Revvs up on its own

[aerocorey]

I start my truck and let it warm up in the driveway before work. When I pull out of the driveway and shift to second gear the engine will revv up really high on its own. It sounds like the turbo is spooling up and taking the engine with it. It gets so high that I think the valves are floating. I'll get it into gear and let the clutch out, then use the brake to keep the truck from running away with me. Then it goes back to normal. Once it gets that one run out of its system it won't do it again until I park it and let it cool down. It usually does it again as I'm pulling out of the parking lot after work. What's going on with it?

[bsmith]

My only thoughts are that its getting oil into the air intake somehow, matbe the turbo seals have worn and oil is getting past when its cold and that is driving the system, If that is the case and the seals wear much more you may not be able to turn it off and it will self destruct. or is the throttle sticking. Take the air hose off and see if its full of oil also chech the intercooler oil may be getting stuck there and setteling ready for the first startup.

Bob

[Lars L]

No intercooler, Mr Smith... But still you have a point. There could also be some problem with the injection pump sticking. After all, the throttle cable doesn't act directly to the fuel supply. Internally, there is a spring that more or less "tells" the pump what you want to happen. Then there are all sorts of other springs and levers that finally meter the fuel according to various inputs like revs etc.

[aerocorey]

No intercooler, Mr Smith... But still you have a point. There could also be some problem with the injection pump sticking. After all, the throttle cable doesn't act directly to the fuel supply. Internally, there is a spring that more or less "tells" the pump what you want to happen. Then there are all sorts of other springs and levers that finally meter the fuel according to various inputs like revs etc.

Throttle return spring is good. I haven't had much chance to dig into the engine. I'll check for oil leaks. There's an electrical plug on the fuel pump. Is it a heater? It wasn't plugged in right before.

[ThreeSheds]

There's an electrical plug on the fuel pump. Is it a heater? It wasn't plugged in right before.

I don't know what the connection is, but it can't be anything to do with the engine running away - this has to be caused by excessive 'fuel' getting into the system and the only possible causes of that are the injection pump supplying way too much fuel (I have never heard of this - does it happen?) or engine oil. .

IMHO The most obvious scenario is the one (mentioned in a higher post) where leaking turbo oil seal(s) are allowing oil into the inlet tract when you are parked up and this is what your engine is running on after start-up. It is also possible that it's coming from the inlet valve seals, or the engine breather blowing oil into the inlet, but I think these are less likely.

Either way you really should not drive the car with it in this condition - apart from the obvious safety issues, it is perfectly possible (or even likely judging from your earlier description) that before too long the engine will blow itself to pieces.

Roger

[poohbear]

Assuming the problem is not an oil leak check your smoke inhibitor diahpram -

see uncle Les's 'how to' in the tech archive.

My TD did this after prolonged periods at idle - it seems that when idling there is just enough suction to draw fuel part way up the pipe towards the turbo, when you open the throttle suction goes up and it gets a big gulp of exccess fuel, runs away and scares the nuts off you and leaves an almighty cloud of smoke behind you!

Swapped the diaphram and have had no problems since.

Hope that helps.

Dave.

[poohbear]

Assuming the problem is not an oil leak check your smoke inhibitor diahpram -

should read - boost diaphram.

D.

[aerocorey]

should read - boost diaphram.

D.

I'll check this out too.

[gruntus]

Just a note in case it tries to run away with you (if turning off the key doesn't work and it continues to run away).

Into a high gear up with clutch and then stop the car with out depressing the clutch.

Or if already stopped hold the brakes on so that your making buttons on your seat and let the clutch up in a high gear.

That should stall the engine.

If not the engine will just continue to self destruct until it runs out of fuel (which could be a build up of engine oil in the induction system).

The issue may not be as serious as you think but formulate your plan for emergency stopping if it does decide to keep running away with you.

Cheers

G

[aerocorey]

Just a note in case it tries to run away with you (if turning off the key doesn't work and it continues to run away).

Into a high gear up with clutch and then stop the car with out depressing the clutch.

Or if already stopped hold the brakes on so that your making buttons on your seat and let the clutch up in a high gear.

That should stall the engine.

If not the engine will just continue to self destruct until it runs out of fuel (which could be a build up of engine oil in the induction system).

The issue may not be as serious as you think but formulate your plan for emergency stopping if it does decide to keep running away with you.

