Electric fuel pump for priming

[Edward B.]

Gents, I've finally reached my "last straw" point with having to crank the starter on my L36 for a minute (or more) before I can get the car started after it's been sitting for several days.

As we all know, today's fuel evaporates almost before you have a chance to pump it into the tank! And with the way the Q-Jet is designed, after a few days the float bowl is dry and you have to crank the starter for up to a minute before it fills up again. This is hard on the starter, hard on the engine, hard on the battery and to be honest, hard on an owner (me) that has absolutely NO patience!

I've been reading several threads in some of the hotrod forums about using an electric fuel pump as a "primer". You put it in-line and using a momentary switch, turn it on for several seconds until the float bowl fills up again then let go of the momentary switch and off you go. Seems simple.

But I've a few questions I can't seem to find any REAL answers to.

1. Can I still use my mechanical pump? I'm assuming I can IF I use a "Free Flow" electric fuel pump. I believe this kind of pump allows fuel to flow through it even when it's not on. Makes since. If you turn off the electric pump and it's NOT a Free Flow, the mechanical pump won't have anything to suck on!

2. I'm thinking about THIS ONE ON EBAY. It's very small, so it's inconspicuous, 3/8" inlet and outlet so it fits on the original lines, has a 2 year warranty and is rated between 2 and 3.5 PSI. (I don't think I need anything higher than a few PSI just to fill the float bowl.) The only thing the ad doesn't say is if it's Free Flow or not. I just contacted the seller, but no reply as of yet. Can I assume that if you're able to blow through it, it's Free Flow?

3. Any sage words of advice would of course be welcome.

Ed

[Michael W.]

Re: Electric fuel pump for priming

As we all know, today's fuel evaporates almost before you have a chance to pump it into the tank!

I have to question this. E10 is 90% gasoline. Why does it evaporate faster than in the good old days?

[Keith B.]

Re: Electric fuel pump for priming

I have to question this. E10 is 90% gasoline. Why does it evaporate faster than in the good old days?

Becouse the Internet told him so. I wonder if the he is starting the car correctly by pumping the gas pedal several times before trying to start.

[Lawrence M.]

Re: Electric fuel pump for priming

Hi Edward,
I'm thinking your problem sounds more like gas leaking out of the float bowl than evaporating. My 69 L46 with Quadrajet will start after about 4 seconds of cranking after sitting for a month or more. Some early Q-Jets had plugs underneath that could leak and cause the problem you are having. You shouldn't need an auxiliary fuel pump to start your L36 if everything is good with the Q-jet.

[Edward B.]

Re: Electric fuel pump for priming

Read THIS from Duke. Unless I don't understand what he's saying, the newer fuels evaporate quicker than the old fuels did.

Ed

[Lawrence M.]

Re: Electric fuel pump for priming

Hi Edward,
I agree todays gasoline evaporates faster than the old gas. I don't think it would evaporate at a rate that would make it so hard to start your car after just a few days. I run the 10% ethanol gas in my L46. It sits in a heated garage where the humidity gets down to 15% in the winter. The car starts with no problem after sitting for 1-2 months. Many of the people who contribute to the TDB are at the Indiana Regional this weekend. Perhaps when they return you can get some more ideas as to what the problem could be.

[Mark E.]

Re: Electric fuel pump for priming

Edward,

Before a fix is implemented (electric pump), be sure you understand the root cause of the problem.

- Are you sure the cold hard start is due to an empty fuel bowl? Pull the airhorn and check. Cold hard starting can also be due to improper starting procedure (not setting the choke), weak ignition, choke improperly adjusted.

- If the bowl is empty, there are three possible reasons-
1. A leak in the fuel bowl. With Q-Jets, a common culprit is the main well plugs. Since this drains fuel into the intake manifold, a common symptom is black exhaust and an engine running very rich for a few seconds.

