next to no boost

[CowboyX]

My truck is a 1996 silverado 1500 4X4 with the L56 6.5 td. Stock exhaust with cat and muffler and stock air box/ filter
I just replaced the vacuum pump and waste gate solenoid. The small hard plastic vacuum line that is connected to the rubber hose from the vacuum pump broke when I was changing the pump so I had to make a new one. I put a new rubber hose onto the pump that was longer than the oem one was so the coupling is now on top of the motor instead of behind the alternator bracket. I include this because I'm not sure if a longer, bigger hose affects the vacuum.
I don't get any DTC'S and the truck does seem to accelerate a little better.
I don't think it's as good as it should be, the truck produces very little boost , maybe 2 psi max. When the truck is idling there is no vacuum to the waste gate actuator.I tested the actuator with vacuum directly from the pump and the lever slowly pulled in.
0 to 60 is around 24 seconds.

[Artworks]

Check / replace line going from your selonoid to waste gate. My lines were real brittle 7 cracked after my manifold replacement. You may try and put vac. gauge on lines & see how much you have. I can't remember the exact numbers, but some where here are the numbers, but 20+ " vac. seems to stick.

[DmaxMaverick]

Check / replace line going from your selonoid to waste gate. My lines were real brittle 7 cracked after my manifold replacement. You may try and put vac. gauge on lines & see how much you have. I can't remember the exact numbers, but some where here are the numbers, but 20+ " vac. seems to stick.

Yes, 20" minimum at the pump (22-25" typical, 25-26" ideal), and 15" modulated at the solenoid outlet to the actuator ("Hg at idle, operating temp).

The vacuum pumps are fairly robust and will tolerate some leakage. What usually happens over time is an overwhelming number of leaks that prevent sufficient vacuum by the time you get to the actuator. Cracks at the rubber connectors/adhesive and the plastic lines are common on older trucks.

[CowboyX]

I'm going to make a new line from pump to solenoid out of 3/16 brake line.
I'm just wondering if it could be the PCM or my map sensor

[Robyn]

Not likely either of those.

Get good lines from pump to valve on LH valve cover and then from valve to controller.

Waste gate should be closed tight at idle with good vacuum to the controller.

If the vacuum is minimal at controller then there are issues with the electrical feed or ??? to the solenoid.

Under hard acceleration there should be about 7-8 psi boost and this is with a good load on it, such as a hill.


Keep us posted

Missy

[CowboyX]

O.K. Now the line going from pump to solenoids is 3/8th rubber. The line from solenoid to actuator is 3/16th rubber. Perhaps I'll have to buy all OEM fittings and lines.
The one thing I didn't mention before is that the previous owner had the waste gate wired shut and had a potentiometer wired in series with the green wire from the map sensor. Here is a picture of the map after I removed the potentiometer

[CowboyX]

O.K People, what do you make of this?
I disconnected my map sensor ans went for a ride. It didn't make any difference and my code reader didn't pick up any codes.

[DmaxMaverick]

What boost? What load conditions? We need some numbers to know what it's (not) doing.

[CowboyX]

On my boost gauge it's reads 1.5 psi max under heavy acceleration

[DmaxMaverick]

(assuming you have sufficient vacuum and no leaks)

Check the wastegate. It should be relatively loose with engine off, and held very tight, engine idling. It should be a very noticeable difference.

Have you changed the fuel filter lately? (air filter, as well)

Confirm the fuel pump is maintaining positive pressure, and there is no air getting in. With engine idling, open the water drain valve (route hose into a container). Fuel should flow at a good rate, and the engine should not stumble or stall.

If the wastegate is operating correctly, and you aren't getting boost, then it's not getting fuel, or the PCM is defueling. It could be a bad MAP sensor, which won't always set a code, depending on how it's failed.

If it's making "some" boost and isn't making a bunch of racket, the turbo is probably OK. Although, it is possible the wastegate may not be closing (internal mechanical problem, like an obstruction or damage).

A plugged catalytic converter can also cause this.

[DmaxMaverick]

Also, if you aren't seeing a lot of black smoke on hard acceleration with only 1.5 PSI, it isn't getting fuel. If you aren't seeing smoke, then it's probably not the WG system.

[lee.sauto]

Hey neighbour to the north, the green wire that is butchered is the signal return from the boost sensor to the ecm. Obviously the previous owner put a potentiometer to cheat the signal for what ever reason. First thing is to check gray wire for 5V with key on engine off, the black is ground ref should be close to zero ohms. Also you need to verify that sensor is a boost sensor and not a map off a car, will not work ever! You really need a scan tool to see what the computer is seeing to diagnos this prob. Code readers dont cut it. Disconecting the plug should have simulated 60lbs boost to the ecm and put the light on imediately. I'm thinking you have an ecm prob thus not calling for boost

[CowboyX]

The fuel filter is maybe a couple of months old. The air is new. The turbo and waste gate were knew 2 years ago when I bought the vehicle. I did a simple check for fuel pressure with engine idling I opened the air bleed screw and fuel squirted out. The waste gate with engine off moves freely open and closed, with engine idling it moves freely open and closed,so the 1.5 psi of boost that I see is being produced with the waste gate open.
I have talked with the diesel garage here already about my ip, but from what I have since read , that's the last thing I should look at.

