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Electric fuel pump as a primer to avoid hard starts

Old June 10th, 2019, 12:41 PM
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Electric fuel pump as a primer to avoid hard starts

Hard start after sitting for several days.

As with most cars with carburetors my 70 Cutlass is difficult to start after sitting for several days. I do not like grinding on the starter to get fuel up to the carb. I have been filling the carb bowl through the vent tube and that eliminates the long cranking. I have considered installing a small electric fuel pump in line with the mechanical pump. The thought would be to hook the electric fuel pump to a momentary switch so it could be held on long enough to get gas to the carb and fill fuel bowl, then a couple of pumps on the accelerator and the rocket blasts off. Has anyone ever done this? Looking for input from someone that has. Thanks.

Don W
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Old June 10th, 2019, 01:06 PM
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Don, I wouldn't suggest installing an electric fuel pump in addition to your mechanical fuel pump. If you want to go to an electric fuel pump remove the old mechanical one. You also might consider looking at your carburetor. The fuel shouldn't drain out in a manner of days. Has it been rebuilt?
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Old June 10th, 2019, 04:58 PM
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Its the fuel today. Modern cars have close systems, with electric pumps. Our old iron has carburetors that vent to the outside air, and fuel that evaporate fairly quick. I had the same issue with my Q-Jet, I tried all kinds of tricks to solve it.

I wonder if you teed a small electric pump in the main line, using a separate pickup in the tank, it that would be enough to completely fill the fuel line, and the float bowl. Obviously, some fuel would be pumped back into the tank, hopefully it would also pump enough through the fuel pump and into the float bowl.

Last option would be to eliminate the mechanical pump completely and install an electric pump. You would need some way to safely control the pump if the engine stalled, or the car is in accident.
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Old June 10th, 2019, 08:36 PM
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There is nothing wrong with using an electric pump with a mechanical pump. People have been doing it for years to prevent vapor lock. I only run an electric pump on my 54 Olds. I have a safety switch that keeps the pump running unless I have oil pressure. I do have a toggle switch to bypass the pressure switch that I use if the car has been setting for several days so I don't have to crank the engine enough to build oil pressure. After the car starts I turn the switch off and let the pressure switch do it's job. If you do decide to install an electric pump, be sure to mount it near and below the tank. Electric fuel pumps are a lot better at pushing fuel than they are pulling it. Hope this helps.
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Old June 10th, 2019, 08:41 PM
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Don, you have to go through the system from the tank to the carb and find the weak spots.
Do you see any gas from the carb squirters when it sits?
Is the fuel system OEM both in parts and configuration?
Start with fuel line leakage. filter, needle and seat, pump psi, Is the choke set to spec?
Pull the fuel line and safely hook up a temp rubber line, run it into a can and crank the engine for a sec. Do you see plenty of fuel? (This is a two person job with an extinguisher handy designed to extinguish liquid fuel).

A properly operating carbureted fuel system should be just fine on today's gas including the mechanical pump.
Yes, today's gas has its challenges, easily addressed with tuning and paying attention to the small stuff.
Something in the system is weak.
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Old June 10th, 2019, 08:49 PM
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Red I took my time typing the first reply I'm not contradicting you. You just beat me to the posting punch.
Many have used electrics with success. I'm a stickler for making Lansing's stock engineering work. I'm the **** retentive type.

Now for the infamous Steve ramble....

If my QJeted 400 sits for months I purposely don't kick my gas pedal to set the choke until I see lots of oil pressure. As soon as I set the choke it fires. A little hard on the starting system but it's been dialed to handle it. Crank time is ~15 seconds again on purpose. I figure a starter is cheaper than a dry started engine.

Conversely, If it sits for months I can set the choke and it will fire after 3-4-5 revolutions. That's pretty good right?.

If I take it for the rare cruise and shut it off, minutes or hours later I can literally reach in and touch the key and it starts like an injected car. same holds true if it sits for a day or two after.

Keep in mind I have worked for a while to obtain these results with fine-tuning. I had to overcome problems such as heat soak, ignition, leaking float bowls, plugged tank sock, rotted rubber fuel lines, etc all of which necessitated standard troubleshooting procedures. I am by trade(and by curse) a troubleshooter...none of this was accomplished by crutching the problem or throwing parts at something without logical root cause analysis problem-solving techniques. Don't rule out secondary problems once the primary ones have been addressed. Two root causes are plausible.

