HELP!! Starting issues after running, fuel filter drains!!???!!

B-52 · Guru

HELP!! Starting issues after running, fuel filter drains!!???!!

B-52 · Guru

could it be the wrong filter? or?

B-52 · Guru

The filter is pretty even with the pump, the filter is full of fuel now because its been sitting. Im drawing a blank, I will change the filter to a metal one, is there one maybe that won't let the fuel flow backwards maybe? Can it be something simple like the gas cap? some weird back suction???????? i think i keep bumping this thread someone knows exactly whats going to fix this smile I just want to drive the car and not have to worry about shutting it off somewhere.

-- Edited by B-52 on Wednesday 27th of June 2012 02:25:17 PM

B-52 · Guru

could it be a vacuum issue??? the car starts ok when cold, its after a long drive and being hot, i can see the fuel drain out of the filter back towards the tank. the fuel comes back if its left for a few hours.

dcneric · Poncho Master!

Sounds a little like vapour lock. Not sure if the carb on your car has an internal filter at fuel inlet bung. Some of the newer cars had a built in check valve to get the fuel from draining back.

Sorry no other brilliant ideas.

Pontiacanada · A Poncho Legend!

I really wouldn't know what to tell you ... airlock? gravity? ... is the filter almost even in height with the fuel pump? ... but I do know one thing, I'd change out your plastic filter next time to a metal one for safety's sake.

I have some nice period-correct glass bowl/porous porceline filters. wink

bob53 · Addicted!

I agree with that being a bad place for the filter but mine is located on the carb side of the pump and it still empties. It has me thinking tho, is it possible that the pressure between the carb and pump force's the gas back through the pump? I mean weak valves in the pump. It seems to work fine when its running and the gas is flowing and the pump is pumping but when it's shut off less resistance. I know mines been on there for awhile.

-- Edited by bob53 on Thursday 28th of June 2012 02:53:44 AM

66 Beau · Poncho Master!

Sounds like vapour lock - especially with the filter pushed against the block. How close is it getting to the exhaust?

Also - I can't see all of the hoses in the photo, but is that filter on the fuel tank (feed) side if the pump? I hope not. Should be between pump & carb.

Fitz · Guru

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There is 2 poppets valve in the gas pump, those valve must close and open following the diaphragm position in the pump. On the suck side one poppet must close and the other one open properly to permit the gas going up from the tank. After the diaphragm push the gas up by reversing the poppet opening/closing.

If you don't have any air leak in your fitting connection, those poppets does the job for you, look at it you will found dirt or broken spring. Under the metal bowl, on brand new pump there was a mesh filter, that dissapear over the year. This mesh prevent dirt to go in those poppet and to carb.

Fitz.

-- Edited by Fitz on Thursday 28th of June 2012 06:19:56 AM

bob53 · Addicted!

This is a problem I have been struggling with since I got my 53. I installed a check valve just outside the gas tank and it seemed to do the trick. I had troubles with the charging system so at that time I figured it wasn't cranking well enough to start when hot. Next was the carb, the accelerator pump dried up on me so rebuilt it last year. I installed a glass fuel filter so I can see what's going on. I guess with all this happening I sort of planned my outings around the cars temp gauge. You know two quick stops, drive around then visit while it cooled. Anyways when the engine was hot the only way I could start it right away was to give it a little gas down the carb. So, I just drove for about an hour tonight with cloths pins on the fuel line to act as a heat sink against vapor lock. Got home and shut the car off, by the time I grabbed a flashlight and popped the hood the filter was dry. I cranked for a bit without touching the gas and it wouldn't start, normally I would just let it cool down- still no fuel in the filter. Cranked again this time pressing on the accelerator and it started, this never worked before the carb was rebuilt. Now there was gas in the filter and it stayed there. Tried this again and it started three more times,back when I had the charging problem this never would have happened. When I get a chance I'll make sure the check valve is still working, I put it in about two years ago. If that's not it I don't know why the gas would drain like that. What happens when you try to start yours when its hot? I know these engines build up compression making it harder to crank when hot. I know I haven't found many solid answers looking around the web but keeping the fuel line away from the engine is a good one.

ZAPPER68 · Addicted!

66 Beau wrote:
Sounds like vapour lock - especially with the filter pushed against the block. How close is it getting to the exhaust?

Also - I can't see all of the hoses in the photo, but is that filter on the fuel tank (feed) side if the pump? I hope not. Should be between pump & carb.

I agree, it does look like the filter is on the feed side of the pump. Reposition it on the pressure side of the pump clamping it to make sure it doesn't chafe and end up leaking. The filter should then remain full on the pressure side of the pump diaphragm. Start with that and see how it goes...good luck.

