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Lost some vacuum!
- Thread starter BoostedSUV
- Start date
BoostedSUV
Active member
Re: Lost some vacuum!
Timing is dead on... I even swapped back to my MSD dizzy when I took the intake off.
The vac is consistant with idle, the idle tends to bounce a little though because the truck goes from lean to rich due some other strange issues.
Timing is dead on... I even swapped back to my MSD dizzy when I took the intake off.
The vac is consistant with idle, the idle tends to bounce a little though because the truck goes from lean to rich due some other strange issues.
BoostedSUV
Active member
Re: Lost some vacuum!
Pressure test and leak down test aren't showing anything... What else can I check fellas?
Pressure test and leak down test aren't showing anything... What else can I check fellas?
sly dvl
Ya, it's got a Turbo
Re: Lost some vacuum!
Well, if you're confident that you've checked all the obvious external points, then it's time to look inside.
Maybe start killing cylinders one at a time to see which one make the least difference, and then concentrate on that cylinder. Broken valve spring, collapsed lifter, sticking valve, all of which probably wouldn't show up during a compression or leak down test since you're cranking over @ 300 RPM.
Well, if you're confident that you've checked all the obvious external points, then it's time to look inside.
Maybe start killing cylinders one at a time to see which one make the least difference, and then concentrate on that cylinder. Broken valve spring, collapsed lifter, sticking valve, all of which probably wouldn't show up during a compression or leak down test since you're cranking over @ 300 RPM.
BoostedSUV
Active member
Re: Lost some vacuum!
I just replaced all the lifters and looked at all the springs for broken ones. All the springs look good... I had the entire top half of the motor off and every thing looked ok.
I just replaced all the lifters and looked at all the springs for broken ones. All the springs look good... I had the entire top half of the motor off and every thing looked ok.
dgoodhue
BuSTeD 4.3
Re: Lost some vacuum!
I have never pressurized my intake to check for leaks. Hoewever when i have done valve seals on these and trucks and on SBC's. I never hear the air leaking past the rings. I some time hear it leaking past a valve that isn't fully seated (usually a whack of a dead blow hammer on the top of the valve will fix that) I think the only noise you would hear would be if the intake & exhaust valve were open (assume the rockers were all all adjusted)
Have you thought about trying/borrowing a different intake manifold? I realize you have Vortecs which make a little more difficult to find a spare, but maybe someone who has their SyTy apart (imagine that!?) or is collecting parts would be kind of enough to let you borrow it.
At least the problems and symptoms you have posted in this thread sound an awful like when I have a intake problems. I understand your frustration, it took me 4 years and a lot of work to finally figure out my problems. I spend many many hours brain storming problems. I had fixed what turned out to be an unrelated electrical problem; It took me a good 80 hours to fix one summer, that summer when I started it back up and my problems still existed I was so frustrated, I left my car as is for 9 months. I was so disgusted.
I have never pressurized my intake to check for leaks. Hoewever when i have done valve seals on these and trucks and on SBC's. I never hear the air leaking past the rings. I some time hear it leaking past a valve that isn't fully seated (usually a whack of a dead blow hammer on the top of the valve will fix that) I think the only noise you would hear would be if the intake & exhaust valve were open (assume the rockers were all all adjusted)
Have you thought about trying/borrowing a different intake manifold? I realize you have Vortecs which make a little more difficult to find a spare, but maybe someone who has their SyTy apart (imagine that!?) or is collecting parts would be kind of enough to let you borrow it.
At least the problems and symptoms you have posted in this thread sound an awful like when I have a intake problems. I understand your frustration, it took me 4 years and a lot of work to finally figure out my problems. I spend many many hours brain storming problems. I had fixed what turned out to be an unrelated electrical problem; It took me a good 80 hours to fix one summer, that summer when I started it back up and my problems still existed I was so frustrated, I left my car as is for 9 months. I was so disgusted.
BoostedSUV
Active member
Re: Lost some vacuum!
Well when you pressurize an intake with the valves adjusted properly there will be open valves so the cylinders will see some of that pressure I would presume. Rings obviously don't seal 100 percent so some pressure should leak passed the rings as well as into the exhaust if the ex valve is open. I think what I'm going to try to do is take all of the intake rocker arms off which leaves all the valves closed. I should be able to seal the intake system better and isolate a leak better if there is one.
Well when you pressurize an intake with the valves adjusted properly there will be open valves so the cylinders will see some of that pressure I would presume. Rings obviously don't seal 100 percent so some pressure should leak passed the rings as well as into the exhaust if the ex valve is open. I think what I'm going to try to do is take all of the intake rocker arms off which leaves all the valves closed. I should be able to seal the intake system better and isolate a leak better if there is one.
BoostedSUV
Active member
Re: Lost some vacuum!
I just pulled the stock balancer off and put and aftermarket one on there 2 months because I thought the same thing chasing another issue... I even verified TDC to make sure my adjustable pointer is correct. Timing is good...
