intermitten fuel pump failure?

[scott]

have ya every had a fuel pump fail off and on. the other day ran a tank dry, swtich tanks (exmod stuff) and ran about 6 miles and stopped. aux tank is full, filter and bowl empty. hand operation of pump nets small squirts into the filter but not much. let set for 2 days and it starts, filter and obviously the bowl is getting fuel. i did put 5 g in the main tank and switch back to it. maybe i'll blow air from the valve back through the aux line. but back to the question, can a pump give out intermitently?

[kevkon]

Is your tank well vented and if so is the vent clear? Is the fuel tank switch opening all of the way?

[SeriesShorty]

Are you using the stock MoD switching valve? It may need to be rebuilt. I think mine was sucking air causing the exact same symptoms. Not too long ago someone posted about the part # used to rebuild the valve but I can't find it now...

I junked mine along with the mechanical pump and went electric.

[scott]

stuff i will have to check on. i will be blowing compressed air back thru the switch valve and tank lines

[gudjeon]

Old mechanical pump left me in the lurch. Went to electric, no probs. Several new mechanicals tried, not one worked. Place returned to was great about warranty and refunds, not their fault. Great experience other than not working over, and over again. Need to be reliable when miles from nowhere.

[scott]

i tried electric but it needed to be placed after the switch valve and i think it was too far from the tanks. i've one on the 88 but the tank switch valve and e-pump are located between the tanks and not forward of the bulkhead. e-pumps push better than they suck.

so blow'n thru the lines will let me know if there's an obstruction but not an air leak.

the question isn't why mine isn't getting fuel. i can and will check all this stuff. but what i'm curious about is can a pump fail intermittently or do the just die? c'mon all you mech engineers

[kevkon]

It's not usual for it to be an intermittent problem. Just a diaphragm and a plunger like most of the electric pumps. It can wear out or develop a leak, the results are simply a loss of fuel pressure. That's why I would look first at anything that could impede the flow of fuel. You should be able to check this by simply disconnecting the line at the pump. With a full tank of gas, gravity should let the fuel run freely.

[gudjeon]

I do not have a military set up. From what I have heard it is not unusual as mentioned above for the switch-over valve to suck air.

Leccy pumps really do suck. I used to have one mounted on the top of a rad shroud and currently one on the bulkhead. No probs with either one.

[SafeAirOne]

I think it would be very unlikely that a mechanical fuel pump could develop an intermittent problem. Once one of these pumps looses its ability to pump, I can't see what would make it regain that ability.

Is there a suction released when you remove the fuel line at the pump inlet? If so, there is a stoppage upstream. If not, you might check for air entering the plumbing upstream.

[Tim Smith]

I bet it's your tank switch. Fill up the empty tank and switch back to it to see if you still have troubles.

My starboard tank has feeding issues too. On the highway it will starve the carb if I'm really pushing it but the port side tank will feed just fine with the peddle mashed to the floor all day long. I'm sure it's my fuel switch at this point as the relieve valves on the fuel caps work fine and I'm running new fuel lines. Just haven't gotten around to it to be sure.

As a side comment, I'm starting to think the new fuels are eating up my fuel system. My carb leaks like a sieve too and it was rebuild not too long ago.

[kevkon]

I can't remember for certain , but it seeems to me that I had an issue with the tank switch and related plumbing ( done by PO). I took everything apart and found that the valve was somewhat restrictive. I don't remember if it was biased to one port or not since I decided to abandon the whole setup.

[bkreutz]

Tim,
The new fuels do take a toll on the "older" vehicles. I've had problems with every carburetted car I have. I put fuel stabilizer in every tankful and it seems to help a lot.

[Tim Smith]

Tim,
The new fuels do take a toll on the "older" vehicles. I've had problems with every carburetted car I have. I put fuel stabilizer in every tankful and it seems to help a lot.

Yeah, I've been suspecting as much. No scientific evidence of it, but it just seems like something has been changing with the way the fuel system has been holding up in the last couple of years.

I bet ethanol and rubber are a bad combination. I'm sure google could tell us the specifics but I don't have the time to look.

[gudjeon]

This ^^^^ is another reason to go with a higher pressure, recirculating electric fuel system. Vapour lock is a distant memory and fuel doesn't start to boil on a hot day at high altitudes.

[kevkon]

There are some down sides to an electric pump, though. They can have an intermittent problem due to several reasons. They are not usually field rebuilable like the stock Series unit. They really should be used with a regulator. Most of the ones offered today are of questionable quality. Failure to hook them up properly and with the proper pressure can lead to overwhelming the float /needle valve in the carb. The stock oem mech. pump is really very good and is more than adequate for the 2.25 motor. I'm not so sure about the newer replacements. Personally, I think the oem unit is worth keeping and rebuilding. Besides, you can use that glass fuel bowl for shots if your in a pinch