53ryder
Well-Known Member
Found this in digging around through some of my dad's stuff. Vacuum gauge?
Glenn
Glenn
Rough idle...
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53ryder
Well-Known Member
Starting to do some more real detective work here on the vacuum lines. Took a picture of the vacuum hose diagram mounted on the underside of the hood so I would have something to refer to. Removed air filter housing to get a clearer view of carb and connecting hoses. At back of carb there 2 hoses that meet at a 3-way tee. One hose comes from the back side of the carb down low on the housing. Another hose comes from a diaphragm mounted up higher on the side of the carb. They meet together and a single hose leading away goes nowhere! It's loose! See pictures. Not sure where the loose end goes, so I took a picture of a couple of small boxes (?) mounted on firewall. In the picture you can see a fitting on the top being unused (it has been like that since I bought car and noticed nothing attached to it). Today I did notice an unused fitting on the bottom of one of these boxes (not sure what to call them). It's there in the picture if you look hard enough.
Should that loose hose connect to one of these fittings? Or should I keep looking for something else?
Should that loose hose connect to one of these fittings? Or should I keep looking for something else?
Mikes5thAve
Well-Known Member
All inches.
Technically, Chrysler started to convert to Metric about the time the first F-bodies came out. They would only convert an item to Metric when a part, component or system was re-designed.
For the most part, there is not much metric on any FMJ except for a few minor things.
One example is the P/S pump (to bracket) fasteners are Metric (but the bracket fasteners to engine are still SAE).
All of the vacuum hoses are all SAE - but sometimes odd sizes are used.
One example is the PVC and brake booster hoses are 11/32". A 5/16" hose is too small and the 3/8" hose is too large to seal correctly (even with hose clamps).
If you walk into a parts store and ask for a 11/32" hose (P/S or vacuum) - you will get a blank stare look back from them.
For the most part, there is not much metric on any FMJ except for a few minor things.
One example is the P/S pump (to bracket) fasteners are Metric (but the bracket fasteners to engine are still SAE).
All of the vacuum hoses are all SAE - but sometimes odd sizes are used.
One example is the PVC and brake booster hoses are 11/32". A 5/16" hose is too small and the 3/8" hose is too large to seal correctly (even with hose clamps).
If you walk into a parts store and ask for a 11/32" hose (P/S or vacuum) - you will get a blank stare look back from them.
53ryder
Well-Known Member
Dorman vacuum hoses okay?
Mikes5thAve
Well-Known Member
spend some time to look at that vacuum diagram and I'll tell you everything.
The hoses and T coming off the carb look like it should go to heated air temp sensor which is on the bottom of the air cleaner. It shows that one solenoid doesn't have something on the top and another doesn't have something on the bottom. Originally they usually had pieces of foam over them as filters but they come apart over time.
For vacuum hoses it doesnt matter what make only that they're the right size.
In my opinion, there are two different kind of vacuum hoses. New (or good) or wore out/bad (ie: broken, swollen or hard as a rock) hoses.
I'd have no problem with Dorman hoses. That said, Dorman is not my favorite brand name, but pretty much any name brand will work for hoses.
These pictures are from my '77 318. The later BBD's and Holley 2280/6280 used a "T" on this hose and earlier BBD's (like my '77) used a different carburetor port.
For your situation, the "T" goes where marked by yellow markings (below) or purple circle (above).
To confuse things, the hose marked with pink arrow goes nowhere (so pay no attention to it).
The Yellow T (above picture goes to the green circle (top picture) - which is the air cleaner door temp sensor. This hose is common to be "not re-connected" after an air cleaner removal - because you don't see it.
This is the underside of a '77 318 air cleaner - but is mostly the same as any FMJ cleaner:
on any Chrysler air cleaner, with factory temp sensor still installed, the hose (white arrow above), always use the nipple closest to the hose clip (also white arrow) - just in case both hoses were removed. The white arrow hose goes to the hot air door valve which is above the drivers side exhaust manifold.
The other nipple goes to the yellow "T" (two pictures above).
With this hose being disconnected, it will A) run rough due to a good size vacuum leak and B) run poor due to choke pull-off not functioning.
With air cleaner removed, I recommend taking a golf tee a small phillips screwdriver, a small stick or something to plug that vacuum hose hole. The plus side to using a golf tee or a screwdriver is you can see it when re-installing the air cleaner to remind you your tool is in place and to remind you to reattach that hose when done.
