Fuel Pump Pulsator - Keep it or Eliminate it?

[The Car Whisperer]

I just replaced the fuel level sender unit in my 86' because it was giving erratic level readings. While I was at it I replaced the fuel pump. Only used original Ac Delco parts for the replacement. I did not realize that there was a pulsator between the pump and fuel line so I had to use the old one over. I am sure it was the original pulsator that came from the factory. My question is should I replace the pulsator with a new one or eliminate it alltogether and just use a piece of fuel line in it's place. I have always had a slight hesitation in my Vette when I blip the throttle, have replaced TPS and IAC and adjusted according to Factory Service manual and completely dis-assembled and cleaned the throttle body but still have that slight hesitation problem. Could it be that the pulsator has a slight leakage problem? Since the pulsator just pushes onto the fuel pump and fuel line I don't get a good feeling about it being able to hold the 40 PSI fuel line pressure. Any body have experince with this part of the fuel supply system. I have a new pulsator on order and will probably install it if it ever shows up, but was hoping someone here could give the definitive answer on the pros and cons of keeping it in the system or removing it and replacing it with a piece of fuel line.

 

[Schrade]

Keep it original.

Was current getting to the old sender? Ground working OK? How's static fuel pressure now?

 

[boomdriver]

The pulsator is just a dampner that has no effect on anything as far as engine performance. All it does it take the VERY mild pressure spikes out. You can see very little difference on a fuel pressure test gauge with or without the dampner. If anything, the gauge needle MIGHT be a bit more stable. The pulsator does not increase or decrease fuel flow or pressure. When the pump runs it has cycles or gaps in pressure, but these are so small that there is no effect. At the speed that the pump turns and the fuel return system, pressure remains stable. I wondered IF there was any fuel loss at the slip-on dampner, but if there is, it does not matter. The pump makes up the lost vol unless the line comes apart in the tank.. Pressure at the fuel rail is all thats important. I would'nt open the tank again just for that. Everytime that sender has to be pulled, you risk tweaking the float-arm and loosing the accuracy and allowing dirt to enter. That screen on the pump IS BY FAR the most critical part of that assembly in the tank.

 

[aklim]

Ditch the B1tch.

 

[The Car Whisperer]

Can a bad Pulsator cause my fuel lines to rattle also? The motor runs fine with the old pulsator, but maybe a new one would help the ratlle problem. I had good fuel pressure before I changed out the bad sender, I haven't checked the pressure with the new sender and pump though. It might be my imagination, but I think the acceleration from a stop has increased significantly. Can the new fuel pump alone be responsible for that?

 

[TedC]

Can the new fuel pump alone be responsible for that? Sure it can. Checking fuel pressure under engine load is an important test. Position pressure gauge so that you can see it from the drivers seat (lower windshield) and partially latch the hood to avoid pinching the hose. You can now verify fuel pressures under different engine load conditions.

 

[LT4man]

How many miles on your Vette?

Are your fuel injectors original?

Have you ever ohm checked your fuel injectors?

Old, tired fuel injectors can give you a hesitation when accelerating.

 

[aklim]

How many miles on your Vette?

Are your fuel injectors original?

Have you ever ohm checked your fuel injectors?

Old, tired fuel injectors can give you a hesitation when accelerating.

That only tells you the status of the solenoids. It does not tell you whether there is any build up in the injector pintles. Even if the solenoid is perfect, it could be spraying badly. Best to take the injectors out every few years and have them tested.

 

[TedC]

Fuel Pump Pulsator - A small accumulator between the fuel pump outlet and the fuel pressure regulator. Reduces the fuel pressure variations that occur as the fuel injectors open and close, and to reduce operating noise. Failure of the in-tank units would result in increased noise or loss of fuel pressure or volume. The pulsator isn't a routine maintenance item, although replacing the in-tank unit is recommended with a fuel pump replacement.

 

[TedC]

1. Verify fuel pressure under load conditions, especially when you are having the hesitation. Is this happening in open or closed loop (engine just started or hot)?
2. Check each fuel injector for resistance value (ohms).
3. Check engine timing and minimum air speed (some people have no clue how a TPI works so they adjust this screw thinking it is idle speed. Then the ECM can't properly manage idle and off idle).
4. You said you replaced the IAC. Did you verify the pintel shape matched? I think there are three different shapes, but the IAC housing are all the same. Don't assume your throttle body is original. Look for date code and verify the year. I do this when it is off the plenum and cleaning it.
5. When was the 02 sensor replaced?
Just because injectors ohm out ok and show no pressure leak down, they can still cause driveablility issues as pointed out aklim.

