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Scottn59c
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Joined: December 22, 2016
Posts: 308
Location: Northern CA
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 Posted: Fri Sep 24, 2021 8:31 am Post subject: Advice on Vacuum Leaks |
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Hi Guys,
I'm trying to sort my '81 Vanagon out. After it failed on me a couple of weeks ago and reverted into a crank no start situation, I put in a new fuel pump. The new fuel pump got the van to start, but it immediately dies after it fires. It didn't do this before when the van was running well prior to the pump going. I'm thinking I might have tweaked something or let air into the system while I was troubleshooting.
I believe I'm dealing with a vacuum leak (or two). About 9 times out of 10, if I start the engine, it just catches and dies immediately, but once in a while it runs with wonky idling. I can feel the brake pedal pulse as I hold it when the idling vacillates as the engine warms up. I think that might be a sign that there's unwanted air in the system?
I'm a novice, so it's okay to speak to me like you would an idiot. Does this sound like a vacuum leak to you? If not, what can you tell me? And how do I go about addressing vacuum leaks?
Thanks!
Scott
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rottenkid
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Joined: June 19, 2015
Posts: 236
Location: Warkworth, ontario
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| Posted: Fri Sep 24, 2021 8:41 am Post subject: Re: Advice on Vacuum Leaks |
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| I had an issue similar with my bus. I pulled off the valve covers and cranked the engine. I Found a hydraulic lifter had collapsed and would not pump up. It is not a hard job to remove the hydraulic lifter and refill. There are several videos on YouTube for help. |
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busdaddy
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Joined: February 12, 2004
Posts: 51149
Location: Surrey B.C. Canada, but thinking of Ukraine
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Wildthings
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Joined: March 13, 2005
Posts: 50350
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| Posted: Fri Sep 24, 2021 8:59 am Post subject: Re: Advice on Vacuum Leaks |
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| Sounds to me like you could have a leaky booster or at least a leaky hose going to the booster. The booster should hold enough vacuum after engine shut down to give you boost for several applications of the brakes. If the brakes get hard quickly after shutdown then you have either a bad check valve or from the sounds of it some bad leak in the booster vacuum system. |
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Scottn59c
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Joined: December 22, 2016
Posts: 308
Location: Northern CA
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| Posted: Fri Sep 24, 2021 9:37 am Post subject: Re: Advice on Vacuum Leaks |
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| Wildthings wrote: |
| Sounds to me like you could have a leaky booster or at least a leaky hose going to the booster. The booster should hold enough vacuum after engine shut down to give you boost for several applications of the brakes. If the brakes get hard quickly after shutdown then you have either a bad check valve or from the sounds of it some bad leak in the booster vacuum system. |
Thanks, Wildthings. I'll take a close look at the tubes and hoses going to the booster.
Because I didn't have the problems prior to troubleshooting my original crank no start condition, do you think it's possible that the hoses are good, but that I let air into the system when I took them on and off? I'm just trying to answer the question of "why now, all of a sudden?"
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Wildthings
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Joined: March 13, 2005
Posts: 50350
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| Posted: Fri Sep 24, 2021 10:33 am Post subject: Re: Advice on Vacuum Leaks |
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| Scottn59c wrote: |
| Wildthings wrote: |
| Sounds to me like you could have a leaky booster or at least a leaky hose going to the booster. The booster should hold enough vacuum after engine shut down to give you boost for several applications of the brakes. If the brakes get hard quickly after shutdown then you have either a bad check valve or from the sounds of it some bad leak in the booster vacuum system. |
Thanks, Wildthings. I'll take a close look at the tubes and hoses going to the booster.
Because I didn't have the problems prior to troubleshooting my original crank no start condition, do you think it's possible that the hoses are good, but that I let air into the system when I took them on and off? I'm just trying to answer the question of "why now, all of a sudden?" |
You might have accidentally knocked a vacuum line loose or if you got a backfire blown one off. Still think you are going to find something is wrong with you vacuum going to your booster though this may have been a problem that was already there and now you have another vacuum leak on top of it. |
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Fri Sep 24, 2021 12:55 pm Post subject: Re: Advice on Vacuum Leaks |
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put a teaspoon of extra gasoline in the plenum or S boot and see it changes things. A bad ignition switch or double relay can pull that start then die as soon as the key is let go.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Scottn59c
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Joined: December 22, 2016
Posts: 308
Location: Northern CA
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| Posted: Fri Sep 24, 2021 3:22 pm Post subject: Re: Advice on Vacuum Leaks |
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Guys, just one more thought I wanted to add in.
I got some help from a mobile mechanic to install the fuel pump. It took us awhile of monkeying around to determine that I had gotten the terminals crimped on backwards when I had tried installing it myself.
Before we realized that, we had messed around with the fuel pressure regulator to make sure that fuel was indeed getting to it. We cracked the gas valve to it and saw gas, checked the pressure, and saw plenty of it. We pulled the vacuum lines off and put them back on.
After we got the fuel pump wired correctly, we got the van to fire up, but with the new symptom of dying right away unless the key is turned and held for awhile. My oil PSI gauge is also pinned and no longer functioning.
All this stuff is likely related. And I really think it's a matter of air in the system. Can you think of what would cause the oil pressure gauge to go haywire and for the van to develop a low idle?
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Wasted youth
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Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Tue Sep 28, 2021 2:53 pm Post subject: Re: Advice on Vacuum Leaks |
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If you have a 1981 Vanagon with stock engine management system, you will need to check the Idle Speed Controller also. A failed ISC will give those symptoms. Unfortunately, the only 'test' I know on that is a parts swap.
This piece: https://www.busdepot.com/4d0905351my
It's located near the coil.
Hopefully, you are using your Vanagon Bentley.
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Wildthings
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Joined: March 13, 2005
Posts: 50350
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| Posted: Tue Sep 28, 2021 3:39 pm Post subject: Re: Advice on Vacuum Leaks |
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| Wasted youth wrote: |
If you have a 1981 Vanagon with stock engine management system, you will need to check the Idle Speed Controller also. A failed ISC will give those symptoms. Unfortunately, the only 'test' I know on that is a parts swap.
This piece: https://www.busdepot.com/4d0905351my
It's located near the coil.
Hopefully, you are using your Vanagon Bentley.
PM sent |
You are probably thinking of the Digital Idle Stabilizer
https://www.busdepot.com/251906083 |
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Wasted youth
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Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Tue Sep 28, 2021 3:50 pm Post subject: Re: Advice on Vacuum Leaks |
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Hmm. That is not the part that failed, it was the one I showed. We could get the van to fire up and it would immediately die. We changed out the controller I referenced and it ran fine after that. I might not be calling it by the correct name?
The Digital Idle Stabilizer can be tested by disconnecting the two plugs and connecting them together. As I recall, that is part of process for checking ignition timing. |
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Wildthings
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Joined: March 13, 2005
Posts: 50350
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| Posted: Tue Sep 28, 2021 4:32 pm Post subject: Re: Advice on Vacuum Leaks |
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| Wasted youth wrote: |
Hmm. That is not the part that failed, it was the one I showed. We could get the van to fire up and it would immediately die. We changed out the controller I referenced and it ran fine after that. I might not be calling it by the correct name?
The Digital Idle Stabilizer can be tested by disconnecting the two plugs and connecting them together. As I recall, that is part of process for checking ignition timing. |
The part you linked to is the Ignition Control Module. |
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Wasted youth
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Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Tue Sep 28, 2021 4:44 pm Post subject: Re: Advice on Vacuum Leaks |
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| Okay, right. I definitely called it by the wrong name. I linked to the right part, but did not make the correct identity |
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