Engine One Side Hot, One Side Cold, Runs Like Crap
Instructor
Joined: Aug 2009
Posts: 146
Likes: 0
From: Broadway Virginia
I am not sure whether a leaky injector would immediately cause a wet plug. The intake valve would have to be open, I think.
If the pressure is good after energizing the pump by turning the key on, you might try what has been suggested on other threads....taping the pressure gauge to the windshield so you can see it and monitor the pressure while you are taking a drive. See what the pressure is when the thing acts up.
Alternatively you could retest and go back through the diagnosis in the FSM and double check that the lines are pinched off to your satisfaction.
If the pressure is good after energizing the pump by turning the key on, you might try what has been suggested on other threads....taping the pressure gauge to the windshield so you can see it and monitor the pressure while you are taking a drive. See what the pressure is when the thing acts up.
Alternatively you could retest and go back through the diagnosis in the FSM and double check that the lines are pinched off to your satisfaction.
Instructor
Joined: Aug 2009
Posts: 146
Likes: 0
From: Broadway Virginia
IIRC, that is what mine did. Although I am not sure if my FP went that low at idle. The pressure goes back up when the FPR senses less manifold vacuum.
I would take another hard look at the injectors and go back through the FSM flow chart making sure the hoses are well pinched. If you get the same result........its likely leaky injector(s)
I would take another hard look at the injectors and go back through the FSM flow chart making sure the hoses are well pinched. If you get the same result........its likely leaky injector(s)
Last edited by walter schweigert; Jun 26, 2010 at 11:17 PM.
Burning Brakes
Joined: Aug 2000
Posts: 1,146
Likes: 2
From: Albuquerque NM
Last year I chucked the whole wiring harness and replaced it with an economical thruster..
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
Is there supposed to be a ground strap going from the engine to the frame? Is so is it connected at the same spot on the bell housing as the rest of the grounds and where on the frame does it connect? Thanks!
Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
The ground strap on my 86 is mounted to the same bolt on block, that contains the other 6 ground wires. The other end is somewhere under booster near battery, but due to my widebands extra wire being coiled up and zip tied in that area, I cannot see exactly where.
As for your fuel pressure tests, I would try them again and be sure you are stopping 100% of the flow. I use needle nose vise grips with a couple of 1/4" drive sockets, attached and taped to the ends.
As for your fuel pressure tests, I would try them again and be sure you are stopping 100% of the flow. I use needle nose vise grips with a couple of 1/4" drive sockets, attached and taped to the ends.
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
I was able to get a better grip on the fuel hoses and still lost pressure on the feed line but when I pinched off the return line the pressure went to about 65 and held at 60. According to the test procedures it’s telling me it’s the pressure regulator which I have already replaced?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Instructor
Joined: Aug 2009
Posts: 146
Likes: 0
From: Broadway Virginia
If you have a hand operated vacuum pump w/ gauge. You could check the diaphragm by drawing a vacuum on the FPR (about 10" -18" vac), just to confirm that it has not split, even though you do not see fuel at the port. Might try exercising it a bit by applying and releasing vacuum to it a few dozen times to see if it will free it up if it is stuck open. Might be some corrosion or trash on the sealing surface.
I suppose it could stick open somehow allowing fuel to return to the tank.
Having never replaced one, I do not know if improper installation could be an issue, so that may be possible too. The only other thing I can think of is that it is getting way too much vacuum for some reason, which just doesn't make sense. Usually, its a vacuum leak (ie. disconnected hose or hole rubbed in line) causing the opposite problem.
T in a vacuum gauge and start it up to see how much vacuum you get at the FPR just for grins.
How long did it take for it to drop from 65psi to 60psi? Did it hold at 60 for a good long while?
If you take the runners off to get to the FPR, I would be tempted to replace the injectors while you're there. But that is just me. I know alot of viewers just hate to replace injectors *****-Nilly.
I suppose it could stick open somehow allowing fuel to return to the tank.
Having never replaced one, I do not know if improper installation could be an issue, so that may be possible too. The only other thing I can think of is that it is getting way too much vacuum for some reason, which just doesn't make sense. Usually, its a vacuum leak (ie. disconnected hose or hole rubbed in line) causing the opposite problem.
T in a vacuum gauge and start it up to see how much vacuum you get at the FPR just for grins.
How long did it take for it to drop from 65psi to 60psi? Did it hold at 60 for a good long while?
If you take the runners off to get to the FPR, I would be tempted to replace the injectors while you're there. But that is just me. I know alot of viewers just hate to replace injectors *****-Nilly.
