Not starting after secondary fuel filter changed - PeachParts Mercedes-Benz Forum

KRGC · #1 03-07-2009, 05:57 PM

I changed the primary and secondary fuel filter. Unfortunately, I drained my battery trying to get fuel to the secondary filter. The problem I'm having now is that I used the primer pump to get fuel to the secondary filter, but it is still not starting. I loosened the banjo bolt closest to the front of car and used the primer pump until fuel squirted out. And I did the same with the second banjo bolt on top of the secondary housing. But it is still not starting. And I'm at my wits end. I used the search feature, but would just like to know if there is something that I'm overlooking?
Thanks in advance
Charlie
Oh the car is a '85 300D

LUVMBDiesels · #2 03-07-2009, 06:14 PM

You might have to pump the primer up to 100 times to get all the air out. To speed things up, take off the secondary filter and fill it with fuel before putting it back on.

Good luck!

KRGC · #3 03-07-2009, 06:21 PM

I'm getting fuel out of the banjo bolts, both of them. But it is just turning over like it's not getting any fuel. I used the primer pump and fuel squirts out of it and the two bolts on the side of the filter housing. Any idea why it wouldn't start?

DeliveryValve · #4 03-07-2009, 06:37 PM

You have air in the system. Since you know you have fuel in the filter, now you need to tighten all the banjos up and continue pumping the pump 100 x's.... Really 100 times... Then crank it over, floor it and it should start.

JackG · #5 03-07-2009, 06:39 PM

Try bleeding the hard lines, you may have sucked air into them
by not filling the can before trying to start it.

KRGC · #6 03-07-2009, 06:40 PM

Ok. so tighten the both banjo bolts and then use primer pump to pump. And the fuel will only come out of the primer pump right?

DeliveryValve · #7 03-07-2009, 06:52 PM

Quote:

Originally Posted by KRGC

....And the fuel will only come out of the primer pump right?

Well it shouldn't be leaking alot while your pumping if it is the old style, might be OK with some fuel coming out and can be sealed by turning it down. Anycase, that tells me your primer pump could be introducing air in the system. You might need to replace it with a newer version if it is not been replaced already. Pumping the pump with all the lines sealed up will move the air through the return line.

KRGC · #8 03-07-2009, 06:58 PM

But that's the whole idea isn't? To remove air from the system.

DeliveryValve · #9 03-07-2009, 07:02 PM

Quote:

Originally Posted by KRGC

But that's the whole idea isn't? To remove air from the system.

Sorry, I don't understand your question. Anycase, unbolting the banjos get you to a point where your filter gets filled up with fuel. Now you still have air in the lines that go beyond the banjo fitting into the IP. You need to purge the air by pumping and pumping. This will move the air from the main feed lines into the return line. But it will only work if everything is sealed.

KRGC · #10 03-07-2009, 07:07 PM

I understand, but won't some fuel still come out of the primer?

DeliveryValve · #11 03-07-2009, 07:13 PM

Yeah some fuel will come out and will seal up when you tighten it down. It is just that there is a possibility you could introducing air in the system from it. You just have to hope it didn't happen. A new style pump will not leak and won't have the issue of getting air in the system. But the drawback is you need to pump it more to move the same amount of fuel as the old style.

cmbdiesel · #12 03-07-2009, 07:25 PM

For next time you change the filters.
I change the primary first, then start the car.
Then I change the secondary, and I fill the new filter with the fuel from the old filter. Start the car. Never had to prime anything.
Maybe I'm missing something, but it has worked like a charm so far.

Palangi · #13 03-07-2009, 07:27 PM

Quote:

Originally Posted by cmbdiesel

For next time you change the filters.
I change the primary first, then start the car.
Then I change the secondary, and I fill the new filter with the fuel from the old filter. Start the car. Never had to prime anything.
Maybe I'm missing something, but it has worked like a charm so far.

What happens if there is water or sand in the old filter ??

DeliveryValve · #14 03-07-2009, 07:36 PM

Quote:

Originally Posted by cmbdiesel

...
Maybe I'm missing something, but it has worked like a charm so far.

What happened here is that air was introduced in the IP when he cranked it over to get fuel into the filters. What you just did is limit the amount of air that can get in the system and the little air that was in there was purged out each time you started it and ran it.

cmbdiesel · #15 03-07-2009, 08:17 PM

Quote:

Originally Posted by DeliveryValve

What happened here is that air was introduced in the IP when he cranked it over to get fuel into the filters. What you just did is limit the amount of air that can get in the system and the little air that was in there was purged out each time you started it and ran it.

That's kind of what I thought I was doing.
As for sand or grit or whathaveyou, I try not to shake the dregs out, and I do have a brand new primary.
BUT, I have never really looked at the lines in and out of the secondary.
Which way does the filter work - inside to outside or outside to inside?
I sorta guessed that the fuel starts on the outside and exits from the middle, meaning that the fuel I would be pouring out is filtered.