Shawnee

Reading your post,you did not mention what the car was doing or how it was acting. As far as the fuel pump issue. If you think that is whats wrong, You said that you replaced the pump before and I think it would take at the most 1 hour to replace a fuel pump. It seems that what you are doing is taking a lot longer. As far as testing everything you should follow the manual and set things up accordingly. Also if you have the program Winalda plug your laptop into the test port and that will give you much information. The pressure sounds pretty good, although I have not check mine I have an inlne guage but didnot get it on yet. I sent my throttle bodies out the be set up and sleaved and ran all the tests with the Manometer etc and mine runs fine.
jimbil208

 

Sorry, meant to mention that the car is having a hard time idling now. It also starts to stumble really bad around 2K rpm. Have to keep pumping the throttle to keep it running. This all started all of a sudden. Car had been running great before (checked the TB balance about 3 months ago) and the last time I check the fuel pressure it was around 13psi. Can no longer adjust the pressure high enough to get the desired 13-14 psi anymore, only about 11. I have investigated the shop manual and cannot seem to get enough fuel pressure no matter what I do. Changing the fuel pump is a PITA and just want to make sure it is not someting else before I do this. Could my regulator spring be too weak or something.

 

Hello again also.

I am QUITE aware of how to balance throttle bodies with a manometer.

The problem began is when you wrote post #154. Increasing the idle while still using the manometer as a reference to see what the water does or if it 'holds' is pointless and has no bearing on the balancing process at all. If you got a result that makes you happy...I am glad...but it is not a standard of how to balance throttle bodies.

You are aware that when the 6 inches of water is obtained on each throttle body during the balancing process....that this 6 inches of water COMPLETELY changes when the idle is set to the 475 rpm's as specific in the manual...don't you??? SO...if you attach a manometer to a throttle body AFTER you set the idle as specified...it WILL NOT read 6 inches of water any longer.

I would be suspect to the hose from the fuel pump to the sending unit is bad or your pump is shot.

Knowing that you checked the pump pressure at the fuel filter area...and got only 7-8 psi...it is telling me that you have an issue in the fuel tank.

When you checked the fuel pressure at the fuel filter area...did the pressure hold...or did it drop off right away?????

I have run into the sending units can have the bracket that is often times welded to then to keep the supply tube and the return tube break and the supply tube has a small hole in it that will not allow the fuel pressure to be as high as needed.

ALSO...depending on what name brand of pump you bought could be part of the problem....and MORE IMPORTANTLY...like I tell many of my customers who have fuel injected Corvettes.

"If you are the type of person who puts a 1/4 of a tank of fuel in your Corvette...and run it down to "E" and then fill it up again to a 1/4 of a tank....your fuel pump will FAIL FASTER." They say:"How's that???" Because the fuel pump is DESIGNED to be submersed in FUEL to keep it cool....and if you are ALWAYS on a 1/4 of a tank or below...the fuel pump is out of the fuel and running...and getting hot...and wearing out...bit by bit. Something to consider if your fueling style fits this comment.

DUB

 

If you have a manual...you do know that the 11 psi is within the limits. But a little higher is better.

Fuel pump is easy..as you know it comes out through the fuel door opening. The hoses are a bit fun...but not that bad.

What year 82 or 84??

One trick I have done....is that by using a close off tool that can slowly pinch a hose shut and be controlled. When I have the fuel pressure gauge and hose assembly hooked up between the throttle bodies. I can slowly close off the return line a little and increase the fuel pressure and see if that corrects the problem...if it does then I KNOW it is fuel pressure related.

ALSO...I guess that when you installed the fuel regulator parts in the throttle bodies...you did ONE at a time...CORRECT????

DUB

 

DUB
Thanks for the information. I usually keep the tank at close to 1/2 full or above. I have an 82 CE. It ran the best around 13-13.5 the last time I set everything. The fuel pressure remained the same at the filter area while the car was running (7-8 psi). I have to adjust the regulator spring as tight as possible to get the 10-11 psi so I would assume something is wrong somewhere. I am suspecting the pump or something in the tank.

On the TB, I am fairly certian that I did them one at a time but it has been several weeks now. I know I have the correct diaphrams in the right locations. Could my springs be reversed or weak? Is there a way to tell the difference? I'll try the pinch method you mentioned tomorrow and see if that helps any. I know if I completely close off the return I have all kinds of pressure.

