fuel pressure problem

[hondaflr]

hey guys, had a weird question about my gn. first after about a hour of driving fuel pressure would drop to 20psi. usually sitting at 37 vacuum line on. changed fuel pump. figured it was going. the problem i having now since i changed the fuel pump, is i can not drop the fuel pressure lower than 45psi with vacuum line off. if i set it to 45 and out vacuum line back on it sits at 45 still. but can raise fuel pressure to 60 psi. i have changed the fuel filter , fuel pump. and changed 2 fuel pump regulators. tried 2 seperate gauges. stays the same. what do i look for or can try changing out next?

 

[TurboBuRick]

Sounds like the return line is restricting.

What pump did you put in?

If the new pump has more gpm the return line may be overwhelmed.

 

[hondaflr]

I have put in a Walbro GSS307. witch they say is 255lph. is this to much for stock fuel lines?

 

[just plain john]

Probably not, lots of 255lph Walbros out there. I'm stumped, looks like you've already adressed all the components. No kink or restriction in the return line?

 

[hondaflr]

i dropped the tank down and sitting onstands so i could check all connections make sure no leaks, followed the lines up past the shock area where its bolted to the flooring and they are perfectly fine. when i had the pump that was dying on me in there i had no problem dropping fuel pressure. could it be a wrong labeled pump? or defective pump. when i installed the new pump i could not get any fuel pressure till i jumped the relay and kept the pump going steady for almost a minute? i have a stock pump i will have to try. but as far as what ive done. i have pretty much covered everything?

and if stock pump does not fix my problem i will have to start buying new fpr, new pump, and so forth?

 

[just plain john]

I'm confused, I thought you had done all that new fpr, pump, ect. already? I can't see where it would be the pump. You already tried 2 fpr's? New ones? Known good?

 

[hondaflr]

the first fpr i tried was an older fpr i just took off to put a new 'one on, looked better. Both were working. I have 3 pumps at home. the one that was dying on me witch i took out and installed this 307 in there, i than changed back to the previous fpr no difference. i have changed everything possible in the fuel line system. this can not be electrical problem. its all mechanical. so the only thing i can try is the third fuel pump now. if that does not correct my problem . i would have to say im not in luck and 2 of the parts i got are just bad.

 

[just plain john]

I don't see how the pump could be bad, but stranger things have happened I guess. Good luck and let us know if that fixes it.

 

[hondaflr]

definetly keep u posted. thanks.

 

[bison]

Bypass the return lines in your car. You can put the regulator on upside down if you news to to make it easier. All you need is a fitting that uses the o ring and you can run a piece of hose into a 5 gallon can and see if you can regulatebit down. My guess is you will be able to. This will take All the factory return line out of the picture

 

[dynoman]

Start at the begining , you had low fp so you changed the pump and now a new & different problem . Did you reverse polarity on the new pump ( turning backwards ) ? Your strange problem started with the pump change and the gage doesn't care which way the fuel is flowing. I have seen strange pressure readings on 3 phase pumps at work when pump rotation was backwards, also fuel lines swapped ? Just a thought . Sam

 

[dynoman]

I just read Razors thread "Fuel tank venting " and post #13 talks about not able to adjust fp because of poor venting . Did you pinch the vent line after replacing the pump? Sam

 

[hondaflr]

today i took apart all the lines and blew all 3 lines going to the fuel talk, disconnected fuel inlet and return line and used a air compressor and blew all the lines out and connected everything back. started up and same problem.
from what i understand i can not change the polarity of the pump cause there is only one way for the plug to go in. rubber lines from the sending unit up to over the axles are 3 different sizes so i cant mix match that. i am going to make adapter at the end of the injector rail and add a hose to it and try see if i can lower the fuel pressure.

does anybody have a diagram of the sending unit and what the 3 lines are suppose to be connected to. doesnt hurt to triple check things now.

 

[just plain john]

The big line is the feed, the small line is the return, and the other is the vapor line to the cannister

 

[turbofrank]

bad fuel pressure gauge.