77 modified fuel system ?'s

[TBK]

hey guys, pulled the engine out of my 77 and dropped in a modified 2600 with triple webbers and having acouple issues.

 

have added a fuel regulator with a bypass funtion, used the line with fitler as the feed , used the other line that was on the fuel rail as the "Bypass" line. rubber capped the line that went to the "Tank vent" on The "vacumm/carbon Canister".

Using the mechanical fuel pump with the 2600. DID NOT remove the electric fuel pump.

 

first issue is I can onlt get 3lbs psi out of the mechanical fuel pump, is this standard?

next is occasionally the engine will start bogging down down down and then die, like it is getting no fuel or missing on half or more cylinders. Pumping pedal has no effects or makes it die quicker.

and at this time the fuel tank has an "ENORMOUS" amount of pressure built up, enough to blow the cap acouple feet when you lossen it.

when it dies you can open the cap and release pressure and take off the rubber cap off vent line and starts and runs fine. even with the rubber cap left off the tank builds big pressure.

Dont like the issue of having an open/uncapped line in the engine compartment.

Any inputs/advice/suggestions would be greatly appreciated!

[brokebolt]

You have multiple issues I see why no one was brave enough to tackle this one. First off you need to find what is causing pressure, that is a very bad thing; very, very bad. Your tank should be placed in a vacuum condition not pressureization, if all is normal...no! This does not mean you should have 30 in of vacuum only that as you are drawing fuel out is a slight vacuum condition should or could exist. You can disconnect the power wires form the electronic pump to see if the problem continues, as it sounds you are leaning on that. I can't see how that would cuase any issues but try it and see what happens.

 

Are you 100% sure you only have 3 PSI from the fuel pump? I would gain to venture you have more presure and your guage is skewed a bit. The carb dieing problem may be related to the tank over pressureization, and maybe due to excessive fuel not starving. Pumping the throttle should surge the accelerator pump circuit in the carbs and that would be adding more fuel, thus it loads and dies faster due to fuel being added at a faster rate.

 

Do you have a chilton book or factory service maual? If not, "invest" in one, your not "buying" one, your "investing" in one like a house or stocks. Re-plumb all your hoses to location that are in the manual to like locations in your existing set up. Example; all things that hook to the intake manifold "vacuum side", that is behind the thorttle body, should hook to the same location on your triple manifold, behind the throttle blades. All things that are under the air filter should be moved to the same location, under the air cleaner. You may need to add air cleaners you didn't mention if you were running them or not. Be advised that if your hooking something up to one runner only, like you break booster and there is a leak in the hose or plumbing somewhere, than that cylinder will run lean, not that it could run lean it WILL run lean. That sets the stage for major catastrophic engine damage...which is never fun for anyone...except the guy you pay to rebuild another engine. Keep us posted.

[TBK]

Thanks brokebolt,I was beginning to think I was a Lepper or something!

Well I think the prob was the elect pump. I removed it and changed the tank hoses. The problem of dropping press seems to have stopped.

Still only getting 3.5 lbs press from mechnical pump buy have not tried to adjust since the changes were made. Havent checked the pressure build up yet on this tank of fuel, but did manage 18 mpg on the last one, Ill check the press build up next time I get it out to drive. All the lines are correct, yes I do have the FSM. Still playing with setting on everthing, but trying them one at a time to guage effects. just checked the plugs and 1-5 are a "TAD" lean but not bad. 6 was alittle rich but think that may have been a bad plug wire not firing all the time.

Ill keep this updated as I go along.

still have a smalll miss at idle type speeds that driving me nuts. But cant speek as to the age and condition of the tune up items that were already on the car.

Have a new set of plug wires, cap and rotor for unilite on order so gonna wait till they arrive for futher adjustments. (easy stuff first)

[brokebolt]

K.I.S.S., Keep It Simple Stupid. Words to live by. Yes, changing one thing at a time and measure the effects is a very effective way to trouble shoot...but very time consuming. Easy stuff first is also a good ideology.

 

If your fuel pump is the stock version, you may not be able to get more than that due to age and leaking check valves. I don't know if they still offer a rebuild kit for those old pumps. I need one for a pump I have on the shielf that has a hole in the diaphram.

 

That is the one bad thing about triples, if you start to play with the tuning parts everthing is in quantities of six. I've been suggesting it for years that triple carb guys ban together and "Group Buy" a large selection of parts and then when they have there stuff dialed in they "buy out" the parts from the group. Check out a local club, if you already haven't, and see if they offer something like this. Also clubs are an excellent source for guys that have gone down the road before you; so they have already made all the "stupid mistakes":cuss:, this would help in diagnozing some issues and pehaps give you some advice in other areas besides your triples, just a suggestion. Keep us posted, happy trails Mike