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Coast Steve

Diesel injector question

8 posts in this topic

Hey guys,

I have a question for any diesel mechanics out there.

My truck is a 2000 Mitsubishi FG and it has a 3.9 liter Mitsubishi Fuso 4D34 engine.

Lately it's been a bit low on power so I took out the injectors and sent them to be cleaned and set up.

When I got them back he told me the spray patterns were a bit wonky and not good plus some of the pressure values were set at 180-210 bar.

The setting calls for 230 bar so he set them there.

Anyway I reinstalled them and have been driving for a few hours. Now, the truck has much less power. What's with that?

All filters are new BTW.

It seems to rev ok but has no power like before. And it was pretty gutless before.

He pulled them again and rechecked them all but he said they are as good as new. So I'm stumped.

I'm hoping a diesel mechanic is in the club.

Steve

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Strange I know with the vw Tdi's if you upgrade injectors you have to adjust the injection quantity on the injection pump. Maybe check the manual to see what the stock quanty was set at, and have someone look at it. Another thing depending on the engine cam timing effects it as well.

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with much less power, I'm guessing the turbo is not actuating with something lose in wiring or hoses, which might have been touched when removing the injectors

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I am not a diesel mechanic but if you adjust the actuation pressure up won't the injector open later giving less fuel at a set fuel pressure. Adjusting the down would let them open earlier allowing for more fuel at the same pressure.

Alan

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Alan is 100% right. Higher setting pressure means less fuel injected hence less power.

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I am not familiar with Mitsu diesels-is this DI or IDI, computer control or mechanical? Mechanical would be much easier to figure out, computer you have to plug and see what is happening before guessing. Verify the factory settings for the injectors, but I have played with that one many cars and NEVER affected power (from 30 year old Mercedes diesels to more recent VW tdi) going up 25 bar with some (usually installing turbo injectors in non turbo engines).

Are all the vacuum hoses correct? Anything forgotten or frayed will cause boost issues.

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Posted (edited) · Report post

I think it's both mechanically driven and electronic controlled.

It has plugs going into the pump and also runs a computer although the OBD port only has 2 wires on the plug, so I guess it's very simple in the computer stage.

I pulled a code yesterday from the trucks computer and it reads code #21= water temp sender unit.

But this code light had been on for months so I'm not thinking that' the problem

Maybe the computer told the pump to change when it realized the injectors were higher pressure and is now confused?

Anyway I ordered the water sensor.

Injectors will be put to spec again today to double check.

I'm thinking the systems are fine but a bad sensor is telling things to do this.

When the engine light comes on the motor sounds different at the same time.

It idles fine then 30 seconds in the light comes on and the engine changes pitch

It's all drive by wire so there isn't anything to actually see when it changes sound, and it's not engine brake is not engaging, I checked that.

Dealer just says bring it in, They would love that I'm sure. I will need to remortgage if that happens.

Edited by Coast Steve

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