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Turbo+ High Output System problem?[740-760/89] posted by Jim Bradley on
Saturday, 2 May 1998, at 7:53 p.m.

My '89 780 B230FT is equipped with the "High Output System". TP 31472/1 shows the wiring diagram for the system, but I haven't found any further information or troubleshooting info about the system. TP31451/1 give fault tracing for the fuel system, but omits the Turbo+ system. Is there another TP that would give more info and/or fault tracing on this system?

Can anyone give me a brief explanation of how the Turbo+ system is supposed to work? How do I know whether the system is working or not? Will the turbo function without the Turbo+ system working? Where is the fuse for this system located?

The reason that I ask is that I have been experiencing an intermittent problem where, under hard acceleration, the mixture goes very rich, the exhaust spews black smoke like a diesel bus, and the car loses power. The boost gauge looks normal and the system seems to be free of leaks. The temp sensor resistance is normal. I would like to find out if this could possibly be a Turbo+ problem. Any thoughts on this?

Re: Turbo+ High Output System problem?[740-760/89] posted by abe crombie on
Sunday, 3 May 1998, at 6:26 p.m.

The turbo+ system is wired to the full throttle postiton of the throttle switch assy and to the ignition system request for fuel enrichment terminal that is active if the engine knocks excessively.
The output of the control unit for turbo+ goes to a valve that is attached to a hose that is teed into hose between turbo compressor housing and wastegate actuator. The other hose from this valve goes to hose into front of turbo or air cleaner housing (installation varies from year to year). When you floor it, the valve is pulsed to allow pressure in wastegate actuator hose to be lowered which effectively increases boost. The time of this high boost is 30-45 seconds or the instant that the fuel request due to knock signal is sent from ign ECU to fuel ECU whichever occurs first (the time is given as a range due to different values that I've seen printed for how long the high boost is allowed).
BUT, your problem sounds like a fuel pressure regulator that is sticking when it goes to higher fuel pressure that accompanies turbo boost. The turbo+ system wouldn't be able to make it black smoke. Even if the wire to fuel computer for fuel enrichment request were shorted to ground, the resulting enrichment is very little and wouldn't create visible smoke.

Re: Turbo+ High Output System problem?[740-760/89] posted by Jim Bradley on
Monday, 11 May 1998, at 6:06 p.m.

The gremlin has returned. On the way home today, the original symptoms returned. Accelerating under load (going uphill) produced a surging in the engine, loss of power, and black smoke from the tailpipe. Idle and low speed seems to be OK. Tomorrow it may run fine. I'm really stumped.

At this point, I'm thinking that the black smoke is related to the injectors being held open too long by the ECU, the possible breakdown of ignition under load, or ???

I seem to recall that the cycle time of the injectors can be monitored by using a dwell meter. While this wouldn't be able to quantify the problem, comparing the reading when the engine is running well to when it starts spewing smoke might help in determining whether the problem lies in the ECU output or elsewhere. Does this sound reasonable? Any other thoughts on the subject?

Re: Turbo+ High Output System problem?[740-760/89] posted by Michael McBroom on
Monday, 18 May 1998, at 2:31 a.m.

Hmmm . . . Sorry, I didn't catch your previous post. Have you eliminated the obvious first? The surge and black smoke almost sound like a transient rich condition under heavy load that can sometimes be caused by a plugged or dirty air filter. Normally, your car would be running at stochiometric, but under wide open throttle, the efi system goes open loop. So, if you're getting the fuel, but not enough air, this could be a possible result. It would also make sense why it runs normally under normal conditions, since the air flow requirements will not be as high. Anyway, just a thought.

Re: Turbo+ High Output System problem?[740-760/89] posted by Volvoman on
Tuesday, 26 May 1998, at 1:42 a.m.

Check the 3" hose on the outlet side of the intercooler, they tend to split on the underside, causing the symptoms you describe. Duct tape confirms, Dealer stocks. When it smokes, pull over and listen to the fuel pump. If It sounds like it's winding up, then slowing down, it could be the fuel pressure regulator. That would less likely be intermittant. --

Don't overlook the obvious[740-760/89] posted by JohnB on
Tuesday, 5 May 1998, at 1:07 p.m.

90% of problems with turbo engines are vacuum 87 760 exhibited a similar fuelish problem, black smoke, etc. when the turbo popoff valve (some later cars probably have integral wastegates) two bolts holding it on to the main casting loosened up.

I have since replaced the bolts with socket head cap scews and red loctite.
They still loosened in two years.
I'm about ready to try some lock washers too.

Point is the system may be bleeding boost into the atmosphere but the sucker end of the turbo is still pulling mass flow and the ecu thinks you need more fuel.
Alternatively, you may have one of those systems (Regina??) with a pressure sensor vice a mass flow sensor....the pressure sensor may be going tango uniform which could also result in a rich mixture.

The fuse for my Turbo+ system is on a white plastic holder about 1" by 2", the fuse happens to be red, near the driver's side strut tower where the harness runs outside the strut tower. Yours may vary.


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