Red86Z51

I am posting this to make others aware of a sealing defect I've discovered with new replacement fuel regulator diaphragms.

I recently ordered a new replacement fuel regulator diaphragm for my '87 from a well known company here on the forum. After installation and upon trying to start the car, I noticed that I had a cold "hard start" condition which I did not previously have. After checking all of the obvious (ie connections, vacuum hoses, etc...) I hung a fuel pressure gauge on the fuel rail. Turning the key "ON", fuel pressure immediately rose to about 45psi, and as soon as the pump turned off, it dropped like a stone to zero.

Next I clamped off the return line to the tank and brought up pressure again. The pressure remained high, with very slow bleed off. At this point I determined there must be a problem with the newly installed diaphragm.

I removed the new diaphragm, suspecting I may have somehow damaged it during installation, but found that not to be that case. Upon removal, I compared the the new and old diaphragm side by side. What I found was that the machined surface that acts as the seal to the return line on the new diaphragm was very rough, and has visible machining marks. The sealing surface on the original GM diaphragm is actually polished to a "mirror-like" finish, allowing for a tight seal against the return opening in the regulator housing. At this point I suspected the rough machining on the new part to be the source of my pressure loss, as the sealing surfaces of the diaphragm-to-return pipe are metal on metal. (I can actually feel the machine marks in the new unit running my fingernail across the surface)

I reinstalled the original diaphragm, and rechecked pressure, only to find my suspicions were correct. The original diaphragm does indeed allow pressure to remain in the rails once the pump cuts off.

The pictures below are a side by side comparison of the new vs. old diaphragms. As you can see, there is a drastic difference in the quality of the machine work on the surface of the sealing "button" on the center. The 2 "nicks" you see in the outer edge of the new diaphragm were on the unit as received, but I did not concern myself over them as they are outside of the sealing area.

(Note: On the original unit, you can actually see the reflection of the camera I used to photograph with).

ORIGINAL on RH side vs. NEW on LH side




ORIGINAL




NEW




I will be contacting the company that I purchased this from on Monday morning and will update this thread on those results.

Joe C

where did you purchase the FPR? if you don't want to post that info yet, just send me a PM.

Red86Z51

I prefer to withhold the company's name for now until after I've had a chance to speak with them. I don't believe the company is at fault, I believe it is the manufacturer/supplier of this part to this and other companies who resell them.

I just want anyone planning on ordering and installing an original replacement unit to be aware of this issue, and to inspect their unit closely prior to installation.

If the unit looks like the new one in my pictures above, DO NOT install it---it will leak!

Joe C

when you sort through all this, post your findings...

Red86Z51

I certainly will

gerardvg

Thanks for the heads up

ray1979

That looks just like the one I have sitting on my bench waiting to go in. Let me know your findings. Glad I did not install it yet.

383vett

I've always seen a mirror finish on the sealing surface of the regulator disk.

ray1979

any updates?

Red86Z51

Since the company I purchased the defective unit from and I have resolved the issue to my satisfaction, I am more than happy to say that the purchase was made from Fuel Injector Connection.

At the same time I purchased the regulator diaphragm, I also purchased a set of rebuilt Bosch III injectors. I was not having an issue with my regulator, I just thought it would be a good idea to replace the original while replacing the injectors. I am EXTREMELY HAPPY with the Bosch III's!

As for the defective regulator, Paul (@FIC) was more than willing to send me a replacement or refund (my choice) immediately. I opted for the refund since I had already purchased and installed a Borg Warner replacement diaphragm. He sent the money while we were on the phone, directly to my PP account. You can't beat that kind of customer service! Paul also stated that he has not seen an issue with the units he's been selling. We all know defects can and do happen...and this one was no fault of FIC. They are an outstanding company to do business with.

The NEW regulator diaphragm I purchased locally from Advance. I am also happy to say that the new diaphragm is MADE IN THE USA, looked great out of the box, leak-down tested and worked 100% as expected! Below are pics of the new BW unit just prior to install.







As you can see in the pics, the surface of the new diaphragms "button" is not polished as shiny and mirror-like as the original was. It was machined extremely smooth with no "rough" machining marks visible. In fact, the machining was so smooth that I was actually able to see some reflection of the camera (see pic 2 above) in the surface...and that was a good enough visual to convince me it would work. Once installed, it worked 100% as good as the original, as proven in the leak-down analysis I did between the two.

In closing, I hope my experience and this thread helps raise awareness to the importance of the condition of the sealing surface on these regulator diaphragms. After installation of any fuel injection related components, I highly recommend performing a leak-down analysis...never take it for granted that new parts will work...prove it!

leesvet

YES

I have written about this many times.
The "disc" portion that actually seats against the regulator body and creates a seal that holds pressure, can become damaged or scratched and weep fuel directly to the return side of the system. A good fuel pump will keep up with it while engine is running but it allows the residual pressure to bleed off instantly as if a bad check valve would.

To see this, look closely at the sealing/mating surfaces of the plunger/disc. They should be an even finish, smooth with no irregular spots.

cshuman

Will this cause you to have to crank the engine longer to get it to fire? I found the same issue with mine, pressure won't hold after the car is keyed. Sometimes it will fire right up and sometimes it will turn over a second or two before firing. This is great info!!!! Thanks for sharing.

ghoastrider1

I plan to replace mine very shortly, thanks for the advice on the inspection. I agree, its usually not the fault of the resale folks.