I drew a white cube which is where a factory chunk of foam was used as an air filter. That foam block deteriorates over time and once gone, it looks like a vacuum hose goes there.
You can either leave it as is or reattach a piece of open-cell foam to put back on it. This is a controlled vacuum leak and it doesn't affect divisibility nor make engine run rough.
I can't tell by your photos, but I "suspect" your loose vacuum hose goes to the empty port on bottom side of your air cleaner.
BudW
EDIT: Actually, I can tell you that your loose hose DOES go to the empty port on your air cleaner (bottom side).
53ryder
Well-Known Member
This padawan thanks Bud and Mike for the lesson!
53ryder
Well-Known Member
I didn't think to look under the air cleaner housing. There was a 'nipple' looking all lonely so I reconnected the lost hose.
Did it fix the problem?
53ryder
Well-Known Member
Naw. Darn.
Aspen500
Well-Known Member
Yes, that's a vacuum gauge. If you hook it up, just be sure to use a manifold vacuum source and not ported. Any nipple on the vacuum "tree" behind the carb will be manifold vacuum.
53ryder
Well-Known Member
Did a compression test this morning for heck of it. Used Blue Driver compression kit. It had not been used before. I hand tightened everything only! So here goes:
Cylinder 1- 150 psi
Cylinder 2- 150 psi
Cylinder 3- 140 psi
Cylinder 4- 140 psi
Cylinder 5- 140 psi
Cylinder 6- 135 psi
Cylinder 7- 135 psi
Cylinder 8- 150 psi
Not sure if 150psi is high or not, but 10 percent variance from hi to low okay?
Cylinder 1- 150 psi
Cylinder 2- 150 psi
Cylinder 3- 140 psi
Cylinder 4- 140 psi
Cylinder 5- 140 psi
Cylinder 6- 135 psi
Cylinder 7- 135 psi
Cylinder 8- 150 psi
Not sure if 150psi is high or not, but 10 percent variance from hi to low okay?
Last edited:
Aspen500
Well-Known Member
Hmmm, those numbers look just fine. Nothing suggests a base engine problem, such as a valve. If there was a burned valve, that cylinder would be lower or a LOT lower, depending how how bad it was burned. 10% variance is just fine, actually it's excellent for an engine with many miles on it.
I am showing the min compression reading to be 100 PSI (dry) and a max variation of 25 PSI, for an '87 318 2-bbl.
you are above 100 PSI and have a variation of 15 PSI - so your results are within specs.
BudW
you are above 100 PSI and have a variation of 15 PSI - so your results are within specs.
BudW
53ryder
Well-Known Member
Thanks Bud! As you did mention they are 'dry' results, no oil added to cylinders.
Glenn
Glenn
53ryder
Well-Known Member
Got a hose on the end of the compound meter and a couple of different fittings. Will attempt to check vacuum pressure in the morning.
53ryder
Well-Known Member
Vacuum test result this morning. I hooked up vacuum gauge to capped line on manifold behind carb as Bud suggested. Started engine and took pictures of the findings. I used the old gauge that I've had for more than 30 years, then I used a new gauge (picture on bottom) that I just bought (making sure old gauge was working and somewhat accurate). You see results in photos. So what does that tell me?
The two pics Show me that the old one works as well as the new one. 
Seriously, that doesnt tell anything, as needle movement is relevant in various load states.
If thats steady 15inHg in idle, its a bit on the low side. Could be for example a very slight vacuum leak. Did you replace all vac lines in the mean time?
If the needle is shaky (strong or slightly) it points in different direction. Dont habe a link handy, but google "vacuum reading engine" and some good results on interpreting the gauge should pop up.
Maybe someone else will chime in as well.
Seriously, that doesnt tell anything, as needle movement is relevant in various load states.
If thats steady 15inHg in idle, its a bit on the low side. Could be for example a very slight vacuum leak. Did you replace all vac lines in the mean time?
If the needle is shaky (strong or slightly) it points in different direction. Dont habe a link handy, but google "vacuum reading engine" and some good results on interpreting the gauge should pop up.
Maybe someone else will chime in as well.
53ryder
Well-Known Member
Re-checked readings using both gauges. Just watched needle for movement. Both gauges register vacuum in inches of mercury. There was some very slight movement on both gauges. Both gauges are marked off in whole inches and do not show fractions of inches of mercury. I would say the needles moved no more than 1/8th of an inch totally. My best guess.
