Need 12HT VSV (shut down valve) help (1 Viewer)

[CenTXFJ60]

long story short is I'm putting a coaster bus (new old stock) motor in my 60. My build thread is 60 Frankenstein Build. Skip to the last several pages and you'll see where I started the 12HT. So what I understand in the VSV is it requires a constant 12 volts when the key is in the run position. This VSV is new from @beno and my original one works as well when hit with 12 volts. My issue is the vacuum pump seems to be overpowering the VSV and shutting down the motor. I connected the vacuum lines the way they came and even compared it to another 12HT drivetrain I have sitting in my shop. What I understand is the vacuum pump has a small nipple that feeds the line. This line has a T in it and one direction goes to the VSV. The other direction goes to the aluminum vacuum line that runs across the top front of the motor. Then just before the line enters the VSV it T's off and connects to the other end of the aluminum line on the opisits side of the motor. Seems it is a constant vacuum circuit. Regardless if I bypass it or run it direct the VSV engages once I plug in the vacuum canister. I'll try to get these pics in order starting at the vacuum pump. Any suggestions are appreciated.

 

[CenTXFJ60]

Another member sent me this diagram (thanks @sami ). The motor in my shop is set up just like this. I believe my issue is the coaster motor does not have the BVSV on the side of the block along with a few other things. Can someone explain the function of this? I assume it's temp related.

 

[CenTXFJ60]

View attachment 1471276 Another member sent me this diagram (thanks @sami ). The motor in my shop is set up just like this. I believe my issue is the coaster motor does not have the BVSV on the side of the block along with a few other things. Can someone explain the function of this? I assume it's temp related.

Confirmed...I don't have a BVSV. Not even a place to tap one. Is this

because it's a coaster bus motor? If so, is there a different vacuum diagram for the bus motor?

 

[roscoFJ73]

My issue is the vacuum pump seems to be overpowering the VSV and shutting down the motor

Most vacuum pumps have a cut off valve that maintains around 6psi of vacuum.
I only know of 2 vacuum diagrams for the 12HT. One for aircon equipped models and one without aircon.
Do you have a 24v or 12v engine? I think the Coasters are all 24v
What does the BVSV stand for?

 

[ozcrusier]

I'm thinking if you have no oil pressure this will shut the engine down have you had this engine running does it have oil pressure. When I rebuilt my 12ht engine I left the injectors out so I could crank the engine over to obtain pressure and it took some cranking with two battery's to get it.

 

[CenTXFJ60]

Most vacuum pumps have a cut off valve that maintains around 6psi of vacuum.
I only know of 2 vacuum diagrams for the 12HT. One for aircon equipped models and one without aircon.
Do you have a 24v or 12v engine? I think the Coasters are all 24v
What does the BVSV stand for?

Rosco, this is an AC motor. Interesting comment on the cut off valve. It makes sense since my motor runs for a minute or two and once the vacuum canister builds pressure the motor dies. I do have good oil pressure as well. Been running it quite a bit as I've been putting it together. Would like to see what that cut off valve looks like. Also, not sure what BVSV stands for but it's in the diagram and standard on 12HT's out of 61's.

 

[ozcrusier]

That would be the vacuum operated idle up on the back off the pump for the air con and cold starts. It sounds like something is shutting the engine after start up that's why I was thinking oil pressure. Where are you picking up power for the VSV

 

[CenTXFJ60]

That would be the vacuum operated idle up on the back off the pump for the air con and cold starts. It sounds like something is shutting the engine after start up that's why I was thinking oil pressure. Where are you picking up power for the VSV

Oz, I don't have an idle up on the back of my pump. I have a bosh alternator. Have a stock one on another motor and will take a look at it. The power for the vsv (in the square) is coming from the brake master line (arrow)

 

[ozcrusier]

I take it you have checked for constant power from the brake master after engine is running. Most pick up from a agnition source to power the VSV. I have been looking at your photo's and it looks like you have the vac line from the pump going to the wrong side of the VSV valve. I plumbed mine the same as the diagram above with out the idle up side and just use the hand throttle to bump up revs on cold starts.

