Air in lines or injector timing off? - PeachParts Mercedes-Benz Forum

bipolardave · #1 07-29-2011, 10:43 PM

I'm an idiot.

What started out as just a valve adjustment and compression test ended up as a fuel filter replacement, new primer pump, and an emptied/patched fuel tank. Instead of doing the tasks one at a time, I did them all over the course of a week while awaiting parts to finish one or the other task.

Needless so say, pretty much every fuel hose has been disconnected and left that way for a few days.

Since I got it all back together, it's been difficult to start, belches a bit of white smoke at idle, has some nailing, shakes, and leaves a cloud of black smoke when I'm on the pedal.

The clear fuel filter has a fairly good sized bubble, for what it's worth.

I've removed the valve cover and rechecked the valves and the adjustment appears fine. The PO replaced the fuel injectors and engine mounts. He also said there was no timing chain stretch. Compression is 300ish across all cylinders and I removed/replaced the old injector washers. New fuel filters and no crud was found in the tank when I patched a wee hole. There doesn't seem to be any abnormal sounds coming from the vacuum pump.

I've read that injector timing can cause a lot of these same symptoms. However, I don't think that I've done anything to alter it...at least not knowingly.

Could I be mistaken?

Although I don't see any leaking diesel, could it be possible that somehow air's getting into the lines? Given that I've replaced the filters, hand pump, and had the fuel lines off, which are the most likely culprits? Was there perhaps an O ring or something that I might have neglected?

The nearest European specialist is an hour an a half away and my regular mechanic won't touch it. He previously got burned on a bad injector pump install that set him back quite a bit of time and money. So, I'm on my own here in WV.

Diesel911 · #2 07-29-2011, 11:59 PM

There is no Injector Timing; that is done by the Fuel Injection Pump.

What did it run like before you started the work?

If the new Copper gasket/crushwasher that goes between the Hand Primer and the Fuel Supply/Lift pump does not fit well in the recess it will not seal well.
Also was the Old copper gasket/Crush Washer removed?

Submerge your Fuel Return Hose in a partly filled large Jar of Diesl Fuel and see if there are any Air Bubbles coming out while the Engine is going.

Do the Injector Cut Out Test and see if you can locate a specific Cylinder/Injector that is having a problem.

Biodiesel300TD · #3 07-30-2011, 12:02 AM

Sounds like you've still got a lot of air in the system. When you get that far into the fuel system, it can take a lot of pumping with the primer pump to purge the system. Did you fill the new spin on filter with fuel before you put it on? If not it will take a lot more pumping to purge the air. You should have a bubble in the primary fuel filter, but it should be a small portion of the filter. If it's mostly air you've still got a air leak. Make sure all your hose clamps are tight. Also look for air in the hard plastic return line from the injection pump to the fuel filter, if you can see through it, is there bubbles. If so more purging is needed or you've got an air leak.
You might also try cracking open each injector line at the injectors to purge any air out of those.

bipolardave · #4 07-30-2011, 01:01 PM

Good morning, folks.

I buttoned it back up this morning and tried to vent it by looseningthe secondary filter connection. Using the hand pump caused it to spurt as you'd expect.

I also pumped with the system closed. I got the usual IP squeak. However, I also got a bit of "gurgle" coming from somewhere else. Maybe the fuel tank?

It fired up a bit easier this morning but was still nailing until I revved it up, then it disappeared.

There were no bubbles in the clear lines. Each line has fuel when I loosen the injector line.

That being said, it appears as though the primary filter is on the verge of being sucked dry. The darn thing is almost empty at idle.

Could it be something upstream clogging the line? Lifter pump not sucking hard enough? FWIW, the old mesh screen was fine when I pulled the tank and there wasn't anything icky that came out with the last bit of fuel.

Maybe it was how I installed the secondary filter? I removed the canister lid, plucked out the old one, and inserted the new one. There was still diesel in the canister and it overflowed when I pushed the new one in place so I didn't see the need to add any. That being said, it didn't want to go down all the way by hand, but seemed to be ok once the bolt started snugging up. I did replace the filter gasket, btw.

Biodiesel300TD · #5 07-30-2011, 01:25 PM

Sounds like you've got an air leak somewhere between the lift pump/primary filter and the tank. Make sure all the hoses are in good shape, and that the clamps are good and tight. You could also blow air through the lines to try to blow out any build up. But if it was running fine before all the work it's probably not likely that there is gunk in the lines now.

I forgot that you don't have a spin on secondary filter, so you're probably fine there.

Stretch · #6 07-30-2011, 01:32 PM

Check to make sure you've got the supply and return lines from the tank the right way round. If the fuel in the tank is really low then you might be sucking air in that way...

bipolardave · #7 07-30-2011, 01:48 PM

Quote:

Originally Posted by Army

Check to make sure you've got the supply and return lines from the tank the right way round. If the fuel in the tank is really low then you might be sucking air in that way...

Thanks for chiming in.

The tank is very low..about 3-4 gallons.

However, I didn't remove the tank's fuel lines. I removed the drain plug, added a dab of epoxy (PO patched with a brass screw), and replaced the plug.

