It's a small 2 to 3 inch metal or possibly plastic device (non electrical) with a hole through the middle and has a ruber inner core and no clamps to hold it on.It's only purpose is to reduce sound.I have a friend who's a mechanic and he says he throws those things away all the time, because the ruber changes shape causeing an internal fuel leak or reduced fuel pressure.I asked him what he uses and he says they use a ruber fuel line as a replacement.(I also use metal hose clamps).One of the main sources for a noisy fuel pump is not reinstalling the fuel tank pads,sound travels through the body sort like electricity,ruber is a good source to reduce sound,but as for the fuel tank,pads are used on the top and sides,so always remember to try and install the pads on the sides of the fuel tank (2 on each side of the tank), a couple extra on top wouldn't hurt either.
The "pulsator" is actually design to dampen pressure pulses that occur in the fuel lines to the injector rail. These pulses are caused by the fuel pump. When these pulses get to the injectors they vvary the fuel pressure ever so slightly, altering the amount of fuel that goes through the injectors.
JazzMan
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10:33 PM
Aug 14th, 2004
James Bond 007 Member
Posts: 8872 From: California.U.S.A. Registered: Dec 2002
Interesting (not a flame),I never had a fuel pump that pulses.
Think about it... pumps make noise, right? Noise consists of pulses. You're thinking pulsing like a heart beat pulse, but no, this is much higher frequency and lower amplitude, but nonetheless pulses in pressure. Think of it as pressure waves in the fuel line.
JazzMan
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10:45 AM
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
I left the pulsator out when I did my Quad 4 swap. Before starting the engine the first time I ran the fuel pump with a test gauge on the rail. The pressure was rock steady at 43 psig so I doubt that the injectors are being effected much.
Anytime you buy a replacement fuel pump module they always come with a section of hose to replace the pulsator. Most technicians will tell you to throw them away and install a rubber hose because the pulsators can cause problems. The parts house I use to work at, they recalled those pulsators because they weren't selling, we had 25 on the shelf and they all had a thick coating of dust on them. Most fuel pumps aren't the solenoid type, so there really shouldn't be that much pulsing. Most of them are designed like a water pump with vanes that actually push the fuel.
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12:01 AM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
I'm not buying that. The rubber lines in the fuel system would be more than enough to keep any minor pressure variations controlled, not to mention the standing fuel in the filter AND the element itself would dampen a good bit of any pressure variations. The reason it's there is to keep the noise from being transmitted through the metal fuel lines and outside the tank, IMHO. I generally throw them away and replace with good, FI line and two clamps and have never had a problem.
John Stricker
quote
Originally posted by JazzMan:
The "pulsator" is actually design to dampen pressure pulses that occur in the fuel lines to the injector rail. These pulses are caused by the fuel pump. When these pulses get to the injectors they vvary the fuel pressure ever so slightly, altering the amount of fuel that goes through the injectors.
JazzMan
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12:32 AM
Electrathon Member
Posts: 5241 From: Gresham, OR USA Registered: Dec 2002
The engine will run with or without a pulsator. Most people and parts guys do not even know the purpose of the part (as evidanced by the pulsators never selling, you should replace it whenever you replace the pump). It is a simple shock absorber for the fuel system, it helps absorb noise and vibration. It can be replaced with a hose, but the hose that many people generally use is rubber and not silicone like the pulsator is made out of, so the life on the hose is less than the life of the pulsator (but is still likely to last years). The hose piece that often comes with the new pump is there for use in cars that do not have the pulsator, this was considered to be the lower cars to GM, the higher end cars usually always had a pulsator from the factory. I can remember many bullitens fron the 80's that were addressing noise complaints. Several had you remove the factory hose and install the pulsator.
I have always found it odd that anyone would remove a part that was there to fix complaints and downgrade the design in doing so. Personally, I have never known a drivability tech that is knowledged in GM cars that recomended removing a pulsator.
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02:10 AM
Fie Ro Member
Posts: 3735 From: Soest, The Netherlands Registered: Sep 2001
I'm not buying that. The rubber lines in the fuel system would be more than enough to keep any minor pressure variations controlled, not to mention the standing fuel in the filter AND the element itself would dampen a good bit of any pressure variations. The reason it's there is to keep the noise from being transmitted through the metal fuel lines and outside the tank, IMHO. I generally throw them away and replace with good, FI line and two clamps and have never had a problem.
John Stricker
I remember reading about the pressure waves somewhere a couple of years back but can't find the original article. I'll keep looking and if I find it I'll post it here.
If you want to know what a pulsator does... look up a "hammer stop" in the residential/comercial plumbing world. Describing them as a shock absorber for the fuel system is fairly acurate. (Installing hammer stops on the back of your washing machine will make the fill hoses and valves last longer. If you can't fit them there, put them at the wall end of the hoses.)
Some vehicles have it near the pump, others put them up on the fuel rail. Some may have them both places. It serves to reduce vibration in the system from both the pump and the injectors. Pulsators are common on many high pressure systems. Low pressure systems may also have them on some vehicles.
On cars that have them in the tank like Fiero, the Pulsator should be replaced when the pump is replaced.
The fuel flow from the pump isn't perfectly smooth with Fiero type pumps. I'm pretty sure they are Positive Displacement gear pumps more akin to the engine oil pump. They are not centrifugal pumps like most well water pumps. Centrifugal pumps that size can't make the 50-70 PSI needed for most systems without spinning at very high RPM. (Remember the pump has to be able to make more pressure and flow than the engine actually needs. The regulator's job is to manage the actual rail pressure.)
We all know GM, and every other car maker, is cheap... Do you really think they would spend the dollar per car these probably cost them if they didn't feel they have to?
Do pulsators fail? duh. All fuel system parts wear out. That is why they should be replaced, not reused, when the pump is replaced. Replacing them with hose is not the same thing. Will using a simple hose cause problems? hard to say. It could increase noise from the tank considerably and being where Fiero tanks are that usually isn't a good thing. Complaints about pump noise are fairly common in the forums.
------------------ The only thing George Orwell got wrong was the year.