 

[LT4man]

That only tells you the status of the solenoids. It does not tell you whether there is any build up in the injector pintles. Even if the solenoid is perfect, it could be spraying badly. Best to take the injectors out every few years and have them tested.

I agree.

I offered those questions to give the original poster a good place to start troubleshooting. According to his answers, I would have given him more detailed troubleshooting tips.

 

[joshwilson3]

That only tells you the status of the solenoids. It does not tell you whether there is any build up in the injector pintles. Even if the solenoid is perfect, it could be spraying badly. Best to take the injectors out every few years and have them tested.

Who gets their injectors pulled and tested every few years? Never heard of that before.

 

[boomdriver]

why not? injectors are wear parts like plugs or wires. Its not a big deal to pull the rails.

 

[aklim]

Who gets their injectors pulled and tested every few years? Never heard of that before.

I do, depending on the mileage.

 

[joshwilson3]

why not? injectors are wear parts like plugs or wires. Its not a big deal to pull the rails.

I'm sure it may be a good idea. I've just never heard of doing it as a regular maintenance check. I doubt there are hardly anyone here doing that. Except maybe people who track their Vettes.

 

[aklim]

I'm sure it may be a good idea. I've just never heard of doing it as a regular maintenance check. I doubt there are hardly anyone here doing that. Except maybe people who track their Vettes.

I don't track all my cars but I take the injectors out every 100K to test them. At that mileage, I have found some issues here and there.

 

[joshwilson3]

I don't track all my cars but I take the injectors out every 100K to test them. At that mileage, I have found some issues here and there.

Taking them out after 100k is one thing. But you were saying to take them out every couple of years and check them. Which I believe is way overkill unless you are tracking or trying to find a problem. After 100k miles, it would probably be money better spent replacing the injectors from Jon at FIC. Which I believe they are around $180 or so for the set. Might as well do that then spend money getting them cleaned. Especially if they are Multec injectors.

 

[The Car Whisperer]

Ok, I checked the fuel pressure at idle, it is holding at 39 psi at 650 RPM, when I shut off the engine it goes up to 43 psi and it held there for over a half hour. I removed the fuel pressure gage at that point. I have an adjustable regulator. Pressure was measured with the vacuum hose attached to the regulator. I would think the old pulsator is fine and not leaking by at the connections since I got a decent pressure reading and everything held the pressure after the ignition was swithched off. I replaced the injectors about 20,000 miles ago and that was about ten years ago. I beleive they are the newer disk type. I got them from Marren Motorsports back then and they were a flow matched set.

 

[gmjunkie]

Ok, I checked the fuel pressure at idle, it is holding at 39 psi at 650 RPM, when I shut off the engine it goes up to 43 psi and it held there for over a half hour. I removed the fuel pressure gage at that point. I have an adjustable regulator. Pressure was measured with the vacuum hose attached to the regulator. I would think the old pulsator is fine and not leaking by at the connections since I got a decent pressure reading and everything held the pressure after the ignition was swithched off. I replaced the injectors about 20,000 miles ago and that was about ten years ago. I beleive they are the newer disk type. I got them from Marren Motorsports back then and they were a flow matched set.

Fuel pressure is good to go!!
How many miles are actually on the engine???:confused

 

[aklim]

when I shut off the engine it goes up to 43 psi and it held there for over a half hour. I removed the fuel pressure gage at that point. I have an adjustable regulator. Pressure was measured with the vacuum hose attached to the regulator.

I replaced the injectors about 20,000 miles ago and that was about ten years ago. I beleive they are the newer disk type. I got them from Marren Motorsports back then and they were a flow matched set.

IIRC, pressure should be measured with the hose OFF. Still, it does sound like the FPR is good.

That could be an issue. 10 years is a long time and it could have varnished up on you. The spray pattern could be bad. After 5 yrs or 50000 miles, I would take it out. Whichever comes first.