Red86Z51

You're welcome



It sure can. That's exactly what happened to me on a cold start right after the installation of the defective diaphragm...and to note, I did not have that problem prior to install.

To be sure your problem is the regulator, pinch off the return line at the rubber hose between the frame and engine (just behind the RH front wheel), bring up pressure and monitor your fuel pressure. If pressure holds and drops very slowly, your diaphragm is bad. On the other hand, if it drops fast with the return line blocked, your problem can be either injectors or your fuel pump. If your problem is intermittent, you may have to repeat those steps several times to reduplicate the failure.

Allowable pressure drop is less than 20psi @ 20 minutes.

MikeT 90 C4sixer

I think my regulator is now leaking. I got mine from FIC last summer, along with the 24lb Bosch injectors. The injectors needed replacing for sure, and the regulator i just did cuz it was new and rated for ethanol fuel. I didnt have any issues with it last year, but this year i am. Intermittent no start condition, and once it died on me going down a driveway. Tonight i put my FP gage on it, and just with key on would only get up to 20psi. Then came down quick. Started car ok, then watched gage. With vac off it was decent at about 44psi. Motor ran ok. But after shutdown, the pressure fell off very quickly, down to 20 in seconds, and down below 10 under a minute. Now i did NOT pinch off the return fuel line. That rubber flex hose looks impossible to get to. Mine is below the water pump in front of the engine.
I have my original regulator, i could put that back in with the adjustable cover, and see what happens. I dont know what FIC would do for me a year later. And i cannot recall the condition of that regulator, but my stock one has the mirror smooth finish on the seal.
Do these Bosch III injectors bleed off the pressure that fast?

Also, i did a quick check in my IROC camaro, with 350 TPI. I have a permanent gage on the fuel rail, its really helpful. Key on, pressure came up to 40 and held. Took long time to bleed down. So i think that is correct.

Red86Z51

Mike, although it sounds like a regulator issue, pinching off that return line would verify it as the failing component for sure...and personally, I always need proof before tearing into a repair.

You can also pinch off the return line in the rear at the fuel tank filler. Simply remove your fuel door (4 torx screws) and the boot. The return line will be the forward most rubber line (or top depending on how you want to look at it). It will only have 1 clamp on it. The pressure line has 2. Both pressure and return lines point towards the right side. Because of the added length you are blocking off by pinching it off at the tank, it may require you to repeat the pressure cycle 2-3 times to bring pressure up this way to be completely sure, but it will still give you the ability to verify leak-down through the regulator to the return. Simply turn the key on to run the pump to bring up pressure and observe. There's no need to run the car at this point...if it's a failing regulator, the pressure will stay high (with the return line pinched off) as soon as the pump cuts out.

The B3's should not bleed off pressure fast. I'm running the 22# B3's in my '87 and they hold pressure as expected.

Your Iroc is correct, and your '90 should perform the same.

Please post your test findings once you have them.

MikeT 90 C4sixer

Yea, i understand, by pinching off the return line, it should prove it once and for all. But what else could it be? I figured out which rubber hose is the return line, in the front of the engine. It is in a tight spot, but i will try it soon. I have worked on TPI motors quite a bit, so changing the regulator back to the stock should not be a big deal. I just want to run the fuel tank down a bit, before I mess with the fuel lines. I dont want to have a full tank, and loose alot of fuel! This issue is my #1 with my C4, so it will get worked on soon. At least we know one thing, with normal conditions, the FP bleeds down very quickly, so by pinching the line it should be obvious.

Red86Z51

Given all the symptoms you indicated above in the first post (above), it could also be the fuel pump. A defective pump can also cause the hard start, dying, low pressure and fast bleed off you've had.

I know the regulator is easy to swap, but I would want to diagnose this a little more before suspecting it...new ones don't usually just go bad that fast (note I said "usually").

Post your findings...I'll stay tuned

MikeT 90 C4sixer

I didnt get to check that pressure yet with the line pinched, but i have another thought. You say it could be the fuel pump. I thought when they go they just die out completely? I know they need good battery voltage to work good. Here is a new twist for you. My battery is weak. Yesterday it would not start the car. Just made alot of clicking noises. I do not really know the age of it. I hit it with my 40amp booster for a minute or 2, then it cranked right up. Drove to a show, and came back no problem. I think it is just time to replace that thing with a fresh bat. So could a weak bat affect the fuel pump?

Red86Z51

Technically, yes, but...a weak battery would have nothing to do with the fast pressure bleed off you mentioned above.

The fuel pumps can just cut out and fail completely, but they can also become weak over time causing start and overall performance issues. In addition, there is a check valve inside the fuel pump. This check valve allows the system to remain pressurized and keeps fuel from bleeding off back into the tank through the pump itself. Failure of the check valve is most evident while noting pressure bleed off during the "key-on, no start" test. A failing valve can keep pressure from coming up all of the way and will allow what fuel has been pressurized to to bleed off quickly.

These check valves can and do fail. The fuel pump is a possibility at this point with your pressure problem until a little further diagnosis is performed.

On a side note, I got a brand new AC Delco "Red-Top" 5 year warranty battery for my '87 from my local Chevy dealership for $76.00 + tax...they beat the pants off everybody else price-wise...even WalMart!