Added fuel filter... now slow (long time) to start?

[JJorgensen52]

first off, my truck is a 307-2 barrel with at least 100k, probably 200k.

When I first bought it, it would start right up, 1 second or less, even when cold. The started was making horrible noises, so I swapped it out and the noises went away but it still started up quickly.

I added a fuel filter inline over the weekend (right where the line comes out of the cab) this weekend, since I was collecting a lot of rust/particulate in the in-carb filter. The truck wasn't driven much so I figured I'd run one until I pick up most of the junk from the tank.

Now, it takes 4-5 seconds of cranking to get it to start. This says to me either A.) fuel filter has an air leak and I'm loosing my prime or B.) the fuel pump is on it's way out and it's struggling with the filter.

Before I throw a fuel pump at it, am I barking up the wrong tree here?

[old Chevy guy]

If the only thing you changed is adding the filter ,id look there first. Look at the filter (assuming you can see through it ) is there fuel in it before you crank?

[JJorgensen52]

Originally Posted by old Chevy guy

If the only thing you changed is adding the filter ,id look there first. Look at the filter (assuming you can see through it ) is there fuel in it before you crank?

It's got a little pocket of air in it, but I'd say it's 90% full of fuel before I start.

[cdowns]

fuel pump are not really designed to pull fuel thru a filter you weill have better luck by having the filter after the pump

[old Chevy guy]

Oh. I Misread that post I thought it was right before the "carb". That's where I would have put it so I can see how much crap collects in it.

[leftybass209]

Originally Posted by cdowns

fuel pump are not really designed to pull fuel thru a filter you weill have better luck by having the filter after the pump

I agree. You should always have a filter and never rely on the carb screen to clean your fuel. The best thing to do is clean your tank though. I understand money constraints may prevent you from doing so, but really if you are adding a filter to combat rust, it's just a Band-Aid on a gunshot wound. Rust never fixes itself.

On that note, I used POR15 marine clean, followed by POR15 Metal Prep. I did NOT line my tank with any tank liner as I've heard such bad stories about it peeling off. I'd rather just clean my tank every few years until I move it under bed.

[JJorgensen52]

Originally Posted by leftybass209

I agree. You should always have a filter and never rely on the carb screen to clean your fuel. The best thing to do is clean your tank though. I understand money constraints may prevent you from doing so, but really if you are adding a filter to combat rust, it's just a Band-Aid on a gunshot wound. Rust never fixes itself.

On that note, I used POR15 marine clean, followed by POR15 Metal Prep. I did NOT line my tank with any tank liner as I've heard such bad stories about it peeling off. I'd rather just clean my tank every few years until I move it under bed.

It is definitely a band-aid on a gunshot wound, as you say. I'm going to be getting into bodywork on this truck which means the tank will come out, and I'll probably just replace it at that time. Right now, I'm using it as a daily while the weather is still good and wanted to prevent any more harm.

On a different note, I was always under the impression it was bad to add a filter upstream of the pump, due to that being the pressure side? I made sure to use a 3/8" filter (which is oversize for the 5/16" fuel system on the 307) to minimize the restriction

[leftybass209]

Originally Posted by JJorgensen52

On a different note, I was always under the impression it was bad to add a filter upstream of the pump, due to that being the pressure side? I made sure to use a 3/8" filter (which is oversize for the 5/16" fuel system on the 307) to minimize the restriction

I've never heard of that and if you look at any fuel system Chevrolet designed with a mechanical pump in the muscle car era, the fuel filter is sitting a few inches before the carb. As far as using a 3/8 filter on a 5/16 line, all you are doing is alleviating restriction for the length of the filter and line, then adding it right back when the line returns to 5/16 so it negates what you are trying to achieve.

In fact to get extra technical with some pointless rhetoric, you created a wear point where the 3/8 and 5/16 line meet because of the added turbulence created. If left for many years it would wear out at that point before an equally sized filter and line would. Just disregard all of this... I'm rambling.

[68Gold/white]

I don't have the answer you are looking for, BUT...

I've seen many vehicles w/ filter in location as yours, no problems..

Many O.E. vehicles use filters like what you have between the pump and carb, almost all chryslers had them from 1960's and 70's.

There is probably a siphon effect on your line, so the filter shouldn't be a problem. What brand filter??? I DO NOT like the clear plastic filters, seen them fail, I only use metal ones. Seen one clear plastic unit cause an engine fire...

3/8 filter is fine, they generally have an arrow on them indicating flow direction...

[JJorgensen52]

Originally Posted by leftybass209

I've never heard of that and if you look at any fuel system Chevrolet designed with a mechanical pump in the muscle car era, the fuel filter is sitting a few inches before the carb. As far as using a 3/8 filter on a 5/16 line, all you are doing is alleviating restriction for the length of the filter and line, then adding it right back when the line returns to 5/16 so it negates what you are trying to achieve.

Originally Posted by 68Gold/white

There is probably a siphon effect on your line, so the filter shouldn't be a problem. What brand filter??? I DO NOT like the clear plastic filters, seen them fail, I only use metal ones. Seen one clear plastic unit cause an engine fire...

3/8 filter is fine, they generally have an arrow on them indicating flow direction...

I am presently using a clear plastic filter, because I wanted to see what junk I'm trapping coming out of the tank. As to the size restrictions - I just figured if I went up a size from the line, I would (hopefully) minimize additional restriction vice a straight section of 5/16" hose/

I think this might be where I got the "no pressure side" thought from, because I've heard of the cheapo filters failing and spraying fuel under the hood.