I just pulled the stock balancer off and put and aftermarket one on there 2 months because I thought the same thing chasing another issue... I even verified TDC to make sure my adjustable pointer is correct. Timing is good...
WyoSyclone
Active member
Re: Lost some vacuum!
I guess you checked the FP regulator separately with your mighty vac? Pump it up to a few pounds and see if it holds pressure.
Have you replaced the IAC? If it's sporadically opening up (bad coil) it would cause a change in vacuum.
I guess you checked the FP regulator separately with your mighty vac? Pump it up to a few pounds and see if it holds pressure.
Have you replaced the IAC? If it's sporadically opening up (bad coil) it would cause a change in vacuum.
BoostedSUV
Active member
Re: Lost some vacuum!
Rob, I did check the FPR seperately... It will pump up to 20 and slowly bleed back down. I don't think it's supposed to hold is it?
I do have another IAC I can throw in just to see
Rob, I did check the FPR seperately... It will pump up to 20 and slowly bleed back down. I don't think it's supposed to hold is it?
I do have another IAC I can throw in just to see
BoostedSUV
Active member
Re: Lost some vacuum!
If I do that there will be a part out... I will not spend the money and put the truck back together :tdown:
If I do that there will be a part out... I will not spend the money and put the truck back together :tdown:
WyoSyclone
Active member
Re: Lost some vacuum!
It should hold... it's a closed system. If it's bleeding down you'll have decreasing, or not optimum, FP during boost conditions.
It should hold... it's a closed system. If it's bleeding down you'll have decreasing, or not optimum, FP during boost conditions.
dgoodhue
BuSTeD 4.3
Re: Lost some vacuum!
At least in my experience with IAC, I don't think it would cause his problem unless the pintle was almost flopping around. (you would have a noticeably surging idle) I am not really sure if you would lose that much vacuum with an just IAC leak either and it would think it would have appeared in leak testing.
At least in my experience with IAC, I don't think it would cause his problem unless the pintle was almost flopping around. (you would have a noticeably surging idle) I am not really sure if you would lose that much vacuum with an just IAC leak either and it would think it would have appeared in leak testing.
BoostedSUV
Active member
Re: Lost some vacuum!
I tested anothe Mallory fpr that I had laying around for an old carb motor and that did not hold vac either. If I pinched the hose to the barb fitting it held so it wasn't the pump leaking.
I tested anothe Mallory fpr that I had laying around for an old carb motor and that did not hold vac either. If I pinched the hose to the barb fitting it held so it wasn't the pump leaking.
WyoSyclone
Active member
Re: Lost some vacuum!
Well, you really need to give it pressure, not vacuum... and make sure you have a clamp on the hose going onto the fitting.. it will leak otherwise.
Well, you really need to give it pressure, not vacuum... and make sure you have a clamp on the hose going onto the fitting.. it will leak otherwise.
BoostedSUV
Active member
Re: Lost some vacuum!
Just loosened all the intake rockers and pumped the motor with the compressor right at the throttle body. The boost gauge went up to 20psi and stayed there. I am confident that I do not have a vac/boost leak of any sort. I guess that's a good thing. I'm going to throw some plugs In it and fire it up...
A few lifters did come unpumped (again) from sitting so I may watch them closer...
Just loosened all the intake rockers and pumped the motor with the compressor right at the throttle body. The boost gauge went up to 20psi and stayed there. I am confident that I do not have a vac/boost leak of any sort. I guess that's a good thing. I'm going to throw some plugs In it and fire it up...
A few lifters did come unpumped (again) from sitting so I may watch them closer...
BoostedSUV
Active member
Re: Lost some vacuum!
I'm stumped... I put new plugs in tonight, rechecked the timing and fired the motor up. It's idling at 800rpm and only 12-15lbs of vacuum. The idle is not staying steady and wbo2 shows the truck idling lean. I bypassed the PCV system and charcoal canister as well to eliminate things. Seems like a mechanical issue but i don't know how? Motor leaked down tested perfect and it will hold 20psi of pressure with out any leaks....
I'm stumped... I put new plugs in tonight, rechecked the timing and fired the motor up. It's idling at 800rpm and only 12-15lbs of vacuum. The idle is not staying steady and wbo2 shows the truck idling lean. I bypassed the PCV system and charcoal canister as well to eliminate things. Seems like a mechanical issue but i don't know how? Motor leaked down tested perfect and it will hold 20psi of pressure with out any leaks....
Typhoon #2131
SAVE THE TA-TAS
Re: Lost some vacuum!
Sorry I'm new to this and trying to learn all the terms. What is the "bike tube" test? Is that the same as taking carb and choke cleaner and spraying it over the intake and all vac. lines?
Sorry I'm new to this and trying to learn all the terms. What is the "bike tube" test? Is that the same as taking carb and choke cleaner and spraying it over the intake and all vac. lines?