We all should see similar results with all of our cars. They operated this way when new.
Electric pumps belong on large induction systems, alcohol-fed dragsters, not street cruisers.
Electrics are not really safe unless hooked in with a safety shut off system as Red has done.
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Old June 11th, 2019, 05:05 AM
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I agree that an electric fuel pump should be wired to 12V through an oil pressure switch. Here's what you need:

https://www.summitracing.com/parts/a...SABEgL0o_D_BwE
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Old June 11th, 2019, 06:58 AM
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That is a good buy on that switch. I don't remember where I bought mine but I know I paid more for it.
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Old June 11th, 2019, 07:55 AM
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After sitting for a week the car started with no issue last night. The problem I am trying to address is hard starting(cranking engine to get gas to carb) after about 2 weeks. The drivetrain is stock including the numbers matching carb, with the exception of a hei distributor being added.
- I do not like the idea of cranking the engine for 15 + seconds.
- I do not want to eliminate the mechanical pump, only add an electric pump in series as a primer.
- Electric fuel pump would be wired through a switch with momentary contacts.
- Carb was rebuilt to factory specs about 5 years ago.

My questions/concerns are
- Will mechanical pump pull fuel through denergized electric pump?
- Will energized electric pump push fuel through mechanical pump?

Thanks for everyones input

Don W.
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Old June 11th, 2019, 08:41 AM
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As I said earlier, I wouldn't add an electric pump in-line with a mechanical pump. The diaphragm in your mechanical pump could rupture and you could get fuel in your crankcase. I don't know that this is a common way for GM mechanical fuel pumps to fail but it happened to the mechanical fuel pump on my 86 f250.

If you go to the trouble of installing an electric fuel pump it's just an extra 20 minutes to remove the mechanical pump and re route the fuel lines in the engine bay. Of course, it's your car so do what you want.
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Old June 11th, 2019, 09:14 AM
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I really wouldn't worry about it. The cranking time is allowing the oil pump to pressurize the system, which I think in the long run will benefit your crank and cam bearings and anything else that requires oil pressure.
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Old June 11th, 2019, 09:28 AM
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Your engine should not take 15 seconds to start from cold. Half of that is good oiling time and won't hurt the starter. Recommend finding out why it takes so long to start.
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Old June 12th, 2019, 12:02 PM
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Speaking for myself, in such circumstances, I prime the carb by filling the float bowls through the carb vent tubes first.
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Old June 12th, 2019, 12:45 PM
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I do that sometimes; other times I just crank the engine for 10 seconds, pump the pedal a couple times, and repeat until the engine fires. It usually takes 3-4 cycles for it to fire up.
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Old June 12th, 2019, 01:31 PM
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Originally Posted by Fun71 View Post
I do that sometimes; other times I just crank the engine for 10 seconds, pump the pedal a couple times, and repeat until the engine fires. It usually takes 3-4 cycles for it to fire up.
Basically what most of us do. I will add that the carb bowl should not be empty sitting for a week or so.
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Old June 12th, 2019, 01:52 PM
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On one of my cars I installed Facet fuel pump to help with priming the carb. It's a solid state pump which usually lasts a long time and it allows the mechanical pump to pull fuel through when it's not running.
Made in USA.

https://www.pegasusautoracing.com/pr...s.asp?RecID=84
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Old June 13th, 2019, 05:23 AM
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Originally Posted by 70cutty View Post
On one of my cars I installed Facet fuel pump to help with priming the carb.
Those Facet pumps available through Pegasus Auto Racing are highly rated. The guys on the Ford trucks forum I frequent recommend them regularly.
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Old June 14th, 2019, 12:34 PM
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Originally Posted by Mr Shifty Sidney View Post
As with most cars with carburetors my 70 Cutlass is difficult to start after sitting for several days.
Don W
Don,

My 84 S-10 and my Wife's 84 Riviera both have carbs. Both start just fine even after sitting for a week.

I had the same problem with the Riviera. Figured the carb just needed going through. Last year after rebuilding the engine I did the carb but still had the problem.. I have probably done a hundred Q-jets over the years but I just could not get hers to stop having the problem you are having. I found an identical number Q-jet on E-bay, went through it and it is fine. It can sit a week and starts right up with a couple of pumps to set the choke. I still have the original carb sitting there. Some day I might try to figure it out but most likely not
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