[CowboyX]

Hey neighbour to the north, the green wire that is butchered is the signal return from the boost sensor to the ecm. Obviously the previous owner put a potentiometer to cheat the signal for what ever reason. First thing is to check gray wire for 5V with key on engine off, the black is ground ref should be close to zero ohms. Also you need to verify that sensor is a boost sensor and not a map off a car, will not work ever! You really need a scan tool to see what the computer is seeing to diagnos this prob. Code readers dont cut it. Disconecting the plug should have simulated 60lbs boost to the ecm and put the light on imediately. I'm thinking you have an ecm prob thus not calling for boost

Checked the 3 wires in the map/boost plug

green 0 volts 0 ohms
gray 5.04 to 5.05 volts
black 1.95 ohms

[lee.sauto]

Cowboy, I assume the green wire was measured from plug to ecm, if so your wiring should be good to go. Mechanically you seem ok as well.
this is where you really need a scan tool to see what the ecm is seeing and thinking about. A skewed signal is all it takes to mess things up.
I am currently in that boat. My truck thinks that it has 28lbs boost and I havent started it yet! wiriing is good , sensor is good, pcm is good, somehow the signal is skewed so ecm has slamed turbo off and cut fuel delivery into the negatives, talk about a dog. I am sure its a bad wire somewhere, have to get back at it. Advice scan it at this point, save yourself some guess work. Lee

[DmaxMaverick]

Verify the vacuum quality at the WG solenoid, and make sure the solenoid is connected correctly. Also give the solenoid a good soaking with some WD40, just for good measure.

If it's interpreting a continuous overboost condition, it should set a code and trigger the MIL, as well as defuel to the point it will have nearly no power and no throttle response at all.

[CowboyX]

I put 1 lead of my multimeter into the end of the plug where the green wire lives and the other lead I grounded it on the intake. I did this for all 3 measurements.
A scan would be nice, and here is the problem. If I take it to the local diesel garage it will cost me $50 at a minimum and most likely be at least double that. It's not in my nature to bring my vehicles to " other people".
So I would like to get the scanning software for my laptop.
Have you used these and if so can you point me in the right direction?

[CowboyX]

Verify the vacuum quality at the WG solenoid, and make sure the solenoid is connected correctly. Also give the solenoid a good soaking with some WD40, just for good measure.

If it's interpreting a continuous overboost condition, it should set a code and trigger the MIL, as well as defuel to the point it will have nearly no power and no throttle response at all.

The waste gate solenoid is new, and I have just over 20'' before the solenoid

[Dvldog8793]

Howdy

http://www.autoenginuity.com/products/scan-tool.html


I have used this one in the past. It worked great 7 years ago. I have not used it since then. It was capable of doing anything that the dealer scan tool did.
It was not cheap...but it was very useful for many vehicles.

[phantom309]

put a spring on the waste gate see how it goes,.

[CowboyX]

put a spring on the waste gate see how it goes,.

That will give me boost , but I don't know if that will give me more fuel. I'll give it a try

[CowboyX]

I borrowed a hand vacuum gauge from work to test my map/ boost sensor. On the plug at the gray wire I have the reference voltage of 5 volts from the ecm with the key on.I don't see any change in the signal voltage when I apply vacuum, it stays at .06/.07 volts.
Am I doing the test right?
After some research I found out that I should have around 2.5 volts even before before I start the test, so I guess I have found the problem.
New map should get rid of the issue.

[lee.sauto]

Hey cowboy you are on the wrong path with that test. Your map sensor senses boost, ie postive pressure, not vacuum. You have a turbo which is postive pressure thus test is not valid, works for a na engine (no turbo). Sorry spend the $50 on scan, sensors are $80 at carquest! Been in this game for 30 plus years. Lee, will save you yet!

[CowboyX]

Here's a little update

Bought a new map sensor from GM which it turns out was made not in North America. That aside a have new symptoms. The waste gate still doesn't close at idle, however when I took it for a test ride I now get a puff of black smoke when I step on it. It start to pull hard and then at about 2500 it stops pulling , like the ecm started to limit fuel.
Manuals are on the way and if I have to I'll get the scanning software as well.

[CowboyX]

Howdy

http://www.autoenginuity.com/products/scan-tool.html


I have used this one in the past. It worked great 7 years ago. I have not used it since then. It was capable of doing anything that the dealer scan tool did.
It was not cheap...but it was very useful for many vehicles.

I was already to buy this for my truck but I didn't want to use paypal so I called. It's a good thing I called because the guy guy told me I would get minimal use out of the unit because my truck is a diesel.
Anyhow I ordered the 2 volume set of GM service manuals. I just hope they don't travel all the way to LA before it comes up here

[Dvldog8793]

Howdy
Not sure what they mean by minimal use...? I was able to adjust timing, view trans and abs issues. Also anything that the computer saw and was adjusting I could see/adjust. A running scan while dring down the road would show real time data. They are correct in that there is not as much data as a gasser....but that just means that the data isn't there. I guess it all depends on expectations, possible that some customers were expecting more data from the diesel set up.
Good luck!

[CowboyX]

My rebuilt vacuum pump seems to be dead already. I'm thinking 12v electric pump as a replacement. Whats the story on those?

[CowboyX]

My truck is now making boost. I thought my vacuum pump was dead so I removed it and I found an ear plug right down in the pump intake. In my attempt to keep dirt out of the vacuum hose as I threaded it behind the alternator bracket I put an ear plug in the end of the rubber hose. I guess I forgot to take it out when I installed the pump.
So, the parts that I changed to get it running right were, a new vacuum pump, a new boost solenoid , a new boost sensor and new vacuum lines from pump to solenoid and to waste gate actuator.
Just to be on the safe side I'm going to order the molded rubber fittings for the solenoids.

[Dvldog8793]

Howdy
Something to maybe consider....I use a mechanical control on my 6.5. I have removed the vac system completely and run a smaller serp belt. Seems to work great for me. one less driven accessory, one less problematic system, positive easy adjustable boost control.