jv9999

My '87 Vert has the same filter in the return line. Looks like it's always been there.

ezobens

The fact that it doesn't appear in any parts books is very suspect.
Unless it's shown in the official GM assembly manual, I call

AC Delco lists what vehicles this filter was installed on in their on-line parts catalog and it lists a lot of 60s and 70s trucks and some full size GM cars but zero listings for a C4.
Based on the photos, the install looks totally aftermarket-
The mounting bracket is just a piece of angle iron and rubber hoses with hose clamps is not something GM would do from the factory.

I suspect this may have been more of a non-sanctioned repair that dealers or shops may have been doing back then to mask another issue.
Putting a fuel filter on a return line from an engineering standpoint makes no sense on a sealed fuel system.
Just my .02

ezobens

So it appears that I was right and wrong.
Apparently, I am wrong as this WAS a sanctioned "fix" from GM:
http://www.quayle-co.com/tsbs/86-234.htm

However, I believe I am correct that in that this was not done from the factory (see TSB above) and would explain no listing in the parts books as these cars didn't roll out of the factory with them.

What is disturbing is the 'hack' fix for the problem listed.
This is pretty lame even for GM.
Carry on...

AJ123

http://www.corvetteactioncenter.com/...cumulator.html




TO: ALL CHEVROLET DEALERS Some 1985-86 Corvettes may exhibit a hammering/knocking type noise audible in the vehicle passenger compartment after a cold start, which normally diminishes after 3-4 minutes of engine operation. This condition may be caused by pressure pulsations in the fuel system generated by fuel injector operation, resulting in hydraulic hammering in the chassis fuel pipes. Vehicles exhibiting this condition may be repaired by installation of a filter-accumulator assembly in the fuel return system. Service kits containing required parts and installation instructions are noted below by body style and are available from GMSPO. Body Style Service Kit P/N ----------- --------------- Coupe 10068791 Convertible 10068797 Labor Operation Number: T1195 Labor Time: 1.4 Hours Add: 1.1 Hours for Convertible David - See more at: http://www.corvetteactioncenter.com/....QVTnL5ce.dpuf

If you own an 87 Vet they are on all of them. They are a pain in the *** to change filters on. The location sucks. Not done by rocket science I agree with you.

papatioman

I am far from being the expert here but it seems redundant to have a fuel filter on the return line, especially to help reduce the hammering effect. Does not the fuel pressure regulator play some part in the reduction of hammering since it is diaphragm operated? An extra fuel filter is just something else to have to pull maintenance on. I agree on the fuel pump being a rotary vane type pump. I have installed a new one and the diameter of it is not large enough to be any other kind of pump.

Tom400CFI

Apparently some engineer determined that a filter on the RETURN lowers the condition...I don't know how. Once the fuel passes through the regulator, it's out of and isolated from the part of the system that would create any "hammering". I'd think a far more effective solution would be an accumulator on the pressurized part of the fuel system....not the return. Odd TSB.

QZRBLU

Gary,
The pulsator was added to reduce noise, nothing else. I had to replace my original AC Delco fuel pump two years ago and had to go through two pumps to find one with a good check valve. The first one would bleed pressure off in 10 seconds or less (I had new injectors and AFPR). My original pulsator was so loose it would not hold pressure either. I used submersible hose to replace the pulsator and I have never noticed any noise.

Mick


[dampen] To make wet
[damp] To attenuate

papatioman

Getting a lot of good advice here....thanks Mick....I've seen quite a few on here eliminate the pulsator and replace with a section of hose. I'm going to pull the sender/pump assembly out of the tank again, check the hard lines for holes and do away with the pulsator. Because of its slip on design, I can see how it can be the weak link. If the pressure drop continues, at least I have eliminated anything in the tank, unless my new pump has a bad check valve as you mentioned. I can then move on to eliminate the other possible causes.

