More @#$& fuel leaking!

[Christien]

I'm getting sick (literally) of smelling gas all the time... Seems every time I fix one fuel leak another one pops up. Here's the story this time:

Bought a new (used) fuel pump (old one was working but leaked) and installed it Friday night. Saturday morning went to start the car, it started fine, ran about 20-30 seconds, then died. This is typical in colder weather (about -7 or 8 celsius here today). Usually it takes a couple tries to get it to idle properly. Tried to start it again, nothing, just kept turning over. I thought of the spark plugs, but remember, I had it running just a couple minutes prior, so I figure ok, the new fuel pump's a dud, and maybe it was able to run for 20-30 seconds with the gas that was already in the lines.

So I put the old pump back on, and it seems to be starting to catch as it turns over, but then I notice fuel leaking FAST, so I shut it off right away. The gas is leaking out the bottom of the engine, but I can't figure out where from. When I look around the carbs, top of the engine, fan, etc. no gas anywhere, but when I look at the bottom of the engine, it's dripping from a couple places on the muffler. There's not a hole in the muffler, but it's running all over the bottom of the engine and drips from what I'm guessing is the lowest point. (Sort of like how water drips from an eavestrough at a collection point)

What could the source of this leak possibly be? It stops when I stop trying to start the engine, and it doesn't leak when I've just got the pump running (i.e. turn key to last notch before engine begins to turn over). The pump itself isn't leaking, at least not any more than it always has (maybe one drop every minute or so). It seems like gas is coming into the carbs and pouring right through the engine, but this doesn't sound right.

Any ideas will be greatly appreciated. Car is a 72 with Zenith carbs. Let me know if any more info/details are needed.

Thanks,
Chris

[john walker's workshop]

if that were true, you could see it collecting inside one or more of the throttle bores. that would be a float valve (needle and seat) problem. take the air filter off and look down all the bores. a mirror and flashlight helps. also could be from pumping the hell out of them, trying to get it started. expect fouled plugs.

[Christien]

I've looked down into the bores, and can't see any fuel, but not while the engine's cranking (I was working by myself). If that is indeed the problem, what's the fix?

Is it safe to keep trying to start the engine, with the fuel dripping, or am I begging for a fire? I do have a fire extinguisher, plus a garden hose handy :-) If it's safe, I'll have someone turn the ignition while I look to see if fuel collects in there.

Thanks,
Chris

[Britwrench]

Did you buy a MFI transfer pump rather than a carb pump so the fuel presure is too high?

[Christien]

No, from what I was told the pump was taken from a 71 with Zenith carbs. I bought it from Frank at Porsch-a-part, who is, as far as I know, a pretty reputable guy. Certainly quite knowledgable.

Chris

[Britwrench]

I would check the fuel presure, if it ran before, doesn't now and you haven't done anything else there's not much else to focus on until you can confirm the fuel pressure reading. You could always fit the other pump back on and confirm the diagnosis. It could be that the floats are stuck; try turning the pump on and gently tapping the carb with a screwdriver handle.

[Gunter]

Take JW's advise. I would disconnect the coil to prevent sparks. Take the airfilter off, then I would jumper the pump so that it runs, take a strong light and look around the carbs and down the throttle bore, move the throttle. It could be a needle/seat problem in the float chamber or leaks from the lines going to the carbs.

[Christien]

Britwrench: I'm a little confused - the car started & ran fine with the original leaky pump (leaked from the electrical connection on the pump itself), wouldn't start with the new pump, then when I put the original leaky one back on (to test if the new one was dead) the new leak from the engine started (but sounded like it was beginning to catch before I shut it off because of the gas leak). Pressure (with the old pump) shouldn't be an issue. I will try gently tapping the carbs to see if a float is stuck.

Gunter: That all sounds good, but why would a problem start there when it was fine minutes before, with the only intervening action being changing the fuel pump? I'll still try what you're suggesting - I've never messed around *inside* a carb before - anything to be careful of, in terms of causing damage? Obviously I'll be gentle. I'm doubting it's the lines going to the carbs, because there's no gas around the exterior of the carbs at all. One of the braided lines is damp (with gas) but it doesn't seem to be leaking any significant amount, because there's no drip or pooling of gas anywhere on the upper side of the engine.

Thanks guys for the suggestions - sorry if it sounds like I'm being doubting - I'm not, and I'll definitely try all the suggestions.

Chris

[pjv911]

Your replacement pump may have introduced foreign matter to you needle and seats . Try disconnecting the fuel pump ground and try to start the engine with the throttle wide open . Run the engine till its out of fuel(the bowls) . Try racing the motor while its starting to stave for fuel . Let it stall while your at full throttle . This may clear the needle and seat passages . Otherwise go the safe and sure route . Remove the carbs and clean them out . Physically check the Needle valves for proper seating .

