11 replies to this topic

[sushimonster]

SIT BACK AND ENJOY THE MYSTERY NOVEL I HAVE WRITTEN FOR YOU GUYS

 

ok so im still trying to figure out this fuel flow problem with my 86 DX CRX. just a recap of its current condition: all stock 1.5l, auto trans, weber 38/38 DGS (k726-38), new mechanical fuel pump (took out the carter 4070 electric pump cus its still doing the same thing), return line is installed (i dont have the check valve cus i cant find where i put it), i have a new upright canister style fuel filter before the pump (to fill up and act like a reserve tank), new canister fuel filter after the pump before the carb, i have dropped the tank twice and there is no crud and is extremely clean, ive checked for rust pin holes in the pickup tube and there is none, ive capped off and pressure tested the pickup tube in a bucket of water and there is no leak, also, i have removed the pickup strainer. the fuel filter in the back of the car was removed and replaced with the canister style filters. all fuel lines are NEW, i have NO restriction in my fuel lines whatsoever. fuel pressure is at a solid 3 psi as recommended by weber. and 3.1-3.3 psi with return capped.

 

what is happening: the fuel in the fuel filter BEFORE the pump will stay at the normal level, but the fuel in the filter AFTER (between pump and the carb) runs dry. engine can be hot or cold. i can sit there and watch the (lack of) flow from the pump in the crystal clear filter. i can pinch off the return line and some fuel will dribble in and then stop, then ill unpinch the return line and itll dribble a little and stop. 

 

just the other day i was thinking of the fuel tank vent. when i first got the car, there was ALOT of pressure in the tank, like the vent valve was stuck closed. anyways i cut a slit in the gas cap seal to vent. so after all my failed diagnosing and ive thrown enough parts at it and continued to be disappointed, i was thinking that maybe it needs pressure in the gas tank to help push the fuel to the carb. so i got another gas cap. the pressure inside did help push some fuel to the filters and they filled up. 

 

so now with fuel in the filters and something helping push the fuel to the pump, the car was running great!!! then came the next morning, i lifted the hood and the filters were dry again      !! so i checked the fuel tank and it had pressure but still no flow. i still cant explain why the filters filled up with no problems and now i cant get them to fill again.

 

i pulled the fuel supply line at the carb and ran the car for 60 secs into a coolant jug and it was roughly 750ml that it pumped out. and with the pump free flowing, the filters filled up. so i reconnected the hose and drove it around, car starved of gas at part throttle (again). looked under the hood and filters were dry. 

 

so im completely stumped and nobody is helping me and i cant find any answers. so i need the big guns here on red pepper to help me!! if i cant fix this, im gonna take a loss and sell this thing. 

 

heres a link to a recent pic of it, (hope it works) and u can see why im still trying desperately to convince myself not to sell this thing!!!!

http://instagram.com...282366635119873

 

thanks for those that have read it to the end and replied! i will send a beer money to the lucky guy(s) that help me fix it!! no joke!!

 

Travis 

[jjamiemmark]

needle & seat could be stuck. How are you testing fuel pressure, 3 psi seems low. Have you tried running from a gas can to the pump? you should have pretty good flow from the pump just turning the car over.

[eec4tuner]

Seems to me you have 1 too many filters and taxing that poor stock mechanical pump. Did you remove the stock pump and just run the electric pump alone?  From what i get you only have 2 filters. I would remove the filter between pump and the carb. Keep the system simple, as close to stock setup,with your current carb. it should be way more than enough to run a 1.5 motor.

[sushimonster]

Thanks guys for replying.

@jamie, I pulled the seat and needle already to check and clean a couple of times. But would that stop flow to the carb?

@eec, ive ran with only the filter before the pump before and it did the same. The reason why i put the filter after was because i wanted to monitor how much gas is going in and also cus i saw tiny bits of dirt in the carbs bowel (which ive cleaned completely and all the passages were sprayed and blew out). The 3 psi is normal according to the service manual and recommended by weber. The carter pump was pumping 6 psi but no flow.

