Code 45 Turbo Boost Limit Exceeded

[EvilcowRoland]

To test the solenoid, connect one of it's terminals to the POS battery post and the other terminal to the NEG battery post. You should just need to touch it to the posts. If it clicks, the solenoid is probably working. You'll be able to easily tell if it's moving or not. If it works and you're sure it isn't just sticking, then you need to trace the electrical plug back to the computer. I can't help beyond the basics with that because I don't have any '85 wiring diagrams nor have I worked on anything older than '87. But test the solenoid first and we'll go from there. It's just an on/off kinda thing.

[Tim_K]

I used to have an '89 2.5 Turbo automatic Dodge Spirit, and I used a simple G-valve boost controller on it. It was easy to dial in a set amount of boost, right to the edge of the overboost cutout. It also had the Mistu turbo, so it'd spool up very quickly.

I wouldn't worry about the Code 45, all it does it tell you that you overboosted past 14.7 psi. You can unhook the plugs from the coputer to reset it without unhooking your battery.

The Code 45 will go away after you restart the car enough times.

I have another '89 2.5 Turbo Spirit now but it has a 5 speed. The previous owner put some POS TurboXS boost controller on it, I don't like it as much as the G-valve.

Also, when running the lines for your boost controller if you use an aftermarket one, get your pressure / vaccum source from the intake manifold AFTER the throttle body, and run it straight through the G-valve to the wastegate can.

[puppet]

You should be able to just run a vacuum source directly to the wastegate actuator. You'll see about 6-7psi of boost. No need to grainger that.

Is the MAP sensor OK? All the vacuum lines good (solenoids,WG and MAP)? Electrical connections good and clean (solenoid and MAP)?

[JCI400]

The selonoids all work, leastwise as I apply power I hear them click, all 4 click the same.
(Thanks Evilcow)
The Vacuum source at the bottom of each selonoid has 15 pounds of vacuum.

I apply 15 pounds of vacuum to the line from the selonoid to the WG and it holds 15.
I do not se ANY movement on the WG.

If I grab the rod for the WG I can move it, but it takes more than 15 pounds of force.
Vacuum cannot be activating the WG, it takes too much power.

What other power source, is activated by the vacuum signal to move the WG?

[puppet]

The WG actuator is moved by boost pressure not vacuum. Under boost conditions the arm is moved to open a valve in the exhaust housing in order to route exhaust gasses around the turbos turbine. That's what limits boost threshold. If the valve stays closed because of miss routed vacuum lines to and from the solenoid or WG actuator ... the gasses can't be routed past the turbine (at least until such pressure is created in the exhaust housing to overcome the spring in the WG actuator ... could require 15-20+ psi to move it ... depends on the strength of the actuator can spring). In this case the flapper valve in the exhaust housing is being pushed. It takes more pressure to move the WG cans arm this way.

Run a vacuum line straight to the WG can from the intake manifold source to test the WG can function. As I wrote above it should move with 6-7 psi boost pressure. That will/should be all the turbo can produce when hooked up this way.

Sounds like you need to double check your vacuum hose routing to and from the WG solenoid. The diagram is under hood or at
Donovan's Dodge Garage
The bottom solenoid nipple should be open to air ... the top nipple should be connected to the intake manifold (vacuum source) ... the middle nipple should be connected to the WG can with the restrictor orifice inline.

[JCI400]

The TOP should be connected to the vacuum source? There's a bank of four selonoids, ALL have vacuum coming in the bottom. The diagram on the cowl looks like the bottom and the top is the bleed. The middle goes to its function (Baro, WG, EGR, Purge).

The top (bleed) looks like its almost a "T" to the line out of the selonoids.

So if boost pressure opens the WG, what function is the vacuum? Does it open a valve of some sort in the actuator to allow turbo pressure to open the WG?

[puppet]

Quote:

Originally Posted by JCI400 The TOP should be connected to the vacuum source? There's a bank of four selonoids, ALL have vacuum coming in the bottom. The diagram on the cowl looks like the bottom and the top is the bleed. The middle goes to its function (Baro, WG, EGR, Purge). The top (bleed) looks like its almost a "T" to the line out of the selonoids. So if boost pressure opens the WG, what function is the vacuum? Does it open a valve of some sort in the actuator to allow turbo pressure to open the WG?

I'm going by a chart posted at the link I gave above regarding the line placement. My description is what it looked like to me. ... been wrong before though. At any rate, the problem you're experiencing leads me to believe that your vacuum lines aren't run correctly to and from the WG solenoid.