2. Fuel leaking back down the fuel line. This usually isn't a problem because the seat is raised from the bottom of the bowl, so there's usually enough fuel left to start the car. Some guys remove the clip on the needle so the needle/seat stays closed to prevent this.

3. The fuel is evaporating. Symptom: After sitting for a few days, the engine cranks for 5-7 seconds before starting. It then runs fine with no black smoke, and doesn't run rich. My car will do this if it sits more than 4-6 days, depending on the weather.

I live in Dallas with 10% ethanol, and #3 is how a well tuned Q-Jet behaves. These carbs have a small fuel bowl, so it drys up faster than many other carbs. See the forum at http://cliffshighperformance.com for a lot of discussion about this.

What do I do? Well, my engine is original (valuable) but it has a $50 lifetime starter from AutoZone, and a fresh WalMart battery. So I consider the starting system disposable, and the extended cranking as an opportunity for the engine to prime before firing. Good for the motor, not so good for the starter and battery- but that's ok. Sometimes I'll prime the carburetor by filling the bowl, but not often.

And beware of the downsides of an electric pump-

- More fuel pressure may spring a leak somewhere, over power the needle/seat, or rupture the mechanical pump's diaphragm. (Remember- carbs like a lot of fuel, but with low pressure, so be careful.)

- More connections in the fuel line, each a potential leak.

- The fuel line is pressurized even when the engine isn't running- an added hazard.

- If your car now looks original, it won't any longer.

[Douglas L.]

Re: Electric fuel pump for priming

I used to have to deal with this on my 68 L36. After finding VP 100 octane at the pump locally the problem has for the most part disappeared(still exhibits long crank after sitting for over a month or more but much better than before). Before finding the 100 octane I always used a Motion Pro motorcycle fork oil tool(part # 08-0121) to prime the carb. Its essentially a syringe with a tube and length of hose that allowed me to siphon fuel from a can and inject it into the bowl vent with ease and no mess. Not really a total solution but a relatively easy and cheap alternative. Just a thought.

Doug

[Edward B.]

Re: Electric fuel pump for priming

When I had Lars (Grimsrud) rebuild my Q-Jet a few years ago, he sent along a paper he had written regarding hard starting problems with Q-Jets. HERE'S A LINK to most of it, but the main issue is fuel. Most of the other "problems" are conceived and non issues. Here's the main part:

1. Although the problem is exaggerated, it is possible for the bowl well plugs to start leaking on a Q-Jet. When the factory drilled the main jet and secondary fuel transfer passages, they drilled them up from the bottom, through the bottom of the carb. Once the drilling was complete, they pressed lead plugs into the resultant holes in the bottom of the carb. It is possible for these plugs to start leaking. If they do, the fuel level in the bowl can easily and quickly not only drop below the accel pump inlet slot, but can actually empty the bowl completely. This will result in very hard cold-starting.



If fuel does not drip out the bottom of your carb during the leak test, you do not have leaky well plugs, and you have one of the other 2 problems.

He goes on, but since he rebuilt my carb, it runs GREAT, but it STILL has the hard start issue as it did before he rebuilt it. The specs sheet he included in the rebuild indicated there were no leaking issues with the well plugs and he only uses US made needle and seats, so going by what he wrote, I HAVE to believe it's a fuel evaporation problem. And going by what other Q-Jet owners have stated, it's not that uncommon.

Doug, I have a small ladle that I use when I prime the carb, but it's a real pain. I have to pop the hood, pull the air cleaner lid, open the gas cap, dip the ladle in the tank, pour a small amount of gas into the carb, run back inside the car and start it up!

I'd rather flip a momentary switch and have electricity do it for me!

Ed

[Mark E.]

Re: Electric fuel pump for priming

Doug, I have a small ladle that I use when I prime the carb, but it's a real pain. I have to pop the hood, pull the air cleaner lid, open the gas cap, dip the ladle in the tank, pour a small amount of gas into the carb, run back inside the car and start it up!

I'd rather flip a momentary switch and have electricity do it for me!

Ed

Or you can just crank the engine.