'91 Pajero 2.5 TD Dies When Revved

'91 Pajero 2.5 TD Dies When Revved

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stevesingo

Original Poster:

4,848 posts

221 months

Friday 13th April 2018
quotequote all
My friend has a '91 Pajero 2.5TD which has had a few issues. It started with a cracked head which was replaced with a new head. Prior to the head failing it ran absolutely fine, if pretty slow.

Now that it is all back together, it starts on the key, probably not one full revolution before it fires.

Idles absolutely fine with a clean exhaust.

When the revs are brought up, it gets to a point where it just dies with a rich smelling exhaust.

On attempting to restart, it requires bleeding at the injectors before it fires.

In order to isolate air leaks from the tank lines to filter, a seperate tank with clear hose was rigged to feed the high pressure pump
direct. No change.

In order to isolate a blockage in the return from the injectors, this was also fitted with a clear hose drain to a catch tank. Good flow of fuel and no change.

Does anyone have any better ideas?

stevesingo

Original Poster:

4,848 posts

221 months

Tuesday 17th April 2018
quotequote all
I know it is not a very Pistonhead vehicle but really, anyone?

nsa

1,682 posts

227 months

Tuesday 17th April 2018
quotequote all
HT leads / coil is my guess. I had a serious misfire in the mid-range that I traced to bad connection caused by corrosion in an HT lead. Car would start fine.

Sam.

305 posts

120 months

Tuesday 17th April 2018
quotequote all
nsa said:
HT leads / coil is my guess. I had a serious misfire in the mid-range that I traced to bad connection caused by corrosion in an HT lead. Car would start fine.
Its a Diesel..

E-bmw

9,102 posts

151 months

Tuesday 17th April 2018
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Well done.

nsa

1,682 posts

227 months

Tuesday 17th April 2018
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Pwned. Never had a diesel, but that's no excuse I suppose. At the risk of making this hole bigger, I still think it's a "spark" issue rather than fuel.

E-bmw

9,102 posts

151 months

Tuesday 17th April 2018
quotequote all
Keep digging!

stevesingo

Original Poster:

4,848 posts

221 months

E-bmw

9,102 posts

151 months

Tuesday 17th April 2018
quotequote all
Diesel engines are really simple when they are working.

Assuming there is sufficient compression you (pretty much) just need the right amount of fuel to be in the combustion chamber at the right time for it to run.

If I was a gambling man, I would be putting my money on either the HP fuel pump or injectors, assuming it is a common rail diesel.

If these have been off during the work, just make sure everything is connected right & then try to do a test on each injector delivery.

GreenV8S

30,149 posts

283 months

Tuesday 17th April 2018
quotequote all
An injection air leak was my first thought, but you seem to have ruled that out.

I don't know how the fuel is metered on that engine, but if it is done mechanically is there a possibility that the regulator has jammed/got dirt in and is causing overfuelling? As a side effect of bleeding the fuel lines you might be relieving the excess pressure.

stevesingo

Original Poster:

4,848 posts

221 months

Tuesday 17th April 2018
quotequote all
The injection is mechanical indirect injection. It does have a load position sensor on the pump and an engine coolant temp sensor. It also has a boost fuel compensation diaphragm on the pump. I have discounted this as the engine behaves the same when the turbo is plumbed in as when the intercooler is removed and the turbo compressor is blowing to air, hence making no boost.

The pump was not disturbed when replacing the head with the fuel supply and tank returns remaining connected.

Over fuelling as engine speed increases is my theory, due to the engine smoking rich before it cuts out.

Is it possible that the injector leak off pipe is restricted and causing an over fuel when engine speed increases?

nsa

1,682 posts

227 months

Wednesday 18th April 2018
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Vacuum leak?

PositronicRay

26,952 posts

182 months

Wednesday 18th April 2018
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nsa said:
Vacuum leak?
You just keep thinkin', Butch. That's what you're good at.

GreenV8S

30,149 posts

283 months

Wednesday 18th April 2018
quotequote all
stevesingo said:
The injection is mechanical indirect injection.

...

Is it possible that the injector leak off pipe is restricted and causing an over fuel when engine speed increases?
I don't know how that injection system works, but if it does pressure regulation by dumping the excess fuel via a regulator like a two line petrol injection setup then regulator failure or a blockage on the return line would give excess pressure and hence overfuelling. I would have thought it would have to be massively over pressure to be too rich to run at part load though and as a side effect it would be over-sensitive to the throttle pedal input at part throttle, which you haven't mentioned as a symptom.

E-bmw

9,102 posts

151 months

Wednesday 18th April 2018
quotequote all
PositronicRay said:
nsa said:
Vacuum leak?
You just keep thinkin', Butch. That's what you're good at.
Under other circumstances I would say "quit while you are ahead" in these circumstances I will just say quit before you get further behind!

stevesingo

Original Poster:

4,848 posts

221 months

Friday 18th May 2018
quotequote all
UPDATE:

As it turns out it wasn't a vacuum leak nor even a faulty spark plug. confusedhehe

He sent the pump away to be checked and in the process, changed the seals. Now runs great.

Mr2Mike

20,143 posts

254 months

Friday 18th May 2018
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GreenV8S said:
An injection air leak was my first thought, but you seem to have ruled that out.

I don't know how the fuel is metered on that engine, but if it is done mechanically is there a possibility that the regulator has jammed/got dirt in and is causing overfuelling? As a side effect of bleeding the fuel lines you might be relieving the excess pressure.
FWIW overfueling makes a diesel engine produce more power and/or black smoke. It wouldn't stop it running unless the overfueling was so bad it resulted in a holed piston.