 

[CenTXFJ60]

Oz, great suggestion on checking the power. It is not hot. Not sure what happened but it was definitely hot when we first wired it up. Also, I've posted some pics of how it's plumbed. The

 

[CenTXFJ60]

Hit the button a bit too fast the pic at the pump shows the "T" and the arrow points to the VSV the rough line goes up to the aluminum vac line. The below pic shows the line coming from the pump. you'll see the "T" which I temporarily ran over the top to the other end of the aluminum line. the other side of the VSV (has a red square) goes directly to the diaphragm that closes the butterfly. gonna try a temporary hot wire from the fuse box and see if that fixes my problem. still scratching my head as to why the current hookup is not hot both me and my son tested it before wiring it up. no shame either way I've done dumber things during this build I'm just hopeful this is my issue cause it's a simple fix. I'll let uiu know what I find

 

[Ming89FJ62]

VSV = Vacuum Switching Valve
BVSV = Bi-metallic Vacuum Switched Valve

BVSV are temperature sensing and normally in the thermostat housing. Their colors correspond to their opening temps.

VSV are either electric (solenoid) or vacuum actuated.

 

[CenTXFJ60]

Guys...I think I may have figured it out. After screwing around with the connection it's now hot. I believe this is my issue as OZ pointed out. Seems to be working fine at the moment but I'll most likely source a better power source.

 

[ozcrusier]

Great news glad you sorted the problem.
The 12ht is a great engine your going to love the torque.

 

[CenTXFJ60]

Oz, this thing is driving me crazy. It literally works and then stops working. Whenever it stops, I'll try all 3 VSV's I have and none work. Then when it's working I'll switch in the other VSV's and they will work as well. I've tested each one on a 12volt battery as well. I'm at a loss with this thing. I have a brand new VSV and 2 used ones. I've plumbed it up just like the diagram above except I don't have the BVSV. Don't think that matters as long as I have a closed system. I've even tried separate wire harness clips with the different VSV's to see if I can get it to work. If I understand the concept correctly it is....12volts to the VSV while engine is running. This keeps the valve open so vacuum escapes. Once power is killed the valve closes and vacuume pulls the diaphragm and shuts off the motor. I believe this is correct and have had it working a few times and able to shut it down over and over with the key. Then I wait a bit and it does not work as I can't start the motor. Is there some electrical or mechanical pressure regulator that I'm missing????

 

[CenTXFJ60]

Oz, this thing is driving me crazy. It literally works and then stops working. Whenever it stops, I'll try all 3 VSV's I have and none work. Then when it's working I'll switch in the other VSV's and they will work as well. I've tested each one on a 12volt battery as well. I'm at a loss with this thing. I have a brand new VSV and 2 used ones. I've plumbed it up just like the diagram above except I don't have the BVSV. Don't think that matters as long as I have a closed system. I've even tried separate wire harness clips with the different VSV's to see if I can get it to work. If I understand the concept correctly it is....12volts to the VSV while engine is running. This keeps the valve open so vacuum escapes. Once power is killed the valve closes and vacuume pulls the diaphragm and shuts off the motor. I believe this is correct and have had it working a few times and able to shut it down over and over with the key. Then I wait a bit and it does not work as I can't start the motor. Is there some electrical or mechanical pressure regulator that I'm missing????

Right after I did this post the VSV started working again. Very frustrating. Now that the key is working I am moving on to some other things (valve adjustment and changing crossover pipes). Then I'll rewire the VSV directly to the fuse box.

 

[ozcrusier]

Maybe you have a intermediate fault in the circuit your using time to try a different source from ignition. I have mine wired into the glow plug system so if there's a drop in oil pressure it should shut the engine off.

 

[CenTXFJ60]

Maybe you have a intermediate fault in the circuit your using time to try a different source from ignition. I have mine wired into the glow plug system so if there's a drop in oil pressure it should shut the engine off.

Oz, I believe you are right. I think through these many issues while falling asleep. And bam...it hit me the other night that this wire harness had some issues on the ground block feeding the drivers side engine area. My son and I looked at it prior to installing it and figured it was not gonna be a problem. Had some burn areas and tape where some patchwork was done by a PO. In the end, I think this is my issue. Will strip down that side of the harness and redo all the grounds. Got some other things to take care of first (turbo reseal and injector service). Decided to do these to ensure no issues from sitting 30+ years. The turbo is blowing oil.

I'll let you know how it turns out in the next few weeks. Thanks for your input.
Jim

 

[ozcrusier]

Jim
Happy to help
Regards
Brian

 

[CenTXFJ60]

@roscoFJ73 and @ozcrusier I have a question. Someone questioned if i had the VSV plumbed correctly. I felt I did according to the vacuum diagram but when looking the the service manual it looks like the line out to the shut off valve it different. Look at these two pics and let me know if I'm seeing this correctly. I have not worked on this again as I have my turbo and injectors at a shop getting redone. Therefore I'm focusing on other parts of my build. However this one issue seems to keep creeping up in my mind