 

Check the hose on the Fuel Pump itself. Sometimes they rot and collapse.

 

I do not know what you mean by "reversed or weak'...in regards to your springs. They matter where they go...but on one way or another I do not think matters. You cranking the adjustment to death and bottoming it out is not good. Get the fuel pump corrected.

The color of the springs are different. I would have to take a look at a set I have and let you know.

When I am checking the fuel pump...I am checking for 'dead head pressure'. SO I have my gauge assembly attached to the end of the fuel filter and I DO NOT worry about running the engine. I make it so the pump will run and I can see the pressure. I do it the same way when I have the sending unit out of the car.

OBVIOUSLY I AM NOT responsible if you set yourself or anything on FIRE if you are messing around with fuel and electricity. If you do NOT possess COMMON SENSE...then give it to a professional. I am NOT writing that you are that way...but I am not there with you...so what happens is just that. IT IS ALL ON YOU.

Now, I put about 3/4 of a gallon of fuel in a large clean paint mixing bucket and set the fuel pump and strainer in it. I have all of my wiring ready to go AND SAFE...and I have my fuel pressure gauge hooked up the the line coming out of the sending unit and power up the fuel pump for about 1 second. If it is not leaking...I will power it up again and see what is going on. SLOWLY loosen the clamps and allow the pressure to fall to ZERO. Then remove your test equipment.

For what it is worth...the Corvettes that use that higher pressure pump have 2 clamps holding that pressure hose to the tube of the sending unit due to the high pressure. If possible....I would do that also.

DUB

 

Thanks again. Not planning to blow myself up but you never know. Fire extinguisher is always close by when messing with fuel. Pinched off the return line like you mentioned and car ran a lot better. Had it running around 13-14 psi. Still wants to surge occassionally but noting like at the lower psi. Have all the vacuum ports closed off so I don't think I have any leaks. Seems I need to replace the pump.

In regards to the springs, I have a pink spring on the regulator TB and a greenish looking spring on the front. That is what I meant by possibly reversed. I wondered if the spring pressure had weaken since they are 30+ years old. I agree that bottoming out the spring is not good and that what had me so worried in the first place. I'll pull the sending unit/pump out this week. Just love doing this again.

 

hello,this is to DUB

I don't think that you are talking to the right person,because I said nothing about changing the idle and most of the other things you said in the last post. So DUB,lets see who is talking to who.

now to Shawnee,
you gave tests that you did to your car and didnt mention what was wrong with the car. When you said about not idling right and had to pump the pedal to keep it running,I said to change the temperature sensor on the right front side of the engine,with I link to a corvette parts place as to what it looked like. Are we straightened out yet?
Thanks jimbil208

 

The regulator spring can not step up the pressure. It can only step it down and maintain a constant pressure. Example if you have a pump that delivers a maximum of 14 psi the most you can get out of the spring is 14 psi. If the pump delivers 7 psi and you have the spring set at 14 the most you will get is 7 psi. If the pump is bad and kicks in all over the place the pressure on the other side of the spring/regulator will be all over the place up to 14 psi.

If you install an 85 pump that delivers about 40 psi you can use the spring to set the pressure at anything you want but I wouldn't go past 13-14 psi. Anything more will blow the diaphragm.

Jim

 

I am writing to the RIGHT person.....what YOU wrote in post #154...as I wrote before ...is INCORRECT and I am letting you know that even though I do appreciate you trying to help me out...I do not need help in balancing throttle bodies. I am way past your skill level in this.

DUB

 

Hello DUB

I am very sorry in the way that you feel. I still say there is some misunderstanding as I never mentioned the idle screw only the balance. As far as down shifting around 40 mph I think ,it has been over a year since I had the problem. And a GM tech. drive the car and said sometimes a good tune up will take care of that,and that was before a had my throttle bodies rebuilt and tune the car up. Now is doesn't down shift rough anymore like it did. As far as the Manometer, are you saying that I cannot plug the manometer in both throttle bodies when the car is in normal operating condition? Well I did it it sucked the water out the first time. After a couple if times and just tweaking the balancing screw ver little, I can increase rpms and the water stays right there. I dont care if that is part of a test or not,but it sure made my care hum much better. BTW what did you do with the other screw on the front throttle body?
Very Sincerely I Hope We Have An Understanding,
jimbil208

 

The manometer is used ONLY ion one throttle body at a time. When is near operating temperature.....and the CORRECT PROCEDURE it used for disconnecting your Idle Air Control Valves...and then BLOCKING OFF the air passages as REQUIRED so the manometer can be used and adjust the REAR throttle body FIRST to 6" of water. Then removing the manometer and installing it on the front throttle body and adjusting the bolt that is brazed to the linkage to 6" of water.

