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Discussion Starter · #1 ·
Sorry if this has been addressed before. Appreciate any help I can get.
Lately, my Streetrod has been difficult to start. When I turn on the start switch, the fuel pump runs and stops as normal, but fuel pressure drops to zero immediately. I confirmed this with my fuel pressure gage. The pressure goes up to 42 psi, then drops to zero immediately. That's why it cranks over several times before starting(when engine is cold). After engine starts, it shows 58 psi at idle. When I rev the engine, it drops to 50 psi just for a second or two, then back to 58 psi. When I go riding, it seems pretty much normal(at all speeds). Not sure about the psi when riding.
Why does the fuel manifold not hold pressure until the engine is running? Could it be a defective fuel pressure regulator? Thanks in advance for any suggestions.
CG
 

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The bike needs fuel pressure to get started.. Pressure should remain at 55-60 PSI for several minutes after initial switch on.
It could be the regulator but not likely.

Most likely You have a leak in a fuel line inside the tank. Most likely a hose.
The tank components are pressurized. Remove the pressure line and securely fit a length of hose to the nipple. Use an air compressor or your lips and blow air into the tank. If you have a leak you will know it. If you can't blow air then the tank components are good. If you can blow air you have a leak, probably a pin hole in the line. watch for bubbles when blowing air.

Does the problem get better with a full tank but gets worse when you only have 1/2 a tank or less? If yes then its a hoes problem.
 

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Discussion Starter · #3 ·
No, this problem is the same, no matter the fuel level. I did have that problem before. When the tank reached about 1/4 full, the engine would lose power when trying to accelerate at 4000 rpm, or above. I installed a new pump strainer filter and a new pump hose. This corrected that condition. But the hard starting remains. Thanks for your reply.
 

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Could be your regulator. I have had one go bad on me. Easy to check. The regulator is designed to dump fuel back into the tank when pressure exceeds 55-60 lbs.
Turn ignition on then watch the fuel line overflow. If you get fuel pouring out of it when pressure is below 55-60 psi then regulator is bad.
 

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I block the return line to deadhead the pump for a second and see if the pressure drops. If it drops when deadheaded it is not the regulator. If it holds pressure when dead headed then the internal components in tank are good. If pressure drops when deadheaded then there is a leak or pressure loss in the tank. The only other pressure loss deadheaded is a stuck injector, but you would find that immediately.
 

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Discussion Starter · #7 ·
Could be your regulator. I have had one go bad on me. Easy to check. The regulator is designed to dump fuel back into the tank when pressure exceeds 55-60 lbs.
Turn ignition on then watch the fuel line overflow. If you get fuel pouring out of it when pressure is below 55-60 psi then regulator is bad.
Did you mean return line, or the vent line. Either way, nothing came out. Thanks.
 

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Discussion Starter · #8 ·
I block the return line to deadhead the pump for a second and see if the pressure drops. If it drops when deadheaded it is not the regulator. If it holds pressure when dead headed then the internal components in tank are good. If pressure drops when deadheaded then there is a leak or pressure loss in the tank. The only other pressure loss deadheaded is a stuck injector, but you would find that immediately.
No matter what I do, the pressure always goes 40 psi, the falls to zero immediately. Thanks.
 

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I had a problem with mine similar, turned out to be the short corrugated gas line between the fuel pump and the high pressure filter can. It was held to the unit support struts with a plastic cable tie and where it contacted the strut it wore a small hole through the tube. Once started it ran fine but was at times difficult to start. I replaced it with a piece of submersible gas hose and two small hose clamps from the local auto parts store and have been fine since.
 

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I believe there is a check valve in the pump itself that could be the problem if all the hoses check out ok.
Ron
 

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If he deadheaded the pump by blocking the return line. The pressure should have way exceeded 55 lbs of pressure. By only 40 lbs you have a internal tank pressure problem.
 
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Discussion Starter · #13 ·
I appreciate all the replies, guys. You are helping me understand how this fuel system works. I will be pulling out the fuel module again. Thanks again for your time. Let you know what I find.
CG
 

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Good Luck
 
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