Kurt Williams

[Christien]

Thanks Kurt, that makes total sense. I'll try all these suggestions tomorrow or as soon as I get a chance and report back.

Chris

[Christien]

Well, I've checked out the carbs and they look completely fine. Venturis opening and closing as they should, no gas pooling in there. Still sounds like it's going to catch to start running, but the gas is coming out pretty quickly.

If it helps, here's where it's leaking from: (not my car, so not exactly the same, but close enough


Chris

[RoninLB]

I think a floal level test and hooking up a decent fuel psi gauge will be progress twords a fix..

don't forget to keep a couple of fire extinguishers close by at all times. A 5# halon and a 5# powder. You may need all the help you can get?

[Christien]

Just a thought, is it possible that this leak is being caused by hooking the lines up wrong to the fuel pump? For example, does maybe the return line to the tank work at a higher psi than the deliver line to the engine, which would conceivably cause an overflow? I labeled each line before I took them off for the first time, but it's possible I screwed up somewhere.

Chris

[pjv911]

no

[Gunter]

If the gas drips down near the muffler it still comes from the top somewhere. Are Zenith carbs side-draft like SU's? It should not be that hard to find a heavy gas leak. Have you tried what I suggested?

I would disconnect the coil to prevent sparks. Take the airfilter off, then I would jumper the pump so that it runs, take a strong light and look around the carbs and down the throttle bore, move the throttle. It could be a needle/seat problem in the float chamber or leaks from the lines going to the carbs. Without cranking, but the pump running, the leak has to appear.

[Christien]

Hey Gunter, no I haven't tried your idea yet. I haven't been out in the garage in a while, because it's so bloody cold (well below zero, we're in the midst of one of the worst cold snaps I can remember). That's the first thing I'm going to try once I can work without freezing my hands off.

If I remember correctly from a week ago, there was no leak with the pump running but the engine not turning over (i.e. turning the key to the last notch before starting it, so you can hear the pump going). The leak only started when I started to crank the engine. I could be mistaken though - I tried so many different scenarios I'm getting confused.

I'm going to print this entire thread and take it out to the garage once I can get it heated to a decent temperature.

Chris

[Gunter]

Oh yes, Hamilton, it's lovely this time of year. Have you added gas line antifreeze to the tank? It's just Methyl Hydrate and I buy a Gallon and use some in my other car in the winter. If you can make the pump run without jumpering, good. You'll need a good light and room in the engine compartment to see plus a fire extinguisher. Are the Zeniths side-draft, or venturi?

[Christien]

Oops, sorry, forgot to answer your question about what kind of Zeniths. I didn't know there *were* different kinds - how do I tell? They're 40TIN, if that makes a difference.

No, I haven't added antifreeze - the gas hasn't frozen so far, but should I still add it?

Good light, check, fire extinguisher, check, room in the engine compartment, well, I pulled the air filter, but it _is_ a 911 :-)

Thanks a lot for all your help - it's really appreciated.

Chris

[Christien]

Well, I got a few minutes in the garage tonight, with the temperature finally just below freezing (a relative warm spell).

I was able to recreate the leak with the new pump, so at least the old vs. new issue is resolved.

With the pump running (just the pump & CD by turning the key), the gas is pooling in the carbs, though only to a certain level (i.e. didn't overflow). There is slight leaking occuring around the base of the carbs, but not to the extent of the problematic leak (not even close). Again, still working alone so I couldn't crank it while watching the engine for the leak. I'll try that tomorrow.

What's really getting me here is that nothing in the engine bay was changed, moved or replaced during this whole process. The only thing that changed was the fuel pump.

2 safety questions: 1. If the pump is cooled by gas circulating through it, is there any danger of running the pump without starting the engine? I didn't let it run for more than about 20 seconds because of this concern. 2. If I air the garage out well, is there any danger from a spark from a trickle charger on the battery igniting any lingering gas fumes?

[RoninLB]

Originally posted by Christien

With the pump running (just the pump & CD by turning the key), the gas is pooling in the carbs,

There is slight leaking occuring around the base of the carbs,

The only thing that changed was the fuel pump.


safety questions:
1. , is there any danger of running the pump without starting the engine?
2. If I air the garage out well, is there any danger from a spark from a trickle charger on the battery igniting any lingering gas fumes?

Try to disconnect the CD plug at it's base if you're not going to start the engine as part of testing.

It seems that your floats/or a float isn't closing the needle and seat valve. . Gas wasn't pooling on top of every throttle valve, correct? Seems like the gas at the base of the carbs is from leaking thru the throttle shaft.

Gas fumes can get trapped in a garage area "pocket". A large fan is better to flush out fumes than just opening the door. If unsure of the situation give it plenty of time to ventilate. It's a good idea to be paranoid with gas fumes imo. You should have had a fan operatiing throughout this whole repair. Static electricity from sliding on the drivers seat can cause an explosion if you're not paranoid.