Car acts like spin on filter is clogged. Just swapped it. 1982 300TD - PeachParts Mercedes-Benz Forum

curt5446 · #1 01-12-2014, 05:49 PM

So, swapped tank screen, lift pump, blew out fuel lines, swapped feed and return lines to see if the sump in the 300TD tank was full of something, did a diesel purge and changed fuel filters.

Car will idle but as soon as I am under throttle while going down the road, it starts to act like my spin on filter is clogged.
Only thing I can think of now is that there's some crap in the fuel lines preventing fuel from getting to the front of the car.
Air in primary filter.

Previous owner replaced stock hard fuel lines with rubber hose and I think they are about done.

So, ordered 25' of 3/8" aluminum fuel line and will see what happens after I install it.

If you have any ideas, I'm all ears.

Thanks!

dude99 · #2 01-12-2014, 06:36 PM

When the car begins to struggle pull over and unscrew the gas cap. If there is a large whooshing noise and the car then drives normally for a short distance your tank vent may be plugged.

curt5446 · #3 01-12-2014, 06:45 PM

Already checked that. My cap leaks like a seive

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vstech · #4 01-12-2014, 09:22 PM

SLIME in the fuel tank/lines can plug up a 1 day old primary fuel filter... pull your primary, and see if it's got slime in it.

curt5446 · #5 01-13-2014, 06:06 AM

I assume by primary you mean the little clear plastic filter? I've changed that, twice. I've also swapped the feed and return lines from the tank so I pulled from higher in the tank and not through the tank screen thinking it may have clogged after I swapped it.

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curt5446 · #6 01-13-2014, 07:17 AM

Since blowing out the fuel lines I swapped both filters. I'm almost thinking my old fuel lines may be sucking air. When I use the primer pump to refill the system upstream of the lift pump, it seems like it's not pump fluid but rather like it's got air in it. I disconnected the line from the lift pump to the inlet to the spin on filter housing and there was a pronounced and obvious release of pressure. So now I'm wondering if something in the IP isn't clogged.

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sloride · #7 01-13-2014, 09:20 AM

In the OP there was mention of stock hard fuel lines being replaced with rubber lines. I have never heard of that being an acceptable replacement on an IDI diesel, unless you are referring to the return lines from the injectors. It would seem possible that if the stock hard lines from the IP to injectors were replaced with rubber lines that the pressure from IP would expand the rubber lines before causing the injectors to pop. That may be causing less than adequate fuel delivery to combustion prechamber for throttle position.

curt5446 · #8 01-13-2014, 09:34 AM

The hard lines from the IP to the injectors are still intact. The hard lines replaced were those running from the fuel tank to the lift pump. One other thought was that a sufficient vacuum was created in that line so as to cause the rubber line to collapse. I'm planning to replace the rubber line from the tank to the lift pump with hard line this weekend.

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vstech · #9 01-13-2014, 09:34 AM

Quote:

Originally Posted by sloride

In the OP there was mention of stock hard fuel lines being replaced with rubber lines. I have never heard of that being an acceptable replacement on an IDI diesel, unless you are referring to the return lines from the injectors. It would seem possible that if the stock hard lines from the IP to injectors were replaced with rubber lines that the pressure from IP would expand the rubber lines before causing the injectors to pop. That may be causing less than adequate fuel delivery to combustion prechamber for throttle position.

he's talking about the lines to and from the fuel tank.

sloride · #10 01-13-2014, 09:36 AM

Quote:

Originally Posted by curt5446

The hard lines from the IP to the injectors are still intact. The hard lines replaced were those running from the fuel tank to the lift pump. One other thought was that a sufficient vacuum was created in that line so as to cause the rubber line to collapse. I'm planning to replace the rubber line from the tank to the lift pump with hard line this weekend.

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There are plenty of post illustrating how to isolate the the fuel tank with a temporary 2 liter bottle just to remove the possibility of a tank and fuel line problem.

curt5446 · #11 01-13-2014, 10:05 AM

That's my plan for this evening

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curt5446 · #12 01-19-2014, 02:32 PM

Tried the underhood tank and the car ran wonderfully. So the issue was at the rear of the car. Going off of the assumption that the issue was with a collapsed/leaking fuel line, I threw a new 3/8" hard fuel line for the supply. The car ran the same. Drained the tank through the tank screen and discovered that the screen was clogged again. Likely from sediment that the PO had built up with veggie oil. Cleaned the screen really well and threw it back in with a few gallons of fresh dino and it ran the same. Drained tank again and found that the reservoir that the TD has in the tank had collapsed whilst the tank screen was clogged due to vacuum build up when the screen was clogged.

My thought on this is to install a standard 300D tank screen however, I'm not sure if the threads are the same. Can anyone verify that?

tangofox007 · #13 01-19-2014, 02:57 PM

Quote:

Originally Posted by curt5446

...found that the reservoir that the TD has in the tank had collapsed whilst the tank screen was clogged due to vacuum build up when the screen was clogged.

How does a clogged screen cause vacuum in the tank to "build up?"

It seems to me that any pressure differential would have to be associated with a shortcoming in the tank vent system.

curt5446 · #14 01-19-2014, 03:13 PM

If you have a clogged screen, you are creating the same situation, albeit on a smaller scale. Perhaps this illustration will explain it a little better. If you clog the screen, you collapse the reservoir at the bottom of the tank.