaks are.

PS. If I understand correctly these pumps are self regulating soooooo they should NOT overpressure the IP.

IF... you decide to use the elec. premanently read in here (or was it in the Maui Green biofuel B.Board hmmm) about how and why you should remove the stock fuel pump and put a plate in its place.

JimSmith · #4 12-26-2003, 11:20 PM

bmitchell510

First lets try to clear up some of the symptoms. The prefilter has no way to be vented so it will typically be half or so full of air. This is normal. The filter is basically gravity fed from the tank, so the flow rate, pressure and basic geometry of the filter mean it will always have some air in it. And that is no big deal so don't fret over the air you see there.

The same is basically true of the clear line you see coming up and over to the main filter housing. It will often have a small bubble at the top because under normal operation the flow rate is not sufficient to drag the bubble with it, down into the filter housing. So the bubble stays trapped in the high point, which is often in the clear tubing.

So, to check if you have flow to the in-line pre-filter, unhook the fuel line going to the filter and you should get a steady stream of Diesel fuel. If not, you have a problem in the supply line from the fuel tank. If you have a stream, then the hand pump should be getting fuel, and unless it is squirting out the sides of the pump as you push the handle down and pull it back up, you have an air leak somewhere else. When I operate my hand pump, it makes a significantly different noise, like a faint hydraulic version of grinding, when the system begins to become "solid" and I do not really look at the bubbles and froth in the clear line too much. Just enough to check that there is flow there that corresponds to the action of the pump plunger.

If the stiffness of the system never changes (the pump becomes harder to push down on) then you must have a fuel flow probem or a massive air leak in the area of the pump, the main filter or the connection to the injection pump. There should be some evidence of air leaking, either audible as you operate the pump, or you should see some place where Diesel fuel is leaking out.

I hate to be a doubter, but it sounds to me like either the glow plugs are bad or the relay is bad, and you really don't have glow plugs. Leave the dome light on (either leave the door open or turn the light on) then insert and twist the key in the starting switch to glow position. You should see the dome light dim significantly. If you do not see it dim, you do not have power to the glow plugs.

If the car runs fine once started, and you have no visible signs or telltale odors of Diesel fuel in the engine compartment, you likely do not have a leak. Air or fuel.

I am curious about your characterization of the problem as a "ran out of gas (really Diesel fuel) symptom" when you did not indicate that once running you have any problems with the car running. It is only restarting it, especially after sitting for a while in cold weather.

I have a few other questions. When was the last time you changed the oil? What brand and viscosity rating was it? When was the last time you adjused the valves? How do you know the glow plugs are all good (how did you test them?) How old is the battery? When you take the fuel tank fill line cap off, does it make any hissing or sucking noises and is it hard to get the cap to break loose and twist off the filler neck fitting? How is the alternator belt? Tight, good condition?

Well, I hope this eventually helps, Jim

whunter · #5 12-27-2003, 02:23 AM

Hello Brian
First; your car is sucking air.
Second; replace the O rings on the suction/fuel line from tank at the filter housing.
Third; replace all O rings on clear tubes that come out of filter housing.
Fourth; replace fuel filter, make sure to fill it with fuel before you install it.

Contact me direct if you are not running in twenty four hours.
Have a great day.

psfred · #6 12-27-2003, 11:09 AM

Most likely the hand pump is shot and allows air to leak in while the engine is running. This has filled the filter and IP with air, and it' aint' gonna start until you get fuel into the injectors again.

Here's what I would do if you cannot get a replacement hand pump:

Remove main filter and fill with diesel fuel or diesel fuel treatment. Re-install and open either the bleed screw on the IP (if you can find it) or the fitting for the return line. Don't remove the fitting, just loosen the bolt to bypass the pressure relief in it.

Rig up a containter of fuel and some fuel line so you can gravity feed the hand pump -- just a quart jar and some hose may work -- hold jar well above engine level with the hose going down to the hand pump. Try pumping how -- with a little luck, the pump will provide enough suction to get fuel up over the top of the jar. If not, fill the hose and stick it back in.

At the very least, you should get fuel leaking out at the pump now.

Pump like all getout -- you should get fuel at least dribbling out of the IP.

L

osen the injector cap nut about a half turn (17 mm wrench).

Tighten fitting, and will still keeping your "tank" elevated, crank engine -- the lift pump will push the fuel through even if the hadn pump leaks. When fuel starts to run out of the injectors instead of air, tighten the cap nuts and attempt to start. Should go pretty soon.

You will need to charge the battery at least once for this exercise.

Peter