IP Problem?? - PeachParts Mercedes-Benz Forum

currx8 · #1 12-28-2006, 10:07 PM

New to forum, but have used your posts for help in past, excellent work. Now for my problem, I filled up with the ULSD for the first time, and the next morning, the engine started then soon died. Have determined a fuel problem. Fuel pump tested ok. When I've bled the fuel system in the past, I've used a vacuum tester with a bleeder bowl on the return line, worked very well. When attempted with this current problem, fuel hardly moves with pulling over 20 inched of vacuum. Have changed filters. Is there any other test or fix for something plugged or am I in need of an IP? Engine attempts to start but won't.

1984 3ooD Turbo, 184,000

barry123400 · #2 12-28-2006, 11:11 PM

I would expect a fuel problem like too thick a viscosity or some other problem with it before I focussed on the injection pump. You put a new fuel in late yesterday and have nothing this morning. It is your probable variable. Get some known good fuel from another source and try to run your engine on a can. Then decide if it is the fuel or not.

currx8 · #3 12-28-2006, 11:29 PM

I'll try that tomorrow, would some cleaner trying to push through the IP help out??

compress ignite · #4 12-28-2006, 11:41 PM

'Chances are that the USLD has dissolved and/or broken loose some form of
contaminant (OR dissolved one or more of the rubber components which were
used to LSD).

The CLEAN source of a can of #2 (or Diesel Purge) hooked up to your lift pump
will confirm! [unless the fuel filters are completely clogged!]

barry123400 · #5 12-29-2006, 12:32 AM

If the new fuel is acting on old rubber etc in as litttle as 12 hours we all might be in big problems. I liked the last posters suggestion it may have dissolved residue in the tank basically. This is the first I have heard it might also be a powerful solvent as well though. This quick acting if so is not good. The present expectations are for the oil companies to do basically nothing. At some point the best we might hope for is they will no longer claim it is harmless if they are still using the line of compatability at all.

yellit · #6 12-29-2006, 01:01 AM

Which return line are you connecting the hand vacuum pump to....?
There are 3...
Return line from the injectors...
Return line from the IP...
Return line to the tank...(Cigar Hose)

currx8 · #7 12-29-2006, 01:42 AM

I'm tapping in at the return line the cigar hose attaches to. I'll be testing with the diesel purge tomorrow.

yellit · #8 12-29-2006, 03:23 AM

For a quick test....disconnect the rubber line from the spin-on filter top fitting that comes from the output side of the IP....put the open end in a plastic coke bottle and see what type flow you have from the output of the IP while cranking the engine....If you do not have a good flow here then the spin-on filter must be stopped up...I think the flow path is from tank > clear plastic filter > lift pump > spin-on filter > IP side input > IP other side output > return manifold on filter housing > cigar hose > steel line back to tank...

The fuel in and out chambers in the IP are fairly large so I do not think a restriction could be there....I think you stated that the lift pump had good output....... so the next suspect would be the the spin-on filter....even though you said it was fairly new....

yellit · #9 12-29-2006, 03:31 AM

The diesel purge is just for minor injection component cleaning....It will not help a major restriction .....might be best to get your flow problem corrected before the diesel purge...It wont hurt anything...just would hate to waste it if you are still plugged and end up having to take lines and filters off with the certain spillage that happens when working on flow problems.....

Shorebilly · #10 12-29-2006, 07:40 AM

If you do a Diesel Purge...as directed...suction and discharge to a mason jar....your car should run, and you will be cleaning the IP at the same time as eliminating the IP as the source of the problem....kinda like "two birds with one stone".....

SB

currx8 · #11 12-29-2006, 03:29 PM

Good news, I tried some good diesel in a jar, tapped the inlet straight to the pump and the outlet from the cigar fitting. The engine started and ran great like it should. When I hooked up the hoses back, the flow stopped and so did the engine. I'm guessing I need to pull the filter housing and do a thorough cleaning. Thanks for the input, I'll let you know by Monday, must go to work, bummer...

yellit · #12 12-29-2006, 04:06 PM

That would indicate that the spin on filter is not stopped up... The lift pump pushes fuel through the spin-on filter through the IP and back to the return manifold on the filter housing......The way you had the jar fuel feed shows all this as ok....

This all points to a restriction in the fuel tank output screen......The lift pump cannot pull from the tank because of the stoppage...that is why you get the vacuum.....
Might want to try blowing some low pressure air into the feed line under the engine compartment that comes from the tank...this might clear the screen as a temp. fix......(back flush)

Looks like you need to change the fuel screen in the tank....may have to change several times until all the sediment or whatever is blocking it is gone.....or flush the tank real good to be sure....

I just put some ULSD in the 240D last week...I may get to join this party also.....Barry1234 might be dead on with the ULSD diesel of doom forecast....

currx8 · #13 12-29-2006, 05:35 PM

I'll try that, but when I put my vacuum pump on the inlet side of the first filter, I can pull fuel easily, and when I was testing the fuel pump first, the fuel (oil) flowed through the pump easily right into my jar. I'll have more time on Monday to play around...thanks

yellit · #14 12-29-2006, 07:39 PM

I am still a little confused on your test.....With the vacuum pump hooked to the input side of the first filter you would be pulling the fuel in the opposite direction of its normal flow as you applied vacuum.....
The new backwards flow direction would be from the return manifold into the output of the IP...through the IP in reverse flow...out of the input to the IP....backwards through the spin-on filter..backwards through the lift pump...through the first filter and finally to the vacuum pump attached to the filter...
This would let you know that things are flowing but it would not test the screen and feed line from the tank....unless I am missing something here....

barry123400 · #15 12-30-2006, 04:20 AM

If you decide to blow air down the fuel line into the tank remember to remove the fuel cap first. That is unless you want a larger fuel tank.

I know you knew this already. Also give the service station a call and ask if they have had any complaints on their fuel reciently just in case you have to dump the tankful. Some people are honest. Really bad fuel gets out once in a while, Ocasionally a delivery tanker that had a load of bunker C for example is not cleaned out well enough before loading a lighter base fuel.