Gary

AJ123

As with anything on a vet just take your time hold on to the part for a while. Just in case the hammering starts. Good luck

papatioman

will do on keeping the part for a while....will post any results I get.

papatioman

Well....my weekend didn't turned out as I planned. A ole boy was advertising a set of (4) 5 spoke chrome wheels on craigslist. Drove to McKinney, Texas a 3 hour drive each way Saturday and picked up the wheels. Took my wife along and we went to Dallas for some shopping while we were in Texas. Got lots of atta boy points Saturday.

Sunday I did replace the pulse dampener with a section of hose. With key on only my pressure was 43 psi before and immediately dropped to 38psi once the pump shut off. Now with key on my pressure is 48psi and drops to 42psi when the pump stops. My running pressure is 40 versus the 38 I had before. This is a definite improvement in pressure but it still leaks down. It leaks down considerably slower than it did before but is still at 0 within 1 minute. Checked the vacuum hose on the regulator, it was dry with no smell of gas. Did not get around to the line pinch off test, one of my renters called with a no heat problem at their house....always something. I am leaning towards a leaky injector for now. Smelled the oil and I believe it has a taint of gas smell to it.......hard to tell with my nose.

Gary

AJ123

There is a check valve in the fuel pump assembly. I removed mine and replaced it with fuel hose with my new pump.

Fuel pressure will drop when it sits for an extended period of time. One of the reasons the fuel system primes with the key on before firing.

Diaphragm can cause pressure loss.

The fuel pressure diaphragm was damaged and when I replaced it we removed lines at tank fuel filter and blow out the lines. lots of crud like cholesterol 87 vet
You can have your injectors rebuilt or do what I did.
My injectors weren't bad but the original. I was installing a Super Ram so I called Jon at FIC and bought 24 lb Bosh 3 injectors.



http://www.ebay.com/itm/FIC-FUEL-INJECTORS-24LB-1992-1997-CAMARO-V-8-Bosch-3-/111194610246?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item19e3b71a46

papatioman

Thanks AJ.......good photos,

I installed a new fuel pump last weekend which is where the check valve is....correct? I will probably pull the rail system off and replace the injectors & regulator all at the same time. The car has 128K miles on it and probably over due anyway.

Gary

AJ123

Gary here is a thread on furl injectors from Jon of FIC all the answers of how to test and comparison of injectors

Unless you have a problem with the injectors the corvette is a money pit. I am 60 and for now spend money on my baby because I am single and have no bills.

Steve

https://www.corvetteforum.com/forums...questions.html

papatioman

Steve,

Thanks for the link.....will read up on it. I am 57 years old, kids moved out and I have my first vette. Car runs fine....this fuel rail leak down is bugging me because I know its not supposed to be that way. I also have a concern of what damage a leaking injector will do if any.

Gary

Tom400CFI

At a minimum, it makes it hard to start hot, as it "floods" the engine while it's sitting hot, dripping fuel into the intake.

Worst case, it can do engine damage by washing down the affected cylinder (gas washes oil of the cylinder wall and piston) and could dilute the oil as well.

papatioman

Tom,

Those were my concerns exactly.........thanks.

Gary

QZRBLU

Gary,
The REAL worst case would be if the leaking injector(if you have one) could coincide with a cylinder that happened to stop with it's intake valve open. You 'could' have about a cup of fuel dumped into that cylinder and the next time the starter runs, bent rod or worse. Fuel does NOT compress.

[I had this happen once on my '61 Fuelie. The needle valve in my spider did NOT seal and the fuel reservoir (about 1/2quart) drained into the#1 cylinder. This was a much more prevalent problem on the Rochester Ram Jet Injection]

Mick

Tom400CFI

A '61 fuelie is not a '90's EFi. Where is the "cup of fuel" stored?? There is no "cup of fuel" sitting anywhere that can dump into the cylinder. Worst case, you might leak a 1/2 a tea spoon into the port.

papatioman

OK....don't make me afraid to drive it!.... I'm assuming that once the pressure bleeds off, the remaining volume of gas in the rails and lines stays. I'm also assuming my next best step is to replace the injectors & pressure regulator while I have it tore apart. I'm assuming it all bolts together like everything else and no special knowledge is needed. Like I said before, not new to cars, just corvettes & fuel injection.

Gary