Last edited by walter schweigert; Jun 30, 2010 at 12:25 PM.
Race Director
Joined: Jun 2009
Posts: 10,428
Likes: 9
From: Southside of Western Norte Americano State of Confusion, ColoFornia
St. Jude '13
Thruster?? whats that? (I ask as the painless replacement isnt "econmical" at all)
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
Not much can go wrong with installation it’s just a diaphragm, cover and six screws.
The injectors are new with very few miles on them. I know from driving the car home the previous owner was not able to put any miles on it so the only miles on them is from me getting it home and back and forth to work one time.
It held at 60 long enough for me to get tired of waiting for it to drop which it didn’t.
So at this point I guess I either purchase a vacuum pump or just replace the FPR again?
The injectors are new with very few miles on them. I know from driving the car home the previous owner was not able to put any miles on it so the only miles on them is from me getting it home and back and forth to work one time.
It held at 60 long enough for me to get tired of waiting for it to drop which it didn’t.
So at this point I guess I either purchase a vacuum pump or just replace the FPR again?
Instructor
Joined: Aug 2009
Posts: 146
Likes: 0
From: Broadway Virginia
That about sums it up.
Is there a spring between the diaphragm and the cover?
Let me know what you find when you take the current one off.
Is there a spring between the diaphragm and the cover?
Let me know what you find when you take the current one off.
Last edited by walter schweigert; Jun 30, 2010 at 06:44 PM.
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
[QUOTE=walter schweigert;1574558656]That about sums it up.
Is there a spring between the diaphragm and the cover?
I believe there is, it’s been a couple months sense I put it in. Got a whole 20 or 30 miles out of it.
Bought a vacuum pump and worked the FPR but it didn’t do any good, still have the same problem. It takes a lot to get it started and even more to keep it running. Give it gas and it wants to die, sounds like its sucking air. You really have to feather the pedal.
Is there a spring between the diaphragm and the cover?
I believe there is, it’s been a couple months sense I put it in. Got a whole 20 or 30 miles out of it.
Bought a vacuum pump and worked the FPR but it didn’t do any good, still have the same problem. It takes a lot to get it started and even more to keep it running. Give it gas and it wants to die, sounds like its sucking air. You really have to feather the pedal.
Instructor
Joined: Aug 2009
Posts: 146
Likes: 0
From: Broadway Virginia
Sounds like its sucking air?????
You don't have a intake manifold leak anywhere do you? Can you locate it? I guess you had to take the intake plenum off to get at the FPR the first time, is it possible that there is a gasket leak you are hearing?
The noise still wouldn't account for the loss of fuel pressure...or would it? I don't think so.
You don't have a intake manifold leak anywhere do you? Can you locate it? I guess you had to take the intake plenum off to get at the FPR the first time, is it possible that there is a gasket leak you are hearing?
The noise still wouldn't account for the loss of fuel pressure...or would it? I don't think so.
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
I think I have confirmed that it’s the FPR. I added some clear hose to the return line at the tank and as soon as the pump turns on fuel comes gushing out the return line.
Sound like a logical conclusion?
Sound like a logical conclusion?
Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
It is possible to put a diaphragm in upside down and not get the proper operating PSI. Does the stock diaphragm have an obvious choice, or do both sides look similar ?
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
The diaphragm has two totally different sides. On one side you have a spring about 1” tall and the other is like a plunger? That is only about ¼” tall and could only go in one direction. Other then getting a code it ran great the one day I took it to work. Cleared the code and this is what happen the next time I tried to start it. I’m guessing it’s a lack of fuel because it takes forever to get it to fire when you turn the key.
I’m going to take the plenum off this morning and lift the fuel rails and see if they are spraying or not and remove the FPR and check it as well. I bought another one at NAPA last night to have on hand in case I need it.
Anything else I should look for while I have it apart?
I’m going to take the plenum off this morning and lift the fuel rails and see if they are spraying or not and remove the FPR and check it as well. I bought another one at NAPA last night to have on hand in case I need it.
Anything else I should look for while I have it apart?
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
I pulled the FPR and it looked fine and the plunger seemed to work okay, Hard to tell it’s a pretty strong spring. I have another FPR but did not replace it.
I also pulled the fuel rails high enough to see if the injectors are leaking and they are not.
I had my wife turn the key so I could see if the injectors had a spray and the only one that sprayed anything at all was number one cylinder. So what would cause this?
I also pulled the fuel rails high enough to see if the injectors are leaking and they are not.
I had my wife turn the key so I could see if the injectors had a spray and the only one that sprayed anything at all was number one cylinder. So what would cause this?