And yes ive tried the electric pump in the back of the car with a new filter before it. Ive even tried using the electric pump feeding the mechanical pump. And it still will not flow to the carb or at least keep the filters full.

Silly question, does the check valve in the return line have anything to do with this? Cus even pinched off itll fill the filter a little and then stop again after i drive it.

I havent tried to run a supply line from a gas can yet cus im afraid to drive with it in the car lol. But at this point i have no choice.

Thanks
Travis

[eec4tuner]

try bypassing the check valve and return line all together.

[sushimonster]

Well i dont have the check valve to begin with and i initially had it setup without the return line as per the paperwork that came with my carb kit. Does the same, no fuel flow. I was thinking it needed the check valve if i was gonna use the return line. But since i ran without a return line, i guess that proves that the check valve wont help anything.

[1985 CRX SI]

If your fuel pump passes the factory service manual out put test, I would believe the carb is where the problem is.
http://www.redpepper...1a/aav.png.html
Jeff

[sushimonster]

i have performed those tests already. i didnt have a properly gauged container tho. the pump puts out the correct pressure 3 psi with return and 3.2ish with return pinched off and the volume is where around 750(ish) mL, it was 3/4 under 1 liter mark on a coolant jug. so according to the specs in the manual, thats roughly 168 mL. so i have more than enough volume at the pump. im no scientist but this car seems to defy the laws of physics haha.

 

so would the carb actually stop the flow completely? cus its still getting enough volume to barely fill the bowl to run at idle and drive the car around very slowly.  

 

travis

[sushimonster]

i actually wanna try and put an inline check valve in the feed line before the pump, let the pump run without the carb to bleed all the air out and hook it back to the carb and see what happens. im thinking that the fuel is flowing back to the tank and allowing all this air in the line and filters that im unable bleed out. but im not sure if its possible that fuel would flow back to the tank if theres pressure in the tank 

 

travis

[jjamiemmark]

The float and needle will stop the flow if they are out if spec or stuck. With the carb empty you should be able to force air into it. Take a hose and attach it to the fuel inlet and blow with your mouth. In reality you should be able to gravity feed some fuel into the carb.

[eec4tuner]

That is weird. Needle and seat,hmmm... Float level set as per Weber service manual? I read where you said all new fuel lines does it include the hardlines as well? If so, get a Holley "Blue" pump, small filter before the pump ( to ram fuel in with no mercy!) pressure regulator, no return line. And be done with it. Seriously though, This is one interesting driveability problem.

Edited by eec4tuner, 22 March 2013 - 03:25 AM.

[sushimonster]

Indeed its very weird! Ive been chasing this for roughly 6 months! By far this is one of the strangest cars ive worked on and ive been working on bmws and benzs for over 12 years professionally. A car this simple shouldnt be this hard to diagnose.

I have set the float level to just about every spec ive found and none made a difference except one extreme setting had it flooding. But ive set it back to what the manual says, 18mm from top of float to gasket while not depressing ball and spring and 2mm needle drop. I have a new carter 4070 electric pump that i mounted to the rear tow eye that i ran for a while and that wasnt helping either, would still run dry (that really had me scratching my head) and the pump sounded like it was sucking air. I checked multiple times to find where it could have been sucking air and i found nothing so i just took it out and used the mechanical pump before the carter burned out or something.

So this is what i did last night and it seemed to work so far: i removed the canister filter before the mechnical pump and i found a one-way check valve from a bmw washer line i had laying around (praying it wont get eaten by the gas!) and i put it in the return line like factory. I put a fuel pressure/vac gauge on the pump suction side hose and noticed the before and after. The check valve seemed to dampen the pulses from the pump. I guess it needed to properly feed the carb??

Anyways im gonna continue to monitor it and play with jetting. Cus now i have a small stumble that i didnt have before with all this extra fuel flow.