Vacuum Pump?

[jmperkins]

Since installing the Unwired Tools ACCII Upgrade kit on my '78 280SE, US Version, it is obvious that When the engine is under load, my vacuum is lower and since the a/c operation requires a constant vacuum, my a/c goes warm.  Unwired tools doc states the vaccum supply must come from the engine AND 2 vacuum lines going into the firewall which I'm under the impression they lead to an electric vacuum pump. Having looked under the instrument panel a couple of times, it is hard to verify that one is actually there or is there just a reservoir? I don't see a pump in the W116 manual but then it appears to just doc the european version of all of this.

I'm not getting any vacuum from this other source under the instrument panel. Is there a vacuum pump there? Thanks!

[pez]

I believe only the diesels had vacuum pumps.

[jmperkins]

Thanks Pez, Time to get out my vacuum pump. There must be a reservoir under the dash that is buffering up vacuum to supplement the engine's vacuum.

[pez]

The ACC system is something that few people on this excellent forum really know much about....I am in the US, but have a euro car, which did not have the ACC system. I believe all the cars down under did not have it either...

Sorry I can't be of more help!

[jmperkins]

Thanks for the reply, Pez.

In 2 of my recent heat/cool problems with non-diesel U.S. ACC Systems, the amplifier has been the culprit. It sits behind the glove compartment. I replaced it on one of my 6.9's when I was not getting any heat and when I put the Unwired Tools ACCII Upgrade kit in, it eliminates the amplifier.

I'll be happy to share as I learn more.

Later,
Joe

[koan]

Don't have ACC (fortunate?) but have a manual for it. There isn't a vacuum pump under the dash but there is a picture of a reservoir but not sure where it is.

Does the Unwired installation manual mention any colour codes on the lines?

koan

[pez]

I would also suggest re-titling this thread to something like 'ACC help needed' or 'help needed with unwired tools acc upgrade' to try to attract the attention of any folks out there that have experience installing that kit.

[Papalangi]

I'm pretty sure that the reservoir is inside the LH front fender (wing).  There are 2 vacuum lines behind the heater control panel that end in coils of what look like wire.  They act as bleeds for vacuum.  Why?  I don't know.

Try disconnecting the vacuum supply to the cabin, should be two or three lines through the firewall.  Now check your vacuum.  Mine was way too low to trip the vacuum switch under the dash until I bumped the timing up something like 10 degrees.  The engine runs much better also.

Micheal

[Big_Richard]

US carby 280 m110 engines are fitted with vacuum pumps, which will bolt straight onto your injected m110. The trouble is finding one that isn't completely screwed.

there are also electric automatic vacuum pumps fitted to w126s which you could probably install.

[jmperkins]

Thanks everyone for your input and help  as I found the reservoir for the vacuum. It looks like a low profile egg carton located  in the trunk just as the W116 manual states/points out in the body section. The problem I had is that the yellow with brown striped plastic line goes from the engine compartment into the reservoir had a lose connection where there is a rubber boot holding the line tight against the reservoir. Now I have constant vacuum to my ACC from a combination of input from my engine vacuum and stored vacuum supply from the reservoir!

I ordered a new master vacuum valve (has three lines coming into it)that sets on the inside of the driver's front door also in hopes that I will have my centralized door locks working. I figure I will have to replace  one or two of the door vacuum bevels as well.

Take care,
Joe

[koan]

Good to hear you got things sorted.

The rear boot/trunk reservoir is only used for the doors on AUS cars. I think papalangi is right about there being a reservoir in the left front gaurd for heater flaps and maybe cruise control.

Is it only your replacement servo that uses "door" vacuum or is that the way ACC systems get vacuum?.

koan

[jmperkins]

Hi Koan,
Thanks for the response.
My unwired tools doc states that the reservoir on the 107 is located on the front drivers fender area in the engine compartment and implies that the w116 is much further away.

My conventional system didn't rely on this auxillary source of vacuum specifically the door locks as you guessed. I need to research further as perhaps the conventional system utilizes a a/c reservoir instead.

Take care,
Joe

[jmperkins]

Hello Again,
I see this in the w116 manual for heating and a/c:


"The supply tank is behind partition at the left between the front wall pillar and front fender". This apparently is the "reservoir" for the a/c/heat system. Perhaps Unwired tools uses the door lock reservoir as it is larger.

[oscar]

Been meaning to post this ol pic.  That's the reservoir I thought UT meant, which is for HVAC.  A few days ago I looked up the instructions but it's all a bit lost on me.  The reservoir under the parcel shelf is for locks as stated but I thought too perhaps that if that supply line was out, the front reservoir wouldn't charge with a vacuum either because of the vacuum tree at the firewall is from a common source.  Purely guessing.

[koan]

The reservoir under the parcel shelf is for locks as stated but I thought too perhaps that if that supply line was out, the front reservoir wouldn't charge with a vacuum either because of the vacuum tree at the firewall is from a common source.

On my system manifold vacuum feeds the leg of a "Y" piece, the outputs of the "Y" piece  connect via one-way vacuum valves to the two vacuum system reservoirs, one for the locks and one for HVAC. The one way valves prevent vacuum loss when no vacuum is available (engine stopped or large throttle openings with engine running) and also isolate the two reservoirs from each other.

koan