Vacuum has nothing to do with the turbo WG actuators operation. Vacuum is just a state that the engine is in when not in boost. Those "vacuum" lines carry positive pressure which trigger the boost control via the MAP and the WG solenoid. The MAP is seeing an overboost condition tells the WG solenoid to open but the solenoid is unable to trigger the WG actuator because the lines are routed incorrectly or cracked/leaking. The pressure is either being held at the solenoid (hoses wrong) or being bled off (crack lines) holding the WG actuator closed. The MAP/ECU sees this and sets a code 45.

[EvilcowRoland]

The boost pressure and vacuum pressure are only readings of what is going on in the intake system of the engine. The "vacuum" lines carry both vacuum and boost as puppet said. The solenoids are nothing but switches, like a railroad track switch. They don't care what's in the system. They only open or close when the computer tells them to. As for the wastegate itself, it's always in a closed state naturally. Pushing the arm out opens the door and lets exhaust bypass the turbine (hence boost forces it open). Vacuum does nothing because the door is already at its limit in the other direction at closed. Try hooking a vacuum line from the wastegate to the intake source directly. Like puppet said again, this will give you the minimum boost pressure based on the strength of the spring in the can (usually 5-7 PSI).

The diagram of the solenoids is misleading. Looking at the solenoid as it is mounted to the fender wall, the intake manifold source should go to the TOP fitting. The middle fitting should be closer to the top than the bottom, and it will be going to whatever source you need to get vacuum/boost to (in this case the wastegate itself). The bottom fitting should be left open.

[JCI400]

So I don't understand the purpose of the "vacuum" line running from the WG selonoid and the WG actuator, is it activating a 'switch' in the actuator?

At vacuum or under boost, do all vacuum lines carry the same pressure, whether + or - PSI. Or are there restrictors that change (lower) that vacuum/boost in some lines.

If all vacuum lines carry the same pressure it would then be easy to plumb in a vacuum/boost guage, like the line running to the MAP (easy routing).

[EvilcowRoland]

No, the solenoid is the switching mechanism. The wastegate can (actuator) is just a diapharm with a spring inside to hold it in the closed position until boost pressure pushes it open.

All of the vacuum lines will carry the same pressure unless there is a 1-way check valve in the system. An example would be the heater system. It uses vacuum from the engine to open the coolant flow valve to the heater core. If this system saw boost, it would probably blow up the diaphram in the control valve. So the factory put a check valve on there to keep that from happening (and it only ever sees - (vacuum) pressure. That's just an example, it's part of the brake booster vacuum system so you shouldn't be messing with it as long as everything works.

There is a restrictor in the factory setup between the wastegate solenoid and the actuator. It doesn't reduce the pressure. What it does is makes it take longer to create full pressure on the non-source side of the restrictor. The factory added these to intentionally cause a short boost spike (because it takes longer for the boost to reach the actuator after it gets past the solenoid. What you would see in car is maybe a spike to 9 PSI and then it would settle to the computer limit of 7. You do not "need" any restrictors in the vacuum system unless you want that spike to occur.

You can technically T a boost gauge in anywhere that sees boost and vacuum, so anywhere off the intake really.

[JCI400]

Quote:

Originally Posted by EvilcowRoland No, the solenoid is the switching mechanism. The wastegate can (actuator) is just a diapharm with a spring inside to hold it in the closed position until boost pressure pushes it open.

I understand the selonoid being a switch. The computer opens the selonoid when it sees to much boost at the MAP.


But why a line to the WG Can? If the turbo's boost pushes the WG open, why the vacuum line? Is boost in the vacuum line (from WG selonoid to WG Can) essentially opening the can? Then the can is a switch looking for boost. Does boost at the can need boost pushing on the WG to open the WG?

[puppet]

Is this a long Prince Albert joke?

[EvilcowRoland]

That's what we've been saying, the vacuum lines carry both vacuum and boost. If your engine is seeing boost there is boost pressure in the vacuum lines. That boost pressure has to get to the wastegate can actuator to open the wastegate, so that's why there's a vacuum line to the actuator from the solenoid. Without that vacuum line, boost would never get to the can and the wastegate would not open, making the turbo overboost. Boost pressure forces the wastegate open, but the boost has to travel through the intake and vacuum lines first. The actuator does NOT get boost straight from the turbo.

[EvilcowRoland]

Quote:

Originally Posted by puppet Is this a long Prince Albert joke?

No, I think he's being serious. Maybe it's my fault. I could be over-complicating this. I mean, it makes sense to me but I already understand how the system works. I don't know.

[JCI400]

No maybe I am overcomplicating it. I'm normally a NA Big Block person, turbo's are new to me.

How does the actuator work? Its hard as heck to see. I see a vacuum line in and that rod to the wastegate out. What else is there to it? Is it manufacturered to look for a certain positive pressure in the vacuum line to operate? Does positive PSI in the actuator combine with pressure from the turbo to open the WG?

Its hard to debug something when you don't understand how it works. The WG I get, the selonoid I get, I'm trying to figure out how the can works.