Need help with vacuum leak

[rhipsher]

Sorry Jeff. Just had a lousy day at work yesterday. Didn't mean to snap at you. My apologies.

Originally Posted by rhipsher

Sorry Jeff. Just had a lousy day at work yesterday. Didn't mean to snap at you. My apologies.

No worries dude

[detch]

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again.
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

[tccrab]

Originally Posted by detch

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again.
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

Mike:

A bad check valve?
Hmmm..
Gonna go dig out my FSM...

Your '95 is a little different under the plenum than my '90, but they work the same. There is a check valve (item #15 pg 6A2A-33 LT5 Service Manual Supplement) located inline with that hose which is connected to the plenum. If that check valve is breached, it will allow the vacuum pump to suck air past the valve and cause the vacuum pump to run continuously.
If I read the diagram correctly, the check valve allows the vacuum pump to pull a vacuum on the secondary system until the engine starts producing suitable vacuum. When the magic pressure is reached, the check valve opens and the ECM directs the vacuum pump to stop.

I'm just guessing, but if you were to plug this line it's possible that the secondaries might not have enough vacuum to:
A: open the secondaries completely, or;
B: hold them open for any appreciable lenght of time.

TomC
'Crabs"

[detch]

Bad check valve was it, all fixed.
thanks all for the help

Mike

!

[tomtom72]

Good deal Mike! Now go play with the toy!

[RJC061500]

This is my first post on this site, and first I would like to thank everyone for the great information posted. I am in the process of changing injectors on my 90. I have everything ready to go, however, I’m chasing a vacuum leak. On the passenger side I can plug the pump and it will shut off. Also have vacuum up to the Vacuum Solenoid, which I just replaced. I made a filter out of hose and wax applicator (As I learned on this site.) I also blew into the vacuum line near the check valve and it one side did not allow air to pass (Also learned from this site.) Now when I test the pump, it cycles on and off every few seconds. I can block the vacuum line on the drier side, mid plenum and the pump stops. My questions are:
1: Could the check valve be clogged even though I could only blow air through one side?
2. If the check valve is the cause of the problem, is it better to clean the check valve with carb cleaner or replace it with an aftermarket one?
3: And finally, if I should replace the check valve, how to I get the factory one disconnected from the vacuum lines?
Sorry for so many questions, but I’m afraid to cause damage to the vacuum lines trying to replace the valve.

Thanks in advance for any replies to this post.

[Hammer]

If you pulled the hose off the driver's side of the plenum (about the middle) and the pump stopped, it's the check valve...you can still get them from the dealer. But, I replaced one under both cars and they both ahve since failed. BS.

I rigged up a little loop for outside. After market check valve from any auto parts store that has them, two rubber lines, different sizes and a reducer fitting and both are fine now. The only check valves I have seen available are different sizes in and out.

I don't know why these valves last for 18-20 years and then you replace them and they go kapoot in two months. But mine did.

[rhipsher]

Originally Posted by Hammer

If you pulled the hose off the driver's side of the plenum (about the middle) and the pump stopped, it's the check valve...you can still get them from the dealer. But, I replaced one under both cars and they both ahve since failed. BS.

I rigged up a little loop for outside. After market check valve from any auto parts store that has them, two rubber lines, different sizes and a reducer fitting and both are fine now. The only check valves I have seen available are different sizes in and out.

I don't know why these valves last for 18-20 years and then you replace them and they go kapoot in two months. But mine did.

Just like I said way back when this thread was started Just clean it with carb cleaner or break clean and blow out with air and spray WD40 in it. It will be good as new and last another 18 years. Trust me on this. All it takes is a little dirt to get on that little bee bee ball inside of it.

[secondchance]

Originally Posted by RJC061500

This is my first post on this site, and first I would like to thank everyone for the great information posted. I am in the process of changing injectors on my 90. I have everything ready to go, however, I’m chasing a vacuum leak. On the passenger side I can plug the pump and it will shut off. Also have vacuum up to the Vacuum Solenoid, which I just replaced. I made a filter out of hose and wax applicator (As I learned on this site.) I also blew into the vacuum line near the check valve and it one side did not allow air to pass (Also learned from this site.) Now when I test the pump, it cycles on and off every few seconds. I can block the vacuum line on the drier side, mid plenum and the pump stops. My questions are:
1: Could the check valve be clogged even though I could only blow air through one side?
2. If the check valve is the cause of the problem, is it better to clean the check valve with carb cleaner or replace it with an aftermarket one?
3: And finally, if I should replace the check valve, how to I get the factory one disconnected from the vacuum lines?
Sorry for so many questions, but I’m afraid to cause damage to the vacuum lines trying to replace the valve.

Thanks in advance for any replies to this post.

Welcome to the Forum!

Answers:
1. No. These are 3 way check valve. You should not be able to blow into single large side. 2 smaller side, closing one or the other, you should be able to blow through it.
2. Replace. Less than $5 at dealership. On 94 there are 2 check valves (pretty sure 90 have 2 also).
3. They pull of from vacuum lines (twist first since time and heat may have sort of fused them).

If you get some leak, check all rubber fittings to hard vacuum lines. You may find some loose connections. If you do, use high temp sealant and small zip-ties to seal them.

Hand held vacuum pump is helpful in tracking fitting to fitting and locating leaks.

Good luck!