Will this fix my code 78 or do I need to do something else?

Yes. It most likely will. But so would replacing the failing part. You should diagnose first.

My vac pump is not pulling strong anymore. I found the heaviest spring I could and put it on the wg arm and I'm getting a little under normal but enough for right now.

Would the vacume pump be the one located under the a/c compressor. Just noticed this afternoon late that it is frozen up and the belt is just sliding by it!!

Ahhh! Get it off! Get it off!


The cheapest vac pump I know of is $84 at bluridge diesel but check www.gmpartdirect.com (http://www.gmpartdirect.com)


of course all you have to have is enough tension to build stock boost or a heavy spring for more boost.Or you can buy the Heath TM for $70 USD or so.


If you leave the vac pump off you have to run a two inch shorter belt.Edited by: quantum mechanic

Can I do away with the vac pump, that is what it is isn't it?, if I get the the Heath? The pump is locked up in one spot but will turn around both ways till it gets to that spot. FUBARed.

The bearing seized on the pump shaft. It's about the same to get a new pump @ $84 or the TM and a new belt.

How does the Heath work? Mechancisal control?

For starters, get a new serpintine belt, and replace your vacuum pump. Believe it or not, the vacuum system is a very good idea IMO now that I understand how it works. If you want more boost, ya just need to do the pot mod to the MAP to run more boost after you have a pyro gauge. This explains WG/vacuum system in detail:


http://www.dieselplace.com/forum/forum_posts.asp?TID=17278&a (http://www.dieselplace.com/forum/forum_posts.asp?TID=17278&a%20mp;PN=1) mp;a mp;a%20mp;PN=1


When you go to replace it, it's gonna be a PITA. You will have to unbolt the AC compressor and move it so you have more room, then you will need to pull the bracket off of the block that the pump is bolted to. Then remove the bracket from the pump once outside of the engine bay.... While you are doing this, ya may as well check out the vacuum lines and make sure they arent cracked and can bend without breaking. (If they break then you needed new lines anyhow...lol)Edited by: Bumpin' Yota

Cool thing is that I saw a vav pump on the motor I pulled the pump and PMD off of today.Edited by: DavidW

From Heath's site:


"The factory control used on the '92-'93 6.5's is a spring-loaded canister. It does not use vacume like the '94-newer engines. This controller typically operates the turbo to 3.5-6 psi and is not adjustable. Our Turbo-Master waste gate controller is created as a direct, bolt on replacement for the factory vacume canister. In combination with the factory waste gate valve, the Turbo-Master forms a fully adjustable, turbine inlet-pressure (drive pressure) relief system. With the Turbo-Master, turbine inlet pressure is retained up to the preset point of bypass"





Does this mean that I need the vacume pump to run this set up or does it do away with it. If so is there a belt to fit that bypasses the vac pump pulley?

It does away with vac, run a 2" shorter belt. do a search for the part number.

Would the vac pump being out have anything to do with the ac compressor not kicking in?

No, that's the low pressure switch on the receiver/dryer.

my opinion, go with the turbomaster. why fix a system that is prone to failure? the turbomaster bypasses all the need for vaccum and is very reliable and easy to install and use.


i took my vaccum pump off a while ago. no point in keeping it on there if i dont need it. not planning on blowing the money on a jake brake. just one more thing to sieze up.


there are two springs that come with the turbomaster kit. one for the stock pcm and one for a reflashed pcm. after doing quantum's boost fooling with 10k on the map, i am able to use the reflash spring at 2". according to heath this should be around 12 lbs of boost.

I put on the Turbo Master and because the those phoney little plastic vacum lines were cracked and broken. I then dumped the vacum pump put a 1993 belt on and no more vacum problems ever again. IMHO why the heck fix something that you will have to fix again and again when for $70 you can get rid of the need. I can adjust boost with the turn of a 1/2 inch wrench.http://www.dieselplace.com/forum/smileys/smiley4.gif

I've lost all vacuum from the pump. So.. to allow boost to build I put on a heavy return spring I found in my scap pile. I removed the wg-arm/ actuator and welded a nut on it to hold the spring. The other end is on the actuator bracket. This took maybe 20 min.


http://www.dieselplace.com/forum/uploads/quantummechanic/2004-11-12_120717_spring.jpg


I've put 400 miles on my one piston rebuild and I decieded it was going to make it and it was time for some fun.


I did some WOT runs uphills and I was stunned to see 20 psi!!! I've been happy with 15 psi and with the vac pump on the way out, it hasn't made that much in awhile.


I tried a 0-60 run and got 16 sec. the guage went to 20 psi and didn't drop past 19 psi through the acceleration. I figure the extra heat is counterproductive and an Ic is going in asap. I don't care if I have to remove the grill for good and weld a bumper to hide it.

i think i need more resistance on the map. i had the spring screwed down to 1 3/4" and 1 7/8" and it goes into limp mode toward the top when i hit certain hills and get into the throttle.

I had the pot. at 92% WGDC (just above the point where it sets off a boost range code) and it didn't even notice 20 psi. I'd like to see the exhaust back pressure for this psi on my GM-4.


http://www.dieselplace.com/forum/uploads/quantummechanic/2004-11-12_142048_scan.jpgEdited by: quantum mechanic

2" is supposed to be only 12psi so 1 3/4" couldnt be that much more.