Help!! Turbo Lights are on?? 90 HDJ81

[onefsatchevy]

In my recently acquired 1990 HDJ81 (1HD-T) both the green and red Turbo lights come on at about 1/3 brightness (dim enough that it is barley noticeable in daylight) at start up (no matter how cold) and stay on as long as the truck is running. The green light lights up fully at around 1500 RPM, which I assume is normal. and this has been the norm since I got it (about 2 weeks). Today the green light started lighting up fully when I turn on the headlights, and it flashes with the signal lights, and flickers when in reverse (I assume because the back up lights are on). Basically if there is more than normal current draw the thing lights up. ANY IDEA WHAT THE PROBLEM IS?? I am at a loss.... Should the red light be on ever?? What does this light mean?? Could it be a bad sensor?

Any help or ideas would be greatly appreciated.

Thanks Guys

James

[BURGER]

Sounds to me like a wiring problem. Maybe a short of two wires and or connectors causing voltage to run between to seperate circuits

[Japan4X4]

Check your air filter.

[mac]

Did you not just change your alternator?

[Tapage]

I start with the boost sensor and air filter as Jap4x4 recomend .. and not, the red light only come when you are in overboost or boost problems ..

The green light it's supose tu light up when you are full boost, it means 2000 rpm ..

[onefsatchevy]

Changed the filter.... no luck....

What is "overboost"? too much PSI? if so the red light should never come on at idle, even if the turbo is having issues?

Any chance it could be a bad battery? I am a bit suspect of one of the two.

I am still running a factory alternator I "borrowed" out of another HDJ81 that is out of commission for a while, I haven't had a chance to put in the new one just yet. And the problem existed before the alt swap. Hmmm.. Mabey I can "borrow" the boost sensor too.... Hope to try that in the morning....

[onefsatchevy]

Oh and I would suspect that it may be a wiring problem, but the truck is prity much stock... Aside from an after market sound system and an espar heater.... I don't think too much has been done to it.

[onefsatchevy]

Well That Didn't Work!!

Replaced, what I believe is, the boost sensors (mounted to the side of the air cleaner with a small rubber hose running over to the intake pipe on top of the motor) and nothing, same problem....

Replaced both batteries,.... nothing.....

re-did some loose grounds.... nothing.....

Running out of ideas here!!

The only thing the manual makes mention of is to check for an open circuit in the wire harness between the low/high pressure switches and the tach, and for a ground connection for the switch..... anyone know where I can find a wiring diagram? I have the motor manual, but it doesn't touch on anything electrical... However I am guessing that this is referring to a light that is full on... not dim like mine.....

Any Help??

Thanks again guys...

James

[Gold Boy]

is the wastegate hose ok?

[onefsatchevy]

Didn't think to check it.... Thanks I will look...

[Tapage]

If you have a chance to get and install some provisional boost gauge, you will see if this a reall pturbo issue or only wirring issue ..

Also check for leaks of boost on the compresor outlet to the throtle body .. as same as oil signals in the intake ..

Check for play in the turbo shaft ..

[onefsatchevy]

Do I have to remove the turbo to check for play in the shaft?... New to the whole turob thing, all previous trucks & cars were O'natural...

[Tapage]

Originally Posted by onefsatchevy

Do I have to remove the turbo to check for play in the shaft?... New to the whole turob thing, all previous trucks & cars were O'natural...

Naaaa only the intake hose .. pretty easy.

[Tapage]

just this and you gain acces to the shaft ..

[Adam B]

Based on my experiences with my truck...

Both lights should come on with your ignition on and the engine not running. Once the engine starts, they should both be off.

The green light comes on at 2psi, pretty much as soon as you start making positive boost pressure.

The red light comes on at 15psi. I don't know of any other condition that is supposed to make this light come on with the engine running. As I understand it, it's just there to let you know you're overboosting, probably because your wastegate hose is disconnected or badly leaking.

As Tapage suggested, you should get a real boost gauge in there to see what's really happening, because you can't trust your idiot lights right now.

Neither light should be "partly illuminated". The circuits should be open or closed. My guess is that there's a wiring gremlin somewhere...

[byrd39]

James
Ck the alternator and the connection at the plug in the alternator, when this started on my 80 all the dash
lights would flash including the boost lights, I replaced the plug and the alternator and all was well

Bill

[onefsatchevy]

Hey guys.... Well I fixed it.... not sure what I did, but the light is gone!!

The problem occurred with 2 different alternators, so I don't think that was it. I did however take off the intake pipe (to check the turbo shaft and the waste gate pipe, both of which were fine I think... read more later) and now I'm guessing that one of the pipes (mabey intake or the pcv tube) was a bit loose, and by removing them and then re-seating I fixed a slight air leak??? Thats about the only thing I can think of...

As for the turbo shaft I have about 1/16 play up and down (perpendicular to the shaft) and mabey a couple of thousandths in and out (parallel to shaft). I seem to remember reading that that was about right somewhere on mud, but I'm not sure... Does that sound right??

Thanks for all the advice guys.... nice to have a group here who is willing to help.

James

[Tapage]

Keep looking your turbo shaft play .. I'm more concern right now with the in and out play ..

[onefsatchevy]

barely moves in and out, in fact I'm not sure it does at all, might be just me feeling things that aren't there....

[Tapage]

Originally Posted by onefsatchevy

barely moves in and out, in fact I'm not sure it does at all, might be just me feeling things that aren't there....

that's good .. when you have time and money get IMOP the 3 more important gauges in a turbo diesel cruiser .. oil, boost and pyro

[onefsatchevy]

Why Oil?? is the factory meter not sufficient? am going to invest in boost and pyro soon.

[dieseldan]

some trust them but many people will attest that the factory oil 'indicator' is just that - definately not accurate...

[Tapage]

Originally Posted by dieseldan

some trust them but many people will attest that the factory oil 'indicator' is just that - definately not accurate...

Ditto .. it give a general idea about yoru oil press and you wil be surprised see how your oil press drop after a hard run ..

[onefsatchevy]

Fair enough, I will pick up one of those too... what numbers should I be seeing?? for pyro and oil??

[Tapage]

Originally Posted by onefsatchevy

Fair enough, I will pick up one of those too... what numbers should I be seeing?? for pyro and oil??

Your EGT numbers depends much on how your engine is and your boost .. but usually I considera max 1250F max safe temp. Usually the lowes EGT you will see after normal driving at idle should be 350 - 450 F and the recomended oil press range are from 36 PSI to 64 PSI at normal operative temp @ 2000 rpm .. at least 4 PSI @idle ( I was scared when read this in the FSM and more if seen in my engine )