Hard starting after fuel pump relocation Options

[Jameel]

I recently did an engine out service, replacing all the fuel lines with new SS from Tangerine, new lines to the carbs which I also rebuilt, and relocated the fuel pump to the front trunk, alongside the spare.

When the car sits overnight or for more than say, a few hours, it takes a lot of cranking for it to fire up. It catches right away, and fires very briefly, but never stays running. I have to pump the hell out of the gas before it starts. It acts like its just getting little bursts of fuel, so when cranking it will fire on an off during cranking, but only finally roar to life after maybe 30 seconds or more of cranking. Once it fires, its fine.

Is it possible that my fuel pump being up front has caused this change? It's a Carter pump, 3.5psi, brand new. I was running what looked like an old 70's era Bugpack pump before, right under the engine on the firewall, and it performed great. Never had a hard time starting.

I have tried letting the fuel pump run (key on 2 clicks) for about 30 seconds, then cranking. It usually fires after 2-3 brief successive cranks when doing that. Perhaps that's just my new starting procedure?

[GeorgeRud]

I assume you are running carbs because of the low pressure pump. I'd let the pump run for a bit to fill the float bowls before trying to start it as some fuel may have percolated out while sitting (especially if it was recently shut down hot). Modern fuel injected engines have made many folks forget how carbs with no chokes run when cold.

[Keith914]

A fuel pressure gauge located near the carbs will help you determine whether you have a fuel flow/pressure problem or carb clean/setting problem.

[iankarr]

Sounds like a kinked fuel line under the gas tank. Very easy to happen...especially if you use plain rubber hoses instead of the braided ones. Check out this link...

http://www.914world.com/bbs2/index.php?sho...282633&st=0

[danschy]

Not familiar with your system, but I've had similar issues due to a check valve failing, allowing fuel to slowly drain out of the system. My "fix" was exactly what you are doing - a couple fuel pump cycles before attempting to start.

[rhodyguy]

Attach a long piece of fuel line to the pump outlet running to a catch container. Have someone energize the pump and check the flow. Given the pump location the flow should begin quickly. Flow slow to build? My guess is a problem upstream.

[porschetub]

A fuel pressure gauge located near the carbs will help you determine whether you have a fuel flow/pressure problem or carb clean/setting problem.

(IMG:style_emoticons/default/agree.gif) important part of a carb conversion I feel.
I recently did fuel level checks on my fuel bowls using PMO level gauge,my under tank carter pump filled the bowls quickly,sounds like a blockage ,are you sure your fuel filter is clean ? for starters.

[Jameel]

I just did my fuel lines under the tank and took great pains to ensure no kinking. Checked them twice two separate times since then. Car runs great once its fired up. So good flow.

Fuel filter between tank and pump is brand new, tank is clean.

Sounds like its just how it is with carbs and a front mounted fuel pump. I'll try the fuel pump priming again in the morning and see what happens. It's been pretty chilly here (40s) so it will be a good test. Thanks.

[rhodyguy]

Is the pump mounted on the trunk floor or the trunk bulkhead?

[porschetub]

Is the pump mounted on the trunk floor or the trunk bulkhead?

He mentioned the pump is along side the spare so that would be similar to the location as per the later cars,my pump is mounted on the front suspension crossmember and has a constant "head" of fuel no matter how much fuel is in the tank.
Personally I'am lost for a solution here......it should work (IMG:style_emoticons/default/confused24.gif)

[Mikey914]

I have found it very easy to kink a fuel line. Try the catch can system to check volume being moved. What you describe is exactly the effect of a pinched line.

[Jameel]

Here's a pic of my fuel pump. Unless something has shifted around (and I don't know how it's even possible) I don't see how I could have a kink. I spent probably 4-5 hours fiddling with the lines, an elbow adapter I made, getting lengths just right, and checking and double checking the lines through the hole in the underside of the tub. I was super meticulous about making sure all my lines had nice gentle curves during the tank install and after. Even used a mirror in the access hole to double check it all. Again, it runs great after the cold start. It's just after it sits for a few hours that it takes a lot of cranking (or key-on pump priming) to start it.

[theer]

Sounds as if the fuel is siphoning back to the tank, which you've probably already figured out.

I have carbs with a low pressure pump up front, and do not have that problem. I am also running a Holley fuel pressure regulator mounted in the engine compartment, with a single supply fuel line (no return).

Are you running a return line?

[iankarr]

Here's a pic of my fuel pump. Unless something has shifted around (and I don't know how it's even possible) I don't see how I could have a kink. I spent probably 4-5 hours fiddling with the lines, an elbow adapter I made, getting lengths just right, and checking and double checking the lines through the hole in the underside of the tub. I was super meticulous about making sure all my lines had nice gentle curves during the tank install and after. Even used a mirror in the access hole to double check it all. Again, it runs great after the cold start. It's just after it sits for a few hours that it takes a lot of cranking (or key-on pump priming) to start it.

Hmmm. Maybe the carbs are getting heat soaked after you park the car and the fuel in the carb bowls is evaporating out. That would explain why it takes 15 seconds or so to refill the bowls and start the car. Are you using spacer/gaskets at the manifold?

[rhodyguy]

If it's a hot carb issue, the longer and repeated cranking duration is not uncommon. You're not going to get away with a few throttle stabs and fire up. Is there a reason you opted for the trunk placement rather than the rear firewall closer to the stock location? There, you can use the stock (with a connector change) pump harness and power it thru the engine relay board.

[Jameel]

Ok. So here's an update. I'm not running a return line. No regulator.

Did a cold start a couple days ago. It was in the afternoon, so maybe 65 or 70 degrees outside. Car had been sitting for at least a day. I turned the key on to the 2nd click, and while the fuel pump was running for about 15-20 seconds I pumped the gas about 5 times. After 20 seconds total of letting the fuel pump run, I cranked it. It fired right up and stayed running on the first crank. So I'm going to try this for a while and see how consistent this starting procedure is. It doesn't bother me at all.

[Elliot Cannon]

What kind of problems were you having that made you relocate the pump to the front?

[rhodyguy]

Encouraging.

[Spoke]

After 20 seconds total of letting the fuel pump run, I cranked it.

Turning the key ON without cranking the engine is not good for points or the coil as high currents could flow if the points are closed. First generation Pertronix may be damaged with ON and engine stationary. I believe 2nd gen Pertronix and beyond are protected from key ON/engine stationary.