B-52 · Guru

Here are the 2 caps to compare, the New "oe replacement style" on the left and the old one on the right, i know you guys could have figured that out lol. Looks to me that the old cap is a non-vented cap, in my mind it would be creating suction in the tank while i drive and when the car shuts off, the tank would want the air area replaced and suck the fuel all the way back to the tank and after sitting the natural flow of fluid would return as the tank relaxes. just my thought as the new cap would balance out any tank pressure issues, I put the new cap on, drove and ran it for about an hour, the car seems to have a little more gitty up in her step but not too much. got the car home, popped the hood while running, shut the car off and watched the wonderful filter empty back out. I was like, i guess its not the issue but i tried to start the car anyways with the drained filter and you would never guess what happened.........she started, i shut it off and it started again. im not going to put money down on the table just yet thinking that this was the way too easy of a fix, i will take it for a good run later and see how it acts.

-- Edited by B-52 on Thursday 28th of June 2012 01:48:35 PM

B-52 · Guru

ZAPPER68 wrote:
66 Beau wrote:
Sounds like vapour lock - especially with the filter pushed against the block. How close is it getting to the exhaust?

Also - I can't see all of the hoses in the photo, but is that filter on the fuel tank (feed) side if the pump? I hope not. Should be between pump & carb.
I agree, it does look like the filter is on the feed side of the pump. Reposition it on the pressure side of the pump clamping it to make sure it doesn't chafe and end up leaking. The filter should then remain full on the pressure side of the pump diaphragm. Start with that and see how it goes...good luck.

I will also take the advice and change the location of the filter. Its just the fuel line that rests on the engine block and in turn shakes the crap out of the filter when it running, I will also make sure to pop the fuel line back into its clip on the passanger side Rad cradle clip and route the connecting line properly. I have to thank everyone for their help and great tips. Oh and the fuel line and filter are still a good ways away from the exhaust about 10-12 inches maybe

-- Edited by B-52 on Thursday 28th of June 2012 02:18:45 PM

B-52 · Guru

Nailhead wrote:
........check if your gas tank is vented or has a cap that is vented. You could even try running it without the cap on and see what happens . Check all the fuel lines for possible leaks as it could be sucking air thus the drain back result when stopped. Fitz's tip on the pump could be it too. A clogged pickup screen in the tank ( if has one ? ) can cause grief too. There are fuel filters with the check valve in them . Installing a electric fuel pump would help cure things.

-- Edited by Nailhead on Thursday 28th of June 2012 11:26:28 AM

The tank is non-vented, I was thinking last night to check the gas cap, you never know what could have been put on the car over the 60 years that its been on and "off" the road. even if the cap was correct, the internal vent on it could have been non-functional.

B-52 · Guru

Fitz wrote:

There is 2 poppets valve in the gas pump, those valve must close and open following the diaphragm position in the pump. On the suck side one poppet must close and the other one open properly to permit the gas going up from the tank. After the diaphragm push the gas up by reversing the poppet opening/closing.

If you don't have any air leak in your fitting connection, those poppets does the job for you, look at it you will found dirt or broken spring. Under the metal bowl, on brand new pump there was a mesh filter, that dissapear over the year. This mesh prevent dirt to go in those poppet and to carb.

Fitz.

-- Edited by Fitz on Thursday 28th of June 2012 06:19:56 AM

I understand what you're saying Fitz but am I right in thinking in my issue even if the the poppets are or aren't working, because the filer is on the inlet side, I would still see the fuel drain out? In Bob53's case he would be able to see the issue if the poppets are not working properly because his filter would drain through the pump????

66 Beau · Poncho Master!

I was worried about the filter being pushed toward the manifold if it was not secured anywhere. It might look OK when idling, but at highway speeds, things can move around.

The fact that the filter sits up against the block made me wonder - it will wear over time for one (not good), and second, when you shut off a warm engine, the heat will leak into the filter causing the gas inside to boil (hence the 'vapor lock" comment).

PS
A quick Thank you to Fitz. We're lucky to have you on this site - I always learn something from your posts. Some very good advise on these older cars.

bob53 · Addicted!

Well I feel pretty stupid right now, I took the pump apart and the bowl was packed full of rust from before I did the tank. Cleaned everything up including poppets and everything is much better. Also taking everything apart I noticed the brass fitting to the carb was loose.

66 Beau · Poncho Master!

No sweat - glad you didn't spend even more time tracking down the problem.

The only good thing about these kinds of problems is the knowledge you gain for next time .... and knowing it could have been a lot wor$$e.

Fitz · Guru

66 Beau wrote:
I was worried about the filter being pushed toward the manifold if it was not secured anywhere. It might look OK when idling, but at highway speeds, things can move around.

The fact that the filter sits up against the block made me wonder - it will wear over time for one (not good), and second, when you shut off a warm engine, the heat will leak into the filter causing the gas inside to boil (hence the 'vapor lock" comment).

PS
A quick Thank you to Fitz. We're lucky to have you on this site - I always learn something from your posts. Some very good advise on these older cars.

I'm happy to be able to help someone to keep those beautiful Canadian Pontiac on the road. I have learned a lot on the 49-54 by working on it and other flathead engines, now it's time to give all I know to some who need or ask for, with ease by this forum.
PS: and you are kind with my «not so good» english.

Fitz.

classicsincanada · Member

Check the gas cap it needs to vent the tank and may need to be replaced