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Right size for return lines?

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Old Jan 20, 2004 | 04:15 AM
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Right size for return lines?

Right size for return line...?????
My setup is: tank- -10 line-aeromotiv filter- -8 feed line- rails-aeromotiv regulator- stock return line on a '85 GSLSE (about 1/4 inch tubing)

what the car is doing:
1. It won't start right up unless push the gas or keep it floored......seems to me like it's overflooding

2. When turn the key on for the line to charge, the pump sounds real loud and pulsates(I mean really loud), after it charges it settles and is not as noise.

3. The worst part is when the car starts moving if not accelerated hard enough the car will start jerking, it repeats this behavior in pretty much every gear. If cruising on the highway and let off the gas just a bit, the car will jerk.

4. The pressure gage on the regulator pulsates continuosly while the car idles,....somewhere betwen 25 and 30 #

5. When accelerating hard and then let off the gas completely the car will detonate and become a dragon with flames as long as 4 feet.

The car works great as long as you are driving it hard.....try driving around town in it or just cruise and it becomes a pain because it pretty much jeks all the time.

An idea that came to mind was the it is overpressuring the return line due to it's small size.

Any ideas?
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Old Jan 20, 2004 | 04:51 AM
  #2  
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Alright, looks like you've got a few problems at hand.

Now, the jerking at low throttle is caused by a lean condition; check your TPS and timing. Also, bad injectors/ECU can cause this, as well as vacuum leaks.

As for the fuel pressure thing... here's my best shot: At startup, the pump should whirrr HARD but not loud. Remember, at startup, you're going to get full fuel pressure until vacuum is developed, and the FPR ajusts accordingly. The pulsing may just be air in the line being squeezed out. Also, you didn't mention having an aftermarket pump, so if you've still got the stocker, it may be a good idea to replace it.

The insane flame-thrower action is caused by the injectors not immediately cutting the fuel when the accelerator is let off. To a certain level, this is normal and unharmful. But 4 feet?!?! Man, I wish my car could do that.... I don't think it'd be the fuel pump since the pump's actual output line is the same size as 1/4" hose (unless it's aftermarket).

Now, you may have a clog in the return line. Try blowing some compressed air through it (make sure to remove the gas cap before trying this!) and see if it's got a restriction in it.

If everything is normal (fuel pressure, sensors are good, no vacuum leaks, et cetra....) then it's usually the ECU.
Do a one-at-a-time sensor check with a multimeter per the FSM (haynes/chilton) specs. Main points of interest should be the boost sensor, TPS, MAF, water-temp sensor (the one on the pump housing), and the intake air-temp sensor (on the UIM; there should also be one inside the MAF). If they all check out okay, test your FPR. A good way to do this is to hook a hose from an air compressor to it, and slowly turn the pressure up via the regulator on the air compressor. This way, you can see exactly what it's "WOT" pressure is, as well as the "check pressure" (full vacuum). With no vacuum, you should see a higher reading than with a vacuum obviously. Get a fuel pressure reading directly from the pump; make sure it's got enough pressure as well as flow. As a last resort, take the ECU apart and look for scorched components.

Test your injectors. Zip-tie them to the fuel rail and turn the car to the "run" position. They should NOT be squirting at this point. Have a friend try to start the car (being serriously careful as to not ignite the fuel) and observe the spray pattern; it should be a fine mist (highly flamable; almost explosive). If they leak (with the key just turned on, but not trying to start) or the spray pattern is "drippy" have them cleaned/replaced. They should turn off cleanly and completely when the switch is turned "off."

That's all I can think of at the moment; hope it helps.
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Old Jan 21, 2004 | 01:40 PM
  #3  
a1670's Avatar
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Thank you. I appreciate your time.
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