Come to think of it, my Buick has a metal filter between the pump and the carb. D'oh!

[In The Ten Ring]

If rust is the issue then GET RID OF THE RUST.

Here is what I did. I pumped out all of my gasoline and saved that (later gave it away as it was 8 years old).

I then removed my seat and fuel tank. I looked inside the tank and IT WAS COATED WITH FLASH RUST. I took it over to a radiator shop and they boiled it out and sandblasted the inside. Then they coated the inside with "renew" which has a lifetime warranty.

They were going to coat the outside of the tank with that too but I opted for painting mine. Two coats of red primer and two coats of "hammered silver." It looks good.

I am making my own fuel lines now (actually I was doing that, I've been working on my house here of late).

I plan to put a fuel filter in like you did but if you had that problem maybe I shouldn't.....I could instead put one in after the fuel pump....

[Lee H]

I agree with all those that say filter before the pump is not ideal. On most of the older cars and trucks I've had over the years I have incorporated a GM filter like the GF481 or a smaller one like the Summit SUM-G1517 into the metal or braided line from the pump to the carb. It's very easy to splice into the line and add a quality filter. A few fittings, two flares, a beer and it's done, safe, and easy to change once a year.

I think in your case the longer start time is a coincidence, maybe weather related?

All that being said I had a metal filter under the cab of my 72 for many years with no issues.

[GuyO]

If there is fuel in the clear plastic filter, it sounds like your due for a tune up - especially timing. That will help starting.

[dirtyjim]

if you add a filter before the pump it needs to be a 100 micron filter with a stainless element and they don't sell them at the auto parts stores. it doesn't take much to clog a normal 40 micron filter enough to stop a mechanical pump and when they do stop you don't get much notice

[jjzepplin]

You may have already plugged that cheap filter with small junk you cannot see. Simple check- take it out and replace- try to start. Replace with newer bigger better quality.

[volksworld]

as dumb as this sounds,remove the filter,replace it temporarily with a section of 5/16 hose and see if the problem goes away...if it does you have your answer...if it doesnt keep troubleshooting....when you first fire up the truck it should be running off the fuel in the float bowl and the pump doesn't need to replenish it till it's run for a while...maybe hi underhood temperatures are making it evaporate overnight,something is letting it slowly leak out,or your accelerator pump isnt shooting or choke is stuck open

[JJorgensen52]

Originally Posted by volksworld

when you first fire up the truck it should be running off the fuel in the float bowl and the pump doesn't need to replenish it till it's run for a while...maybe hi underhood temperatures are making it evaporate overnight,something is letting it slowly leak out,or your accelerator pump isnt shooting or choke is stuck open

This is why I don't understand why it would suddenly change with the addition of a fuel filter.

I'm leaning towards issues with the carb that I exacerbated by opening up and cleaning the filter housing. I'm picking up a rebuild kit on my way home from work today.

[jeffahart]

I don't like coincidences. Problem started with addition of filter.
Go in order of easiness. Because either: the filter is bad, the fuel pump check valve is bad or the carb well plugs are draining.
1. bypass filter
2. change fuel pump
3. pull carb and see if fuel drains out the bottom, if so... well plugs.

[MARKDTN]

You are trying to suck through a filter and it is clogged with rust. That could definitely be the problem. As said above, those pumps are not meant to suck through a filter. And the only difference in a 5/16 and 3/8 inlet is the inlet, the filter element itself is exactly the same. I once added a filter to my '83 K20 right where the tank splitter valve would go. I added it at the same time as a new Delco fuel pump. About 6 months later it killed the pump. I took the filter out and moved it between the pump and the carb. Pump lasted until I changed the engine to fuel injection.

If you are having rust issues, you will not be able to "stop the bleeding with a bandaid" You are better off fixing it now than being stranded beside the road or losing power in traffic.

[Hubscrub]

I agree you don't need to have a filter before the pump, that what the screen on the sending unit is for. Gm just had one built into the carb. I was left stranded once with a fuel problem got it running enough to get back home finally and took the filter off (inline type before the carb since i had an edelbrock) it was full of rust you could barley blow through it. Surprised i made it home, i pulled the tank one day and just cleaned it at home and never had a problem since, seems i took a piece of chain and worked it around in there and flushing out, blow dry with air good then re installed.

[Old Truck Man]

Ive always ran a fuel filter between the tank & pump. I install a wix solid metal one in the line at the back of the cab. No problems. In fact I started a thread on this forum about the pros & cons of installing a filter between the tank & fuel pump. In fact GM factory installed a canister type fuel filter between the gas tank & fuel pump. My C65 77 chev has one. Ive got a 62 GMc 1/2 ton that has one also. On your stock 307 there should be a sintered bronze filter installed inside the carb. remove the carb inlet to acces it. Its a pretty good filter and it filters very fine particles. It could be clogged with rust. Ok you state the tank is rusty if the sock on the sending unit fuel pickup is deteoriated you have been pumping rust particles through your fuel pump. What do you suppose those rusty bits have done to the fuel pump seats? Fuel pumps arent that expensive and one with a bad diaphragm can let fuel into the oil = very hard on bearings ect. One other fact is ethanol gas will cause deposits in the tank & fuel system to turn loose. You could have caused a air leak in your filter installation.

[JJorgensen52]

Rebuilt the carb, thoroughly cleaned everything out, and the problem is gone