Then this is when the rear throttle body idle adjustment screw is then used to set the curb idle at 475 rpm. Some want me to set it a little bit higher...which helps out the spark plugs....and if the idle is set higher than the 475 rpm....the idle when the engine is running will be higher than the 500 rpm when in GEAR and when in PARK it will be higher than the 700 rpm.

SO...just going in and installing the manometer on your throttle bodies when the IAC's are still connected and the air passages are open is POINTLESS. BECAUSE when the idle is being set...the end result of the 6" of water that was obtained during the balancing process is NO LONGER 6" of water.

That screw...as I described in the above text is what is used to make sure that the front throttle body is balanced to the rear throttle body.

NOW...the screw on the FRONT throttle body that is at the rear...down by the bottom. That screw is not used...other than using it for the basic set up when the throttle body is off the engine...so you can get it adjusted as outlined and close enough to crank and run the engine so it can be balanced correctly. It also needs to be backed off a little bit to the linkage DOES NOT rest on it. This screws is not an idle stop for the engine....ONLY the rear throttle body idle screws is used for that.

DUB

 

I agree.

The main reason that if a 85 pump being used is that when teh pump starts to fail/wear out....and the pressure begins to drop....you will have more time... due to it can keep running at 22 psi (for example). And your engine will still run because it is still above the 13-14 psi. BUT 22 psi running pressure on a Tuned Port ....it will not run well at all.

BUT...a correct pump for the 82-84...does not have a really high peak pressure....so when it begins to fail....it will show up sooner. which is why many people change to it.

DUB

 

Finally got back to this again. Pulled the fuel pump and checked the dead-head pressure - 55psi. Pump appears to be working fine so will install it back in now. Checked the dead-head pressure at the inlet line to the front TB - same 55psi. So it appears I do not have any problems with supplying enough pressure to the TB's. Will now installed everything back and check the pressure between the TB's again. For some reason I cannot increase the pressure at the regulator to 13-14 psi to get the car to run smoother. I have changed the TB diaphram seals and everything appears to be correct there as well. Open to ideas on how to correct.

I do remember when I first got the car back running again a year or so ago after sitting for several years I changed the diaphram gaskets to new ones and had this similar type problem. Switched back to the original diaphram and I could adjust. Unfortunitly, that is not helping this time and one of them has come loose in the center now.

 

Remember that just because you have fuel pressure at 13-14psi...does not mean that there is something else wrong. So DO NOT get so hung up on the fuel pressure. The benefit you have is so when the pump starts to wear out.,..it will give you more time...so thinking that 20 psi is going to fix you problem...is unlikely...even though you pinched off the fuel return and increased the fuel pressure....and wrote that it idled better.

Vacuum leaks...MAP sensor reading and coolant temp sensor can cause a problem. Also...bad IAC's can be part of it.

DUB

 

Shawnee
Did you get my post about testing or just replacing your temperature sensor which is located on the front right side of the engine,it probably has a plastic cover over it, It doesn't always show up on tests unless you are using the test port , but it probable isn't going into closed loop.
jimbil208

 

Shawnee....How are things going????

Current fuel pressure between the throttle bodies is?????

DUB

 

I know there are plenty of threads about this but I would like a little input from '82 owners. It is a different beast from the other C3's.

First off, I gutted my Cat when the exhaust was off for the fuel tank swap. It changed the sound for sure and sounds a lot better. The catch is that it has some crappy NAPA universal mufflers on it.

I'm either going to put some Magnaflow mufflers on it for sound only, or go true dual.

Any extra power is a nice plus but so is a good deep muscle car sound.

Am I going to get any more power or a better sound by going true duals than just putting some decent mufflers on it? Enough to justify the extra coat of duals? (remember, the cat isn't causing any restriction now)

 

Do the mufflers first. If you are happy with the performance and sound, you're done. I went with true duals on mine and Magnaflows. The cat was gutted and it had glass packs on it when I bought it. It sounds much better now and the performance increase was there, but it was minor. If you decide to later upgrade your engine you will be happier with a true dual system.