The fuel hoses at the tank look like they're weeping. So replacing them is on the list. That's why the fuel level is low.

Also, it could be the case that the PO had removed the tank for that original patch and reversed the lines. Are they clearly marked? How does one know the difference?

FWIW, the fuel level gauge acted all screwy when I put everything back together. It read empty despite having just added 3 gallons. After a few restarts if finally jumped up. Possibly not related, but I thought that I'd throw that out there.

shadetree77 · #8 07-30-2011, 01:58 PM

i'm thinking the lines might not be connected right; i did the same thing when i changed the flexible lines from the fuel tank to the hard lines

Biodiesel300TD · #9 07-30-2011, 02:09 PM

If the lines are weeping then there is a good chance that you're sucking air. Fuel leaking out means air can get in.

Stretch · #10 07-30-2011, 02:13 PM

Quote:

Originally Posted by bipolardave

Thanks for chiming in.

The tank is very low..about 3-4 gallons.

However, I didn't remove the tank's fuel lines. I removed the drain plug, added a dab of epoxy (PO patched with a brass screw), and replaced the plug.

The fuel hoses at the tank look like they're weeping. So replacing them is on the list. That's why the fuel level is low.

Also, it could be the case that the PO had removed the tank for that original patch and reversed the lines. Are they clearly marked? How does one know the difference?

FWIW, the fuel level gauge acted all screwy when I put everything back together. It read empty despite having just added 3 gallons. After a few restarts if finally jumped up. Possibly not related, but I thought that I'd throw that out there.

I was actually thinking that if filters had been changed up front the lines might have been connected the wrong way (at some point or other). To check I'm sorry to say the best way is to get crawling under the car. The supply line is the one with the screen at the tank and it should connected to the little clear filter at the engine end.

EDIT:-

Fuel gauge - that'll be gunk in the sender - not related. And don't start on that yet!

bipolardave · #11 07-30-2011, 02:52 PM

Quote:

Originally Posted by Army

I was actually thinking that if filters had been changed up front the lines might have been connected the wrong way (at some point or other). To check I'm sorry to say the best way is to get crawling under the car. The supply line is the one with the screen at the tank and it should connected to the little clear filter at the engine end.

EDIT:-

Fuel gauge - that'll be gunk in the sender - not related. And don't start on that yet!

Tracked them down and they appear to be right and not leaking. The supply hose a the tank isn't leaking too bad, but I'll order another one anyway.

I've new fuel filters and a diesel purge set up on order. We'll see what comes of it during and after the purge.

Just to double check, the primary filter has an arrow that should be pointing toward the IP, correct? That is the direction of flow? Also, how regarded are Fram filters? This is what the PO gave me so I used it.

Not much more I can do for now.

Thanks, all!

Stretch · #12 07-31-2011, 01:44 PM

Quote:

Originally Posted by bipolardave

Tracked them down and they appear to be right and not leaking. The supply hose a the tank isn't leaking too bad, but I'll order another one anyway.

I've new fuel filters and a diesel purge set up on order. We'll see what comes of it during and after the purge.

Just to double check, the primary filter has an arrow that should be pointing toward the IP, correct? That is the direction of flow? Also, how regarded are Fram filters? This is what the PO gave me so I used it.

Not much more I can do for now.

Thanks, all!

Yes that's the correct direction of flow.

I've not used Fram on a MB yet - but they were OK for Hondas!

bipolardave · #13 08-03-2011, 08:58 PM

OK, gang.

I performed the diesel purge this afternoon.

I had just replaced both filters, but removed the secondary filter again and siphoned out the diesel. There was a monster of a mess at the bottom of the housing. I'm not sure if it's crud from the recent tank drain or if it had been there for some time, but it was icky.

Anyway, I filled the secondary up with Diesel Purge and connected everything to my makeshift tank.

About 15 seconds after firing it up, I reved the throttle a bit the nailing and rough idle went away immediately. I goosed it off and on for the duration of the purge but whatever issue I had before disappeared while it sucking on the Purge. It was even silky smooth at low idle with the AC on max!

One thing I noticed was that the primary filter filled up to the max. I could never get it more than half way full while connected to the fuel tank.

We took it for a test drive and it definitely has more power. Making left hand turns is no longer a matter of crossed fingers and rattled nerves. We'll see what happens tomorrow when it's cooled back down. If the nailing went away, then a good cleaning was all it needed.

However, the primary filter is still back to only being half full.

Why would it be 95% filled while on the makeshift tank but only 50% full when connected normally?

sixto · #14 08-03-2011, 09:26 PM

Check your tank vent.

Sixto
87 300D

bipolardave · #15 08-03-2011, 09:29 PM

Quote:

Originally Posted by sixto

Check your tank vent.

Sixto
87 300D

You know...it's very odd that you mention that.

I found one of the vent lines disconnected. I tracked it inside the trunk and found it laying beneath the plastic panel by the spare. I pushed it back through and reconnected it.

You think a PO disconnected it on purpose?

Why?