Cheers

G

It's pretty managable when you are expecting it. When it happens it's usually in the middle of a shift. I just finish the shift, let the clutch out, and tap the brakes if nessecary. It did it once when I was driving in reverse. That one scared the tar out of me.

[jack54turbo]

that wire on the back of the injector pump is a fuel sender wire, if u remove it the fuel is cut off

jack.

[LandyManLuke]

that wire on the back of the injector pump is a fuel sender wire, if u remove it the fuel is cut off

jack.

'Solenoid' is the word you're looking for, and yes, its the single wire connection on the back of the pump.

Connectors mounted to a lump on the top of the throttle spindle are EGR related (throttle position pot)

[aerocorey]

that wire on the back of the injector pump is a fuel sender wire, if u remove it the fuel is cut off

jack.

Thanks, that's what I thought it might be. I think PO had some kind of crappy secret fuel cut-off switch.

[aerocorey]

I read the boost diaphragm how to. I think this is my problem. The truck does smoke alot. It's getting smokier, and my fuel economy is going to carp as well. I pulled the hose going to the turbo and it's wet inside. The only trouble with the boost diaphragm theory is that I can hear my turbo spooling, and the how to says my turbo shouldn't work with a bad diaphragm. It looks like a cheap and easy to replace part, so I'll buy one when I get paid. In the meantime can I simply plug the hose going into the turbo? Can I wire the wastegate one way or the other to keep the turbo from spooling uncontrolled? Today I was idleing the truck and it revved up all by itself. It had only been running for a minute. I pulled the key out and it stopped. Right before it did this it started chugging out TONS of white smoke. I understand plugging this hose and disabling wil turn my engine into a dog until I fix it, but it's better than hurting someone in traffic with a surging truck. Parking it is not an option.

[poohbear]

Hi there,

the only thing that will 'spin' the turbo is the exhaust gassess, so i'ts actually the engine running away that increases gas flow - which in turn spools the turbo creating more vacuum on the fresh air side of the turbo and sucks more fuel up the boost tube from the FIP - which then fuels the engine increasing exhaust gas flow - and so on.

As far as I know the wastegate is exactly that and only opens on to let exhaust gas bypass the turbine and so prevents wear and tear - although I am no turbo expert

disconnecting the boost tube from the turbo will prevent the engine running away - infact if the diaphram is damaged anyway then you could argue that it is surplus to requirements! At least if the truck doesn't run away with itself when this is disconnected you can be pretty sure that you have found the problem.

Any way there should be an adult along shortly who can give you a definitive answer

[aerocorey]

I decided to just try it. It did the trick. At first it puffed all kinds of white smoke, but then it settled down. I ran an errand that needed running. On the way back it wasn't making any smoke at all with the exception of a healthy little puff of black when I stomped on the loud pedal. I haven't seen black smoke from my truck since I brought it home, just a steady stream of white until today. The diaphragm is so bad that there's diesel literally pouring from the hose that was plugged into the turbo. I tried to plug it with a screw, but it still drips. That explains the poor fuel economy of late. I'm sure once I replace the diaphragm and hook everything back up it'll run great.

[Pepé le Pew]

Hi there,

the only thing that will 'spin' the turbo is the exhaust gassess, so i'ts actually the engine running away that increases gas flow - which in turn spools the turbo creating more vacuum on the fresh air side of the turbo and sucks more fuel up the boost tube from the FIP - which then fuels the engine increasing exhaust gas flow - and so on.

As far as I know the wastegate is exactly that and only opens on to let exhaust gas bypass the turbine and so prevents wear and tear - although I am no turbo expert

disconnecting the boost tube from the turbo will prevent the engine running away - infact if the diaphram is damaged anyway then you could argue that it is surplus to requirements! At least if the truck doesn't run away with itself when this is disconnected you can be pretty sure that you have found the problem.

Any way there should be an adult along shortly who can give you a definitive answer

I can't see how the fuel can go up the boost tube towards the turbo as there should be boost pressure going down the tube towards de boost diaphram.

Even at idle the turbo is spinning and the only way the fuel is going to go up this tube is if the fuel pressure is higher than the turbo pressure.

If the fuel pressure at the diaphram is only at spill-pipe pressure it is not very high I should think.

Or am I missing somerhing?